10-K

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

Form 10-K

ANNUAL REPORT PURSUANT TO SECTIONS 13 OR 15(d)

OF THE SECURITIES EXCHANGE ACT OF 1934

(Mark One)

x ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934

For the fiscal year ended September 30, 2011

or

¨ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934

For the transition period from                    to                    .

Commission File Number 000-26041

F5 Networks, Inc.

(Exact name of Registrant as specified in its charter)

WASHINGTON	91-1714307
(State or other jurisdiction of	(I.R.S. Employer
incorporation or organization)	Identification No.)

401 Elliott Ave West

Seattle, Washington 98119

(Address of principal executive offices)

(206) 272-5555

(Registrant’s telephone number, including area code)

Securities registered pursuant to Section 12(b) of the Act:

Title of Each Class	Name of Each Exchange on Which Registered
Common stock, no par value	NASDAQ Global Select Market

Securities registered pursuant to Section 12(g) of the Act:

None

Indicate by check mark if the registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities Act.    Yes  x    No  ¨

Indicate by check mark if the registrant is not required to file reports pursuant to Section 13 or Section 15(d) of the Act.    Yes  ¨    No  x

Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the Registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days.    Yes  x    No  ¨

Indicate by check mark whether the registrant has submitted electronically and posted on its corporate Web site, if any, every Interactive Data File required to be submitted and posted pursuant to Rule 405 of Regulation S-T (§ 232.405 of this chapter) during the preceding 12 months (or for such shorter period that the registrant was required to submit and post such files).    Yes  x    No  ¨

Indicate by check mark if disclosure of delinquent filers pursuant to Item 405 of Regulation S-K is not contained herein, and will not be contained, to the best of the Registrant’s knowledge, in definitive proxy or information statements incorporated by reference in Part III of this Form 10-K or any amendment to this Form 10-K.  ¨

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, or a smaller reporting company. See the definitions of “large accelerated filer,” “accelerated filer” and “smaller reporting company” in Rule 12b-2 of the Exchange Act. (Check one):

Large accelerated filer  x		Accelerated filer  ¨
Non-accelerated filer  ¨	(Do not check if a smaller reporting company)	Smaller reporting company  ¨

Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act).    Yes  ¨    No  x

As of March 31, 2011, the aggregate market value of the Registrant’s Common Stock held by non-affiliates of the Registrant was $8,230,608,207 based on the closing sales price of the Registrant’s Common Stock on the NASDAQ Global Select Market on that date.

As of November 17, 2011, the number of shares of the Registrant’s common stock outstanding was 79,484,124.

DOCUMENTS INCORPORATED BY REFERENCE

Information required in response to Part III of this Form 10-K (Items 10, 11, 12, 13 and 14) is hereby incorporated by reference to the specified portions of the Registrant’s Definitive Proxy Statement for the Annual Shareholders Meeting for fiscal year 2011, which Definitive Proxy Statement shall be filed with the Securities and Exchange Commission pursuant to Regulation 14A within 120 days of the end of the fiscal year to which this Report relates.

F5 NETWORKS, INC.

ANNUAL REPORT ON FORM 10-K

For the Fiscal Year Ended September 30, 2011

Table of Contents

		Page
PART I
Item 1.	Business		3
Item 1A.	Risk Factors		15
Item 1B.	Unresolved Staff Comments		21
Item 2.	Properties		21
Item 3.	Legal Proceedings		22
Item 4.	(Removed and Reserved)		22
PART II
Item 5.	Market For Registrant’s Common Equity, Related Stockholder Matters and Issuer Purchases of Equity Securities		23
Item 6.	Selected Financial Data		25
Item 7.	Management’s Discussion and Analysis of Financial Condition and Results of Operations		26
Item 7A.	Quantitative and Qualitative Disclosure About Market Risk		36
Item 8.	Financial Statements and Supplementary Data		37
Item 9.	Changes in and Disagreements With Accountants on Accounting and Financial Disclosure		62
Item 9A.	Controls and Procedures		62
Item 9B.	Other Information		62
PART III
Item 10.	Directors, Executive Officers and Corporate Governance		63
Item 11.	Executive Compensation		63
Item 12.	Security Ownership of Certain Beneficial Owners and Management and Related Stockholder Matters		63
Item 13.	Certain Relationships and Related Transactions, and Director Independence		64
Item 14.	Principal Accountant Fees and Services		64
PART IV
Item 15.	Exhibits and Financial Statement Schedules		64
SIGNATURES			65

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Trademarks and Tradenames

F5, F5 Networks, F5 [DESIGN], F5 Management Pack, F5 WORLD, BIG-IP, CloudFucious, Data Manager, VIPRION, WA, WAN Optimization Manager, WOM, APM, Application Security Manager, ASM, Local Traffic Manager, LTM, Global Traffic Manager, GTM, IBR, Link Controller, Enterprise Manager, Traffic Management Operating System, TMOS, WANJet, FirePass, WebAccelerator, TrafficShield, iControl, TCP Express, Fast Application Proxy, 3DNS, iRules, iRules on Demand, Packet Velocity, ZoneRunner, OneConnect, AskF5, Intelligent Compression, Transparent Data Reduction, TDR, L7 Rate Shaping, LC, IPv6 Gateway, SSL Acceleration, Fast Cache, iHealth, Intelligent Browser Referencing, Message Security Module, PSM, MSM, Netcelera, Protocol Security Module, IT AGILITY. YOUR WAY., DEVCENTRAL, DEVCENTRAL (DESIGN), Edge Client, Edge Gateway, EM, IQUERY, Real Traffic Policy Builder, STRONGBOX, SYN Check, Access Policy Manager, Acopia, Acopia Networks, Advanced Client Authentication, Advanced Routing, ARX, Cloud Extender, CMP, DSI, DNS Express, DSC, Edge Portal, iApps, iSession, ScaleN, SuperVIP, UNITY and vCMP are trademarks or service marks of F5 Networks, Inc., or its subsidiaries in the U.S. and other countries. Any other trademarks, service marks and/or trade names appearing in this document are the property of their respective owners.

Unless the context otherwise requires, in this Annual Report on Form 10-K, the terms “F5 Networks,” “the Company,” “we,” “us,” and “our” refer to F5 Networks, Inc. and its subsidiaries. Our fiscal year ends on September 30, and fiscal years are referred to by the calendar year in which they end. For example, “fiscal year 2011” and “fiscal 2011” refer to the fiscal year ended September 30, 2011.

Forward-Looking Statements

This Annual Report on Form 10-K contains forward-looking statements within the meaning of Section 21E of the Securities Exchange Act of 1934 and Section 27A of the Securities Act of 1933. These statements include, but are not limited to, statements about our plans, objectives, expectations, strategies, intentions or other characterizations of future events or circumstances and are generally identified by the words “expects,” “anticipates,” “intends,” “plans,” “believes,” “seeks,” “estimates,” and similar expressions. These forward-looking statements are based on current information and expectations and are subject to a number of risks and uncertainties. Our actual results could differ materially and adversely from those expressed or implied by these forward-looking statements. Factors that could cause or contribute to such differences include, but are not limited to, those discussed under “Item 1A. Risk Factors” below and in other documents we file from time to time with the Securities and Exchange Commission. We assume no obligation to revise or update any such forward-looking statements.

Item 1. Business

General

F5 Networks is a leading provider of Application Delivery Networking (ADN) technology that optimizes the delivery of network-based applications and the security, performance and availability of servers, data storage devices and other network resources. As strategic points of control within a network, our products collectively function as a dynamic control plane that simplifies the management of data center operations and the delivery of services across diverse data center resources.

Founded in 1996, F5 Networks pioneered load-balancing technology that distributes internet traffic evenly across multiple servers, making them appear like a single device. Today, our BIG-IP application delivery controllers (ADCs) are generally positioned in front of web and application servers, balancing traffic and performing compute-intensive functions such as encrypting and un-encrypting transmissions, screening traffic for security threats, maintaining open connections with servers, speeding the flow of traffic, managing access to applications and data and a variety of other functions that improve the security, performance, and availability of applications.

By offloading functions from servers, BIG-IP ADCs make servers more efficient, reduce the number of servers needed to run specific applications, lower the cost of power and cooling, and drive down operating costs by simplifying the management of servers and applications. In virtual environments, this allows customers to increase the density of virtual servers running on physical servers and reduces the added complexity of managing a dynamic environment.

The core of our ADN technology is our full-proxy Traffic Management Operating System (TMOS) that enables our products to inspect and modify traffic flows to and from servers at network speed and supports a broad and growing array of functions that enhance the security, performance and availability of applications. iRules, a scripting language based on Tool Command Language (TCL), is a unique feature of TMOS that enables customers and third parties to write customized rules to inspect and modify traffic.

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TMOS also supports a common software interface called iControl, which enables our products to communicate with one another and with third-party products, including custom and commercial enterprise applications. TMOS is designed to support the addition of new functionality as software modules and to exploit the performance-enhancing features of our purpose-built hardware platforms. Correspondingly, our hardware architecture integrates industry standard components with components we design ourselves to optimize TMOS and deliver performance that is demonstrably superior to competing products.

Just as our ADCs make many servers look like one, ARX storage virtualization products sit in front of network attached storage (NAS), making multiple storage devices from different vendors look like a single device to the individual clients, servers and applications that use them. In addition, ARX products simplify the migration of data between storage devices, the addition of new storage devices, and the distribution of files across tiers of storage, including cloud storage services, that reflect their relative immediacy or importance.

In connection with our products, we offer a broad range of services including consulting, training, installation, maintenance and other technical support services.

F5 Networks was incorporated on February 26, 1996 in the State of Washington. Our headquarters is in Seattle, Washington, and our mailing address is 401 Elliott Avenue West, Seattle, Washington 98119. The telephone number at our executive offices is (206) 272-5555. We have subsidiaries or branch offices in Australia, Belgium, Brazil, Canada, China, Denmark, France, Germany, Hong Kong, India, Indonesia, Italy, Japan, Malaysia, Mexico, Netherlands, New Zealand, Norway, the Philippines, Singapore, South Africa, South Korea, Spain, Sweden, Taiwan, Thailand, the United Arab Emirates, the United Kingdom and Vietnam. Our annual reports on Form 10-K, quarterly reports on Form 10-Q, current reports on Form 8-K and all amendments to those reports are available free of charge on our website, www.f5.com, as soon as reasonably practicable after such material is electronically filed with the Securities and Exchange Commission.

Industry Background

Growth and Evolution of IP-Based Infrastructures

Internet Protocol (IP) is a communications language used to transmit data over the Internet. For more than two decades, large business and government organizations have been gradually replacing older data center architectures with IP-based infrastructures, deploying new IP-based applications and replacing or upgrading legacy applications with new IP-enabled versions. At the same time, organizations have become more geographically dispersed, and increasingly mobile workforces depend on access to corporate applications and data from remote locations and a variety of client devices including smartphones, tablets and laptops.

Within the past three years, the information technology landscape has changed dramatically as organizations have responded to the slowdown in the global economy by using technologies such as virtualization and the growing availability and sophistication of cloud computing to reduce capital and operating costs and enhance the flexibility and efficiency of their information infrastructures. These efforts are reflected in the ongoing trend toward data center consolidation that includes a reduction in both the number and size of data centers. In addition, a growing number of organizations are turning to social networking and other online vehicles to help target customers and compete more effectively in an environment of reduced consumer spending. The rapid growth of social networks such as Facebook and Twitter, coupled with the explosion of mobile devices and applications, has challenged the abilities of content and service providers to keep up with growing demand.

Along with the growth of Internet traffic, the proliferation of unstructured data such as voice, video, images, email, spreadsheets and formatted text files continues to present an enormous and increasing challenge to IT organizations. Historically, IT organizations have responded to this challenge primarily by adding more storage. File virtualization is a relatively new technology that enables organizations to store and manage files across a heterogeneous array of storage devices and lower their overall cost of storage.

Emergence of the Dynamic Data Center

From a broad perspective, the goal of IT organizations is to optimize the secure delivery of applications and data to users wherever they are and whenever they need them. In a recent survey by a leading industry research firm, global CIOs ranked developing or managing a flexible IT infrastructure as their number one priority. To achieve these goals, IT organizations are embracing virtualization technologies that enable them to group or partition data center resources to meet user demand and reconfigure these virtual resources easily and quickly as demand changes. Many are also taking advantage of the growing availability of external cloud resources as a flexible, secure and reliable alternative to owning and managing everything themselves. As a result, IT infrastructure

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has become increasingly dynamic, complex and reliant on IP-based networks for the delivery of applications and data. At the same time, these changes have created new challenges to the security of IP networks and the applications and data accessible over the Internet. Within the past year, sophisticated denial of service attacks have exposed a major vulnerability in the security perimeter of corporate networks by overwhelming firewalls and effectively shutting down the networks. In addition, many network-level security threats are directly related to the improper use of the same protocols applications depend on to transmit data over the wire. Intrusion detection and prevention devices, which rely on signature databases of known threats, afford some protection against these types of attack. However, they offer no protection against many of the most common threats, including information leakage, content spoofing, cross-site request forgery or “day zero” attacks designed to exploit a variety of application vulnerabilities.

In addition to preventing the threat of attacks designed to disrupt, destroy or block access to network applications, organizations are faced with the equally daunting challenge of controlling access to applications and data. The proliferation of mobile devices has given users with smart phones, tablets, and laptops the ability to access corporate data centers from virtually anywhere. This, in turn, has increased the difficulty of ensuring that mobile users are able to access applications and data for which they are authorized, and that applications and data are protected from access by unauthorized users.

Need to Optimize the Secure Delivery of Applications and Data

With the ongoing evolution and increasing complexity of IT infrastructures, there is a growing need to optimize the secure delivery of applications and data over IP networks. IP-based traffic passing between client devices and servers is divided into discrete packets that travel by multiple routes to their destination where they are reassembled. The disassembly, routing, and reassembly of transmissions are relatively straightforward and require little intelligence. By contrast, managing, inspecting, modifying, redirecting and securing application traffic going to and from servers requires intelligent systems capable of performing a broad array of functions. Broadly speaking, all of those functions are aspects of application delivery networking.

ADCs dynamically manage the flow of traffic between users and servers (physical or virtual), making them look like a single resource to the user. In addition they free up resources by offloading common network functions, such as encryption, IPv4/IPv6 translation, compression, authentication, rate-shaping, and a variety of specialized functions, including network and application security services, policy management, and WAN optimization, that would otherwise run on the servers or be coded into the applications. Since most large enterprises have hundreds — if not thousands — of servers and applications, it is not practical to replicate these functions on each server or within each virtual instance of an application. Doing so would take up valuable network resources and reduce the number of applications that could run on each server. Maintenance costs would be prohibitive and the net result would be a negative impact on the overall performance of servers and applications. Offloading specific functions onto point solutions can eliminate those problems but introduces a new set of challenges. Using point solutions from multiple vendors can create interoperability issues, and problems that do occur can be difficult to troubleshoot. From a security standpoint, it is also much more difficult to audit traffic passing through multiple devices. Providing a comprehensive set of integrated application delivery features and functions on a single, high-performance platform simplifies management of the device and the servers it sits in front of and reduces overall capital and operating costs. File virtualization delivers similar benefits by reducing the cost and complexity of file storage.

Along with other types of IP traffic, the volume of file-based information created and accessed by Internet users and network applications is growing rapidly. File virtualization allows IT organizations to map individual users and applications to a single device that can distribute files across a heterogeneous array of storage devices, keep track of their location, and retrieve them as needed. File virtualization devices maximize storage utilization and simplify the migration of data from one vendor’s storage devices to another’s. They can also be programmed to allocate files across tiers of storage systems, matching the cost, capacity, and performance of the storage devices to the type of information being stored, frequency of usage, and relative importance, substantially reducing both the capital and operating costs associated with file storage.

F5’s Strategy

Our objective is to lead the industry in delivering network architectures that integrate IP networks with applications and data, enabling the delivery of dynamic services in the data center. Those services include security, optimization and orchestration of data center operations and resources, as well as coordination of services spanning multiple data centers. Our products are designed to be strategic points of control in the IT infrastructure that allow business policies to be implemented where information is exchanged. This enables organizations to respond quickly to changing business needs, improve costly and time consuming business processes and develop new sources of revenue through highly differentiated offerings. Key components of our strategy include:

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Offering a complete, integrated application delivery product suite.

Since the introduction of our TMOS architecture for application delivery networking, we have developed TMOS-based versions of our own legacy products, such as GTM and Link Controller, and acquired technology, including ASM, WebAccelerator, WAN Optimization Module (WOM), Edge Gateway and Application Policy Manager (APM). All of these products are currently available as integrated software modules on our BIG-IP family of ADCs. We believe this approach sharply differentiates our products from our competitors’ offerings and provides customers with an expanding array of integrated application delivery networking solutions that can be customized to meet their specific needs.

Investing in technology to meet evolving customer needs.

We continue to invest in research and development to provide our customers with comprehensive, integrated solutions. In application delivery networking, our product development efforts leverage the unique attributes of our software-based platforms to deliver new features and functions that address the complex, changing needs of our customers. Although the bulk of our investment in application delivery and file virtualization technologies is software development, concurrent development of tightly integrated, high-performance hardware is a key part of our investment strategy. We also look for opportunities to acquire technologies that will enable us to broaden the scope of our offerings and expand into adjacent markets.

Continuing to build and expand relationships with strategic technology partners.

To compete successfully against Cisco Systems, Inc. and other large competitors who have an established presence in our target accounts, we have developed strategic technology partnerships with enterprise software vendors, such as Microsoft, Oracle, VMware and SAP, who often have an established or growing presence in those accounts. By taking advantage of our open application programming interface, called iControl, these vendors can equip their applications to control our products in the network, enhancing overall application performance. In return, they provide us significant leverage in the selling process by recommending our products to their customers. We have also worked closely with several of these vendors to develop configurations of our products, called iApps, that are specifically designed to simplify deployment and optimize the performance of their applications. These solutions are available as templates which allow quick and easy configuration of our products for specific applications. We plan to continue building on our existing relationships and to extend our competitive edge by developing new relationships with other strategic partners.

Leveraging DevCentral, our online community of network architects and developers.

Customization of our products using iRules enhances their “stickiness” by allowing customers to solve problems in both their applications and their networks that would be difficult if not impossible to solve by other means. To promote the use of iRules, we host an online community, DevCentral, where network architects and developers can discuss and share the ways in which they use iRules to solve problems and enhance the security, performance and availability of applications. A corollary benefit is that many of the iRules solutions posted by DevCentral participants have become standard features in new releases of TMOS. DevCentral also provides a valuable window into our customers’ constantly evolving needs.

F5 Solutions

We design integrated software products that run on purpose-built hardware and are also available as virtual (software only) editions. Our products function as strategic points of control in IP networks, inspecting, modifying and directing traffic to optimize the security, availability and delivery of applications and data to any user, anywhere. We believe our products offer the most intelligent architecture and advanced functionality in the marketplace along with performance and flexibility that enable organizations to simplify management of their data center operations and integrate disparate resources to reduce operating costs, enhance productivity and improve service to employees, customers and partners.

Application Delivery Networking

Since 2004 we have expanded the breadth of features and functionality we offer well beyond the scope of application delivery networking as it has been traditionally defined. Today, we offer solutions that include application security, secure remote access, WAN optimization and access policy management, opening up large opportunities in several adjacent markets. Many of the features and functions that differentiate our products are built into TMOS, our full-proxy operating system. Others are available as software modules that run on TMOS.

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Software

The core of our technology is TMOS, our Traffic Management Operating System, introduced in September 2004. The full-proxy characteristics of the TMOS architecture enable our products to intercept, inspect and act on the contents of traffic from virtually every type of IP-enabled application. In addition, the modularity of the TMOS architecture allows us to deliver tightly integrated solutions that secure, optimize and ensure the availability of applications and the networks they run on.

Traffic Management Operating System (TMOS)

Since TMOS was launched, we have introduced two major upgrades, adding hundreds of new features designed to interpret and act on specific content in the traffic passing between users and applications. TMOS Version 11.0, announced in July 2011, includes enhancements to iRules, a built-in programming language, that allows customers to create or modify policies that provide direct, granular control over how our products act on traffic at any moment within the application transaction or flow. In addition, Version 11.0 includes several new features and functions that are unique to our products:

• iApps is a set of portable, customizable, reusable templates that enable the rapid and predictable deployment of our products in front of more than 20 applications from vendors including Microsoft, Oracle, VMware, BEA, and SAP. iApps also allows customers and partners to create templates that simplify the deployment and provisioning of their own applications.

• Scale^N is a set of three unique capabilities that enhance the flexibility of our products:

• Clustered Multiprocessing (CMP) allows customers to cluster and aggregate multiple processors (cores) within a BIG-IP appliance and across blades in our VIPRION chassis products.

• Virtual Clustered Multiprocessing (vCMP) enables the creation of separate virtual ADCs within an appliance or chassis, each running a separate instance of TMOS with a different configuration and assigned to a different application.

• Device Service Clustering (DSC) gives customers the ability to group devices and services across an array of ADCs (appliances, VIPRION chassis, or virtual editions). Devices can be added to or removed from a DSC without disrupting application services, and application services can be independently managed within the cluster.

TMOS Version 11.0 also includes a number of new security features that enhance the ability of our products to protect networks and applications against denial of service attacks and other types of security threats. Other enhancements include centralized management of multiple devices and improved visibility that allows customers to monitor and record the performance of applications and users.

Feature Modules

Many of the basic network functions our products perform are embedded as standard features in TMOS and available to our customers at no extra cost. These features include:

• Advanced Client Authentication: Reduces costs and frees up server cycles by eliminating the need to manage and enforce authentication individually across applications.

• Advanced Routing: Allows our products to manage the routing information used by traffic traversing networks and to share that information with other devices.

• Fast Cache: Improves server and application performance by eliminating the need for servers to handle repeated requests for identical content.

• Intelligent Compression: Reduces the volume of outgoing traffic as necessary to optimize transmission to individual users.

• IPv6 Gateway: Provides complete translation and load-balancing between v4 and v6 networks, and directs traffic across mixed IPv6 and IPv4 devices.

• L7 Rate Shaping: Reserves bandwidth for higher priority applications to ensure that low-priority traffic doesn’t interfere with critical business applications.

• Protocol Security: Prevents security attacks directed at HTTP, SMTP and FTP servers.

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• SSL Acceleration: Frees up valuable space on physical and virtual servers by offloading compute-intensive SSL encryption and decryption. Basic SSL Acceleration is included with every product. Depending on the hardware platform, customers can purchase up to 200,000 transactions per second of incremental performance.

Product Modules

In addition to the features and functions embedded in TMOS, we offer a family of integrated software solutions that cover a broad range of application-aware network functions from load-balancing to application security. Depending on a number of factors, including the hardware platform they have purchased, the application they are running, and their performance and security requirements, customers may purchase one or more of these modules in addition to Local Traffic Manager (LTM), which is included with every hardware product. The following software modules are currently available on all BIG-IP and VIPRION products except BIG-IP 1600:

• Local Traffic Manager (LTM): LTM, which provides intelligent load-balancing and traffic management, is standard on all BIG-IP appliances and VIPRION chassis-based systems. As a strategic point of control between servers and users, LTM manages the flow and distribution of all traffic passing through our products, ensuring that applications are secure, fast and available.

• Global Traffic Manager (GTM): GTM automatically directs users to the closest or best-performing data center based on business policy, geolocation, and volume spikes, regardless of their cause. When users try to access a data center that is overloaded or unreachable, GTM automatically and seamlessly directs them to a secondary data center. It also automates the process of tracking and managing interdependencies among individual services in distributed applications. In addition, GTM enhances DNS security by automatically scaling to absorb a rapid increase in queries resulting from a denial of service attack.

• Access Policy Manager (APM): APM provides secure, granular, context-aware control of access to applications while simplifying authentication, authorization, and accounting (AAA) management. An optional endpoint security service validates client devices to protect organizations from viruses or malware infections, accidental data loss, and rogue device access. This allows users to apply repeatable access policies across many applications and servers with centralized visibility of their authorization infrastructure. APM’s Visual Policy Editor makes it easy to create individual and group access policies for many different identities, locations, and web authentication environments. APM also provides dynamic access control by creating access control lists based on user identity, IP address, and attributes such as group membership pulled from standard directory services.

• Application Security Manager (ASM): ASM is an application firewall that provides comprehensive, proactive, application-layer protection against both generalized and targeted attacks. Combining a positive security model (“deny all unless allowed”) with signature-based detection, ASM can prevent “day-zero” attacks in addition to known security threats.

• Link Controller: For organizations with more than one Internet Service Provider (ISP), Link Controller monitors the health and availability of each connection. In the event of a failure, traffic is dynamically directed across other available links so users and external customers stay connected. Link Controller includes an optional compression feature that reduces WAN link bandwidth for lower ISP costs and cuts down on bandwidth bottlenecks for faster application delivery.

• WAN Optimization Manager (WOM): WOM integrates application delivery with WAN optimization technologies, enabling traditional acceleration functions, such as SSL offloading, compression, caching, and traffic prioritization, to combine with optimization technologies like symmetric adaptive compression and application quality of service. As the foundation for site-to-site communication, iSessions, a basic feature of TMOS, allows any two BIG-IP devices to be deployed symmetrically, creating a secure site-to-site connection, improving transfer rates and bandwidth usage, and offloading applications for more efficient data center to data center WAN communication.

• WebAccelerator: WebAccelerator speeds web transactions by optimizing individual network object requests, connections, and end-to-end transactions from the browser through to databases. WebAccelerator enhances web application performance from any location, speeding up interactive performance, improving download times, utilizing bandwidth more efficiently, and dramatically reducing the cost and response time of delivering Web-enabled applications to distributed users where it is not possible to deploy an end-point device. Devices running WebAccelerator can also be placed at key remote locations to provide acceleration to end-users above and beyond TCP optimizations and HTTP compression.

• Message Security: Reputation-based, perimeter anti-spam solution that extends security for message applications to the edge of the corporate network and eliminate unwanted e-mail.

Virtual ADCs

Currently, Local Traffic Manager (LTM), Global Traffic Manager (GTM), Application Security Manager (ASM), Access Policy Manager (APM), and WAN Optimization Manager (WOM) are also available as virtual editions of BIG-IP, designed to run on standard servers and to supplement our other products in hybrid environments. BIG-IP VEs also give our customers a cost-effective way to test and configure our products and help determine which systems and modules will best meet their specific needs.

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Hardware

All of our purpose-built hardware platforms are designed to enhance the performance of our software. Currently we offer two lines of ADN products: our BIG-IP family of ADCs; and our scalable, chassis-based VIPRION ADCs. Both BIG-IP and VIPRION run TMOS and support all of our product software modules. We also sell specialty appliances that integrate specific software services and are only available as standalone products.

Data sheets for all of our hardware platforms are available in the products section of our website.

BIG-IP Application Delivery Controllers

Products in our family of BIG-IP application delivery controllers differ primarily in their performance characteristics resulting from the hardware components and configurations that make up each system. Our current family of BIG-IP appliances includes BIG-IP 1600, BIG-IP 3600, BIG-IP 3900, BIG-IP 6900, BIG-IP 8900, BIG-IP 8950, and BIG-IP 11050.

VIPRION Application Delivery Controllers

Currently we offer two products in our line of chassis-based application delivery controllers. VIPRION 4400 and VIPRION 2400 both consist of a chassis with slots for one to four blades, each equipped with two dual-core processors. VIPRION’s unique architecture distributes traffic across all available processors and allows customers to add or remove blades without disrupting traffic. It also helps customers simplify their networks by consolidating ADCs, saving management costs as well as power, space, and cooling in the datacenter.

VIPRION 4400 was introduced in January 2008 and has remained the high end of our application delivery controller product family in both performance and price. The current P200 blades, introduced in January 2010, doubled the overall performance of the platform.

VIPRION 2400, introduced in June 2011, was designed to make the VIPRION architecture available to customers who want the features and benefits of the platform but do not require the top-end performance of VIPRION 4400. A VIPRION 2400 chassis with one blade has a retail price comparable to the mid-range of our BIG-IP product family. A fully-loaded VIPRION 2400 (chassis with four blades) delivers approximately half the throughput of a fully-loaded VIPRION 4400 at roughly half the price.

Both VIPRION products support all the features, functions and capabilities of TMOS Version 11.0, including clustered multiprocessing (CMP), virtual clustered multiprocessing (vCMP), and device service clustering (DSC).

Specialty Appliances

FirePass

FirePass appliances provide SSL VPN access for remote users of IP networks and any applications connected to those networks from any standard Web browser on any device. The components of FirePass include a dynamic policy engine, which manages user authentication and authorization privileges, and special components that enable corporations to give remote users controlled access to the full array of applications and resources within the network. FirePass also supports Application Ready Access, providing full reverse-proxy services for market-leading application portals including those of SAP, Oracle, Microsoft, and others.

The FirePass appliance is available in three configurations — FirePass 1200, FirePass 4100 and FirePass 4300 — designed to support up to 2,000 concurrent users. In addition, we offer FirePass Virtual Edition, which runs in a VMware virtual environment.

Edge Gateway

BIG-IP Edge Gateway is an advanced remote access product that provides context-aware, policy controlled, secure remote access to applications at LAN speed. Edge Gateway integrates our SSL VPN remote access technology with application acceleration and optimization services at the edge of the network, giving customers remote access, access control, site-to-site security, and application acceleration on one efficient, scalable, cost-effective platform. An optional endpoint security service validates client devices with policy to protect organizations from viruses or malware infections, accidental data loss, and rogue device access.

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Edge Gateway is available as a standalone solution on the BIG-IP 1600, 3600, 3900, 6900 and 8900 platforms.

Enterprise Manager

Enterprise Manager provides a single, centralized management console for our application delivery controllers. Enterprise Manager allows customers with dozens or hundreds of our products to discover and view those products in a single window, and to upgrade or modify the software on those products simultaneously. This lowers the cost and simplifies the task of deploying, managing and maintaining our products and reduces the likelihood of error when blanket changes are implemented.

Enterprise Manager is available on three hardware platforms — Enterprise Manager 4000, Enterprise Manager 3000, and Enterprise Manager 500 — and as a virtual edition.

Data Solutions

F5’s data solutions products address many of the problems associated with managing today’s rapidly expanding file storage infrastructure. The ARX product family is a series of high performance, enterprise-class, intelligent file virtualization devices that simplify the management of file storage environments and lower total storage costs by automating data management tasks and eliminating the disruption associated with storage management operations. Unique capabilities of our ARX products include:

• Non-disruptive Data Migration. Automated movement of files between heterogeneous storage devices without affecting access or requiring client reconfiguration.

• Automated Storage Tiering. Automated storage of data on tiers of heterogeneous storage devices.

• Dynamic Load-balancing. Dynamic distribution of files across multiple file storage devices, eliminating “hotspots” or bottlenecks.

• Efficient Data Replication. Replication of files between heterogeneous storage platforms for efficient and cost effective disaster recovery and centralized backup applications.

• Centralized Data Management. Data Manager, a Windows-based reporting tool, simplifies file virtualization deployments and helps organizations monitor multiple file storage resources through a centralized and extensible storage management platform.

Currently, the ARX series includes three products. ARX 500 and ARX 2000 are stand-alone devices that can support up to 600 and 6,000 users, respectively. ARX 4000 is a fixed form-factor device supporting 10 gigabit Ethernet, capable of managing more than 2 billion files, and able to support up to 12,000 users. ARX is also available in a virtual edition.

To enable our customers to take advantage of inexpensive cloud storage alternatives, we offer ARX Cloud Extender, a software solution that works in concert with the automated storage tiering capabilities of ARX to extend the file storage infrastructure seamlessly from the data center to the cloud.

Product Development

We believe our future success depends on our ability to maintain technology leadership by continuing to improve our products and by developing new products to meet the changing needs of our customers. Our product development organization employs a standard process for the development, documentation and quality control of software and systems that is designed to meet these goals. This process includes working with our business development and marketing teams, product managers, customers and partners to identify new or improved solutions that meet the evolving needs of our addressable markets.

Our principal software engineering team is located in our headquarters in Seattle, Washington. Product development for FirePass, APM, WOM and WebAccelerator is located in San Jose, California. ASM product development is located in Tel Aviv, Israel. ARX product development is located in Lowell, Massachusetts. Our hardware engineering team is located in Spokane, Washington. In addition, we maintain a dedicated facility for product testing and quality control in Tomsk, Russia. Members of all our product development teams collaborate closely with one another to ensure the interoperability and performance of our hardware and software systems.

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During the fiscal years ended September 30, 2011, 2010 and 2009, we had research and product development expenses of $138.9 million, $118.3 million, and $103.7 million, respectively.

Customers

Our customers include a wide variety of enterprise customers and service providers among Fortune 1000 and Business Week Global 1000 companies, including those in technology, telecommunications, financial services, transportation, education, manufacturing and healthcare, along with government customers. In fiscal year 2011, international sales represented 41.2% of our net revenues. Refer to Note 10 of our consolidated financial statements included in this Annual Report on Form 10-K for additional information regarding our revenues by geographic area.

Sales and Marketing

Sales

We sell our products and services to large enterprise customers and service providers through a variety of channels, including distributors, value-added resellers (VARs) and systems integrators. A substantial amount of our revenue for fiscal year 2011 was derived from these channel sales. Our sales teams work closely with our channel partners and also sell our products and services directly to major accounts.

F5 sales teams. Our inside sales team generates and qualifies leads for regional sales managers and helps manage accounts by serving as a liaison between the field and internal corporate resources. Our field sales personnel are located in major cities in four sales regions: the Americas (primarily the United States); Europe, the Middle East, and Africa (EMEA); Japan; and the Asia Pacific region (APAC). Field sales personnel work closely with our channel partners to assist them, as necessary, in the sale of our products and services to their customers. We also sell our products and services directly to customers, primarily large enterprises, whose accounts are managed by our major account services team. Field systems engineers support our regional sales managers and channel partners by participating in joint sales calls and providing pre-sale technical resources as needed.

Distributors and VARs. As a key component of our sales strategy, we have established relationships with a number of large national and international distributors, local and specialized distributors and VARs. We derive a majority of our product sales from these distributors and VARs.

Our agreements with these channel partners are not exclusive and do not prevent them from selling competitive products. These agreements typically have terms of one year with no obligation to renew, and typically do not provide for exclusive sales territories or minimum purchase requirements.

For fiscal year 2011, sales to two of our worldwide distributors, Avnet Technology Solutions and Ingram Micro, represented 18.1% and 10.7% of our total revenues, respectively. Our agreements with these distributors are standard, non-exclusive distribution agreements that renew automatically on an annual basis and can be terminated by either party with 30 days prior written notice. The agreements grant Avnet Technology Solutions and Ingram Micro the right to distribute our products to resellers in North America and certain other territories internationally, with no minimum purchase requirements.

Systems integrators. We also market our products through strategic relationships with systems integrators, including Dell Services, HP Enterprise Services and IBM Global Services, who include our products as core components of application or network-based solutions they deploy for their customers. In most cases, systems integrators do not directly purchase our products for resale to their customers. Instead they typically recommend our products as part of broader solutions, such as enterprise resource planning (ERP) or customer relationship management (CRM) solutions that incorporate our products for high availability and enhanced performance.

Marketing

Our marketing strategy is driven by the belief that our continued success depends on our ability to understand and anticipate the dynamic needs of our addressable markets and to develop valuable solutions that meet those needs. In line with this belief, our marketing organization works directly with customers, partners and our product development teams to identify and create innovative solutions to further enhance our leadership position. In addition, our business development team, which is a component of our marketing organization, closely monitors technology companies in adjacent and complementary markets for opportunities to acquire or partner with those whose solutions are complementary to ours and could enable us to expand our addressable market.

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Another key component of our marketing strategy is to develop and expand our iControl partnerships. Working closely with our partners, we have developed customizable solutions templates called iApps that help ensure the successful deployment and delivery of their applications over the network. These solution templates have been integrated into TMOS Version 11.0 and allow customers to configure our products quickly and easily to optimize the performance of specific applications from major software vendors such as Microsoft, Oracle, SAP and VMware.

To support the growing number of developers using our products, including network and application architects, we continue to promote and expand DevCentral, our on-line community website that provides technical resources to customers, prospects and partners wanting to extend and optimize F5 solutions using iRules. A key aspect of DevCentral is an on-line forum where developers as well as application and network architects discuss and share solutions they have written with iRules. At the end of fiscal year 2011, DevCentral had more than 87,500 registered members.

We also engage in a number of marketing programs and initiatives aimed at promoting our brand and creating market awareness of our technology and products. These include actively participating in industry trade shows and joint marketing events with channel and technology partners, and briefing industry analysts and members of the trade press on our latest products, business relationships and technology partnerships. In addition, we market our products to chief information officers and other information technology professionals through targeted advertising, direct mail and high-profile Web events.

Backlog

At the end of fiscal years 2011 and 2010, we had product backlog of approximately $40.9 million and $50.3 million, respectively. Backlog represents orders confirmed with a purchase order for products to be shipped generally within 90 days to customers with approved credit status. Orders are subject to cancellation, rescheduling by customers or product specification changes by customers. Although we believe that the backlog orders are firm, purchase orders may be cancelled by the customer prior to shipment without significant penalty. For this reason, we believe that our product backlog at any given date is not a reliable indicator of future revenues.

Customer Service and Technical Support

We believe that our ability to provide consistent, high-quality customer service and technical support is a key factor in attracting and retaining large enterprise customers. Accordingly, we offer a broad range of support services that include installation, phone support, hardware repair and replacement, software updates, online tools, consulting and training services.

We provide these services directly to end users and also utilize a multi-tiered support model, leveraging the capabilities of our channel partners when applicable. Our technical support staff is strategically located in regional service centers to support our global customer base.

Prior to the installation of our products, our services personnel work with customers to analyze their network needs and determine the best way to deploy our products and configure product features and functions to meet those needs. Our services personnel also provide on-site installation and training services to help customers make optimal use of product features and functions.

Our customers typically purchase a one-year maintenance contract which entitles them to an array of services provided by our technical support team. Maintenance services provided under the contract include online updates, software error correction releases, hardware repair and replacement, and, in the majority of cases, round-the-clock call center support. Free updates of our software are available to customers with a current maintenance contract. Our technical support team also offers seminars and training classes for customers on the configuration and use of products, including local and wide area network system administration and management. In addition, we have a professional services team able to provide a full range of fee-based consulting services, including comprehensive network management, documentation and performance analysis, and capacity planning to assist in predicting future network requirements.

As part of our maintenance service, we offer an online, automated, self-help customer support function called “Ask F5” that provides answers to many commonly asked questions, allowing customers to get information and solve problems quickly while significantly reducing the number of calls to our support desk. This enables us to provide comprehensive customer support while keeping our support-related expenses at a manageable, consistent level. We also offer an online service called iHealth, which allows

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customers to diagnose up-to-the-minute snapshots of their BIG-IP systems. Diagnoses include tailored feedback about configuration issues or code defects, a description of the issue, recommendations for resolution, and a link to further information in the AskF5™ Knowledge Base.

Manufacturing

We outsource the manufacturing of our pre-configured hardware platforms to third party contract manufacturers for assembly according to our specifications.

Flextronics manufactures our ADC product line, and Sanmina-SCI manufactures our ARX product line. The subcontracting activity at Flextronics and Sanmina-SCI encompasses prototype builds, full production and direct fulfillment. Our contract manufacturers perform the following activities on our behalf; material procurement, PCB assembly and test, final assembly, system test, quality control, direct shipment and warranty repairs. We provide a rolling forecast that allows our contract manufacturers to stock component parts and other materials, plan capacity and build finished goods inventory in anticipation of end user demand. Each of the contract manufacturers procures components in volumes consistent with our forecast, necessary to assemble the products and tests the products according to our specifications. Products are then shipped to our distributors, value-added resellers, or end users. Generally, we do not own the components. Title to the products transfers from the contract manufacturers to us and then to our customers upon delivery at a designated shipment location. If the components are unused or the products are not sold within specified periods of time, we may incur carrying charges or obsolete material charges for components that our contract manufacturers purchased to build products to meet our forecast or customer orders.

Hardware platforms for our products consist primarily of commodity parts and certain custom components designed and approved by our hardware engineering group. Most of our components are purchased from sources which we believe are readily available from other suppliers. However, several components used in the assembly of our products are purchased from a single or limited source.

During fiscal year 2010, we transitioned certain sub-assembly and testing processes of our BIG-IP products from Flextronics’s facilities in Milpitas, California, to the Flextronics facility in ZhuHai, China. All sub-assemblies are configured and final tested at Flextronics’s Milpitas, California for distribution to our end users.

Competition

The expanding capabilities of our product offerings have enabled us to address a growing array of market opportunities, many of which are outside the bounds of the application delivery networking market as defined and measured by industry analysts such as Gartner Group, Dell’Oro and others. In addition to server load-balancing and other functions normally associated with application delivery, our suite of integrated product modules has expanded our addressable market into security, WAN optimization, and policy management, where we compete with a growing number of companies not included among traditional ADC vendors. The ability to create custom network services using iRules has also enabled us, our customers, and our partners to design solutions to problems for which there is no off-the-shelf solution. As a result, we believe the traditional definitions of our market do not encompass all of the features, functions and capabilities of our products or accurately represent the addressable market for those products.

Within the more narrowly defined traditional ADC market, several companies sell server load-balancing products. These include Brocade Communications Systems, Inc., Cisco Systems, Inc., Citrix Systems, Inc., Radware Ltd., and a number of smaller competitors: A10 Networks, Array Networks, Inc., Barracuda Networks, Inc., and Riverbed Technology, which recently acquired Zeus Technology Ltd.

While file virtualization remains an early-stage market, we believe our ARX products are unique in terms of technology and functionality and are well positioned within this emerging market.

The principal competitive factors in the markets in which we compete include product features and performance, customer support, brand recognition, the scope of distribution and sales channels and pricing. Certain of our competitors have and may in the future adopt aggressive pricing policies to gain market share. However, because of the superior performance, broad functionality and unique capabilities of our products, which have resulted in high levels of customer satisfaction and growing brand awareness, we believe that we can and will compete effectively against such pricing policies.

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Intellectual Property

We rely on a combination of patent, copyright, trademark and trade secret laws and restrictions on disclosure to protect our intellectual property rights. We have obtained 95 patents in the United States, 10 foreign patents and have applications pending for various aspects of our technology. Our future success depends in part on our ability to protect our proprietary rights to the technologies used in our principal products. Despite our efforts to protect our proprietary rights, unauthorized parties may attempt to copy aspects of our products or to obtain and use trade secrets or other information that we regard as proprietary. In addition, the laws of some foreign countries do not protect our proprietary rights as fully as do the laws of the United States. Any issued patent may not preserve our proprietary position, and competitors or others may develop technologies similar to or superior to our technology. Our failure to enforce and protect our intellectual property rights could harm our business, operating results and financial condition.

In addition to our own proprietary software, we incorporate software licensed from several third-party sources into our products. These licenses generally renew automatically on an annual basis. We believe that alternative technologies for these licenses are available both domestically and internationally.

Employees

As of September 30, 2011, we had 2,488 full-time employees, including 610 in product development, 1,080 in sales and marketing, 528 in professional services and technical support and 270 in finance, administration and operations. None of our employees is represented by a labor union. We have experienced no work stoppages and believe that our employee relations are good.

Executive Officers of the Registrant

The following table sets forth certain information with respect to our executive officers as of November 22, 2011:

Name	Age		Position
John McAdam		60	President, Chief Executive Officer and Director
Mark Anderson		49	Senior Vice President of Worldwide Sales
Jeffrey A. Christianson		54	Senior Vice President and General Counsel
Edward J. Eames		53	Senior Vice President of Business Operations
Dan Matte		45	Senior Vice President of Marketing and Business Development
Andy Reinland		47	Senior Vice President and Chief Finance Officer
Manuel F. Rivelo		47	Senior Vice President of Security and Strategic Solutions
John Rodriguez		51	Senior Vice President and Chief Accounting Officer
Karl Triebes		44	Senior Vice President of Product Development and Chief Technical Officer

John McAdam has served as our President, Chief Executive Officer and a director since July 2000. Prior to joining us, Mr. McAdam served as General Manager of the Web server sales business at International Business Machines Corporation from September 1999 to July 2000. From January 1995 until August 1999, Mr. McAdam served as the President and Chief Operating Officer of Sequent Computer Systems, Inc., a manufacturer of high-end open systems, which was sold to International Business Machines Corporation in September 1999. Mr. McAdam holds a B.S. in Computer Science from the University of Glasgow, Scotland.

Mark Anderson has served as our Senior Vice President of Worldwide Sales since October 2007. He joined F5 Networks in October 2004 as Vice President of North American Sales. Prior to joining F5, Mr. Anderson served as Executive Vice President of North American Sales at Lucent Technologies from 2003 to 2004. From 2002 through 2003, Mr. Anderson was Vice President of Business Development at RadioFrame Networks. From 1997 to 2001, he served as a Sales Director at Cisco Systems, Inc. From 1986 to 1996, he was Vice President of Western U.S. Sales at Comdisco. Mr. Anderson holds a B.A. in Business and Economics from York University in Toronto.

Jeffrey A. Christianson has served as our Senior Vice President and General Counsel of the Company since December 2006. From February 2000 to July 2006, Mr. Christianson was Sr. Vice President and General Counsel of Western Wireless Corporation, a wireless service provider. From March 1996 to January 2000, Mr. Christianson served as Sr. Vice President of Business Development, General Counsel and Corporate Secretary at Wizards of the Coast, Inc., a game and software company. From September 1992 to March 1996, he served as General Counsel and Secretary of Heart Technology, Inc., a medical device company. From September 1990 to September 1992, he was Vice-President and General Counsel of Spider Staging Corporation and Vice President of Administration and Corporate Counsel for Flow International Corporation after its acquisition of Spider Staging Corporation. Mr. Christianson holds a B.A. from Whitman College and a J.D. from the University of Washington, and serves on the Board of Overseers of Whitman College and the Board of Directors of the Humane Society for Seattle/King County.

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Edward J. Eames has served as our Senior Vice President of Business Operations since January 2001 and as our Vice President of Professional Services from October 2000 to January 2001. From September 1999 to October 2000, Mr. Eames served as Vice President of e-Business Services for International Business Machines Corporation. From June 1992 to September 1999, Mr. Eames served as the European Services Director and the Worldwide Vice President of Customer Service for Sequent Computer Systems, Inc., a manufacturer of high-end open systems. Mr. Eames holds a Higher National Diploma in Business Studies from Bristol Polytechnic and in 1994 completed the Senior Executive Program at the London Business School.

Dan Matte has served as our Senior Vice President of Marketing since June 2004, and as Vice President of Product Marketing and Management from March 2002 through May 2004. He served as our Senior Director of Product Marketing and Management from February 2001 through February 2002. From March 1999 to February 2001, Mr. Matte served as our Director of Product Management. Mr. Matte joined F5 in February 1997. He holds a Bachelor of Commerce from Queens’s University and an MBA from the University of British Columbia.

Andy Reinland has served as our Senior Vice President and Chief Finance Officer since October 2005. Mr. Reinland joined F5 in 1998, serving as a senior financial analyst and, most recently, Vice President of Finance. Prior to joining F5, Mr. Reinland was Chief Financial Officer for RTIME, Inc., a developer of real-time 3D software for Internet applications, which was acquired by Sony. Mr. Reinland started his career in public accounting. Mr. Reinland holds a B.A. in Business from Washington State University.

Manuel F. Rivelo has served as Senior Vice President of Security and Strategic Solutions at F5 Networks since October 2011. Prior to joining F5, Mr. Rivelo served as Senior Vice President — Engineering Operations and Systems for Cisco Systems, Inc. During his 19-year career at Cisco, Rivelo was a member of the Cisco Development Counsel, the senior leadership team of the Cisco Development Organization. While at Cisco, he also served as head of the worldwide systems engineering organization. His managerial career spans over 25 years in product engineering, strategic planning, business operations, field engineering sales and IT. Rivelo serves on the board of directors of Apollo Group, Inc., one of the world’s largest private education providers. He holds a bachelor’s and master’s degree in Electrical Engineering from the Stevens Institute of Technology.

John Rodriguez has served as our Senior Vice President and Chief Accounting Officer since October 2005. For SEC reporting purposes, Mr. Rodriguez is the principal financial officer. Rodriguez joined F5 in 2001 as Corporate Controller. His most recent position held was Vice President and Corporate Controller. Prior to F5, Mr. Rodriguez was Vice President and Chief Financial Officer of CyberSafe, a security solutions company, and Senior Director of Finance and Operations at Mosaix, which was acquired by Lucent Technologies. Mr. Rodriguez started his career in public accounting. Mr. Rodriguez holds a B.A. in Business from the University of Washington.

Karl Triebes has served as our Senior Vice President of Product Development and Chief Technical Officer since August 2004. Prior to joining us, Mr. Triebes served as Chief Technology Officer and Vice President of Engineering of Foundry Networks, Inc. from January 2003 to August 2004. From June 2001 to January 2003, he served as Foundry’s Vice President of Hardware Engineering. From May 2000 to June 2001, Mr. Triebes was Vice President of Engineering at Alcatel U.S.A., a telecommunications company. From December 1999 to May 2000, he was Assistant Vice President of Newbridge Networks Corp., a networking company subsequently acquired by Alcatel. Mr. Triebes holds a B.S. in Electrical Engineering from San Diego State University.

Item 1A. Risk Factors

In addition to the other information in this report, the following risk factors should be carefully considered in evaluating our company and its business.

Our quarterly and annual operating results may fluctuate in future periods, which may cause our stock price to fluctuate

Our quarterly and annual operating results have varied significantly in the past and could vary significantly in the future, which makes it difficult for us to predict our future operating results. Our operating results may fluctuate due to a variety of factors, many of which are outside of our control, including the changing and recently volatile U.S. and global economic environment, which may cause our stock price to fluctuate. In particular, we anticipate that the size of customer orders may increase as we continue to focus on larger business accounts. A delay in the recognition of revenue, even from just one account, may have a significant negative impact on our results of operations for a given period. In the past, a majority of our sales have been realized near the end of a quarter. Accordingly, a delay in an anticipated sale past the end of a particular quarter may negatively impact our results of operations for that quarter, or in some cases, that fiscal year. Additionally, we have exposure to the credit risks of some of our customers and sub-tenants.

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Although we have programs in place that are designed to monitor and mitigate the associated risk, there can be no assurance that such programs will be effective in reducing our credit risks adequately. We monitor individual payment capability in granting credit arrangements, seek to limit the total credit to amounts we believe our customers can pay and maintain reserves we believe are adequate to cover exposure for potential losses. If there is a deterioration of a sub-tenant’s or a major customer’s creditworthiness or actual defaults are higher than expected, future losses, if incurred, could harm our business and have a material adverse effect on our operating results. Further, our operating results may be below the expectations of securities analysts and investors in future quarters or years. Our failure to meet these expectations will likely harm the market price of our common stock. Such a decline could occur, and has occurred in the past, even when we have met our publicly stated revenue and/or earnings guidance.

In addition to other risks listed in this “Risk Factors” section, factors that may affect our operating results include, but are not limited to:

• fluctuations in demand for our products and services due to changing market conditions, pricing conditions, technology evolution, seasonality, or other changes in the global economic environment;

• changes or fluctuations in sales and implementation cycles for our products and services;

• reduced visibility into our customers’ spending and implementation plans;

• reductions in customers’ budgets for data center and other IT purchases or delays in these purchases;

• fluctuations in our gross margins, including the factors described herein, which may contribute to such fluctuations;

• our ability to control costs, including operating expenses, the costs of hardware and software components, and other manufacturing costs;

• our ability to develop, introduce and gain market acceptance of new products, technologies and services, and our success in new and evolving markets;

• any significant changes in the competitive environment, including the entry of new competitors or the substantial discounting of products or services;

• the timing and execution of product transitions or new product introductions, and related inventory costs;

• variations in sales channels, product costs, or mix of products sold;

• our ability to establish and manage our distribution channels, and the effectiveness of any changes we make to our distribution model;

• the ability of our contract manufacturers and suppliers to provide component parts, hardware platforms and other products in a timely manner;

• benefits anticipated from our investments in sales, marketing, product development, manufacturing or other activities; and

• changes in tax laws or regulations, or other accounting rules.

Our success depends on our timely development of new products and features, market acceptance of new product offerings and proper management of the timing of the life cycle of our products

The application delivery networking and file virtualization markets are characterized by rapid technological change, frequent new product introductions, changes in customer requirements and evolving industry standards. Our continued success depends on our ability to identify and develop new products and new features for our existing products to meet the demands of these changes, and the acceptance of those products and features by our existing and target customers. If we are unable to identify, develop and deploy new products and new product features on a timely basis, our business and results of operations may be harmed.

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The current development cycle for our products is on average 12-24 months. The introduction of new products or product enhancements may shorten the life cycle of our existing products, or replace sales of some of our current products, thereby offsetting the benefit of even a successful product introduction, and may cause customers to defer purchasing our existing products in anticipation of the new products. This could harm our operating results by decreasing sales, increasing our inventory levels of older products and exposing us to greater risk of product obsolescence. We have also experienced, and may in the future experience, delays in developing and releasing new products and product enhancements. This has led to, and may in the future lead to, delayed sales, increased expenses and lower quarterly revenue than anticipated. Also, in the development of our products, we have experienced delays in the prototyping of our products, which in turn has led to delays in product introductions. In addition, complexity and difficulties in managing product transitions at the end-of-life stage of a product can create excess inventory of components associated with the outgoing product that can lead to increased expenses. Any or all of the above problems could materially harm our business and results of operations.

Our success depends on sales and continued innovation of our Application Delivery Networking product lines

For the fiscal year ended September 30, 2011, we derived approximately 97.4% of our net product revenues, or approximately 61.0% of our total net revenues, from sales of our Application Delivery Networking (ADN) product lines. We expect to continue to derive a significant portion of our net revenues from sales of our ADN products in the future. Implementation of our strategy depends upon these products being able to solve critical network availability and performance problems for our customers. If our ADN products are unable to solve these problems for our customers or if we are unable to sustain the high levels of innovation in our ADN product feature set needed to maintain leadership in what will continue to be a competitive market environment, our business and results of operations will be harmed.

We may not be able to compete effectively in the emerging application delivery networking and file virtualization markets

The markets we serve are new, rapidly evolving and highly competitive, and we expect competition to persist and intensify in the future. Our principal competitors in the application delivery networking market include Brocade Communications Systems, Inc., Cisco Systems, Inc., Citrix Systems, Inc. and Radware Ltd. In the adjacent WAN Optimization Controller market, we compete with Blue Coat Systems, Inc., Cisco, Citrix, Juniper Networks, Inc. and Riverbed Technology, Inc. In the file virtualization market, we compete with EMC Corporation. We expect to continue to face additional competition as new participants enter our markets. As we continue to expand globally, we may see new competitors in different geographic regions. In addition, larger companies with significant resources, brand recognition, and sales channels may form alliances with or acquire competing application delivery networking solutions from other companies and emerge as significant competitors. Potential competitors may bundle their products or incorporate an Internet traffic management or security component into existing products in a manner that discourages users from purchasing our products. Any of these circumstances may limit our opportunities for growth and negatively impact our financial performance.

The average selling price of our products may decrease and our costs may increase, which may negatively impact gross profits

It is possible that the average selling prices of our products will decrease in the future in response to competitive pricing pressures, increased sales discounts, new product introductions by us or our competitors or other factors. Therefore, in order to maintain our gross profits, we must develop and introduce new products and product enhancements on a timely basis and continually reduce our product costs. Our failure to do so will cause our net revenue and gross profits to decline, which will harm our business and results of operations. In addition, we may experience substantial period-to-period fluctuations in future operating results due to the erosion of our average selling prices.

It is difficult to predict our future operating results because we have an unpredictable sales cycle

Our products have a lengthy sales cycle and the timing of our revenue is difficult to predict. Historically, our sales cycle has ranged from approximately two to three months and has tended to lengthen as we have increasingly focused our sales efforts on the enterprise market. Also, as our distribution strategy has evolved into more of a channel model, utilizing value-added resellers, distributors and systems integrators, the level of variability in the length of sales cycle across transactions has increased and made it more difficult to predict the timing of many of our sales transactions. Sales of our products require us to educate potential customers in their use and benefits. Sales of our products are subject to delays from the lengthy internal budgeting, approval and competitive evaluation processes that large corporations and governmental entities may require. For example, customers frequently begin by evaluating our products on a limited basis and devote time and resources to testing our products before they decide whether or not to purchase. Customers may also defer orders as a result of anticipated releases of new products or enhancements by our competitors or us. As a result, our products have an unpredictable sales cycle that contributes to the uncertainty of our future operating results.

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Our business may be harmed if our contract manufacturers are not able to provide us with adequate supplies of our products or if a single source of hardware assembly is lost or impaired

We outsource the manufacturing of our hardware platforms to third party contract manufacturers who assemble these hardware platforms to our specifications. We have experienced minor delays in shipments from contract manufacturers in the past. However, if we experience major delays in the future or other problems, such as inferior quality and insufficient quantity of product, any one or a combination of these factors may harm our business and results of operations. The inability of our contract manufacturers to provide us with adequate supplies of our products or the loss of one or more of our contract manufacturers may cause a delay in our ability to fulfill orders while we obtain a replacement manufacturer and may harm our business and results of operations. In particular, we currently subcontract manufacturing of our application delivery networking products to a single contract manufacturer with whom we do not have a long-term contract. If our arrangement with this single source of hardware assembly was terminated or otherwise impaired, and we were not able to engage another contract manufacturer in a timely manner, our business, financial condition and results of operation could be adversely affected.

If the demand for our products grows, we will need to increase our raw material and component purchases, contract manufacturing capacity and internal test and quality control functions. Any disruptions in product flow may limit our revenue, may harm our competitive position and may result in additional costs or cancellation of orders by our customers.

Our business could suffer if there are any interruptions or delays in the supply of hardware components from our third-party sources

We currently purchase several hardware components used in the assembly of our products from a number of single or limited sources. Lead times for these components vary significantly. The unavailability of suitable components, any interruption or delay in the supply of any of these hardware components or the inability to procure a similar component from alternate sources at acceptable prices within a reasonable time, may delay assembly and sales of our products and, hence, our revenues, and may harm our business and results of operations.

We are subject to governmental export and import controls that could subject us to liability or impair our ability to compete in international markets

Our products are subject to U.S. export controls and may be exported outside the U.S. only with the required level of export license or through an export license exception because we incorporate encryption technology into our products. In addition, various countries regulate the import of certain encryption technology and have enacted laws that could limit our ability to distribute our products or our customers’ ability to implement our products in those countries. Changes in our products or changes in export and import regulations may create delays in the introduction of our products in international markets, prevent our customers with international operations from deploying our products throughout their global systems or, in some cases, prevent the export or import of our products to certain countries altogether. Any change in export or import regulations or related legislation, shift in approach to the enforcement or scope of existing regulations or change in the countries, persons or technologies targeted by such regulations, could result in decreased use of our products by, or in our decreased ability to export or sell our products to, existing or potential customers with international operations. For example, we will need to comply with Waste Electrical and Electronic Equipment Directive laws, which are being adopted by certain European Economic Area countries on a country-by-country basis. Failure to comply with these and similar laws on a timely basis, or at all, could have a material adverse effect on our business, operating results and financial condition. Any decreased use of our products or limitation on our ability to export or sell our products would likely adversely affect our business, operating results and financial condition.

We may not be able to adequately protect our intellectual property, and our products may infringe on the intellectual property rights of third parties

We rely on a combination of patent, copyright, trademark and trade secret laws, and restrictions on disclosure of confidential and proprietary information to protect our intellectual property rights. Despite our efforts to protect our proprietary rights, unauthorized parties may attempt to copy or otherwise obtain and use our products or technology. Monitoring unauthorized use of our products is difficult, and we cannot be certain that the steps we have taken will prevent misappropriation of our technology, particularly in foreign countries where the laws may not protect our proprietary rights as fully as in the United States.

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Our industry is characterized by the existence of a large number of patents and frequent claims and related litigation regarding patent and other intellectual property rights. In the ordinary course of our business, we are involved in disputes and licensing discussions with others regarding their claimed proprietary rights and cannot assure you that we will always successfully defend ourselves against such claims. We expect that infringement claims may increase as the number of products and competitors in our market increases and overlaps occur. Also, as we have gained greater visibility, market exposure and competitive success, we face a higher risk of being the subject of intellectual property infringement claims. If we are found to infringe the proprietary rights of others, or if we otherwise settle such claims, we could be compelled to pay damages or royalties and either obtain a license to those intellectual property rights or alter our products so that they no longer infringe upon such proprietary rights. Any license could be very expensive to obtain or may not be available at all. Similarly, changing our products or processes to avoid infringing upon the rights of others may be costly or impractical. In addition, we have initiated, and may in the future initiate, claims or litigation against third parties for infringement of our proprietary rights, or to determine the scope and validity of our proprietary rights or those of our competitors. Any of these claims, whether claims that we are infringing the proprietary rights of others, or vice versa, with or without merit, may be time-consuming, result in costly litigation and diversion of technical and management personnel or require us to cease using infringing technology, develop non-infringing technology or enter into royalty or licensing agreements. Further, our license agreements typically require us to indemnify our customers, distributors and resellers for infringement actions related to our technology, which could cause us to become involved in infringement claims made against our customers, distributors or resellers. Any of the above-described circumstances relating to intellectual property rights disputes could result in our business and results of operations being harmed.

Many of our products include intellectual property licensed from third parties. In the future, it may be necessary to renew licenses for third party intellectual property or obtain new licenses for other technology. These third party licenses may not be available to us on acceptable terms, if at all. The inability to obtain certain licenses, or litigation regarding the interpretation or enforcement of license rights and related intellectual property issues, could have a material adverse effect on our business, operating results and financial condition. Furthermore, we license some third party intellectual property on a non-exclusive basis and this may limit our ability to protect our intellectual property rights in our products.

We may not be able to sustain or develop new distribution relationships, and a reduction or delay in sales to significant distribution partners could hurt our business

We sell our products and services through multiple distribution channels in the United States and internationally, including leading industry distributors, value-added resellers, systems integrators, service providers and other indirect channel partners. We have a limited number of agreements with companies in these channels, and we may not be able to increase our number of distribution relationships or maintain our existing relationships. Recruiting and retaining qualified channel partners and training them in our technologies requires significant time and resources. If we are unable to establish or maintain our indirect sales channels, our business and results of operations will be harmed. In addition, two worldwide distributors of our products accounted for 28.8% of our total net revenue for fiscal year 2011. Two worldwide distributors of our products accounted for 24.7% of our total net revenue for fiscal year 2010. A substantial reduction or delay in sales of our products to these distribution partners, if not replaced by sales to other indirect channel partners and distributors, could harm our business, operating results and financial condition.

Undetected software or hardware errors may harm our business and results of operations

Our products may contain undetected errors or defects when first introduced or as new versions are released. We have experienced these errors or defects in the past in connection with new products and product upgrades. We expect that these errors or defects will be found from time to time in new or enhanced products after commencement of commercial shipments. These problems may cause us to incur significant warranty and repair costs, divert the attention of our engineering personnel from our product development efforts and cause significant customer relations problems. We may also be subject to liability claims for damages related to product errors or defects. While we carry insurance policies covering this type of liability, these policies may not provide sufficient protection should a claim be asserted. A material product liability claim may harm our business and results of operations.

Our products must successfully operate with products from other vendors. As a result, when problems occur in a network, it may be difficult to identify the source of the problem. The occurrence of software or hardware problems, whether caused by our products or another vendor’s products, may result in the delay or loss of market acceptance of our products. The occurrence of any of these problems may harm our business and results of operations.

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Adverse general economic conditions or reduced information technology spending may adversely impact our business

A substantial portion of our business depends on the demand for information technology by large enterprise customers and service providers, the overall economic health of our current and prospective customers and the continued growth and evolution of the Internet. International, national, regional and local economic conditions, such as recessionary economic cycles, protracted economic slowdown or further deterioration of the economy could adversely impact demand for our products. The purchase of our products is often discretionary and may involve a significant commitment of capital and other resources. Continued weak economic conditions or a reduction in information technology spending even if economic conditions improve would likely result in longer sales cycles and reduced product sales, each of which would adversely impact our business, results of operations and financial condition.

Our investments in auction rate securities are subject to risks that may cause losses and affect the liquidity of these investments

At September 30, 2011, the fair value of our AAA/A- (or equivalent) rated municipal auction rate securities (ARS) was approximately $13.0 million. We may not be able to liquidate these ARS and realize their full carrying value unless the issuer calls the security, a successful auction occurs, a buyer is found outside of the auction process, or the security otherwise matures. While we do not believe the decline in the carrying values of these municipal ARS is permanent, if the issuers of these securities are unable to successfully close future auctions and their credit ratings are lowered, we may be required to record future impairment charges related to these investments, which would harm our results of operations. We believe certain of these available-for-sale investments may remain illiquid for longer than twelve months and as a result, we have classified these investments as long-term as of September 30, 2011.

Our operating results are exposed to risks associated with international commerce

As our international sales increase, our operating results become more exposed to international operating risks. These risks include risks related to recessionary economic cycles or protracted slowdowns in economies outside the United States, foreign currency exchange rates, managing foreign sales offices, regulatory, political or economic conditions in specific countries, military conflict or terrorist activities, changes in laws and tariffs, inadequate protection of intellectual property rights in foreign countries, foreign regulatory requirements and natural disasters. All of these factors could have a material adverse effect on our business. We intend to continue expanding into international markets. International sales represented 41.2% and 41.4% of our net revenues for the fiscal years ended September 30, 2011 and 2010, respectively.

Changes in governmental regulations could negatively affect our revenues

Our products are subject to various regulations promulgated by the United States and various foreign governments including, but not limited to, environmental regulations and regulations implementing export license requirements and restrictions on the import or export of some technologies, especially encryption technology. Changes in governmental regulation and our inability or failure to obtain required approvals, permits or registrations could harm our international and domestic sales and adversely affect our revenues, business and operations.

Changes in financial accounting standards may cause adverse unexpected revenue fluctuations and affect our reported results of operations

A change in accounting policies can have a significant effect on our reported results and may even affect our reporting of transactions completed before the change is effective. New pronouncements and varying interpretations of existing pronouncements have occurred with frequency and may occur in the future. Changes to existing rules, or changes to the interpretations of existing rules, could lead to changes in our accounting practices, and such changes could adversely affect our reported financial results or the way we conduct our business.

Acquisitions present many risks and we may not realize the financial and strategic goals that are contemplated at the time of the transaction

With respect to our past acquisitions, as well as any other future acquisitions we may undertake, we may find that the acquired businesses, products or technologies do not further our business strategy as expected, that we paid more than what the assets are later worth or that economic conditions change, all of which may generate future impairment charges. Our acquisitions may be viewed negatively by customers, financial markets or investors. There may be difficulty integrating the operations and personnel of the acquired business, and we may have difficulty retaining the key personnel of the acquired business. We may have difficulty in integrating the acquired technologies or products with our existing product lines. Our ongoing business and management’s attention

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may be disrupted or diverted by transition or integration issues and the complexity of managing geographically and culturally diverse locations. We may have difficulty maintaining uniform standards, controls, procedures and policies across locations. We may experience significant problems or liabilities associated with product quality, technology and other matters.

Our inability to successfully operate and integrate newly-acquired businesses appropriately, effectively and in a timely manner, or to retain key personnel of any acquired business, could have a material adverse effect on our ability to take advantage of further growth in demand for integrated traffic management and security solutions and other advances in technology, as well as on our revenues, gross margins and expenses.

Our success depends on our key personnel and our ability to attract and retain qualified sales and marketing, operations, product development and professional services personnel

Our success depends to a significant degree upon the continued contributions of our key management, product development, sales, marketing and finance personnel, many of whom may be difficult to replace. The complexity of our application delivery networking products and their integration into existing networks and ongoing support, as well as the sophistication of our sales and marketing effort, requires us to retain highly trained professional services, customer support and sales personnel. Competition for qualified professional services, customer support and sales personnel in our industry is intense because of the limited number of people available with the necessary technical skills and understanding of our products. Our ability to retain and hire these personnel may be adversely affected by volatility or reductions in the price of our common stock, since these employees are generally granted restricted stock units. The loss of services of any of our key personnel, the inability to retain and attract qualified personnel in the future or delays in hiring qualified personnel may harm our business and results of operations.

We face litigation risks

We are a party to lawsuits in the normal course of our business. Litigation in general, and intellectual property and securities litigation in particular, can be expensive, lengthy and disruptive to normal business operations. Moreover, the results of complex legal proceedings are difficult to predict. Responding to lawsuits has been, and will likely continue to be, expensive and time-consuming for us. An unfavorable resolution of these lawsuits could adversely affect our business, results of operations or financial condition.

Anti-takeover provisions could make it more difficult for a third party to acquire us

Our Board of Directors has the authority to issue up to 10,000,000 shares of preferred stock and to determine the price, rights, preferences, privileges and restrictions, including voting rights, of those shares without any further vote or action by the shareholders. The rights of the holders of common stock may be subject to, and may be adversely affected by, the rights of the holders of any preferred stock that may be issued in the future. The issuance of preferred stock may have the effect of delaying, deferring or preventing a change of control of our company without further action by our shareholders and may adversely affect the voting and other rights of the holders of common stock. Further, certain provisions of our bylaws, including a provision limiting the ability of shareholders to raise matters at a meeting of shareholders without giving advance notice, may have the effect of delaying or preventing changes in control or management of our company, which could have an adverse effect on the market price of our common stock. In addition, our articles of incorporation provide for a staggered board, which may make it more difficult for a third party to gain control of our Board of Directors. Similarly, state anti-takeover laws in the State of Washington related to corporate takeovers may prevent or delay a change of control of our company.

Item 1B. Unresolved Staff Comments

Not applicable.

Item 2. Properties

We lease our principal administrative, sales, marketing, research and development facilities, which are located in Seattle, Washington and consist of approximately 300,000 square feet. In April 2010, we amended and restated the lease agreement for the three buildings that serve as our corporate headquarters. The lease commenced in April, July and August of 2010 for various sections of the first building; and August 2010 for the second and third buildings. The lease for all three buildings will expire in 2022 with an option for renewal. In October 2006, we entered into an agreement to lease a building adjacent to the three buildings that serve as our corporate headquarters. This lease will expire in 2018. During 2008, we entered into two separate sublease agreements to sublease approximately 112,500 square feet of this building. One sublease will expire in 2013. In March 2010, we amended the second sublease, which expanded the subleased space by approximately 11,700 square feet and extended the term of the sublease to 2018.

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We believe that our existing properties are in good condition and suitable for the conduct of our business. We also lease office space for our product development personnel in Spokane, Washington, San Jose, California, Lowell, Massachusetts, Israel, and Russia and for our sales and support personnel in Georgia, Illinois, New York, Washington D.C., Australia, Belgium, Brazil, Canada, China, Denmark, France, Germany, Hong Kong, India, Indonesia, Italy, Japan, Malaysia, Mexico, Netherlands, New Zealand, Norway, the Philippines, Singapore, South Africa, South Korea, Spain, Sweden, Taiwan, Thailand, the United Arab Emirates, the United Kingdom and Vietnam. We believe that our future growth can be accommodated by our current facilities or by leasing additional space if necessary.

Item 3. Legal Proceedings

We are not aware of any pending legal proceedings that, individually or in the aggregate, are reasonably possible to have a material adverse effect on our business, operating results, or financial condition. We may in the future be party to litigation arising in the ordinary course of business, including claims that we allegedly infringe upon third-party intellectual property rights. Such claims, even if not meritorious, could result in the expenditure of significant financial and managerial resources.

Item 4. (Removed and Reserved)

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PART II

Item 5. Market for Registrant’s Common Equity, Related Stockholder Matters and Issuer Purchases of Equity Securities

Market Prices of Common Stock

Our common stock is traded on the Nasdaq Global Select Market under the symbol “FFIV.” The following table sets forth the high and low sales prices of our common stock as reported on the Nasdaq Global Select Market.

	Fiscal Year 2011				Fiscal Year 2010
	High		Low		High		Low
First Quarter	$	143.75	$	89.05	$	53.59	$	37.93
Second Quarter	$	145.76	$	91.10	$	65.10	$	47.11
Third Quarter	$	114.90	$	92.03	$	77.10	$	60.50
Fourth Quarter	$	119.69	$	69.01	$	107.30	$	66.79

The last reported sales price of our common stock on the Nasdaq Global Select Market on November 17, 2011 was $107.10.

As of November 17, 2011, there were approximately 70 holders of record of our common stock. As many of our shares of common stock are held by brokers and other institutions on behalf of shareholders, we are unable to estimate the total number of beneficial holders of our common stock represented by these record holders.

Dividend Policy

Our policy has been to retain cash to fund future growth. Accordingly, we have not paid dividends and do not anticipate declaring dividends on our common stock in the foreseeable future.

Unregistered Securities Sold in 2011

We did not sell any unregistered shares of our common stock during the fiscal year 2011.

Issuer Purchases of Equity Securities

On October 26, 2010, we announced that our Board of Directors approved a new program to repurchase up to an additional $200 million of our outstanding common stock. On August 15, 2011, we announced that our Board of Directors authorized an additional $200 million for our common stock share repurchase program. This new authorization is incremental to the existing $200 million program, approved in October 2010. Acquisitions for the share repurchase programs will be made from time to time in private transactions or open market purchases as permitted by securities laws and other legal requirements. The programs may be discontinued at any time. As of November 17, 2011, we had repurchased and retired 7,601,631 shares at an average price of $58.21 per share under the programs.

Shares repurchased and retired as of November 17, 2011 are as follows (in thousands, except shares and per share data):

	Total Number  of Shares Purchased		Average Price Paid per  Share		Total Number of Shares  Purchased per the Publicly Announced Plan		Approximate Dollar Value of Shares that May Yet be Purchased Under the Plan
October 1, 2010 — October 31, 2010		—	$	—		—	$	237,564
November 1, 2010 — November 30, 2010		126,125	$	120.30		126,125	$	222,384
December 1, 2010 — December 31, 2010		71,519	$	137.24		71,519	$	212,565
January 1, 2011 — January 31, 2011		43,200	$	106.71		43,200	$	207,953
February 1, 2011 — February 28, 2011		203,785	$	118.36		203,785	$	183,823
March 1, 2011 — March 31, 2011		157,948	$	112.55		157,948	$	166,038
April 1, 2011 — April 30, 2011		—	$	—		—	$	166,038
May 1, 2011 — May 31, 2011		265,720	$	103.66		265,720	$	138,481
June 1, 2011 — June 30, 2011		205,913	$	108.94		205,913	$	116,038

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July 1, 2011 — July 31, 2011	26,657	$	99.45	26,657	$	113,386
August 1, 2011 — August 31, 2011	1,091,868	$	77.61	1,091,868	$	228,595
September 1, 2011 — September 30, 2011	794,244	$	78.71	794,244	$	166,038
October 1, 2011 — October 31, 2011	—	$	—	—	$	366,038
November 1, 2011 — November 17, 2011	82,300	$	108.03	82,300	$	157,144

On October 25, 2011, we announced that our Board of Directors authorized an additional $200 million for our common stock share repurchase program. This new authorization is incremental to the existing $400 million program, initially approved in October 2010 and expanded in August 2011.

Performance Measurement Comparison of Shareholder Return

The following graph compares the annual percentage change in the cumulative total return on shares of our common stock, the Nasdaq Composite Index and the Nasdaq Computer Index for the period commencing September 30, 2006, and ending September 30, 2011.

Comparison of Cumulative Total Return

On Investment Since September 30, 2006*

The Company’s closing stock price on September 30, 2011, the last trading day of the Company’s 2011 fiscal year, was $71.05 per share.

* Assumes that $100 was invested September 30, 2006 in shares of Common Stock and in each index, and that all dividends were reinvested. Shareholder returns over the indicated period should not be considered indicative of future shareholder returns.

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Item 6. Selected Financial Data

The following selected consolidated historical financial data are derived from our audited financial statements. The consolidated balance sheet data as of September 30, 2011 and 2010 and the consolidated statement of operations data for the years ended September 30, 2011, 2010 and 2009 are derived from our audited consolidated financial statements and related notes that are included elsewhere in this report. The consolidated balance sheet data as of September 30, 2009, 2008 and 2007 and the consolidated statement of operations for the years ended September 30, 2008 and 2007 are derived from our audited consolidated financial statements and related notes which are not included in this report. The information set forth below should be read in conjunction with our historical financial statements, including the notes thereto, and “Management’s Discussion and Analysis of Financial Condition and Results of Operations,” included elsewhere in this report.

	Years Ended September 30,
	2011		2010		2009		2008		2007
	(In thousands, except per share data)
Consolidated Statement of Operations Data
Net revenues
Products	$	721,975	$	561,142	$	406,529	$	452,929	$	392,921
Services		429,859		320,830		246,550		197,244		132,746
Total		1,151,834		881,972		653,079		650,173		525,667
Cost of net revenues
Products		129,325		113,834		95,209		102,400		84,094
Services		78,679		58,118		47,517		46,618		34,230
Total		208,004		171,952		142,726		149,018		118,324
Gross profit		943,830		710,020		510,353		501,155		407,343
Operating expenses
Sales and marketing		370,735		293,201		225,193		237,175		175,555
Research and development		138,910		118,314		103,664		103,394		69,030
General and administrative		83,523		68,503		55,243		56,001		49,256
In-process research and development(1)		—		—		—		—		14,000
Loss on facility exit and sublease(2)		—		—		—		5,271		—
Restructuring charges(3)		—		—		4,329		—		—
Total		593,168		480,018		388,429		401,841		307,841
Income from operations		350,662		230,002		121,924		99,314		99,502
Other income, net		10,089		7,625		9,724		18,950		28,191
Income before income taxes		360,751		237,627		131,648		118,264		127,693
Provision for income taxes		119,354		86,474		40,113		43,933		50,693
Net income	$	241,397	$	151,153	$	91,535	$	74,331	$	77,000
Net income per share — basic(4)	$	2.99	$	1.90	$	1.16	$	0.90	$	0.93
Weighted average shares — basic(4)		80,658		79,609		78,842		82,290		83,205
Net income per share — diluted(4)	$	2.96	$	1.86	$	1.14	$	0.89	$	0.90
Weighted average shares — diluted(4)		81,482		81,049		80,073		83,428		85,137
Consolidated Balance Sheet Data
Cash, cash equivalents, and short-term investments	$	542,550	$	428,496	$	317,128	$	190,186	$	258,465
Restricted cash(5)		162		195		2,729		2,748		3,959
Long-term investments		470,203		433,570		257,294		261,086		216,366
Total assets		1,568,549		1,362,192		1,068,645		939,223		944,288
Long-term liabilities		90,806		71,409		46,611		34,143		20,301
Total shareholders’ equity		1,105,436		1,003,698		799,020		718,259		770,577

(1) In-process research and development (IPR&D) expense represents the amount of IPR&D that we acquired in the Acopia Networks, Inc. (“Acopia”) acquisition.

(2) Loss on facility exit and sublease expense represents a charge related to the closure of our office space in Bellevue, Washington and the consolidation of our corporate headquarters in Seattle, Washington.

(3) Restructuring charges represent the expense related to the consolidation of facilities, accelerated depreciation on tenant improvements, and a reduction in workforce that took place in the second quarter of fiscal 2009 as part of a comprehensive restructuring program.

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(4) Share and per share amounts have been adjusted as appropriate to reflect a two-for-one stock-split effective August 2007.

(5) Restricted cash represents escrow accounts established in connection with lease agreements for our facilities.

Item 7. Management’s Discussion and Analysis of Financial Condition and Results of Operations

The following discussion of our financial condition and results of operations contains forward-looking statements within the meaning of Section 21E of the Securities Exchange Act of 1934 and Section 27A of the Securities Act of 1933. These statements include, but are not limited to, statements about our plans, objectives, expectations, strategies, intentions or other characterizations of future events or circumstances and are generally identified by the words “expects,” “anticipates,” “intends,” “plans,” “believes,” “seeks,” “estimates,” and similar expressions. These forward-looking statements are based on current information and expectations and are subject to a number of risks and uncertainties. Our actual results could differ materially from those expressed or implied by these forward-looking statements. Factors that could cause or contribute to such differences include, but are not limited to, those discussed under “Item 1A. Risk Factors” herein and in other documents we file from time to time with the Securities and Exchange Commission. We assume no obligation to revise or update any such forward-looking statements.

Overview

We are a global provider of appliances consisting of software and hardware and services that help companies efficiently and securely manage the delivery, optimization and security of application and data traffic on Internet-based networks, and to optimize the performance and utilization of data storage infrastructure and other network resources. We market and sell our products primarily through multiple indirect sales channels in the Americas (primarily the United States); Europe, the Middle East, and Africa (EMEA); Japan; and the Asia Pacific region (APAC). Enterprise customers (Fortune 1000 or Business Week Global 1000 companies) in the technology, telecommunications, financial services, transportation, education, manufacturing and health care industries, along with government customers, continue to make up the largest percentage of our customer base.

Our management team monitors and analyzes a number of key performance indicators in order to manage our business and evaluate our financial and operating performance. Those indicators include:

• Revenues. The majority of our revenues are derived from sales of our Application Delivery Networking (ADN) products including our high end VIPRION chassis and related software modules; BIG-IP Local Traffic Manager, BIG-IP Global Traffic Manager, BIG-IP Link Controller, BIG-IP Application Security Manager, BIG-IP Edge Gateway, BIG-IP WAN Optimization module, BIG-IP Access Policy Manager, and WebAccelerator; FirePass SSL VPN appliance; and our ARX file virtualization products. We also derive revenues from the sales of services including annual maintenance contracts, training and consulting services. We carefully monitor the sales mix of our revenues within each reporting period. We believe customer acceptance rates of our new products and feature enhancements are indicators of future trends. We also consider overall revenue concentration by customer and by geographic region as additional indicators of current and future trends.

• Cost of revenues and gross margins. We strive to control our cost of revenues and thereby maintain our gross margins. Significant items impacting cost of revenues are hardware costs paid to our contract manufacturers, third-party software license fees, amortization of developed technology and personnel and overhead expenses. Our margins have remained relatively stable; however, factors such as sales price, product mix, inventory obsolescence, returns, component price increases and warranty costs could significantly impact our gross margins from quarter to quarter and represent significant indicators we monitor on a regular basis.

• Operating expenses. Operating expenses are substantially driven by personnel and related overhead expenses. Existing headcount and future hiring plans are the predominant factors in analyzing and forecasting future operating expense trends. Other significant operating expenses that we monitor include marketing and promotions, travel, professional fees, computer costs related to the development of new products, facilities and depreciation expenses.

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• Liquidity and cash flows. Our financial condition remains strong with significant cash and investments and no long term debt. The increase in cash and investments for fiscal year 2011 was primarily due to cash provided by operating activities of $416.9 million. This increase was partially offset by $271.5 million of cash used to repurchase outstanding common stock under our share repurchase program in fiscal year 2011. Going forward, we believe the primary driver of cash flows will be net income from operations. Capital expenditures for fiscal year 2011 were comprised primarily of information technology infrastructure and equipment to support the growth of our core business activities. We will continue to evaluate possible acquisitions of, or investments in businesses, products, or technologies that we believe are strategic, which may require the use of cash.

• Balance sheet. We view cash, short-term and long-term investments, deferred revenue, accounts receivable balances and days sales outstanding as important indicators of our financial health. Deferred revenues continued to increase in fiscal 2011 due to growth in the amount of annual maintenance contracts purchased on new products and maintenance renewal contracts related to our existing product installation base. Our days sales outstanding for the fourth quarter of fiscal year 2011 was 47.

Critical Accounting Policies

Our consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America. The preparation of these financial statements requires us to make estimates and judgments that affect the reported amounts of assets, liabilities, revenues and expenses, and related disclosure of contingent assets and liabilities. We base our estimates on historical experience and on various other assumptions that are believed to be reasonable under the circumstances. Actual results may differ from these estimates under different assumptions or conditions.

We believe the following critical accounting policies affect the more significant estimates and judgments used in the preparation of our financial statements.

Revenue Recognition. We sell products through distributors, resellers, and directly to end users. Revenue is recognized provided that all of the following criteria have been met:

• Persuasive evidence of an arrangement exists. Evidence of an arrangement generally consists of a purchase order issued pursuant to the terms and conditions of a distributor, reseller or end user agreement.

• Delivery has occurred. We use shipping or related documents, or written evidence of customer acceptance, when applicable, to verify delivery or completion of any performance terms.

• The sales price is fixed or determinable. We assess whether the sales price is fixed or determinable based on payment terms associated with the transaction and whether the sales price is subject to refund or adjustment.

• Collectability is reasonably assured. We assess collectability primarily based on the creditworthiness of the customer as determined by credit checks and related analysis, as well as the Customer’s payment history.

In certain regions where we do not have the ability to reasonably estimate returns, we defer revenue on sales to our distributors until they have received information from the channel partner indicating that the product has been sold to the end-user customer. Payment terms to domestic customers are generally net 30 days to net 45 days. Payment terms to international customers range from net 30 days to net 120 days based on normal and customary trade practices in the individual markets. We offer extended payment terms to certain customers, in which case, revenue is recognized when payments are due.

Whenever product, training services and post-contract customer support (PCS) elements are sold together, a portion of the sales price is allocated to each element based on their respective fair values as determined when the individual elements are sold separately. Revenue from the sale of products is recognized when the product has been shipped and the customer is obligated to pay for the product. When rights of return are present and we cannot estimate returns, we recognize revenue when such rights of return lapse. Revenues for PCS are recognized on a straight-line basis over the service contract term. PCS includes a limited period of telephone support updates, repair or replacement of any failed product or component that fails during the term of the agreement, bug fixes and rights to upgrades, when and if available. Consulting services are customarily billed at fixed hourly rates, plus out-of-pocket expenses, and revenues are recognized when the consulting has been completed. Training revenue is recognized when the training has been completed.

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In October 2009, the Financial Accounting Standards Board (FASB) amended the accounting standards for revenue recognition to remove from the scope of industry-specific software revenue recognition guidance any tangible products containing software components and non-software components that operate together to deliver the products essential functionality. In addition, the FASB amended the accounting standards for certain multiple element revenue arrangements to:

• Provide updated guidance on whether multiple elements exist, how the elements in an arrangement should be separated, and how the arrangement consideration should be allocated to the separate elements;

• Require an entity to allocate arrangement consideration to each element based on a selling price hierarchy, where the selling price for an element is based on vendor-specific objective evidence (VSOE), if available, third-party evidence (TPE), if available and VSOE is not available; or the best estimate of selling price (BESP), if neither VSOE or TPE is available; and

• Eliminate the use of the residual method and require an entity to allocate arrangement consideration using the selling price hierarchy.

We adopted this guidance in the first quarter of fiscal year 2011 on a prospective basis for applicable arrangements originating or materially modified after October 1, 2010. The impact of this adoption was not material to our financial position and results of operations for the fiscal year ended September 30, 2011.

The majority of our products are hardware appliances that contain software essential to the overall functionality of the products. Accordingly, we no longer recognize revenue on sales of these products in accordance with the industry-specific software revenue recognition guidance.

For all transactions entered into prior to the first quarter of fiscal year 2011 and for sales of nonessential and stand-alone software after October 1, 2010, we allocate revenue for arrangements with multiple elements based on the software revenue recognition guidance. Software revenue recognition guidance requires revenue earned on software arrangements involving multiple elements to be allocated to each element based on the relative fair values of those elements. The fair value of an element must be based on VSOE. Where fair value of certain elements is not available, revenue is recognized on the “residual method” based on the fair value of undelivered elements. If evidence of the fair value of one or more undelivered elements does not exist, all revenue is deferred and recognized at the earlier of the delivery of those elements or the establishment of fair value of the remaining undelivered elements.

For transactions entered into subsequent to the adoption of the amended revenue recognition standards that are multiple-element arrangements, the arrangement consideration is allocated to each element based on the relative selling prices of all of the elements in the arrangement using the fair value hierarchy in the amended revenue recognition guidance.

Consistent with the methodology used under the previous accounting guidance, we establish VSOE for our products, training services, PCS and consulting services based on the sales price charged for each element when sold separately. The sales price is discounted from the applicable list price based on various factors including the type of customer, volume of sales, geographic region and program level. Our list prices are generally not fair value as discounts may be given based on the factors enumerated above. We believe that the fair value of our consulting services is represented by the billable consulting rate per hour, based on the rates we charge customers when they purchase standalone consulting services. The price of consulting services is not based on the type of customer, volume of sales, geographic region or program level.

We use historical sales transactions to determine whether VSOE can be established for each of the elements. In most instances, VSOE is the sales price of actual standalone (unbundled) transactions within the past 12 month period that are priced within a reasonable range, which we have determined to be plus or minus 15% of the median sales price of each respective price list.

VSOE of PCS is based on standalone sales since we do not provide stated renewal rates to our customers. In accordance with our PCS pricing practice (supported by standalone renewal sales), renewal contracts are priced as a percentage of the undiscounted product list price. The PCS renewal percentages may vary, depending on the type and length of PCS purchased. We offer standard and premium PCS, and the term generally ranges from one to three years. We employ a bell-shaped-curve approach in evaluating VSOE of fair value of PCS. Under this approach, we consider VSOE of the fair value of PCS to exist when a substantial majority of our standalone PCS sales fall within a narrow range of pricing.

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We are typically not able to determine TPE for our products or services. TPE is based on competitor prices for similar elements when sold separately. Generally, our go-to-market strategy differs from that of other competitive products or services in our markets and our offerings contain a significant level of differentiation such that the comparable pricing of products with similar functionality cannot be obtained. Furthermore, we are unable to reliably determine the selling prices on a stand-alone basis of similar products offered by our competitors.

When we are unable to establish the selling price of our non-software elements using VSOE or TPE, we use BESP in our allocation of arrangement consideration. The objective of BESP is to determine the price at which we would transact a sale if the product or service were sold on a stand-alone basis. We are generally not able to establish VSOE for non-software product sales. Under software revenue recognition guidance, these product sales were accounted for utilizing the residual method. With the adoption of the new revenue recognition guidance, we have been able to establish BESP for non-software product sales through the list price, less a discount deemed appropriate to maintain a reasonable gross margin. Management regularly reviews the gross margin information. Non-software product BESP is determined through our review of historical sales transactions within the past 12 month period. Additional factors considered in determining an appropriate BESP include, but are not limited to, cost of products, pricing practices, geographies, customer classes, and distribution channels.

We have established and regularly validate the VSOE of fair value and BESP for elements in our multiple element arrangements. We account for taxes collected from customers and remitted to governmental authorities on a net basis and excluded from revenues.

Reserve for Doubtful Accounts. Estimates are used in determining our allowance for doubtful accounts and are based upon an assessment of selected accounts and as a percentage of our remaining accounts receivable by aging category. In determining these percentages, we evaluate historical write-offs, current trends in the credit quality of our customer base, as well as changes in the credit policies. We perform ongoing credit evaluations of our customers’ financial condition and do not require any collateral. If there is deterioration of a major customer’s credit worthiness or actual defaults are higher than our historical experience, our allowance for doubtful accounts may not be sufficient.

Reserve for Product Returns. In some instances, product revenue from distributors is subject to agreements allowing rights of return. Product returns are estimated based on historical experience and are recorded at the time revenues are recognized. Accordingly, we reduce recognized revenue for estimated future returns at the time revenue is recorded. When rights of return are present and we cannot estimate returns, revenue is recognized when such rights lapse. The estimates for returns are adjusted periodically based upon changes in historical rates of returns and other related factors. It is possible that these estimates will change in the future or that the actual amounts could vary from our estimates.

Accounting for Income Taxes. We are required to estimate our income taxes in each of the jurisdictions in which we operate as part of the process of preparing our consolidated financial statements. This process involves estimating our actual current tax exposure, including assessing the risks associated with tax audits, together with assessing temporary differences resulting from the different treatment of items for tax and accounting purposes. These differences result in deferred tax assets and liabilities. Due to the evolving nature and complexity of tax rules combined with the large number of jurisdictions in which we operate, it is possible that our estimates of our tax liability could change in the future, which may result in additional tax liabilities and adversely affect our results of operations, financial condition and cash flows.

Stock-Based Compensation. We account for stock-based compensation using the straight-line attribution method for recognizing compensation expense over the requisite service period of the related award. We recognized $89.7 million and $70.8 million of stock-based compensation expense for the years ended September 30, 2011 and 2010, respectively. As of September 30, 2011, there was $105.5 million of total unrecognized stock-based compensation cost, the majority of which will be recognized over the next two years. Going forward, stock-based compensation expenses may increase as we issue additional equity-based awards to continue to attract and retain key employees.

We issue incentive awards to our employees through stock-based compensation consisting of restricted stock units (RSUs). The value of RSUs is determined using the fair value method, which in this case, is based on the number of shares granted and the quoted price of our common stock on the date of grant. No stock options were granted in fiscal years 2011, 2010 and 2009.

We recognize compensation expense for only the portion of RSUs that are expected to vest. Therefore, we apply estimated forfeiture rates that are derived from historical employee termination behavior. Based on historical differences with forfeitures of stock-based awards granted to our executive officers and Board of Directors versus grants awarded to all other employees, we developed separate forfeiture expectations for these two groups. In fiscal year 2011, the estimated forfeiture rate for grants awarded to our executive officers and Board of Directors was approximately 3% and the estimated forfeiture rate for grants awarded to all other employees was approximately 9%. If the actual number of forfeitures differs from those estimated by management, additional adjustments to stock-based compensation expense may be required in future periods.

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We recognize compensation costs for awards with performance conditions when we conclude it is probable that the performance condition will be achieved. We reassess the probability of vesting at each balance sheet date and adjust compensation costs based on our probability assessment.

Common stock repurchase. On October 26, 2010, we announced that our Board of Directors approved a new program to repurchase up to an additional $200 million of our outstanding common stock. Our Board of Directors authorized an additional $200 million on August 15, 2011 and an additional $200 million on October 25, 2011, for our common stock share repurchase program. These new authorizations are incremental to the existing $200 million program, previously announced as authorized in October 2010. As of November 17, 2011, we had repurchased and retired 7,601,631 shares at an average price of $58.21 per share.

Goodwill and intangible assets. We have goodwill and intangible assets on our balance sheet related to acquisitions. Intangible assets are carried and reported at acquisition cost, net of accumulated amortization subsequent to acquisition. Intangible assets are amortized over the estimated useful lives, which generally range from three to five years. Intangible assets are reviewed for impairment whenever events or circumstances indicate impairment might exist. Projected undiscounted net cash flows expected to be derived from the use of those assets are compared to the respective net carrying amounts to determine whether any impairment exists. Impairment, if any, is based on the excess of the carrying amount over the fair value of those assets.

The determination of the net carrying value of goodwill and intangible assets and the extent to which, if any, there is impairment are dependent on material estimates and judgments on our part, including the useful life over which the intangible assets are to be amortized, and the estimates of the value of future net cash flows, which are based upon further estimates of future revenues, expenses and operating margins. We review our goodwill annually for impairment in the second fiscal quarter, or whenever events or changes in circumstances indicate that the carrying amount of goodwill may not be recoverable. The first step of the test identifies whether potential impairment may have occurred, while the second step of the test measures the amount of the impairment, if any. Impairment is recognized when the carrying amount of goodwill exceeds its fair value. In March 2011, we completed our annual impairment test and concluded that there was no impairment of goodwill. We have considered the assumptions used in the test and noted that no reasonably possible changes would reduce the fair value of the reporting unit to such a level that would cause an impairment charge. Additionally, we considered potential impairment indicators at September 30, 2011 and noted no indicators of impairment.

Investments. Our investments are diversified among high-credit quality debt securities in accordance with our investment policy. We classify our investments as available-for-sale, which are reported at fair market value with the related unrealized gains and losses included in accumulated other comprehensive income or loss in stockholders’ equity. Realized gains and losses and declines in value of these investments judged to be other than temporary are included in other income (expense). To date, we have not deemed it necessary to record any charges related to other-than-temporary declines in the estimated fair values of our marketable debt securities. However, the fair value of our investments is subject to volatility. Declines in the fair value of our investments judged to be other than temporary could adversely affect our future operating results.

Our investments also include auction rate securities (ARS) that are classified as available-for-sale. ARS are reported at fair market value with the related unrealized gains and losses included in accumulated other comprehensive income or loss in stockholders’ equity. We believe these investments may remain illiquid for longer than twelve months and as a result, we have classified these investments as long-term as of September 30, 2011. We used the income approach to determine the fair value of our ARS using a discounted cash flow analysis. The assumptions we used in preparing the discounted cash flow model include estimates for interest rates; estimates for discount rates using yields of comparable traded instruments adjusted for illiquidity and other risk factors, amount of cash flows and expected holding periods for the ARS.

Results of Operations

The following discussion and analysis should be read in conjunction with our consolidated financial statements and related notes included elsewhere in this Annual Report on Form 10-K.

	Years Ended September 30,
	2011			2010			2009
	(In thousands, except for percentages)
Net Revenues
Products	$	721,975		$	561,142		$	406,529
Services		429,859			320,830			246,550
Total	$	1,151,834		$	881,972		$	653,079
Percentage of net revenues
Products		62.7	%		63.6	%		62.2	%
Services		37.3			36.4			37.8
Total		100.0	%		100.0	%		100.0	%

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Net Revenues. Total net revenues increased 30.6% in fiscal year 2011 from fiscal year 2010, compared to an increase of 35.0% in fiscal year 2010 from the prior year. Overall revenue growth for the year ended September 30, 2011 was primarily due to increased service and product revenues as a result of our increased installed base of products and increased demand for our core ADN products, including application security and WAN optimization products. International revenues represented 41.2%, 41.4% and 44.7% of net revenues in fiscal years 2011, 2010 and 2009, respectively. We expect international sales will continue to represent a significant portion of net revenues, although we cannot provide assurance that international revenues as a percentage of net revenues will remain at current levels.

Net product revenues increased 28.7% in fiscal year 2011 from fiscal year 2010, compared to an increase of 38.0% in fiscal year 2010 from the prior year. The increase of $160.8 million in net product sales for fiscal year 2011 was primarily due to growth in the volume of product sales of our ADN products of $157.6 million. In addition, net product revenue from our ARX file virtualization products increased $3.2 million in fiscal year 2011. The increase of $154.6 million in net product sales for fiscal year 2010 was primarily due to growth in the volume of product sales of our ADN products of $152.2 million. In addition, net product revenue from our ARX file virtualization products increased $2.3 million in fiscal year 2010. Sales of our ADN products represented 97.4%, 97.2% and 96.7% of total product revenues in fiscal years 2011, 2010 and 2009, respectively. We are now including our FirePass SSL VPN product as a component of ADN revenue.

Net service revenues increased 34.0% in fiscal year 2011 from fiscal year 2010, compared to an increase of 30.1% in fiscal year 2010 from the prior year. The increases in service revenue were the result of increased purchases or renewals of maintenance contracts driven by additions to our installed base of products.

Avnet Technology Solutions, one of our worldwide distributors, accounted for 18.1%, 14.5% and 15.4% of our total net revenues in fiscal years 2011, 2010 and 2009, respectively. Ingram Micro, Inc., another worldwide distributor, accounted for 10.7% of our total net revenues in fiscal year 2011. Tech Data, another worldwide distributor, accounted for 10.2% of our total net revenues in fiscal year 2010. Avnet Technology Solutions and Ingram Micro, Inc. accounted for 15.0% and 14.5% of our accounts receivable as of September 30, 2011, respectively. Avnet Technology Solutions, Tech Data and Ingram Micro, Inc. accounted for 13.2%, 11.8% and 13.2% of our accounts receivable as of September 30, 2010, respectively. Avnet Technology Solutions and Ingram Micro, Inc. accounted for 11.6% and 10.7% of our accounts receivable as of September 30, 2009, respectively. No other distributors accounted for more than 10% of total net revenue or receivables for fiscal years 2011, 2010 and 2009.

	Years Ended September 30,
	2011			2010			2009
	(In thousands, except for percentages)
Cost of net revenues and Gross margin
Products	$	129,325		$	113,834		$	95,209
Services		78,679			58,118			47,517
Total		208,004			171,952			142,726
Gross margin	$	943,830		$	710,020		$	510,353
Cost of net revenues and Gross margin (as a percentage of related net revenue)
Products		17.9	%		20.3	%		23.4	%
Services		18.3			18.1			19.3
Total		18.1			19.5			21.9
Gross margin		81.9	%		80.5	%		78.1	%

Cost of Net Product Revenues. Cost of net product revenues consist of finished products purchased from our contract manufacturers, manufacturing overhead, freight, warranty, provisions for excess and obsolete inventory and amortization expenses in connection with developed technology from acquisitions. Cost of net product revenues increased 13.6% in fiscal year 2011 from the prior year, primarily due to a higher volume of units shipped along with an increase in warranty expense. Cost of net product revenues increased to $113.8 million in fiscal year 2010 from $95.2 million in fiscal year 2009. The year over year increase was primarily due to the higher volume of units shipped and an increase in warranty expense, partially offset by a decrease in expense related to obsolete inventory. Product cost as a percentage of related net revenue decreased to 20.3% in fiscal year 2010 from 23.4% in fiscal year 2009 primarily due to reduced manufacturing costs and decreased indirect product costs.

Cost of Net Service Revenues. Cost of net service revenues consist of the salaries and related benefits of our professional services staff, travel, facilities and depreciation expenses. Cost of net service revenues as a percentage of net service revenues remained relatively consistent with the prior year at 18.3%. Cost of net service revenues as a percentage of net service revenues decreased to 18.1% in fiscal year 2010 from 19.3% in fiscal year 2009 primarily due to the scalability of our existing customer support infrastructure and increased revenue from maintenance contracts. Professional services headcount at the end of fiscal year 2011

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increased to 528 from 421 at the end of fiscal year 2010 and 330 at the end of fiscal year 2009. In addition, cost of net service revenues included stock-based compensation expense of $7.8 million, $6.0 million and $4.8 million for fiscal years 2011, 2010 and 2009, respectively.

	Years Ended September 30,
	2011			2010			2009
	(In thousands, except for percentages)
Operating expenses
Sales and marketing	$	370,735		$	293,201		$	225,193
Research and development		138,910			118,314			103,664
General and administrative		83,523			68,503			55,243
Restructuring charges		—			—			4,329
Total	$	593,168		$	480,018		$	388,429
Operating expenses (as a percentage of net revenue)
Sales and marketing		32.2	%		33.2	%		34.5	%
Research and development		12.1			13.4			15.9
General and administrative		7.2			7.8			8.4
Restructuring charges		—			—			0.7
Total		51.5	%		54.4	%		59.5	%

Sales and Marketing. Sales and marketing expenses consist of salaries, commissions and related benefits of our sales and marketing staff, the costs of our marketing programs, including public relations, advertising and trade shows, travel, facilities, and depreciation expenses. Sales and marketing expense increased 26.4% in fiscal year 2011 as compared to a year over year increase of 30.2% in fiscal year 2010 and a year over year decrease of 5.1% in fiscal year 2009. The increase in sales and marketing expense for fiscal year 2011 was primarily due to an increase in commissions and personnel costs of $45.4 million, compared to the prior year. The increased commissions and personnel costs were driven by growth in sales and marketing employee headcount and increased sales volume for fiscal year 2011 over the previous year. The increase in sales and marketing expense for fiscal year 2011 was also due to an increase of $14.5 million in marketing promotions and initiatives aimed at promoting our brand and creating market awareness of our technology and our products. The increase in sales and marketing expense for fiscal year 2010 was primarily due to an increase in commissions and personnel costs of $43.9 million as well as an increase of $9.2 million in marketing promotions and initiatives aimed at promoting our brand and creating market awareness of our technology and our products. Sales and marketing headcount at the end of fiscal 2011 increased to 1,080 from 856 at the end of fiscal 2010 and 696 at the end of fiscal 2009. Sales and marketing expense included stock-based compensation charges of $34.7 million, $27.3 million and $22.6 million for fiscal years 2011, 2010 and 2009, respectively.

Research and Development. Research and development expenses consist of the salaries and related benefits for our product development personnel, prototype materials and other expenses related to the development of new and improved products, facilities and depreciation expenses. Research and development expense increased 17.4% in fiscal year 2011, compared to the prior year. The increase in research and development expense for fiscal year 2011 was primarily due to increased personnel costs of $14.0 million, which is consistent with the increase in revenue for the corresponding period. In addition, research and development expense included a year over year increase in computer equipment and software costs of $1.5 million to support the development of new and improved products. In fiscal year 2010, research and development expense increased 14.1%, compared to the prior year. The increase in research and development expense for fiscal year 2010 was primarily due to increased personnel costs of $7.1 million, which is consistent with the increase in revenue for the corresponding period. In addition, research and development expense included a year over year increase in computer equipment and software costs of $3.8 million to support the development of new and improved products. Research and development headcount at the end of fiscal 2011 increased to 610 from 509 at the end of fiscal 2010 and 430 at the end of fiscal 2009. Research and development expense included stock-based compensation charges of $23.3 million, $19.4 million and $16.7 million for fiscal years 2011, 2010 and 2009, respectively. We expect research and development expenses to remain consistent as a percentage of net revenue in the foreseeable future.

General and Administrative. General and administrative expenses consist of the salaries, benefits and related costs of our executive, finance, information technology, human resource and legal personnel, third-party professional service fees, bad debt charges, facilities and depreciation expenses. General and administrative expense increased 21.9% in fiscal year 2011, compared to the prior year. The increase in general and administrative expense for fiscal year 2011 was primarily due to an increase in personnel costs of $5.3 million, compared to the prior year. In addition, fees paid to outside consultants for legal, accounting and information technology services increased $4.2 million for fiscal year 2011 compared to the prior year. In fiscal year 2010, general and administrative expense increased 24.0%, compared to the prior year. The increase in general and administrative expense was primarily due to an increase of $4.1 million in personnel costs for the year ended September 30, 2010, compared to the prior year. General and

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administrative headcount at the end of fiscal 2011 increased to 270 from 226 at the end of fiscal 2010 and 190 at the end of fiscal 2009. General and administrative expense included stock-based compensation charges of $22.4 million, $17.0 million and $11.6 million for fiscal years 2011, 2010 and 2009, respectively.

Restructuring. Beginning in the second quarter of fiscal 2009 we implemented a comprehensive restructuring program as part of an overall initiative to reduce certain operating expenses. Restructuring actions included the consolidation of facilities, accelerated depreciation on tenant improvements and a reduction in workforce. In the second quarter of fiscal 2009, we recorded restructuring expenses of $4.3 million, which included a $2.1 million charge for severance and related costs and a $2.2 million charge for the exit of certain offices worldwide. All accrued restructuring costs had been incurred as of September 30, 2011.

	Years Ended September 30,
	2011			2010			2009
	(In thousands, except for percentages)
Other Income and Income Taxes
Income from operations	$	350,662		$	230,002		$	121,924
Other income, net		10,089			7,625			9,724
Income before income taxes		360,751			237,627			131,648
Provision for income taxes		119,354			86,474			40,113
Net income	$	241,397		$	151,153		$	91,535
Other Income and Income Taxes (as percentage of net revenue)
Income from operations		30.4	%		26.1	%		18.7	%
Other income, net		0.9			0.8			1.5
Income before income taxes		31.3			26.9			20.2
Provision for income taxes		10.4			9.8			6.2
Net income		20.9	%		17.1	%		14.0	%

Other Income, Net. Other income, net, consists primarily of interest income and foreign currency transaction gains and losses. Other income, net increased 32.3% in fiscal year 2011, as compared to fiscal year 2010 and decreased 21.6% in fiscal year 2010 as compared to fiscal year 2009. Interest income was $8.1 million, $8.1 million and $9.9 million for fiscal years 2011, 2010 and 2009, respectively. The increase in other income, net for fiscal year 2011 as compared to fiscal year 2010 was primarily due to a one-time charge of $1.5 million related to a legal settlement in fiscal year 2010 that was not incurred in fiscal year 2011. In addition, foreign currency transaction gains increased $1.0 million, compared to the prior year. The decrease in other income, net for fiscal year 2010 as compared to fiscal year 2009 was primarily due to decreased interest income of $1.8 million, partially offset by increased foreign currency transaction gains of $1.0 million. The decrease in interest income for fiscal year 2010 was primarily due to a decline in interest rates for the year.

Provision for Income Taxes. We recorded a 33.1% provision for income taxes for fiscal year 2011 compared to 36.4% in fiscal year 2010 and 30.5% in fiscal year 2009. The decrease in the effective tax rate from fiscal year 2010 to fiscal year 2011 was primarily due to an increased benefit resulting from the United States Domestic Production Activities Deduction, the reinstatement of the federal research and development credit on December 17, 2010 and a change in our uncertain tax positions as a result of the settlement of audits and expiration of statutes of limitation in various jurisdictions.

At September 30, 2011, we did not have a valuation allowance on any of our deferred tax assets in any of the jurisdictions in which we operate because we believe that the assets are more likely than not to be realized. In making this determination we have considered projected future taxable income and ongoing prudent and feasible tax planning strategies in assessing the appropriateness of a valuation allowance. Our net deferred tax assets as of fiscal year end 2011, 2010 and 2009 were $43.2 million, $46.6 million and $57.0 million, respectively. Our worldwide effective tax rate may fluctuate based on a number of factors, including variations in projected taxable income in our various geographic locations in which we operate, changes in the valuation of our net deferred tax assets, resolution of potential exposures, tax positions taken on tax returns filed in the various geographic locations in which we operate, and the introduction of new accounting standards or changes in tax laws or interpretations thereof in the various geographic locations in which we operate. We have recorded liabilities to address potential tax exposures related to business and income tax positions we have taken that could be challenged by taxing authorities. The ultimate resolution of these potential exposures may be greater or less than the liabilities recorded, which could result in an adjustment to our future tax expense.

Liquidity and Capital Resources

We have funded our operations with our cash balances, cash generated from operations and proceeds from public offerings of our securities.

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	Years Ended September 30,
	2011			2010			2009
	(In thousands)
Liquidity and Capital Resources
Cash and cash equivalents and investments	$	1,012,753		$	862,066		$	574,422
Cash provided by operating activities		416,938			313,612			201,981
Cash used in investing activities		(139,719	)		(238,223	)		(99,109	)
Cash used in financing activities		(226,664	)		(16,798	)		(70,706	)

Cash and cash equivalents, short-term investments and long-term investments totaled $1,012.8 million as of September 30, 2011 compared to $862.1 million as of September 30, 2010, representing an increase of $150.7 million. The increase was primarily due to cash provided by operating activities of $416.9 million for fiscal year 2011, compared to $313.6 million for fiscal year 2010, which was partially offset by $271.5 million of additional cash required for the repurchase of outstanding common stock under our share repurchase program in fiscal 2011. In fiscal year 2010, the increase was primarily due to cash provided by operating activities of $313.6 million, compared to $202.0 million for fiscal year 2009, which was partially offset by $75.0 million of additional cash required for the repurchase of outstanding common stock under our share repurchase program in fiscal 2010.

At September 30, 2011, we held $13.0 million in fair value of tax-exempt ARS, which are variable-rate debt securities and have a long-term maturity with the interest rates being reset through Dutch auctions that are typically held every 7, 28 or 35 days. The securities have historically traded at par and are callable at par at the option of the issuer. Interest is typically paid at the end of each auction period or semi-annually. We limit our investments in ARS to securities that carry a AAA/A- (or equivalent) rating from recognized rating agencies and limit the amount of credit exposure to any one issuer. At the time of initial investment and at the date of this Annual Report on Form 10-K, all of our ARS were in compliance with our investment policy.

Beginning in February 2008, auctions failed for approximately $53.4 million in par value of municipal ARS we held because sell orders exceeded buy orders. When these auctions failed to clear, higher interest rates for those securities went into effect. However, the funds associated with these failed auctions will not be accessible until the issuer calls the security, a successful auction occurs, a buyer is found outside of the auction process or the security matures.

We have no reason to believe that any of the underlying issuers of our ARS are presently at risk of default. The underlying assets of the municipal ARS we hold, including the securities for which auctions have failed, are generally student loans that are guaranteed by the U.S. government. During fiscal years 2011 and 2010, we liquidated $4.0 million and $26.1 million of ARS that we held at par value, respectively. Through September 30, 2011, we have continued to receive interest payments on the ARS in accordance with their terms. We believe we will be able to liquidate our investments without significant loss primarily due to the government guarantee of the underlying securities. However, due to uncertainty in the ARS market, we believe certain of these available-for-sale investments may remain illiquid for longer than twelve months and as a result, we have classified $15.0 million (par value) of our ARS as long-term as of September 30, 2011.

Cash provided by operating activities during fiscal year 2011 was $416.9 million compared to $313.6 million in fiscal year 2010 and $202.0 million in fiscal year 2009. Cash provided by operating activities resulted primarily from cash generated from net income, after adjusting for non-cash charges such as stock-based compensation, depreciation and amortization charges and changes in operating assets and liabilities.

Cash used in investing activities during fiscal year 2011 was $139.7 million compared to cash used in investing activities of $238.2 million in fiscal year 2010 and cash used in investing activities of $99.1 million in fiscal year 2009. Cash used in investing activities for fiscal year 2011 was primarily the result of the purchase of investments and capital expenditures related to maintaining our operations worldwide partially offset by the sale and maturity of investments. Cash used in investing activities for fiscal year 2010 was primarily the result of the purchase of investments and capital expenditures related to maintaining our operations worldwide partially offset by the sale and maturity of investments. Cash used in investing activities for fiscal year 2009 was primarily the result of the purchase of investments and capital expenditures related to maintaining our operations worldwide partially offset by the sale and maturity of investments.

Cash used in financing activities was $226.7 million for fiscal year 2011, compared to cash used in financing activities of $16.8 million for fiscal year 2010 and cash used in financing activities of $70.7 million for fiscal year 2009. Cash used in financing activities for fiscal year 2011 included $271.5 million to repurchase common stock under our share repurchase program, which was partially offset by cash received from the exercise of employee stock options and stock purchases under our employee stock purchase plan of $21.2 million and excess tax benefits related to share-based compensation of $23.6 million. Cash used in financing activities for fiscal 2010 included $75.0 million to repurchase common stock under our share repurchase program, which was partially offset by

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cash received from the exercise of employee stock options and stock purchases under our employee stock purchase plan of $31.7 million and excess tax benefits related to share-based compensation of $26.5 million. Cash used in financing activities for fiscal 2009 included $87.4 million to repurchase common stock under our share repurchase program, which was partially offset by the exercise of employee stock options and purchases under our employee stock purchase plan.

Based on our current operating and capital expenditure forecasts, we believe that our existing cash and investment balances, excluding ARS, together with cash generated from operations should be sufficient to meet our operating requirements for the next twelve months. Our future capital requirements will depend on many factors, including our rate of revenue growth, the expansion of our sales and marketing activities, the timing and extent of expansion into new territories, the timing of introductions of new products and enhancements of existing products, and the continuing market acceptance of our products.

Obligations and Commitments

The following table summarizes our contractual payment obligations and commitments as of September 30, 2011:

	Payment Obligations by Year
	2012		2013		2014		2015		2016		Thereafter		Total
	(In thousands)
Operating leases	$	42,317	$	17,673	$	16,185	$	15,786	$	15,072	$	65,370	$	172,403
Purchase obligations		13,572		—		—		—		—		—		13,572
Total	$	55,889	$	17,673	$	16,185	$	15,786	$	15,072	$	65,370	$	185,975

We lease our facilities under operating leases that expire at various dates through 2022.

We adopted the provisions of FASB Interpretation No. 48, “Accounting for Income Taxes” on October 1, 2007. As of September 30, 2011, we had approximately $6.0 million of tax liabilities, including interest and penalties, related to uncertain tax positions (See Note 5 to our Consolidated Financial Statements). Because of the high degree of uncertainty regarding the settlement of these liabilities, we are unable to estimate the years in which future cash outflows may occur.

Purchase obligations are comprised of purchase commitments with our contract manufacturers. The agreement with our primary contract manufacturer allows it to procure component inventory on our behalf based on our production forecast. We are obligated to purchase component inventory that the contract manufacturer procures in accordance with the forecast, unless cancellation is given within applicable lead times.

Recent Accounting Pronouncements

In May 2011, the FASB issued ASU 2011-04, Amendments to Achieve Common Fair Value Measurement and Disclosure Requirements in U.S. GAAP and IFRS (ASU 2011-04), which amends current fair value measurement and disclosure guidance to converge with International Financial Reporting Standards (IFRS) and provides increased transparency around valuation inputs and investment categorization. The amendments in this standard are effective for fiscal years, and interim periods within those years beginning after December 15, 2011. We will adopt ASU 2011-04 in the first quarter of fiscal 2013 and do not expect the adoption of this standard to have an impact on our consolidated financial statements.

In June 2011, the FASB issued ASU 2011-05, Comprehensive Income, Presentation of Comprehensive Income (ASU 2011-05), which eliminates the option of presenting other comprehensive income as part of the statement of changes in stockholders’ equity and instead requires the entity to present other comprehensive income as either a single statement of comprehensive income combined with net income or as two separate but continuous statements. The amendments in this standard are to be applied retrospectively and are effective for fiscal years, and interim periods within those years beginning after December 15, 2011. We will adopt ASU 2011-05 in the first quarter of fiscal 2013 and do not expect the adoption of this standard to have an impact on our consolidated financial statements.

In September 2011, the FASB issued ASU 2011-08, Intangibles—Goodwill and Other, Testing Goodwill for Impairment (ASU 2011-08), which simplifies how an entity tests goodwill for impairment by allowing the entity to first assess qualitative factors to determine whether it is necessary to perform the two-step quantitative goodwill impairment test. If an entity determines, as a result of its qualitative assessment, that it is more-likely-than-not that the fair value of a reporting unit is less than its carrying amount, the quantitative impairment test is required. Otherwise, no further testing is required. ASU 2011-08 is effective for annual and interim goodwill impairment tests performed for fiscal years beginning after December 15, 2011, with early adoption permitted. We are likely to early adopt this standard for the goodwill impairment test to be performed in fiscal 2012. This standard will impact how we assess goodwill for impairment but will not change the measurement or recognition of a potential goodwill impairment charge.

35

Item 7A. Quantitative and Qualitative Disclosure About Market Risk

Interest Rate Risk. Our cash equivalents consist of high-quality securities, as specified in our investment policy guidelines. The policy limits the amount of credit exposure to any one issue or issuer to a maximum of 5% of the total portfolio with the exception of U.S. treasury and agency securities, commercial paper and money market funds, which are exempt from size limitation. The policy requires investments in securities that mature in three years or less, with the average maturity being no greater than one and a half years. These securities are subject to interest rate risk and will decrease in value if interest rates increase. A decrease of one percent in the average interest rate would have resulted in a decrease of approximately $7.9 million in our interest income for the fiscal year 2011.

	Maturing in
	Three Months or Less			Three Months to One Year			Greater Than One Year			Total		Fair Value
	(In thousands, except for percentages)
September 30, 2011
Included in cash and cash equivalents	$	33,740		$	—		$	—		$	33,740	$	33,740
Weighted average interest rate		0.1	%		—			—			—		—
Included in short-term investments	$	133,713		$	192,053		$	—		$	325,766	$	325,766
Weighted average interest rates		0.9	%		0.9	%		—			—		—
Included in long-term investments	$	—		$	—		$	470,203		$	470,203	$	470,203
Weighted average interest rates		—			—			0.9	%		—		—
September 30, 2010
Included in cash and cash equivalents	$	26,987		$	—		$	—		$	26,987	$	26,987
Weighted average interest rate		0.1	%		—			—			—		—
Included in short-term investments	$	43,970		$	215,772		$	—		$	259,742	$	259,742
Weighted average interest rates		1.4	%		1.6	%		—			—		—
Included in long-term investments	$	—		$	—		$	433,570		$	433,570	$	433,570
Weighted average interest rates		—			—			1.4	%		—		—
September 30, 2009
Included in cash and cash equivalents	$	19,790		$	—		$	—		$	19,790	$	19,790
Weighted average interest rate		1.0	%		—			—			—		—
Included in short-term investments	$	59,981		$	146,310		$	—		$	206,291	$	206,291
Weighted average interest rates		3.1	%		3.0	%		—			—		—
Included in long-term investments	$	—		$	—		$	257,294		$	257,294	$	257,294
Weighted average interest rates		—			—			2.8	%		—		—

At September 30, 2011, the fair value of our AAA/A- (or equivalent) rated municipal ARS was approximately $13.0 million. ARS are collateralized long-term debt instruments that provide liquidity through a Dutch auction process that resets the applicable interest rate at pre-determined intervals, typically every 7, 28 or 35 days. Beginning in February 2008, auctions failed for approximately $53.4 million in par value of municipal ARS we held because sell orders exceeded buy orders. When these auctions failed to clear, higher interest rates for those securities went into effect. However, the funds associated with these failed auctions will not be accessible until the issuer calls the security, a successful auction occurs, a buyer is found outside of the auction process, or the security matures. The underlying assets of the municipal ARS we hold, including the securities for which auctions have failed, are generally student loans that are guaranteed by the U.S. government. Based on our expected operating cash flows and our other sources of cash, we do not believe that any reduction in liquidity of our municipal ARS will have a material impact on our overall ability to meet our liquidity needs. We have no intent to sell, won’t be required to sell, and believe we will hold these securities until recovery. We believe certain of these available-for-sale investments may remain illiquid for longer than twelve months and as a result, we have classified $15.0 million (par value) of securities as long-term as of September 30, 2011.

Foreign Currency Risk. The majority of our sales and expenses are denominated in U.S. dollars and as a result, we have not experienced significant foreign currency transaction gains and losses to date. While we have conducted some transactions in foreign currencies during the fiscal year ended September 30, 2011 and expect to continue to do so, we do not anticipate that foreign currency transaction gains or losses will be significant at our current level of operations. However, as we continue to expand our operations internationally, transaction gains or losses may become significant in the future. We have not engaged in foreign currency hedging to date. However, we may do so in the future.

36

Item 8. Financial Statements and Supplementary Data

F5 NETWORKS, INC.

INDEX TO CONSOLIDATED FINANCIAL STATEMENTS

	Page
Consolidated Financial Statements
Report of Independent Registered Public Accounting Firm		38
Consolidated Balance Sheets		39
Consolidated Income Statements		40
Consolidated Statements of Shareholders’ Equity and Comprehensive Income		41
Consolidated Statements of Cash Flows		42
Notes to Consolidated Financial Statements		43

37

Report of Independent Registered Public Accounting Firm

To the Board of Directors and Shareholders

of F5 Networks, Inc.:

In our opinion, the consolidated financial statements listed in the accompanying index present fairly, in all material respects, the financial position of F5 Networks, Inc. and its subsidiaries at September 30, 2011 and 2010, and the results of their operations and their cash flows for each of the three years in the period ended September 30, 2011 in conformity with accounting principles generally accepted in the United States of America. Also in our opinion, the Company maintained, in all material respects, effective internal control over financial reporting as of September 30, 2011, based on criteria established in Internal Control — Integrated Framework issued by the Committee of Sponsoring Organizations of the Treadway Commission (COSO). The Company’s management is responsible for these financial statements, for maintaining effective internal control over financial reporting and for its assessment of the effectiveness of internal control over financial reporting, included in Management’s Report on Internal Control over Financial Reporting. Our responsibility is to express opinions on these financial statements and on the Company’s internal control over financial reporting based on our integrated audits. We conducted our audits in accordance with the standards of the Public Company Accounting Oversight Board (United States). Those standards require that we plan and perform the audits to obtain reasonable assurance about whether the financial statements are free of material misstatement and whether effective internal control over financial reporting was maintained in all material respects. Our audits of the financial statements included examining, on a test basis, evidence supporting the amounts and disclosures in the financial statements, assessing the accounting principles used and significant estimates made by management, and evaluating the overall financial statement presentation. Our audit of internal control over financial reporting included obtaining an understanding of internal control over financial reporting, assessing the risk that a material weakness exists, and testing and evaluating the design and operating effectiveness of internal control based on the assessed risk. Our audits also included performing such other procedures as we considered necessary in the circumstances. We believe that our audits provide a reasonable basis for our opinions.

A company’s internal control over financial reporting is a process designed to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles. A company’s internal control over financial reporting includes those policies and procedures that (i) pertain to the maintenance of records that, in reasonable detail, accurately and fairly reflect the transactions and dispositions of the assets of the company; (ii) provide reasonable assurance that transactions are recorded as necessary to permit preparation of financial statements in accordance with generally accepted accounting principles, and that receipts and expenditures of the company are being made only in accordance with authorizations of management and directors of the company; and (iii) provide reasonable assurance regarding prevention or timely detection of unauthorized acquisition, use, or disposition of the company’s assets that could have a material effect on the financial statements.

Because of its inherent limitations, internal control over financial reporting may not prevent or detect misstatements. Also, projections of any evaluation of effectiveness to future periods are subject to the risk that controls may become inadequate because of changes in conditions, or that the degree of compliance with the policies or procedures may deteriorate.

PricewaterhouseCoopers LLP

Seattle, WA

November 22, 2011

38

F5 NETWORKS, INC.

CONSOLIDATED BALANCE SHEETS

	September 30,
	2011			2010
	(In thousands)
ASSETS
Current assets
Cash and cash equivalents	$	216,784		$	168,754
Short-term investments		325,766			259,742
Accounts receivable, net of allowances of $2,898 and $4,319		165,676			112,132
Inventories		17,149			18,815
Deferred tax assets		8,391			8,767
Other current assets		29,907			37,745
Total current assets		763,673			605,955
Property and equipment, net		47,998			34,157
Long-term investments		470,203			433,570
Deferred tax assets		34,762			37,864
Goodwill		234,691			234,700
Other assets, net		17,222			15,946
Total assets	$	1,568,549		$	1,362,192
LIABILITIES AND SHAREHOLDERS’ EQUITY
Current liabilities
Accounts payable	$	33,525		$	21,180
Accrued liabilities		67,902			61,768
Deferred revenue		270,880			204,137
Total current liabilities		372,307			287,085
Other long-term liabilities		18,388			16,153
Deferred revenue, long-term		72,418			55,256
Total long-term liabilities		90,806			71,409
Commitments and contingencies (Note 7)
Shareholders’ equity
Preferred stock, no par value; 10,000 shares authorized, no shares outstanding		—			—
Common stock, no par value; 200,000 shares authorized, 79,145 and 80,355 shares issued and outstanding		380,737			517,215
Accumulated other comprehensive loss		(6,422	)		(3,241	)
Retained earnings		731,121			489,724
Total shareholders’ equity		1,105,436			1,003,698
Total liabilities and shareholders’ equity	$	1,568,549		$	1,362,192

The accompanying notes are an integral part of these consolidated financial statements.

39

F5 NETWORKS, INC.

CONSOLIDATED INCOME STATEMENTS

	Years Ended September 30,
	2011		2010		2009
	(In thousands, except per share data)
Net revenues
Products	$	721,975	$	561,142	$	406,529
Services		429,859		320,830		246,550
Total		1,151,834		881,972		653,079
Cost of net revenues
Products		129,325		113,834		95,209
Services		78,679		58,118		47,517
Total		208,004		171,952		142,726
Gross profit		943,830		710,020		510,353
Operating expenses
Sales and marketing		370,735		293,201		225,193
Research and development		138,910		118,314		103,664
General and administrative		83,523		68,503		55,243
Restructuring charges		—		—		4,329
Total		593,168		480,018		388,429
Income from operations		350,662		230,002		121,924
Other income, net		10,089		7,625		9,724
Income before income taxes		360,751		237,627		131,648
Provision for income taxes		119,354		86,474		40,113
Net income	$	241,397	$	151,153	$	91,535
Net income per share — basic	$	2.99	$	1.90	$	1.16
Weighted average shares — basic		80,658		79,609		78,842
Net income per share — diluted	$	2.96	$	1.86	$	1.14
Weighted average shares — diluted		81,482		81,049		80,073

The accompanying notes are an integral part of these consolidated financial statements.

40

F5 NETWORKS, INC.

CONSOLIDATED STATEMENTS OF SHAREHOLDERS’ EQUITY AND

COMPREHENSIVE INCOME

	Common Stock						Accumulated Other Comprehensive Income/(Loss)			Retained Earnings		Total Shareholders’ Equity
	Shares			Amount
	(In thousands)
Balance, September 30, 2008		79,094		$	477,299		$	(6,076	)	$	247,036	$	718,259
Exercise of employee stock options		498			7,243			—			—		7,243
Issuance of stock under employee stock purchase plan		561			11,574			—			—		11,574
Issuance of restricted stock		1,516			—			—			—		—
Repurchase of common stock		(3,344	)		(87,436	)		—			—		(87,436	)
Tax loss from employee stock transactions		—			(1,958	)		—			—		(1,958	)
Stock-based compensation		—			56,064			—			—		56,064
Net income		—			—			—			91,535		—
Foreign currency translation adjustment		—			—			387			—		—
Unrealized gain on securities, net of tax		—			—			3,352			—		—
Comprehensive income		—			—			—			—		95,274
Balance, September 30, 2009		78,325		$	462,786		$	(2,337	)	$	338,571	$	799,020
Exercise of employee stock options		911			17,618			—			—		17,618
Issuance of stock under employee stock purchase plan		458			13,936			—			—		13,936
Issuance of restricted stock		1,849			—			—			—		—
Repurchase of common stock		(1,188	)		(75,000	)		—			—		(75,000	)
Tax benefit from employee stock transactions		—			27,102			—			—		27,102
Stock-based compensation		—			70,773			—			—		70,773
Net income		—			—			—			151,153		—
Foreign currency translation adjustment		—			—			(771	)		—		—
Unrealized loss on securities, net of tax		—			—			(133	)		—		—
Comprehensive income		—			—			—			—		150,249
Balance, September 30, 2010		80,355		$	517,215		$	(3,241	)	$	489,724	$	1,003,698
Exercise of employee stock options		150			2,293			—			—		2,293
Issuance of stock under employee stock purchase plan		257			18,932			—			—		18,932
Issuance of restricted stock		1,370			—			—			—		—
Repurchase of common stock		(2,987	)		(271,526	)		—			—		(271,526	)
Tax benefit from employee stock transactions		—			24,076			—			—		24,076
Stock-based compensation		—			89,747			—			—		89,747
Net income		—			—			—			241,397		—
Foreign currency translation adjustment		—			—			(2,366	)		—		—
Unrealized loss on securities, net of tax		—			—			(815	)		—		—
Comprehensive income		—			—			—			—		238,216
Balance, September 30, 2011		79,145		$	380,737		$	(6,422	)	$	731,121	$	1,105,436

The accompanying notes are an integral part of these consolidated financial statements.

41

F5 NETWORKS, INC.

CONSOLIDATED STATEMENTS OF CASH FLOWS

	Years Ended September 30,
	2011			2010			2009
	(In thousands)
Operating activities
Net income	$	241,397		$	151,153		$	91,535
Adjustments to reconcile net income to net cash provided by operating activities:
Realized gain on disposition of assets and investments		(163	)		(125	)		(9	)
Stock-based compensation		89,747			70,773			56,064
Provisions for doubtful accounts and sales returns		982			1,206			2,638
Depreciation and amortization		20,887			23,833			26,407
Deferred income taxes		4,487			8,243			(6,057	)
Gain on auction rate securities put option		—			(1,491	)		(3,901	)
Loss on trading auction rate securities		—			1,491			3,901
Changes in operating assets and liabilities, net of amounts acquired:
Accounts receivable		(54,526	)		(6,365	)		(12,555	)
Inventories		1,666			(4,996	)		(3,671	)
Other current assets		8,000			(17,064	)		(523	)
Other assets		81			(1,466	)		(226	)
Accounts payable and accrued liabilities		20,476			12,157			10,248
Deferred revenue		83,904			76,263			38,130
Net cash provided by operating activities		416,938			313,612			201,981
Investing activities
Purchases of investments		(979,597	)		(877,003	)		(414,857	)
Maturities of investments		812,042			603,825			315,110
Sales of investments		63,977			45,050			13,000
Decrease in restricted cash		19			2,530			13
Acquisition of intangible assets		(5,715	)		—			(706	)
Purchases of property and equipment		(30,445	)		(12,625	)		(11,669	)
Net cash used in investing activities		(139,719	)		(238,223	)		(99,109	)
Financing activities
Excess tax benefit (loss) from stock-based compensation		23,623			26,532			(1,958	)
Proceeds from the exercise of stock options and purchases of stock under employee stock purchase plan		21,239			31,670			18,688
Repurchase of common stock		(271,526	)		(75,000	)		(87,436	)
Net cash used in financing activities		(226,664	)		(16,798	)		(70,706	)
Net increase in cash and cash equivalents		50,555			58,591			32,166
Effect of exchange rate changes on cash and cash equivalents		(2,525	)		(674	)		368
Cash and cash equivalents, beginning of year		168,754			110,837			78,303
Cash and cash equivalents, end of year	$	216,784		$	168,754		$	110,837
Supplemental Information
Cash paid for taxes	$	84,753		$	67,120		$	48,586

The accompanying notes are an integral part of these consolidated financial statements.

42

F5 NETWORKS, INC.

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS

1.  Summary of Significant Accounting Policies

The Company

F5 Networks, Inc. (the “Company”) provides products and services to help companies manage their Internet Protocol (IP) traffic and file storage infrastructure efficiently and securely. The Company’s application delivery networking products improve the performance, availability and security of applications on Internet-based networks. Internet traffic between network-based applications and clients passes through these devices where the content is inspected to ensure that it is safe and modified as necessary to ensure that it is delivered securely and in a way that optimizes the performance of both the network and the applications. The Company’s storage virtualization products simplify and reduce the cost of managing files and file storage devices, and ensure fast, secure, easy access to files for users and applications. The Company also offers a broad range of services that include consulting, training, maintenance and other technical support services.

Accounting Principles

The Company’s consolidated financial statements and accompanying notes are prepared on the accrual basis of accounting in accordance with generally accepted accounting principles in the United States of America (GAAP).

Principles of Consolidation

The consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries. All intercompany accounts and transactions have been eliminated in consolidation.

Reclassifications

Certain reclassifications have been made to prior year balances to conform to the current period presentation. Such reclassifications did not affect total revenues, operating income or net income.

Use of Estimates

The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosures of contingent assets and liabilities as of the date of the financial statements, and the reported amounts of revenues and expenses during the reporting period. Estimates are used in accounting for revenue recognition, reserves for doubtful accounts, product returns, obsolete and excess inventory and valuation allowances on deferred tax assets. Actual results could differ from those estimates.

Cash and Cash Equivalents

The Company considers all highly liquid investments with original maturities of three months or less to be cash equivalents. The Company invests its cash and cash equivalents in deposits with four major financial institutions, which, at times, exceed federally insured limits. The Company has not experienced any losses on its cash and cash equivalents.

Investments

The Company classifies its investment securities as available-for-sale. Investment securities, consisting of corporate and municipal bonds and notes and United States government and agency securities, are reported at fair value with the related unrealized gains and losses included as a component of accumulated other comprehensive income (loss) in shareholders’ equity. Realized gains and losses and declines in value of securities judged to be other than temporary are included in other income (expense). The cost of investments for purposes of computing realized and unrealized gains and losses is based on the specific identification method. Investments in securities with maturities of less than one year or where management’s intent is to use the investments to fund current operations are classified as short-term investments. Investments with maturities of greater than one year, as well as certain auction rate securities (ARS) that the Company believes it will not be able to liquidate in the next twelve months, are classified as long-term investments.

43

The Company has ARS that are classified as available-for-sale securities and are reported as long-term. The Company has no intent to sell, won’t be required to sell, and believes it will hold these securities until recovery. The Company uses the income approach to estimate the fair value of ARS. The assumptions the Company used in preparing the discounted cash flow model include estimates for interest rates; estimates for discount rates using yields of comparable traded instruments adjusted for illiquidity and other risk factors, amount of anticipated future cash flows and expected holding periods for the ARS.

Concentration of Credit Risk

The Company extends credit to customers and is therefore subject to credit risk. The Company performs initial and ongoing credit evaluations of its customers’ financial condition and does not require collateral. An allowance for doubtful accounts is recorded to account for potential bad debts. Estimates are used in determining the allowance for doubtful accounts and are based upon an assessment of selected accounts and as a percentage of remaining accounts receivable by aging category. In determining these percentages, the Company evaluates historical write-offs, and current trends in customer credit quality, as well as changes in credit policies. At September 30, 2011, Avnet Technology Solutions and Ingram Micro, Inc. accounted for 15.0% and 14.5% of the Company’s accounts receivable, respectively. At September 30, 2010, Avnet Technology Solutions, Ingram Micro, Inc. and Tech Data accounted for 13.2%, 13.2% and 11.8% of the Company’s accounts receivable, respectively.

The Company maintains its cash and investment balances with high credit quality financial institutions. Included within the Company’s investment portfolio are investments in ARS. The Company’s ARS investments are currently not liquid as a result of continued auction failures. If the issuers are not able to meet their payment obligations or if the Company sells its ARS investments before they recover, the Company may lose some or all of its principal invested or may be required to further reduce the carrying value.

Fair Value of Financial Instruments

Short-term and long-term investments are recorded at fair value as the underlying securities are classified as available-for-sale with any unrealized gain or loss being recorded to other comprehensive income. The fair value for securities held is determined using quoted market prices, broker or dealer quotations, or alternative pricing sources with reasonable levels of price transparency with the exception of ARS, which fair market value is estimated using a discounted cash flow model.

Inventories

The Company outsources the manufacturing of its pre-configured hardware platforms to contract manufacturers, who assemble each product to the Company’s specifications. As protection against component shortages and to provide replacement parts for its service teams, the Company also stocks limited supplies of certain key product components. The Company reduces inventory to net realizable value based on excess and obsolete inventories determined primarily by historical usage and forecasted demand. Inventories consist of hardware and related component parts and are recorded at the lower of cost or market (as determined by the first-in, first-out method).

Inventories consist of the following (in thousands):

	Years Ended September 30,
	2011		2010
Finished goods	$	12,917	$	14,949
Raw materials		4,232		3,866
	$	17,149	$	18,815

Property and Equipment

Property and equipment is stated at cost. Depreciation of property and equipment are provided using the straight-line method over the estimated useful lives of the assets, ranging from two to five years. Leasehold improvements are amortized over the lesser of the lease term or the estimated useful life of the improvements. The cost of normal maintenance and repairs is charged to expense as incurred and expenditures for major improvements are capitalized at cost. Gains or losses on the disposition of assets are reflected in the income statements at the time of disposal.

Property and equipment consist of the following (in thousands):

44

	Years Ended September 30,
	2011			2010
Computer equipment	$	77,899		$	59,557
Office furniture and equipment		11,243			9,793
Leasehold improvements		41,344			36,462
		130,486			105,812
Accumulated depreciation and amortization		(82,488	)		(71,655	)
	$	47,998		$	34,157

Depreciation and amortization expense totaled approximately $16.6 million, $17.8 million, and $18.4 million for the fiscal years ended September 30, 2011, 2010 and 2009, respectively.

Goodwill

Goodwill represents the excess purchase price over the estimated fair value of net assets acquired as of the acquisition date. The Company tests goodwill for impairment on an annual basis and between annual tests when impairment indicators are identified, and goodwill is written down when impaired. Goodwill was recorded in connection with the acquisition of Acopia Networks, Inc. in fiscal year 2007, Swan Labs, Inc. in fiscal year 2006, MagniFire Websystems, Inc. in fiscal year 2004 and uRoam, Inc. in fiscal year 2003.

The Company performs its annual goodwill impairment test during the second fiscal quarter, or whenever events or changes in circumstances indicate that the carrying amount of goodwill may not be recoverable. The first step of the test identifies whether potential impairment may have occurred, while the second step of the test measures the amount of the impairment, if any. Impairment is recognized when the carrying amount of goodwill exceeds its fair value. For its annual goodwill impairment analysis, the Company operates under one reporting unit. The Company determined the fair value of its reporting unit based on the Company’s enterprise value. In March 2011, the Company completed its annual impairment test and concluded there was no impairment of goodwill. The Company also considered potential impairment indicators at September 30, 2011 and noted no indicators of impairment.

Other Assets

Other assets primarily consist of software development costs, acquired and developed technology and customer relationships.

Software development costs are charged to research and development expense in the period incurred until technological feasibility is established. Thereafter, until the product is released for sale, software development costs are capitalized and reported at the lower of unamortized cost or net realizable value of each product. Capitalized software development costs are amortized over the remaining estimated economic life of the product. The establishment of technological feasibility and the ongoing assessment of recoverability of costs require considerable judgment by the Company with respect to certain internal and external factors, including, but not limited to, anticipated future gross product revenues, estimated economic life and changes in hardware and software technology. The Company did not capitalize any software development costs in fiscal years 2011, 2010 and 2009. Amortization expense related to capitalized software development was immaterial for fiscal years 2011, 2010, and 2009.

Acquired and developed technology and customer relationship assets are recorded at cost and amortized over their estimated useful lives of five years. The estimated useful life of these assets is assessed and evaluated for reasonableness periodically. Acquired technology of $15.0 million in fiscal 2007 and $8.0 million in fiscal 2006 was recorded in connection with the acquisitions of Acopia and Swan Labs, respectively. Amortization expense related to acquired technology, which is charged to cost of product revenues, totaled $3.1 million, $4.6 million and $5.3 million during the fiscal years 2011, 2010 and 2009, respectively.

Amortization expense of all other intangible assets, including customer relationships, patents and trademarks was not material during the fiscal years 2011, 2010 and 2009.

Impairment of Long-Lived Assets

The Company assesses the impairment of long-lived assets whenever events or changes in business circumstances indicate that the carrying amount of an asset may not be recoverable. When such events occur, management determines whether there has been impairment by comparing the anticipated undiscounted net future cash flows to the related asset’s carrying value. If impairment exists, the asset is written down to its estimated fair value. No impairment of long-lived assets was noted as of and for the year ended September 30, 2011.

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Revenue Recognition

The Company sells products through distributors, resellers, and directly to end users. Revenue is recognized provided that all of the following criteria have been met:

• Persuasive evidence of an arrangement exists. Evidence of an arrangement generally consists of a purchase order issued pursuant to the terms and conditions of a distributor, reseller or end user agreement.

• Delivery has occurred. The Company uses shipping or related documents, or written evidence of customer acceptance, when applicable, to verify delivery or completion of any performance terms.

• The sales price is fixed or determinable. The Company assesses whether the sales price is fixed or determinable based on payment terms associated with the transaction and whether the sales price is subject to refund or adjustment.

• Collectability is reasonably assured. The Company assesses collectability primarily based on the creditworthiness of the customer as determined by credit checks and related analysis, as well as the Customer’s payment history.

In certain regions where the Company does not have the ability to reasonably estimate returns, the Company defers revenue on sales to its distributors until they have received information from the channel partner indicating that the product has been sold to the end-user customer. Payment terms to domestic customers are generally net 30 days to net 45 days. Payment terms to international customers range from net 30 days to net 120 days based on normal and customary trade practices in the individual markets. The Company offers extended payment terms to certain customers, in which case, revenue is recognized when payments are due.

Whenever product, training services and post-contract customer support (PCS) elements are sold together, a portion of the sales price is allocated to each element based on their respective fair values as determined when the individual elements are sold separately. Revenue from the sale of products is recognized when the product has been shipped and the customer is obligated to pay for the product. When rights of return are present and the Company cannot estimate returns, it recognizes revenue when such rights of return lapse. Revenues for PCS are recognized on a straight-line basis over the service contract term. PCS includes a limited period of telephone support updates, repair or replacement of any failed product or component that fails during the term of the agreement, bug fixes and rights to upgrades, when and if available. Consulting services are customarily billed at fixed hourly rates, plus out-of-pocket expenses, and revenues are recognized when the consulting has been completed. Training revenue is recognized when the training has been completed.

In October 2009, the Financial Accounting Standards Board (FASB) amended the accounting standards for revenue recognition to remove from the scope of industry-specific software revenue recognition guidance any tangible products containing software components and non-software components that operate together to deliver the products essential functionality. In addition, the FASB amended the accounting standards for certain multiple element revenue arrangements to:

• Provide updated guidance on whether multiple elements exist, how the elements in an arrangement should be separated, and how the arrangement consideration should be allocated to the separate elements;

• Require an entity to allocate arrangement consideration to each element based on a selling price hierarchy, where the selling price for an element is based on vendor-specific objective evidence (VSOE), if available, third-party evidence (TPE), if available and VSOE is not available; or the best estimate of selling price (BESP), if neither VSOE or TPE is available; and

• Eliminate the use of the residual method and require an entity to allocate arrangement consideration using the selling price hierarchy.

The Company adopted this guidance in the first quarter of fiscal year 2011 on a prospective basis for applicable arrangements originating or materially modified after October 1, 2010. The impact of this adoption was not material to the Company’s financial position and results of operations for the fiscal year ended September 30, 2011.

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The majority of the Company’s products are hardware appliances which contain software essential to the overall functionality of the products. Accordingly, the Company no longer recognizes revenue on sales of these products in accordance with the industry-specific software revenue recognition guidance.

For all transactions entered into prior to the first quarter of fiscal year 2011 and for sales of nonessential and stand-alone software after October 1, 2010, the Company allocates revenue for arrangements with multiple elements based on the software revenue recognition guidance. Software revenue recognition guidance requires revenue earned on software arrangements involving multiple elements to be allocated to each element based on the relative fair values of those elements. The fair value of an element must be based on VSOE. Where fair value of certain elements is not available, revenue is recognized on the “residual method” based on the fair value of undelivered elements. If evidence of the fair value of one or more undelivered elements does not exist, all revenue is deferred and recognized at the earlier of the delivery of those elements or the establishment of fair value of the remaining undelivered elements.

For transactions entered into subsequent to the adoption of the amended revenue recognition standards that are multiple-element arrangements, the arrangement consideration is allocated to each element based on the relative selling prices of all of the elements in the arrangement using the fair value hierarchy in the amended revenue recognition guidance.

Consistent with the methodology used under the previous accounting guidance, the Company establishes VSOE for its products, training services, PCS and consulting services based on the sales price charged for each element when sold separately. The sales price is discounted from the applicable list price based on various factors including the type of customer, volume of sales, geographic region and program level. The Company’s list prices are generally not fair value as discounts may be given based on the factors enumerated above. The Company believes that the fair value of its consulting services is represented by the billable consulting rate per hour, based on the rates they charge customers when they purchase standalone consulting services. The price of consulting services is not based on the type of customer, volume of sales, geographic region or program level.

The Company uses historical sales transactions to determine whether VSOE can be established for each of the elements. In most instances, VSOE is the sales price of actual standalone (unbundled) transactions within the past 12 month period that are priced within a reasonable range, which the Company has determined to be plus or minus 15% of the median sales price of each respective price list.

VSOE of PCS is based on standalone sales since the Company does not provide stated renewal rates to its customers. In accordance with the Company’s PCS pricing practice (supported by standalone renewal sales), renewal contracts are priced as a percentage of the undiscounted product list price. The PCS renewal percentages may vary, depending on the type and length of PCS purchased. The Company offers standard and premium PCS, and the term generally ranges from one to three years. The Company employs a bell-shaped-curve approach in evaluating VSOE of fair value of PCS. Under this approach, the Company considers VSOE of the fair value of PCS to exist when a substantial majority of its standalone PCS sales fall within a narrow range of pricing.

The Company is typically not able to determine TPE for its products or services. TPE is based on competitor prices for similar elements when sold separately. Generally, the Company’s go-to-market strategy differs from that of other competitive products or services in its markets and the Company’s offerings contain a significant level of differentiation such that the comparable pricing of products with similar functionality cannot be obtained. Furthermore, the Company is unable to reliably determine the selling prices on a stand-alone basis of similar products offered by its competitors.

When the Company is unable to establish the selling price of its non-software elements using VSOE or TPE, the Company uses BESP in its allocation of arrangement consideration. The objective of BESP is to determine the price at which the Company would transact a sale if the product or service were sold on a stand-alone basis. The Company is generally not able to establish VSOE for non-software product sales. Under software revenue recognition guidance, these product sales were accounted for utilizing the residual method. With the adoption of the new revenue recognition guidance, the Company has been able to establish BESP for non-software product sales through the list price, less a discount deemed appropriate to maintain a reasonable gross margin. Management regularly reviews the gross margin information. Non-software product BESP is determined through our review of historical sales transactions within the past 12 month period. Additional factors considered in determining an appropriate BESP include, but are not limited to, cost of products, pricing practices, geographies, customer classes, and distribution channels.

The Company has established and regularly validates the VSOE of fair value and BESP for elements in its multiple element arrangements. The Company accounts for taxes collected from customers and remitted to governmental authorities on a net basis and excluded from revenues.

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Shipping and Handling

Shipping and handling fees charged to the Company’s customers are recognized as product revenue in the period shipped and the related costs for providing these services are recorded as a cost of sale.

Guarantees and Product Warranties

In the normal course of business to facilitate sales of its products, the Company indemnifies other parties, including customers, resellers, lessors, and parties to other transactions with the Company, with respect to certain matters. The Company has agreed to hold the other party harmless against losses arising from a breach of representations or covenants, or out of intellectual property infringement or other claims made against certain parties. These agreements may limit the time within which an indemnification claim can be made and the amount of the claim. The Company has entered into indemnification agreements with its officers and directors, and the Company’s bylaws contain similar indemnification obligations to the Company’s agents. It is not possible to determine the maximum potential amount under these indemnification agreements due to the limited history of prior indemnification claims and the unique facts and circumstances involved in each particular agreement.

The Company offers warranties of one year for hardware for those customers without service contracts, with the option of purchasing additional warranty coverage in yearly increments. The Company accrues for warranty costs as part of its cost of sales based on associated material product costs and technical support labor costs. Accrued warranty costs as of September 30, 2011, 2010 and 2009 were not considered material.

Research and Development

Research and development expenses consist of salaries and related benefits of product development personnel, prototype materials and expenses related to the development of new and improved products, and an allocation of facilities and depreciation expense. Research and development expenses are reflected in the statements of income as incurred.

Advertising

Advertising costs are expensed as incurred. The Company incurred $2.2 million, $2.1 million and $1.3 million in advertising costs during the fiscal years 2011, 2010 and 2009, respectively.

Income Taxes

Deferred income tax assets and liabilities are determined based upon differences between the financial statement and income tax bases of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. The realization of deferred tax assets is based on historical tax positions and estimates of future taxable income. A valuation allowance is recorded when it is more likely than not that some of the deferred tax assets will not be realized.

The Company assesses whether tax benefits claimed or expected to be claimed on a tax return should be recorded in the financial statements. The Company may recognize the tax benefit from an uncertain tax position only if it is more likely than not that the tax position will be sustained on examination by the taxing authorities, including resolution of any related appeals or litigation processes, based on the technical merits of the position. The tax benefits to be recognized in the financial statements from such a position is measured as the largest amount of benefit that has a greater than fifty percent likelihood of being realized upon ultimate settlement. The new guidance also provides guidance on de-recognition, classification, interest and penalties on income taxes, accounting in interim periods and requires increased disclosures.

Foreign Currency

The functional currency for the Company’s foreign subsidiaries is the local currency in which the respective entity is located, with the exception of F5 Networks, Ltd., in the United Kingdom that uses the U.S. dollar as its functional currency. An entity’s functional currency is determined by the currency of the economic environment in which the majority of cash is generated and expended by the entity. The financial statements of all majority-owned subsidiaries and related entities, with a functional currency other than the U.S. dollar, have been translated into U.S. dollars. All assets and liabilities of the respective entities are translated at year-end exchange rates and all revenues and expenses are translated at average rates during the respective period. Translation adjustments are reported as a separate component of accumulated other comprehensive income (loss) in shareholders’ equity.

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Foreign currency transaction gains and losses are a result of the effect of exchange rate changes on transactions denominated in currencies other than the functional currency, including U.S. dollars. Gains and losses on those foreign currency transactions are included in determining net income or loss for the period of exchange. The net effect of foreign currency gains and losses was not significant during the fiscal years ended September 30, 2011, 2010 and 2009.

Segments

Management has determined that the Company was organized as, and operated in, one reportable operating segment for fiscal year 2011 and prior years: the development, marketing and sale of application delivery networking products that optimize the security, performance and availability of network applications, servers and storage systems.

Stock-Based Compensation

The Company accounts for stock-based compensation using the straight-line attribution method for recognizing compensation expense. The Company recognized $89.7 million, $70.8 million and $56.1 million of stock-based compensation expense for the fiscal years ended September 30, 2011, 2010 and 2009, respectively. As of September 30, 2011, there was $105.5 million of total unrecognized stock-based compensation cost, the majority of which will be recognized over the next two years. Going forward, stock-based compensation expenses may increase as the Company issues additional equity-based awards to continue to attract and retain key employees.

The Company issues incentive awards to its employees through stock-based compensation consisting of restricted stock units (RSUs). On July 29, 2011, the Company’s Compensation Committee approved 833,739 RSUs to employees and executive officers pursuant to the Company’s annual equity awards program. The value of RSUs is determined using the fair value method, which in this case, is based on the number of shares granted and the quoted price of the Company’s common stock on the date of grant. No stock options were granted in fiscal years 2011, 2010 and 2009. In determining the fair value of shares issued under the Employee Stock Purchase Plan (ESPP), the Company uses the Black-Scholes option pricing model that employs the following key assumptions.

	Employee Stock Purchase Plan Years Ended September 30,
	2011			2010			2009
Risk-free interest rate		0.10	%		0.25	%		0.31	%
Expected dividend		—			—			—
Expected term		0.5 years			0.5 years			0.5 years
Expected volatility		53.87	%		41.04	%		47.00	%

The risk-free rate is based on the U.S. Treasury yield curve in effect at the time of grant. The Company does not anticipate declaring dividends in the foreseeable future. Expected volatility is based on the annualized daily historical volatility of the Company’s stock price commensurate with the expected life of the ESPP option. Expected term of the ESPP option is based on an offering period of six months. The assumptions above are based on management’s best estimates at that time, which impact the fair value of the ESPP option calculated under the Black-Scholes methodology and, ultimately, the expense that will be recognized over the life of the ESPP option.

The Company recognizes compensation expense for only the portion of restricted stock units that are expected to vest. Therefore, the Company applies estimated forfeiture rates that are derived from historical employee termination behavior. Based on historical differences with forfeitures of stock-based awards granted to the Company’s executive officers and Board of Directors versus grants awarded to all other employees, the Company has developed separate forfeiture expectations for these two groups. The estimated forfeiture rate for grants awarded to the Company’s executive officers and Board of Directors was approximately 3% and the estimated forfeiture rate for grants awarded to all other employees was approximately 9% in fiscal 2011. If the actual number of forfeitures differs from those estimated by management, additional adjustments to compensation expense may be required in future periods.

In August 2011, the Company granted 170,390 RSUs to certain current executive officers as part of the annual equity awards program. Fifty percent of the aggregate number of RSUs granted as part of the annual equity awards program vest in equal quarterly increments over three years, until such portion of the grant is fully vested on August 1, 2014. One-sixth of the annual equity awards RSU grant, or a portion thereof, is subject to the Company achieving specified quarterly revenue and EBITDA goals during the period beginning in the fourth quarter of fiscal year 2011 through the third quarter of fiscal year 2012. In each case, 50% of the quarterly performance stock grant is based on achieving at least 80% of the quarterly revenue goal and the other 50% is based on achieving at

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least 80% of the quarterly EBITDA goal. The quarterly performance stock grant is paid linearly above 80% of the targeted goals. At least 100% of both goals must be attained in order for the quarterly performance stock grant to be awarded over 100%. Each goal is evaluated individually and subject to the 80% achievement threshold and 100% over-achievement threshold. The remaining 33.33% of this annual equity awards RSU grant shall be subject to performance based vesting for each of the four quarter periods beginning with the fourth quarters of fiscal years 2012 and 2013 (16.66% in each period). The Compensation Committee of the Board of Directors will set applicable performance targets and vesting formulas for each of these periods.

In August 2010, the Company granted 181,334 and 83,000 RSUs to certain current executive officers as part of the annual equity and retention awards programs, respectively. Fifty percent of the aggregate number of RSUs granted as part of the annual equity awards program vest in equal quarterly increments over three years, until such portion of the grant is fully vested on August 1, 2013. One-sixth of the annual equity awards RSU grant, or a portion thereof, was subject to the Company achieving specified quarterly revenue and EBITDA goals during the period beginning in the fourth quarter of fiscal year 2010 through the third quarter of fiscal year 2011. In each case, 50% of the quarterly performance stock grant is based on achieving at least 80% of the quarterly revenue goal and the other 50% is based on achieving at least 80% of the quarterly EBITDA goal. The quarterly performance stock grant is paid linearly above 80% of the targeted goals. At least 100% of both goals must be attained in order for the quarterly performance stock grant to be awarded over 100%. Each goal is evaluated individually and subject to the 80% achievement threshold and 100% over-achievement threshold. The remaining 33.33% of this annual equity awards RSU grant shall be subject to performance based vesting for each of the four quarter periods beginning with the fourth quarters of fiscal years 2011 and 2012 (16.66% in each period). The Compensation Committee of the Board of Directors will set applicable performance targets and vesting formulas for each of these periods. All RSUs granted as part of the retention awards program fully vest on August 1, 2013.

In August 2009, the Company granted 420,000 RSUs to certain current executive officers. Fifty percent of the aggregate number of RSUs granted at such time vest in equal quarterly increments over two years, until such portion of the grant is fully vested on August 1, 2011. Twenty-five percent of the RSU grant, or a portion thereof, was subject to the Company achieving specified quarterly revenue and EBITDA goals during the period beginning in the fourth quarter of fiscal year 2009 through the third quarter of fiscal year 2010 and the remaining twenty-five percent was subject to the Company achieving specified quarterly revenue and EBITDA goals during the period beginning in the fourth quarter of fiscal year 2010 through the third quarter of fiscal year 2011. In each case, 50% of the quarterly performance stock grant is based on achieving at least 80% of the quarterly revenue goal and the other 50% is based on achieving at least 80% of the quarterly EBITDA goal. The quarterly performance stock grant is paid linearly above 80% of the targeted goals. At least 100% of both goals must be attained in order for the quarterly performance stock grant to be awarded over 100%. Each goal is evaluated individually and subject to the 80% achievement threshold and 100% over-achievement threshold.

The Company recognizes compensation costs for awards with performance conditions when it concludes it is probable that the performance condition will be achieved. The Company reassesses the probability of vesting at each balance sheet date and adjusts compensation costs based on the probability assessment.

In November 2011, as part of the annual review of executive compensation by the Compensation Committee of the Board of Directors and a change in the grant date for the Company’s annual equity awards program for the executive officers, the Company granted 82,968 RSUs to certain current executive officers.

Earnings Per Share

Basic net income per share is computed by dividing net income by the weighted average number of common shares outstanding during the period. Diluted net income per share is computed by dividing net income by the weighted average number of common and dilutive common stock equivalent shares outstanding during the period. The Company’s nonvested restricted stock awards and restricted stock units do not have nonforfeitable rights to dividends or dividend equivalents.

The following table sets forth the computation of basic and diluted net income per share (in thousands, except per share data):

	Years Ended September 30,
	2011		2010		2009
Numerator
Net income	$	241,397	$	151,153	$	91,535
Denominator
Weighted average shares outstanding — basic		80,658		79,609		78,842
Dilutive effect of common shares from stock options and restricted stock units		824		1,440		1,231
Weighted average shares outstanding — diluted		81,482		81,049		80,073
Basic net income per share	$	2.99	$	1.90	$	1.16
Diluted net income per share	$	2.96	$	1.86	$	1.14

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An immaterial amount of common shares potentially issuable from stock options for the years ended September 30, 2011, 2010 and 2009 are excluded from the calculation of diluted earnings per share because the exercise price was greater than the average market price of common stock for the respective period.

Recent Accounting Pronouncements

In May 2011, the FASB issued ASU 2011-04, Amendments to Achieve Common Fair Value Measurement and Disclosure Requirements in U.S. GAAP and IFRS (ASU 2011-04), which amends current fair value measurement and disclosure guidance to converge with International Financial Reporting Standards (IFRS) and provides increased transparency around valuation inputs and investment categorization. The amendments in this standard are effective for fiscal years, and interim periods within those years beginning after December 15, 2011. The Company will adopt ASU 2011-04 in the first quarter of fiscal 2013 and does not expect the adoption of this standard to have an impact on its consolidated financial statements.

In June 2011, the FASB issued ASU 2011-05, Comprehensive Income, Presentation of Comprehensive Income (ASU 2011-05), which eliminates the option of presenting other comprehensive income as part of the statement of changes in stockholders’ equity and instead requires the entity to present other comprehensive income as either a single statement of comprehensive income combined with net income or as two separate but continuous statements. The amendments in this standard are to be applied retrospectively and are effective for fiscal years, and interim periods within those years beginning after December 15, 2011. The Company will adopt ASU 2011-05 in the first quarter of fiscal 2013 and does not expect the adoption of this standard to have an impact on its consolidated financial statements.

In September 2011, the FASB issued ASU 2011-08, Intangibles – Goodwill and Other, Testing Goodwill for Impairment (ASU 2011-08), which simplifies how an entity tests goodwill for impairment by allowing the entity to first assess qualitative factors to determine whether it is necessary to perform the two-step quantitative goodwill impairment test. If an entity determines, as a result of its qualitative assessment, that it is more-likely-than-not that the fair value of a reporting unit is less than its carrying amount, the quantitative impairment test is required. Otherwise, no further testing is required. ASU 2011-08 is effective for annual and interim goodwill impairment tests performed for fiscal years beginning after December 15, 2011, with early adoption permitted. The Company is likely to early adopt this standard for the goodwill impairment test to be performed in fiscal 2012. This standard will impact how the Company assesses goodwill for impairment but will not change the measurement or recognition of a potential goodwill impairment charge.

2.  Fair Value Measurements

In accordance with the authoritative guidance on fair value measurements and disclosure under GAAP, the Company determines fair value using a fair value hierarchy that distinguishes between market participant assumptions developed based on market data obtained from sources independent of the reporting entity, and the reporting entity’s own assumptions about market participant assumptions developed based on the best information available in the circumstances and expands disclosure about fair value measurements.

Fair value is the price that would be received to sell an asset or paid to transfer a liability in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants at the measurement date, essentially the exit price.

The levels of fair value hierarchy are:

Level 1: Quoted prices in active markets for identical assets and liabilities at the measurement date.

Level 2: Observable inputs other than quoted prices included in Level 1, such as quoted prices for similar assets and liabilities in active markets; quoted prices for identical or similar assets and liabilities in markets that are not active; or other inputs that are observable or can be corroborated by observable market data.

Level 3: Unobservable inputs for which there is little or no market data available. These inputs reflect management’s assumptions of what market participants would use in pricing the asset or liability.

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Level 1 investments are valued based on quoted market prices in active markets and include the Company’s cash equivalent investments. Level 2 investments, which include investments that are valued based on quoted prices in markets that are not active, broker or dealer quotations, actual trade data, benchmark yields or alternative pricing sources with reasonable levels of price transparency, include the Company’s corporate bonds and notes, municipal bonds and notes, U.S. government securities and U.S. government agency securities. Fair values for the Company’s level 2 investments are based on similar assets without applying significant judgments. In addition, all of the Company’s level 2 investments have a sufficient level of trading volume to demonstrate that the fair values used are appropriate for these investments.

A financial instrument’s level within the fair value hierarchy is based upon the lowest level of any input that is significant to the fair value measurement. However, the determination of what constitutes “observable” requires significant judgment by the Company. The Company considers observable data to be market data which is readily available, regularly distributed or updated, reliable and verifiable, not proprietary, and provided by independent sources that are actively involved in the relevant market.

The Company’s financial assets measured at fair value on a recurring basis subject to the disclosure requirements at September 30, 2011, were as follows (in thousands):

	Fair Value Measurements at Reporting Date Using
	Quoted Prices  in Active Markets for Identical Securities (Level 1)		Significant Other  Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Fair Value at September 30, 2011
Cash equivalents	$	33,740	$	—	$	—	$	33,740
Short-term investments
Available-for-sale securities — corporate bonds and notes		—		137,156		—		137,156
Available-for-sale securities — municipal bonds and notes		—		82,715		—		82,715
Available-for-sale securities — U.S. government securities		—		799		—		799
Available-for-sale securities — U.S. government agency securities		—		105,096		—		105,096
Long-term investments
Available-for-sale securities — corporate bonds and notes		—		141,150		—		141,150
Available-for-sale securities — municipal bonds and notes		—		30,714		—		30,714
Available-for-sale securities — U.S. government agency securities		—		285,329		—		285,329
Available-for-sale securities — auction rate securities		—		—		13,010		13,010
Total	$	33,740	$	782,959	$	13,010	$	829,709

The Company’s financial assets measured at fair value on a recurring basis subject to the disclosure requirements at September 30, 2010, were as follows (in thousands):

	Fair Value Measurements at Reporting Date Using
	Quoted Prices in Active Markets for Identical Securities (Level 1)		Significant Other  Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Fair Value at September 30, 2010
Cash equivalents	$	26,987	$	—	$	—	$	26,987
Short-term investments
Available-for-sale securities — corporate bonds and notes		—		120,124		—		120,124
Available-for-sale securities — municipal bonds and notes		—		77,063		—		77,063
Available-for-sale securities — U.S. government agency securities		—		62,555		—		62,555
Long-term investments
Available-for-sale securities — corporate bonds and notes		—		174,053		—		174,053
Available-for-sale securities — municipal bonds and notes		—		22,094		—		22,094
Available-for-sale securities — U.S. government agency securities		—		221,380		—		221,380
Available-for-sale securities — auction rate securities		—		—		16,043		16,043
Total	$	26,987	$	677,269	$	16,043	$	720,299

Due to the auction failures of the Company’s auction rate securities (ARS) that began in the second quarter of fiscal year 2008, there are still no quoted prices in active markets for similar assets as of September 30, 2011. Therefore, the Company has classified its ARS as level 3 financial assets. The following table provides a reconciliation between the beginning and ending balances of items measured at fair value on a recurring basis in the tables above that used significant unobservable inputs (Level 3) (in thousands):

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	2011			2010
Balance, beginning of period	$	16,043		$	41,595
Total gains realized or unrealized:
Included in earnings (other income, net)		—			1,491
Included in other comprehensive income		967			498
Recognition of put option to earnings		—			(1,491	)
Settlements		(4,000	)		(26,050	)
Transfers into and/or out of level 3		—			—
Balance, end of period	$	13,010		$	16,043
Gains attributable to assets still held as of the end of the period		967			498

Financial assets are considered Level 3 when their fair values are determined using pricing models, discounted cash flow methodologies or similar techniques and at least one significant model assumption or input is unobservable or there is limited market activity such that the determination of fair value requires significant judgment or estimation. Level 3 investment securities primarily include certain ARS for which there was a decrease in the observation of market pricing. At September 30, 2011, the values of these securities were estimated primarily using discounted cash flow analysis that incorporated transaction details such as contractual terms, maturity, timing and amount of future cash flows, as well as assumptions about liquidity and credit valuation adjustments of marketplace participants at September 30, 2011.

The Company uses the fair value hierarchy for financial assets and liabilities. The Company’s non-financial assets and liabilities, which include goodwill, intangible assets, and long-lived assets, are not required to be carried at fair value on a recurring basis. These non-financial assets and liabilities are measured at fair value on a non-recurring basis when there is an indicator of impairment, and they are recorded at fair value only when impairment is recognized. The Company reviews goodwill and intangible assets for impairment annually, during the second quarter of each fiscal year, or as circumstances indicate the possibility of impairment. The Company monitors the carrying value of long-lived assets for impairment whenever events or changes in circumstances indicate its carrying amount may not be recoverable. During the year ended September 30, 2011, the Company did not recognize any impairment charges related to goodwill, intangible assets, or long-lived assets.

3.  Short-Term and Long-Term Investments

Short-term investments consist of the following (in thousands):

	Cost or Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
September 30, 2011
Corporate bonds and notes	$	137,087	$	251	$	(182	)	$	137,156
Municipal bonds and notes		82,687		62		(34	)		82,715
U.S. government securities		799		—		—			799
U.S. government agency securities		105,050		55		(9	)		105,096
	$	325,623	$	368	$	(225	)	$	325,766

	Cost or Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
September 30, 2010
Corporate bonds and notes	$	119,829	$	318	$	(23	)	$	120,124
Municipal bonds and notes		76,886		182		(5	)		77,063
U.S. government agency securities		62,390		165		—			62,555
	$	259,105	$	665	$	(28	)	$	259,742

Long-term investments consist of the following (in thousands):

	Cost or Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
September 30, 2011
Corporate bonds and notes	$	141,315	$	415	$	(580	)	$	141,150
Municipal bonds and notes		30,575		151		(12	)		30,714
Auction rate securities		15,000		—		(1,990	)		13,010
U.S. government agency securities		285,334		164		(169	)		285,329
	$	472,224	$	730	$	(2,751	)	$	470,203

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	Cost or Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
September 30, 2010
Corporate bonds and notes	$	172,493	$	1,582	$	(22	)	$	174,053
Municipal bonds and notes		22,045		67		(18	)		22,094
Auction rate securities		19,000		—		(2,957	)		16,043
U.S. government agency securities		221,262		200		(82	)		221,380
	$	434,800	$	1,849	$	(3,079	)	$	433,570

The amortized cost and fair value of fixed maturities at September 30, 2011, by contractual years-to-maturity, are presented below (in thousands):

	Cost or Amortized Cost		Fair Value
One year or less	$	325,623	$	325,766
Over one year		472,224		470,203
	$	797,847	$	795,969

The cost or amortized cost values of the Company’s fixed maturities include $15.0 million and $19.0 million of available-for-sale ARS as of September 30, 2011 and 2010, respectively.

The following table summarizes investments that have been in a continuous unrealized loss position for less than 12 months and those that have been in a continuous unrealized loss position for more than 12 months as of September 30, 2011 (in thousands):

	Less Than 12 Months					12 Months or Greater					Total
	Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses
September 30, 2011
Corporate bonds and notes	$	133,752	$	(751	)	$	4,019	$	(11	)	$	137,771	$	(762	)
Municipal bonds and notes		24,304		(38	)		2,543		(8	)		26,847		(46	)
Auction rate securities		—		—			13,010		(1,990	)		13,010		(1,990	)
U.S. government agency securities		171,222		(178	)		—		—			171,222		(178	)
Total	$	329,278	$	(967	)	$	19,572	$	(2,009	)	$	348,850	$	(2,976	)

The Company invests in securities that are rated investment grade or better. The unrealized losses on investments for fiscal year 2011 were primarily caused by reductions in the values of the ARS due to the illiquid markets and were partially offset by unrealized gains related to interest rate decreases.

ARS are variable-rate debt securities. The Company limits its investments in ARS to securities that carry an AAA/A- (or equivalent) rating from recognized rating agencies and limits the amount of credit exposure to any one issuer. At the time of the Company’s initial investment and at the date of this report, all ARS were in compliance with the Company’s investment policy. In the past, the auction process allowed investors to obtain immediate liquidity if so desired by selling the securities at their face amounts. Liquidity for these securities has historically been provided by an auction process that resets interest rates on these investments on average every 7-35 days. However, as has been reported in the financial press, the disruptions in the credit markets adversely affected the auction market for these types of securities.

4.  Balance Sheet Details

Other Assets

Other assets consist of the following (in thousands):

54

	Years Ended September 30,
	2011		2010
Acquired and developed technology and software development cost	$	8,520	$	6,374
Deposits and other		8,540		9,377
Restricted cash		162		195
	$	17,222	$	15,946

Amortization expense related to other assets was approximately $4.3 million, $6.0 million, and $6.7 million for the fiscal years ended September 30, 2011, 2010 and 2009, respectively.

Intangible assets consist of the following (in thousands):

	2011							2010
	Gross Carrying Amount		Accumulated Amortization			Net Carrying Amount		Gross Carrying Amount		Accumulated Amortization			Net Carrying Amount
Acquired and developed technology and software development cost	$	39,109	$	(30,589	)	$	8,520	$	33,474	$	(27,100	)	$	6,374
Customer relationships		2,699		(2,314	)		385		2,699		(1,894	)		805
Patents and trademarks		3,044		(2,214	)		830		2,964		(1,832	)		1,132
Trade names		200		(163	)		37		200		(123	)		77
Non-compete covenants		200		(200	)		—		200		(200	)		—
	$	45,252	$	(35,480	)	$	9,772	$	39,537	$	(31,149	)	$	8,388

Estimated amortization expense for intangible assets for the five succeeding fiscal years is as follows (in thousands):

2012	$	4,428
2013		934
2014		867
2015		867
2016		867
	$	7,963

Accrued Liabilities

Accrued liabilities consist of the following (in thousands):

	Years Ended September 30,
	2011		2010
Payroll and benefits	$	47,824	$	40,904
Sales and marketing		5,062		2,522
Income tax accruals		4,860		2,458
Other		10,156		15,884
	$	67,902	$	61,768

Other Long Term Liabilities

Other long term liabilities consist of the following (in thousands):

	Years Ended September 30,
	2011		2010
Income tax accrual	$	5,675	$	7,029
Deferred rent and other		12,713		9,124
	$	18,388	$	16,153

5.  Income Taxes

The United States and international components of income before income taxes are as follows (in thousands):

55

	Years Ended September 30,
	2011		2010		2009
United States	$	342,741	$	225,698	$	128,537
International		18,010		11,929		3,111
	$	360,751	$	237,627	$	131,648

The provision for income taxes (benefit) consists of the following (in thousands):

	Years Ended September 30,
	2011			2010			2009
Current
U.S. federal	$	103,620		$	79,802		$	41,948
State		7,397			4,722			1,631
Foreign		5,743			3,230			1,790
Total		116,760			87,754			45,369
Deferred
U.S. federal		3,070			(2,049	)		(3,317	)
State		(144	)		(1,091	)		25
Foreign		(332	)		1,860			(1,964	)
Total		2,594			(1,280	)		(5,256	)
	$	119,354		$	86,474		$	40,113

The effective tax rate differs from the U.S. federal statutory rate as follows (in thousands):

	Years Ended September 30,
	2011			2010			2009
Income tax provision at statutory rate	$	126,263		$	83,170		$	46,075
State taxes, net of federal benefit		5,999			2,871			2,121
Impact of foreign income taxes		(892	)		915			(1,262	)
Research and development and other credits		(5,486	)		(2,124	)		(5,954	)
Domestic manufacturing deduction		(9,844	)		(3,766	)		(3,346	)
Impact of stock compensation		5,310			2,825			2,411
Other		(1,996	)		2,583			68
	$	119,354		$	86,474		$	40,113

The tax effects of the temporary differences that give rise to the deferred tax assets and liabilities are as follows (in thousands):

	Years Ended September 30,
	2011			2010
Deferred tax assets
Net operating loss carry-forwards	$	452		$	5,672
Allowance for doubtful accounts		898			1,644
Accrued compensation and benefits		4,879			4,003
Inventories and related reserves		1,564			2,063
Stock-based compensation		8,969			6,247
Deferred revenue		19,400			16,260
Other accruals and reserves		9,629			7,829
Depreciation		1,403			5,239
Tax credit carry-forwards		1,657			4,065
		48,851			53,022
Deferred tax liabilities
Purchased intangibles and other		(5,698	)		(6,391	)
Net deferred tax assets	$	43,153		$	46,631

At September 30, 2011, the Company had U.S. net operating loss carry-forwards of approximately $1.2 million. All U.S. net operating loss carry-forwards relate to entities acquired by the Company and are limited in use by I.R.C. Sec. 382.

United States income and foreign withholding taxes have not been provided on approximately $28.7 million of undistributed earnings from the Company’s international subsidiaries. The Company has not recognized a deferred tax liability for the undistributed earnings of its foreign subsidiaries because the Company currently does not expect to remit those earnings in the foreseeable future. Determination of the amount of unrecognized deferred tax liability related to undistributed earnings of foreign subsidiaries is not practicable because such liability, if any, is dependent on circumstances existing if and when remittance occurs.

56

The decrease in the effective tax rate from fiscal year 2010 to fiscal year 2011 was primarily due to an increased benefit resulting from the United States Domestic Production Activities Deduction, the reinstatement of the federal research and development credit on December 17, 2010 and a change in the Company’s uncertain tax positions as a result of the settlement of audits and expiration of statutes of limitation in various jurisdictions.

The Company recognizes the financial statement impact of a tax position only after determining that the relevant tax authority would more likely than not sustain the position following an audit. For tax positions meeting the more-likely-than-not threshold, the amount recognized in the financial statements is the largest impact that has a greater than fifty percent likelihood of being realized upon ultimate settlement with the relevant tax authority.

The following table provides a reconciliation of the beginning and ending amount of unrecognized tax benefits in fiscal years 2011, 2010 and 2009:

	2011			2010			2009
Balance, beginning of period	$	6,568		$	5,841		$	4,075
Gross increases related to prior period tax positions		1,198			442			642
Gross increases related to current period tax positions		1,659			432			1,124
Decreases relating to settlements with tax authorities		(243	)		—			—
Reductions due to lapses of statute of limitations		(3,230	)		(147	)		—
Balance, end of period	$	5,952		$	6,568		$	5,841

The Company recognizes interest and, if applicable, penalties (not included in the “unrecognized tax benefits” table above) for any uncertain tax positions. This interest and penalty expense will be a component of income tax expense. In the years ended September 30, 2011, 2010 and 2009 the Company accrued approximately $283,000, $390,000 and $193,000, respectively, of interest expense related to its liability for unrecognized tax benefits. No penalties were recognized in fiscal years 2011, 2010 and 2009 or accrued for at September 30, 2011, 2010 and 2009.

All unrecognized tax benefits, if recognized, would affect the effective tax rate. The Company does not anticipate that total unrecognized tax benefits will significantly change within the next twelve months.

The Company and its subsidiaries are subject to U.S. federal income tax as well as the income tax of multiple state and foreign jurisdictions. The Company has concluded all U.S. federal income tax matters for fiscal years through September 30, 2007. Major jurisdictions where there are wholly owned subsidiaries of F5 Networks, Inc. which require income tax filings include the United Kingdom, Japan, Australia and Germany. The earliest periods open for review by local taxing authorities are fiscal years 2010, 2010, 2007 and 2007 for the United Kingdom, Japan, Australia and Germany, respectively. Within the next four fiscal quarters, the statute of limitations will begin to close on the fiscal years ended 2007 and 2008 tax returns filed in various states and the fiscal year ended 2008 federal income tax return.

6.  Stock-based Compensation

The majority of awards consist of restricted stock units and to a lesser degree, stock options. Employees vest in restricted stock units and stock options ratably over the corresponding service term, generally one to four years. The Company’s stock options expire 10 years from the date of grant. Restricted stock units are payable in shares of the Company’s common stock as the periodic vesting requirements are satisfied. The value of a restricted stock unit is based upon the fair market value of the Company’s common stock on the date of grant. The value of restricted stock units is determined using the intrinsic value method and is based on the number of shares granted and the quoted price of the Company’s common stock on the date of grant. Alternatively, the Company used the Black-Scholes option pricing model to determine the fair value of its stock options. Compensation expense related to restricted stock units and stock options is recognized over the vesting period. The Company has adopted a number of stock-based compensation plans as discussed below.

1998 Equity Incentive Plan. In November 1998, the Company adopted the 1998 Equity Incentive Plan, or the 1998 Plan, which provided for discretionary grants of non-qualified and incentive stock options, stock purchase awards and stock bonuses for employees and other service providers. The 1998 Plan expired on November 11, 2008 and no shares remain available for awards under the 1998 Plan. Upon certain changes in control of the Company, all outstanding and unvested options or stock awards under the 1998 Plan will vest at the rate of 50%, unless assumed or substituted by the acquiring entity. During the fiscal years 2011 and 2010, the Company issued no stock options, stock purchase awards or stock bonuses under this plan. As of September 30, 2011, there were options to purchase 132,459 shares outstanding under the 1998 Plan.

57

2011 Employee Stock Purchase Plan. In July 2011, the board of directors amended and restated the Company’s 1999 Employee Stock Purchase Plan, or the Employee Stock Purchase Plan. A total of 6,000,000 shares of common stock have been reserved for issuance under the Employee Stock Purchase Plan. The Employee Stock Purchase Plan permits eligible employees to acquire shares of the Company’s common stock through periodic payroll deductions of up to 15% of base compensation. No employee may purchase more than $25,000 worth of stock, determined at the fair market value of the shares at the time such option is granted, in one calendar year. The Employee Stock Purchase Plan has been implemented in a series of offering periods, each 6 months in duration. The price at which the common stock may be purchased is 85% of the lesser of the fair market value of the Company’s common stock on the first day of the applicable offering period or on the last day of the respective purchase period. As of September 30, 2011 there were 1,718,042 shares available for awards under the Employee Stock Purchase Plan.

2000 Equity Incentive Plan. In July 2000, the Company adopted the 2000 Employee Equity Incentive Plan, or the 2000 Plan, which provides for discretionary grants of non-qualified stock options, stock purchase awards and stock bonuses for non-executive employees and other service providers. A total of 7,000,000 shares of common stock were reserved for issuance under the 2000 Plan. Upon certain changes in control of the Company, all outstanding and unvested options or stock awards under the 2000 Plan will vest at the rate of 50%, unless assumed or substituted by the acquiring entity. As of September 30, 2011, there were options to purchase 165,088 shares outstanding and no shares available for awards under the 2000 Plan. The Company terminated the 2000 Plan effective November 1, 2008 and no additional shares may be issued from the 2000 Plan.

Acquisition Incentive Plans. In connection with the Company’s acquisition of Acopia, the Company assumed the Acopia 2001 Stock Incentive Plan, or the Acopia Plan. Unvested options to acquire Acopia’s common stock were converted into options to acquire the Company’s common stock in connection with the acquisition. A total of 2,230,703 shares of common stock were reserved for issuance under the Acopia Plan. The plan provides for discretionary grants of non-qualified and incentive stock options, restricted stock awards and other stock-based awards to persons who were employees, officers, directors, consultants or advisors to Acopia on or prior to September 12, 2007. During the fiscal year 2011, the Company issued no stock options or restricted stock units under the Acopia Plan. As of September 30, 2011, there were options to purchase 26,287 shares outstanding and no shares available for awards under the Acopia Plan. The Company terminated the Acopia Plan effective November 1, 2008 and no additional shares may be issued from the Acopia Plan.

2005 Equity Incentive Plan. In December 2004, the Company adopted the 2005 Equity Incentive Plan, or the 2005 Plan, which provides for discretionary grants of non-statutory stock options and stock units for employees, including officers, and other service providers. A total of 12,400,000 shares of common stock have been reserved for issuance under the 2005 Plan. Upon certain changes in control of the Company, all outstanding and unvested options or stock awards under the 2005 Plan will vest at the rate of 50%, unless assumed or substituted by the acquiring entity. During the fiscal year 2011, the Company issued no stock options and 908,757 restricted stock units under the 2005 Plan. As of September 30, 2011, there were no options outstanding and 3,501,586 shares available for new awards under the 2005 Plan.

A majority of the restricted stock units granted in fiscal years 2011, 2010 and 2009 vest quarterly over a two-year period. The restricted stock units were granted during fiscal years 2011, 2010 and 2009 with a per-share weighted average fair value of $94.99, $86.32 and $36.31, respectively. The fair value of restricted stock vested during fiscal years 2011, 2010 and 2009 was $145.0 million, $116.4 million and $41.0 million, respectively.

A summary of restricted stock unit activity under the 2005 Plan is as follows:

	Outstanding Stock Units			Weighted Average Grant Date Fair Value
Balance, September 30, 2010		1,985,325		$	62.52
Units granted		908,757			94.99
Units vested		(1,316,253	)		105.59
Units cancelled		(121,143	)		56.04
Balance, September 30, 2011		1,456,686		$	44.40

A summary of stock option activity under all of the Company’s plans is as follows:

58

	Options Outstanding
	Number of Shares			Weighted Average Exercise Price per Share
Balance, September 30, 2010		483,040		$	13.51
Options exercised		(150,416	)		15.24
Options cancelled		(1,200	)		33.92
Balance, September 30, 2011		331,424		$	12.66

No stock options were granted in fiscal years 2011, 2010 and 2009.

The total intrinsic value of options exercised during fiscal 2011, 2010 and 2009 was $15.2 million, $36.6 million and $8.4 million, respectively.

	Number of Shares		Weighted Average Remaining Contractual Life (in Years)		Weighted Average Exercise Price per Share		Aggregate Intrinsic Value(1)
	(In thousands)
Stock options outstanding		331,424		2.31	$	12.66	$	19,353
Exercisable		331,424		2.31	$	12.66	$	19,353
Vested and expected to vest		331,424		2.31	$	12.66	$	19,353

(1) Aggregate intrinsic value represents the difference between the fair value of the Company’s common stock underlying these options at September 30, 2011 and the related exercise prices.

As of September 30, 2011, equity based awards (including stock options and restricted stock units) are available for future issuance as follows:

	Awards Available for Grant
Balance, September 30, 2010		4,289,200
Granted		(908,757	)
Cancelled		125,156
Additional shares reserved (terminated), net		(4,013	)
Balance, September 30, 2011		3,501,586

7. Commitments and Contingencies

Operating Leases

The majority of the Company’s operating lease payments relate to the Company’s three building corporate headquarters in Seattle, Washington. The lease for all three buildings was amended and restated in April of 2010. This lease will now expire in 2022 with an option for renewal. One of the buildings has been partially subleased through 2012. The Company also leases additional office space for product development and sales and support personnel in the United States and internationally.

In October 2006, the Company entered into an agreement to lease a total of approximately 137,000 square feet of office space in a building known as 333 Elliott West, which is adjacent to the three buildings that serve as the Company’s corporate headquarters. The lease expires in 2018. During 2008, the Company entered into two separate sublease agreements to sublease approximately 112,500 square feet of building 333 Elliott West. One sublease will expire in 2013. In March 2010, the Company amended the second sublease, which expanded the subleased space by approximately 11,700 square feet and extended the term of the sublease to 2018.

Future minimum operating lease payments, net of sublease income, are as follows (in thousands):

	Gross  Lease Payments		Sublease Income		Net Lease Payments
2012		42,317		4,321		37,996

59

	Gross  Lease Payments		Sublease Income		Net Lease Payments
2013		17,673		2,611		15,062
2014		16,185		338		15,847
2015		15,786		85		15,701
2016		15,072		—		15,072
Thereafter		65,370		—		65,370
	$	172,403	$	7,355	$	165,048

Rent expense under non-cancelable operating leases amounted to approximately $19.0 million, $17.5 million, and $15.6 million for the fiscal years ended September 30, 2011, 2010, and 2009, respectively.

Purchase Obligations

Purchase obligations are comprised of purchase commitments with the Company’s contract manufacturers. The agreement with the Company’s primary contract manufacturer allows them to procure component inventory on the Company’s behalf based on the Company’s production forecast. The Company is obligated to purchase component inventory that the contract manufacturer procures in accordance with the forecast, unless cancellation is given within applicable lead times. As of September 30, 2011, the Company’s purchase obligations were $13.6 million.

Litigation

The Company is not aware of any pending legal proceedings that, individually or in the aggregate, are reasonably possible to have a material adverse effect on the Company’s business, operating results, or financial condition. The Company may in the future be party to litigation arising in the ordinary course of business, including claims that we allegedly infringe upon third-party intellectual property rights. Such claims, even if not meritorious, could result in the expenditure of significant financial and managerial resources.

8. Restructuring Charges

In January 2009, the Company initiated a restructuring plan to reduce its operating expenses which included the consolidation of facilities, accelerated depreciation on tenant improvements and a reduction in workforce. These initiatives are intended to conserve or generate cash in response to the uncertainties associated with the recent deterioration in the global economy. As a result of these initiatives, the Company recorded a restructuring charge of $4.3 million in the second quarter of fiscal 2009. All accrued restructuring costs had been incurred as of September 30, 2011.

9. Employee Benefit Plans

The Company has a 401(k) savings plan whereby eligible employees may voluntarily contribute a percentage of their compensation. The Company may, at its discretion, match a portion of the employees’ eligible contributions. Contributions by the Company to the plan during the years ended September 30, 2011, 2010, and 2009 were approximately $4.7 million, $3.8 million and $3.3 million, respectively. Contributions made by the Company vest over four years.

10. Geographic Sales and Significant Customers

Operating segments are defined as components of an enterprise for which separate financial information is available and evaluated regularly by the chief operating decision-maker, or decision-making group, in deciding how to allocate resources and in assessing performance. The Company does business in four main geographic regions: the Americas (primarily the United States); Europe, the Middle East, and Africa (EMEA); Japan; and the Asia Pacific region (APAC). The Company’s chief operating decision-making group reviews financial information presented on a consolidated basis accompanied by information about revenues by geographic region. The Company’s foreign offices conduct sales, marketing and support activities. Revenues are attributed by geographic location based on the location of the customer. The Company’s assets are primarily located in the United States and not allocated to any specific region. Therefore, geographic information is presented only for net revenue.

The following presents revenues by geographic region (in thousands):

	Years Ended September 30,
	2011		2010		2009
Americas	$	676,868	$	517,269	$	361,230
EMEA		240,453		201,259		150,776
Japan		74,824		59,151		56,792
Asia Pacific		159,689		104,293		84,281
	$	1,151,834	$	881,972	$	653,079

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One worldwide distributor accounted for 18.1%, 14.5% and 15.4% of total net revenues in fiscal years 2011, 2010 and 2009, respectively. Another worldwide distributor accounted for 10.7% of total net revenues in fiscal year 2011. Another worldwide distributor accounted for 10.2% of total net revenues in fiscal year 2010.

11. Quarterly Results of Operations

The following presents the Company’s unaudited quarterly results of operations for the eight quarters ended September 30, 2011. The information should be read in conjunction with the Company’s financial statements and related notes included elsewhere in this report. This unaudited information has been prepared on the same basis as the audited financial statements and includes all adjustments, consisting only of normal recurring adjustments that were considered necessary for a fair statement of the Company’s operating results for the quarters presented.

	Three Months Ended
	Sept. 30, 2011		June 30, 2011		March 31, 2011		Dec. 31, 2010		Sept. 30, 2010		June 30, 2010		March 31, 2010		Dec. 31, 2009
	(Unaudited and in thousands, except per share data)
Net revenues
Products	$	197,446	$	179,327	$	173,710	$	171,492	$	164,972	$	147,393	$	129,559	$	119,218
Services		117,169		111,386		103,862		97,442		89,302		83,081		76,509		71,938
Total		314,615		290,713		277,572		268,934		254,274		230,474		206,068		191,156
Cost of net revenues
Products		34,485		31,803		31,423		31,614		31,045		29,328		27,419		26,042
Services		21,435		20,645		19,250		17,349		15,783		15,251		13,997		13,087
Total		55,920		52,448		50,673		48,963		46,828		44,579		41,416		39,129
Gross profit		258,695		238,265		226,899		219,971		207,446		185,895		164,652		152,027
Operating expenses
Sales and marketing		100,945		93,633		89,332		86,825		80,696		77,219		69,644		65,642
Research and development		36,552		35,245		34,507		32,606		31,571		30,889		29,134		26,720
General and administrative		21,867		21,126		19,846		20,684		18,876		17,658		16,016		15,953
Total operating expenses		159,364		150,004		143,685		140,115		131,143		125,766		114,794		108,315
Income from operations		99,331		88,261		83,214		79,856		76,303		60,129		49,858		43,712
Other income, net		4,087		1,889		1,568		2,545		68		3,561		2,291		1,705
Income before income taxes		103,418		90,150		84,782		82,401		76,371		63,690		52,149		45,417
Provision for income taxes		35,808		27,601		29,207		26,738		28,136		23,195		19,005		16,138
Net income	$	67,610	$	62,549	$	55,575	$	55,663	$	48,235	$	40,495	$	33,144	$	29,279
Net income per share — basic	$	0.84	$	0.77	$	0.69	$	0.69	$	0.60	$	0.51	$	0.42	$	0.37
Weighted average shares — basic		80,317		80,866		80,809		80,644		80,268		79,864		79,394		78,906
Net income per share — diluted	$	0.84	$	0.77	$	0.68	$	0.68	$	0.59	$	0.50	$	0.41	$	0.36
Weighted average shares — diluted		80,766		81,497		81,622		81,648		81,253		81,031		80,737		80,333

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Item 9. Changes in and Disagreements with Accountants on Accounting and Financial Disclosure

None.

Item 9A. Controls and Procedures

Evaluation of Disclosure Controls and Procedures

The Company maintains disclosure controls and procedures (as defined in Rules 13a-15(e) and 15d-15(e) under the Securities Exchange Act of 1934, as amended (the “Exchange Act”)) that are designed to ensure that required information is recorded, processed, summarized and reported within the required timeframe, as specified in the rules set forth by the Securities Exchange Commission. Our disclosure controls and procedures are also designed to ensure that information required to be disclosed is accumulated and communicated to management, including the Chief Executive Officer and Chief Accounting Officer, to allow timely decisions regarding required disclosures.

Our management, with the participation of our Chief Executive Officer and Chief Accounting Officer, evaluated the effectiveness of our disclosure controls and procedures as of September 30, 2011 and, based on this evaluation, our Chief Executive Officer and Chief Accounting Officer have concluded that our disclosure controls and procedures were effective as of September 30, 2011.

Management’s Report on Internal Control over Financial Reporting

Management is responsible for establishing and maintaining adequate internal control over financial reporting, as such term is defined in Exchange Act Rules 13a-15(f) and 15d-15(f). Internal control over financial reporting is a process designed to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles.

Internal control over financial reporting cannot provide absolute assurance of achieving financial reporting objectives because of its inherent limitations. Internal control over financial reporting is a process that involves human diligence and compliance and is subject to lapses in judgment and breakdowns resulting from human failures. Internal control over financial reporting also can be circumvented by collusion or improper management override. Because of such limitations, there is a risk that material misstatements may not be prevented or detected on a timely basis by internal control over financial reporting. However, these inherent limitations are known features of the financial reporting process. Therefore, it is possible to design into the process safeguards to reduce, though not eliminate, this risk.

Management conducted an assessment of the effectiveness of our internal control over financial reporting as of September 30, 2011. In making this assessment, management used the criteria set forth by the Committee of Sponsoring Organizations of the Treadway Commission in Internal Control — Integrated Framework. Based on the results of this assessment and on those criteria, management concluded that our internal control over financial reporting was effective as of September 30, 2011.

PricewaterhouseCoopers LLP, an independent registered public accounting firm, has audited the Consolidated Financial Statements included in this Annual Report on Form 10-K and, as part of their audit, has issued its attestation report, included herein, on the effectiveness of our internal control over financial reporting.

Changes in Internal Control over Financial Reporting

During the fourth fiscal quarter, there were no changes to our internal control over financial reporting that materially affected, or are reasonably likely to materially affect, our internal controls over financial reporting.

Item 9B. Other Information

None.

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PART III

Item 10. Directors, Executive Officers and Corporate Governance

Certain information required by this item regarding the Company’s directors and executive officers is incorporated herein by reference to the sections entitled “Board of Directors — Nominees and Continuing Directors,” “Corporate Governance — Committees of the Board — Audit Committee” and “— Code of Ethics for Senior Financial Officers” and “— Director Nomination,” and “Security Ownership of Certain Beneficial Owners and Management — Section 16(a) Beneficial Ownership Reporting Compliance” in the Company’s definitive Proxy Statement that will be furnished to the SEC no later than January 28, 2012 (the “Proxy Statement”). Additional information regarding the Company’s directors and executive officers is set forth in Item 1 of Part I of this Annual Report on Form 10-K under the caption “Directors and Executive Officers of the Registrant.”

Item 11. Executive Compensation

The information required by this item is incorporated by reference to the sections entitled “Executive Compensation” and “Corporate Governance — Committees of the Board — Compensation Committee” and “— Compensation Committee Interlocks and Insider Participation” and “— Compensation Committee Report” in the Proxy Statement.

Item 12. Security Ownership of Certain Beneficial Owners and Management and Related Shareholder Matters

Equity Compensation Plan Information

The following table provides information as of September 30, 2011 with respect to the shares of Common Stock that may be issued under the Company’s existing equity compensation plans.

	Column A			Column B		Column C
Plan Category	Number of securities to be issued upon exercise of  outstanding options and rights			Weighted-average exercise price of outstanding options and rights (3)		Number of securities remaining available for future issuance under equity compensation plans (total securities authorized but unissued under the plans, less Column A)
Equity compensation plans approved by security holders(1)		1,589,145	(2)	$	13.05		5,219,628	(4)
Equity compensation plans not approved by security holders(5)		212,234		$	12.40		—
Total		1,801,379		$	12.66		5,219,628

(1) Consists of the F5 Networks, Inc. Amended and Restated 1998 Equity Incentive Plan (the “1998 Equity Incentive Plan”), and the F5 Networks, Inc. 2005 Equity Incentive Plan (the “2005 Equity Incentive Plan”). No additional options may be granted under the 1998 Equity Incentive Plan.

(2) Includes 132,459 shares issuable upon vesting of outstanding options and 1,456,686 shares issuable upon vesting of outstanding RSUs granted under the 2005 Equity Incentive Plan.

(3) The weighted-average exercise price does not take into account the shares issuable upon vesting of outstanding RSUs, which have no exercise price.

(4) Includes 1,718,042 shares reserved for issuance under the Employee Stock Purchase Plan.

(5) Consists of the F5 Networks, Inc. 2000 Employee Equity Incentive Plan (the “2000 Equity Incentive Plan”), F5 Networks, Inc. uRoam Acquisition Equity Incentive Plan (the “uRoam Equity Incentive Plan”), F5 Networks, Inc. MagniFire Acquisition Equity Incentive Plan (the “MagniFire Equity Incentive Plan”), F5 Networks, Inc. Assumed Acopia Networks Inc. 2001 Stock Incentive Plan (the “Acopia 2001 Plan”) and F5 Networks, Inc. Acopia Acquisition Equity Incentive Plan (the “Acopia Acquisition Plan”). The material features of each of these equity compensation plans are set forth in Note 7 in our financial statements, “Summary of

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Significant Accounting Policies — Shareholders’ Equity” included in our Annual Report to Shareholders on Form 10-K for the year ended September 30, 2011. As of the date of assumption of the Acopia 2001 Plan, there were options to purchase 426,821 shares outstanding under the Acopia 2001 Plan, with a weighted average exercise price of $18.94. The Company terminated the 2000 Equity Incentive Plan, Acopia 2001 Plan and the Acopia Acquisition Plan effective November 1, 2008 and no additional shares may be issued from those Plans. In addition, no additional options may be granted under the uRoam Equity Incentive Plan or the MagniFire Equity Incentive Plan.

The information required by Item 403 of Regulation S-K is incorporated by reference to the section entitled “Security Ownership of Certain Beneficial Owners and Management” in the Proxy Statement.

Item 13. Certain Relationships and Related Transactions, and Director Independence

The information required by this item is incorporated by reference to the sections entitled “Board of Directors — Director Independence” and “Corporate Governance — Related Person Transactions Policy and Procedures” and “— Certain Relationships and Related Person Transactions” in the Proxy Statement.

Item 14. Principal Accountant Fees and Services

The information required by this item is incorporated by reference to the section entitled “Executive Compensation — Fees Paid to PricewaterhouseCoopers LLP” and “— Audit Committee Pre-Approval Procedures” and “— Annual Independence Determination” in the Proxy Statement.

PART  IV

Item 15. Exhibits and Financial Statement Schedules

(a) Documents filed as part of this report are as follows:

1. Consolidated Financial Statements:

Our Consolidated Financial Statements are listed in the Index to Consolidated Financial Statements.

2. Financial Statement Schedule:

Financial statement schedules have been omitted because the information required to be set forth therein is not applicable or is shown in the Consolidated Financial Statements or the notes hereto.

3. Exhibits:

The required exhibits are included at the end of this Annual Report on Form 10-K and are described in the Exhibit Index immediately preceding the first exhibit.

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SIGNATURES

Pursuant to the requirements of Section 13 or 15(d) of the Securities Exchange Act of 1934, the Registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

F5 NETWORKS, INC.
By:	/s/    JOHN MCADAM
	John McAdam
	Chief Executive Officer and President

Dated: November 22, 2011

Pursuant to the requirements of the Securities Exchange Act of 1934, this report has been signed below by the following persons on behalf of the Registrant and in the capacities and on the dates indicated.

Signature		Title	Date
By:	/s/    JOHN MCADAM John McAdam	Chief Executive Officer, President, and Director (principal executive officer)	November 22, 2011
By:	/s/    JOHN RODRIGUEZ John Rodriguez	Senior Vice President, Chief Accounting Officer (principal financial officer and principal accounting officer)	November 22, 2011
By:	/s/    A. GARY AMES A. Gary Ames	Director	November 22, 2011
By:	/s/    DEBORAH L. BEVIER Deborah L. Bevier	Director	November 22, 2011
By:	/s/    JONATHAN CHADWICK Jonathan Chadwick	Director	November 22, 2011
By:	/s/    KARL D. GUELICH Karl D. Guelich	Director	November 22, 2011
By:	/s/    ALAN J. HIGGINSON Alan J. Higginson	Director	November 22, 2011
By:	/s/    SCOTT THOMPSON Scott Thompson	Director	November 22, 2011

65

EXHIBIT INDEX

Exhibit Number		Exhibit Description
2.1	—	Agreement and Plan of Merger dated as of May 31, 2004, by and among the Registrant, Fire5, Inc., a wholly owned subsidiary of the Registrant, MagniFire Websystems, Inc., and Lucent Venture Partners III LLC(1)
2.2	—	Agreement and Plan of Merger, dated September 6, 2005, among the Registrant, Sparrow Acquisition Corp., Swan Labs Corporation and the other parties referred to therein.(2)
2.3	—	Agreement and Plan of Merger, dated August 6, 2007, among the Registrant, Checkmate Acquisition Corp., Acopia Networks, Inc. and Charles River Ventures, LLC.(18)
3.1	—	Second Amended and Restated Articles of Incorporation of the Registrant(3)
3.2	—	Amended and Restated Bylaws of the Registrant(3)
3.3	—	Second Amended and Restated Bylaws of F5 Networks, Inc.(22)
3.4	—	Third Amended and Restated Bylaws of F5 Networks, Inc.(23)
4.1	—	Specimen Common Stock Certificate(3)
10.1	—	Amended and Restated Office Lease Agreement dated April 3, 2000, between the Registrant and 401 Elliott West LLC(4)
10.2	—	Sublease Agreement dated March 30, 2001 between the Registrant and Cell Therapeutics, Inc.(5)
10.3	—	uRoam Acquisition Equity Incentive Plan(6) §
10.4	—	Form of Indemnification Agreement between the Registrant and each of its directors and certain of its officers(3) §
10.5	—	1998 Equity Incentive Plan, as amended(7) §
10.6	—	Form of Option Agreement under the 1998 Equity Incentive Plan(3) §
10.7	—	Amended and Restated Directors’ Nonqualified Stock Option Plan(3) §
10.8	—	Form of Option Agreement under the Amended and Restated Directors’ Nonqualified Stock Option Plan(3) §
10.9	—	Amended and Restated 1996 Stock Option Plan(3) §
10.10	—	Form of Option Agreement under the Amended and Restated 1996 Stock Option Plan(3) §
10.11	—	1999 Non-Employee Directors’ Stock Option Plan(3) §
10.12	—	Form of Option Agreement under 1999 Non-Employee Directors’ Stock Option Plan(3) §
10.13	—	NonQualified Stock Option Agreement between John McAdam and the Registrant dated July 24, 2000(8) §
10.14	—	2000 Employee Equity Incentive Plan(9) §
10.15	—	Form of Option Agreement under the 2000 Equity Incentive Plan(10) §
10.16	—	NonQualified Stock Option Agreement between M. Thomas Hull and the Registrant dated October 20, 2003(11) §
10.17*	—	2011 Employee Stock Purchase Plan §
10.18	—	MagniFire Acquisition Equity Incentive Plan(13) §
10.19	—	NonQualified Stock Option Agreement between Karl Triebes and the Registrant dated August 16, 2004(13)
10.20	—	Incentive Compensation Plan for Executive Officers(13) §

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10.21	—	2005 Equity Incentive Plan(14) §
10.22	—	Form of Restricted Stock Unit agreement under the 2005 Equity Incentive Plan (with acceleration upon change of control)(15) §
10.23	—	Form of Restricted Stock Unit agreement under the 2005 Equity Incentive Plan (no acceleration upon change of control)(15) §
10.24	—	Amendment to F5 Networks, Inc. 2005 Equity Incentive Plan Award Agreement, dated March 8, 2006, between the Registrant and John Rodriquez(16) §
10.25	—	Amendment to F5 Networks, Inc. 2005 Equity Incentive Plan Award Agreement, dated March 8, 2006, between the Registrant and Andy Reinland(16) §
10.27	—	Office Lease Agreement with Selig Real Estate Holdings IIX, L.L.C. dated October 31, 2006(17)
10.28	—	First Amendment to Sublease Agreement dated April 13, 2001 between the Registrant and Cell Therapeutics, Inc.(19)
10.29	—	Second Amendment to Sublease Agreement dated March 6, 2002 between the Registrant and Cell Therapeutics, Inc.(19)
10.30	—	Third Amendment to Sublease Agreement dated as of December 22, 2005 between the Registrant and Cell Therapeutics, Inc.(19)
10.31	—	Assumed Acopia Networks, Inc. 2001 Stock Incentive Plan(20) §
10.32	—	Acopia Acquisition Equity Incentive Plan(20) §
10.33	—	Form of Restricted Stock Unit Agreement under the Acopia Acquisition Equity Incentive Plan (with acceleration upon change of control)(21) §
10.34	—	Form of Restricted Stock Unit Agreement under the Acopia Acquisition Equity Incentive Plan (no acceleration upon change of control)(21) §
10.35	—	Form of Change of Control Agreement between F5 Networks, Inc. and each of John McAdam, John Rodriguez, Karl Triebes, Edward J. Eames, Dan Matte and certain other executive officers(24)
10.36	—	2005 Equity Incentive Plan, as amended January 2009(25)
10.37	—	Form of Restricted Stock Unit Agreement under the 2005 Equity Incentive Plan as amended (with acceleration upon change of control) as revised July 2009(26)
21.1*	—	Subsidiaries of the Registrant
23.1*	—	Consent of PricewaterhouseCoopers LLP, Independent Registered Public Accounting Firm
31.1*	—	Certification Pursuant to Section 302 of the Sarbanes-Oxley Act of 2002
31.2*	—	Certification Pursuant to Section 302 of the Sarbanes-Oxley Act of 2002
32.1*	—	Certification Pursuant to Section 906 of the Sarbanes-Oxley Act of 2002
101.INS**	—	XBRL Instance Document
101.SCH**	—	XBRL Taxonomy Extension Schema Document
101.CAL**	—	XBRL Taxonomy Extension Calculation Linkbase Document
101.DEF**	—	XBRL Taxonomy Extension Definition Linkbase Document
101.LAB**	—	XBRL Taxonomy Extension Label Linkbase Document
101.PRE**	—	XBRL Taxonomy Extension Presentation Linkbase Document

67

* Filed herewith.

** XBRL (Extensible Business Reporting Language) information is furnished and not filed herewith, is not a part of a registration statement or Prospectus for purposes of sections 11 or 12 of the Securities Act of 1933, is deemed not filed for purposes of section 18 of the Securities Exchange Act of 1934, and otherwise is not subject to liability under these sections.

§ Indicates a management contract or compensatory plan or arrangement.

(1) Incorporated by reference from Current Report on Form 8-K dated May 31, 2004 and filed with the SEC on June 2, 2004.

(2) Incorporated by reference from Current Report on Form 8-K dated October 4, 2005 and filed with the SEC on October 5, 2005.

(3) Incorporated by reference from Registration Statement on Form S-1, File No. 333-75817.

(4) Incorporated by reference from Quarterly Report on Form 10-Q for the quarter ended June 30, 2000.

(5) Incorporated by reference from Quarterly Report on Form 10-Q for the quarter ended June 30, 2001.

(6) Incorporated by reference from Registration Statement on Form S-8, File No. 333-109895.

(7) Incorporated by reference from Registration Statement on Form S-8, File No. 333-104169.

(8) Incorporated by reference from Annual Report on Form 10-K for the year ended September 30, 2000.

(9) Incorporated by reference from Registration Statement on Form S-8, File No. 333-51878.

(10) Incorporated by reference from Annual Report on Form 10-K for the year ended September 30, 2001.

(11) Incorporated by reference from Registration Statement on Form S-8, File No. 333-112022.

(13) Incorporated by reference from Annual Report on Form 10-K for the year ended September 30, 2004.

(14) Incorporated by reference from Quarterly Report on Form 10-Q for the quarter ended March 31, 2005.

(15) Incorporated by reference from Quarterly Report on Form 10-Q for the quarter ended June 30, 2005.

(16) Incorporated by reference from Current Report on Form 8-K dated March 8, 2006 and filed with the SEC on March 10, 2006.

(17) Incorporated by reference from Current Report on Form 8-K dated October 31, 2006 and filed with the SEC on November 3, 2006.

(18) Incorporated by reference from Current Report on Form 8-K dated August 6, 2007 and filed with the SEC on August 8, 2007.

(19) Incorporated by reference from Annual Report on Form 10-K for the year ended September 30, 2006.

(20) Incorporated by reference from Registration Statement on Form S-8, File No. 333-146195.

(21) Incorporated by reference from Annual Report on Form 10-K for the year ended September 30, 2007.

(22) Incorporated by reference from Annual Report on Form 10-K for the year ended September 30, 2008.

(23) Incorporated by reference from Quarterly Report on Form 10-Q for the quarter ended December 31, 2008.

(24) Incorporated by reference from Current Report on Form 8-K dated April 29, 2009 and filed with the SEC on May 4, 2009.

(25) Incorporated by reference from Quarterly Report on Form 10-Q for the quarter ended March 31, 2009.

(26) Incorporated by reference from Quarterly Report on Form 10-Q for the quarter ended June 30, 2009.

68

EX-10.17

Exhibit 10.17

F5 NETWORKS, INC

2011 EMPLOYEE STOCK PURCHASE PLAN

1. PURPOSE.

(a) The purpose of the Plan is to provide a means by which Employees of the Company and certain designated Affiliates may be given an opportunity to purchase Shares of the Company.

(b) The Company, by means of the Plan, seeks to retain the services of such Employees, to secure and retain the services of new Employees and to provide incentives for such persons to exert maximum efforts for the success of the Company and its Affiliates.

(c) The Company intends that the Rights to purchase Shares granted under the Plan be considered options issued under an “employee stock purchase plan,” as that term is defined in Section 423(b) of the Code.

2. DEFINITIONS.

Certain terms used in the Plan have the meanings set forth in Appendix I.

3. ADMINISTRATION.

(a) The Board shall administer the Plan unless and until the Board delegates administration to a Committee, as provided in subparagraph 3(d). Whether or not the Board has delegated administration, the Board shall have the final power to determine all questions of policy and expediency that may arise in the administration of the Plan.

(b) The Board (or the Committee) shall have the power, subject to, and within the limitations of, the express provisions of the Plan:

(i) To determine when and how Rights to purchase Shares shall be granted and the provisions of each Offering of such Rights (which need not be identical).

(ii) To designate from time to time which Affiliates of the Company shall be eligible to participate in the Plan.

(iii) To construe and interpret the Plan and Rights granted under it, and to establish, amend and revoke rules and regulations for its administration. The Board, in the exercise of this power, may correct any defect, omission or inconsistency in the Plan, in a manner and to the extent it shall deem necessary or expedient to make the Plan fully effective.

(iv) To amend the Plan as provided in paragraph 14.

(v) Generally, to exercise such powers and to perform such acts as it deems necessary or expedient to promote the best interests of the Company and its Affiliates and to carry out the intent that the Plan be treated as an Employee Stock Purchase Plan.

(c) Without limitation on paragraph 3(b) and without amending the Plan, the Board (or the Committee) may grant rights or establish other procedures to provide benefits to Eligible Employees outside of the United States on such terms and conditions different from those specified in this Plan as may, in the judgment of the Board (or the Committee), be necessary or desirable to foster and promote achievement of the purposes of the Plan and shall have the authority to adopt such modifications, procedures, subplans and the like as may be necessary or desirable (i) to comply with provisions of the laws or regulations or conform to the requirements to operate the Plan in a qualified or tax or accounting advantageous manner in other countries or jurisdictions in which the Company or any other Employer may operate or have employees, (ii) to ensure the viability of the benefits from the Plan to Eligible Employees employed in such countries or jurisdictions and (iii) to meet the objectives of the Plan.

(d) The Board may delegate administration of the Plan to a Committee of the Board composed of two (2) or more members, all of the members of which Committee may be, in the discretion of the Board, Non-Employee Directors and/or Outside Directors. If administration is delegated to a Committee, the Committee shall have, in connection with the administration of the Plan, the powers theretofore possessed by the Board, including the power to delegate to a subcommittee of two (2) or more Outside Directors any of the administrative powers the Committee is authorized to exercise (and references in this Plan to the Board shall thereafter be to the Committee or such a subcommittee), subject, however, to such resolutions, not inconsistent with the provisions of the Plan, as may be adopted from time to time by the Board. The Board may abolish the Committee at any time and revest in the Board the administration of the Plan.

4. SHARES SUBJECT TO THE PLAN.

(a) Subject to the provisions of paragraph 13 relating to adjustments upon changes in securities, the Shares that may be sold pursuant to Rights granted under the Plan shall not exceed in the aggregate six million (6,000,000)¹ Shares. If any Right granted under the Plan shall for any reason terminate without having been exercised, the Shares not purchased under such Right shall again become available for the Plan.

(b) The Shares subject to the Plan may be unissued Shares or Shares that have been bought on the open market at prevailing market prices or otherwise.

5. GRANT OF RIGHTS; OFFERING.

(a) The Board may from time to time grant or provide for the grant of Rights to purchase Shares of the Company under the Plan to Eligible Employees in an Offering on an Offering Date or Dates selected by the Board. Each Offering shall be in such form and shall contain such terms and conditions as the Board shall deem appropriate, which shall comply with

¹  As adjusted to reflect two-for-one forward stock split effective August 20, 2007.

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the requirements of Section 423(b)(5) of the Code that all Employees granted Rights to purchase Shares under the Plan shall have the same rights and privileges. The terms and conditions of an Offering shall be incorporated by reference into the Plan and treated as part of the Plan. The provisions of separate Offerings need not be identical, but each Offering shall include (through incorporation of the provisions of this Plan by reference in the document comprising the Offering or otherwise) the period during which the Offering shall be effective, which period shall not exceed twenty-seven (27) months beginning with the Offering Date, and the substance of the provisions contained in paragraphs 6 through 9, inclusive.

(b) If a Participant has more than one Right outstanding under the Plan, unless he or she otherwise indicates in agreements or notices delivered hereunder: (i) each agreement or notice delivered by that Participant will be deemed to apply to all of his or her Rights under the Plan, and (ii) an earlier-granted Right (or a Right with a lower exercise price, if two Rights have identical grant dates) will be exercised to the fullest possible extent before a later-granted Right (or a Right with a higher exercise price if two Rights have identical grant dates) will be exercised.

6. ELIGIBILITY.

(a) Rights may be granted only to Employees of the Company or, as the Board may designate as provided in subparagraph 3(b), to Employees of an Affiliate. Except as provided in subparagraph 6(b), an Employee shall not be eligible to be granted Rights under the Plan unless, on the Offering Date, such Employee has been in the employ of the Company or the Affiliate, as the case may be, for such continuous period preceding such grant as the Board may require, but in no event shall the required period of continuous employment be equal to or greater than two (2) years.

(b) The Board may provide that each person who, during the course of an Offering, first becomes an Eligible Employee will, on a date or dates specified in the Offering which coincides with the day on which such person becomes an Eligible Employee or which occurs thereafter, receive a Right under that Offering, which Right shall thereafter be deemed to be a part of that Offering. Such Right shall have the same characteristics as any Rights originally granted under that Offering, as described herein, except that:

(i) the date on which such Right is granted shall be the “Offering Date” of such Right for all purposes, including determination of the exercise price of such Right;

(ii) the period of the Offering with respect to such Right shall begin on its Offering Date and end coincident with the end of such Offering; and

(iii) the Board may provide that if such person first becomes an Eligible Employee within a specified period of time before the end of the Offering, he or she will not receive any Right under that Offering.

(c) No Employee shall be eligible for the grant of any Rights under the Plan if, immediately after any such Rights are granted, such Employee owns stock possessing five percent (5%) or more of the total combined voting power or value of all classes of stock of the Company or of any Affiliate. For purposes of this subparagraph 6(c), the rules of Section 424(d) of the Code shall apply in determining the stock ownership of any Employee, and stock which such Employee may purchase under all outstanding rights and options shall be treated as stock owned by such Employee.

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(d) An Eligible Employee may be granted Rights under the Plan only if such Rights, together with any other Rights granted under all Employee Stock Purchase Plans of the Company and any Affiliates, as specified by Section 423(b)(8) of the Code, do not permit such Eligible Employee’s rights to purchase Shares of the Company or any Affiliate to accrue at a rate which exceeds twenty five thousand dollars ($25,000) of the fair market value of such Shares (determined at the time such Rights are granted) for each calendar year in which such Rights are outstanding at any time.

(e) The Board may provide in an Offering that Employees who are highly compensated Employees within the meaning of Section 423(b)(4)(D) of the Code shall not be eligible to participate.

7. RIGHTS; PURCHASE PRICE.

(a) On each Offering Date, each Eligible Employee, pursuant to an Offering made under the Plan, shall be granted the Right to purchase up to the number of Shares purchasable either:

(i) with a percentage designated by the Board not exceeding fifteen percent (15%) of such Employee’s Earnings (as defined by the Board in each Offering) during the period which begins on the Offering Date (or such later date as the Board determines for a particular Offering) and ends on the date stated in the Offering, which date shall be no later than the end of the Offering; or

(ii) with a maximum dollar amount designated by the Board that, as the Board determines for a particular Offering, (1) shall be withheld, in whole or in part, from such Employee’s Earnings (as defined by the Board in each Offering) during the period which begins on the Offering Date (or such later date as the Board determines for a particular Offering) and ends on the date stated in the Offering, which date shall be no later than the end of the Offering and/or (2) shall be contributed, in whole or in part, by such Employee during such period.

(b) The Board shall establish one or more Purchase Dates during an Offering on which Rights granted under the Plan shall be exercised and purchases of Shares carried out in accordance with such Offering.

(c) In connection with each Offering made under the Plan, the Board may specify a maximum amount of Shares that may be purchased by any Participant as well as a maximum aggregate amount of Shares that may be purchased by all Participants pursuant to such Offering. In addition, in connection with each Offering that contains more than one Purchase Date, the Board may specify a maximum aggregate amount of Shares which may be purchased by all Participants on any given Purchase Date under the Offering. If the aggregate purchase of Shares upon exercise of Rights granted under the Offering would exceed any such maximum aggregate amount, the Board shall make a pro rata allocation of the Shares available in as nearly a uniform manner as shall be practicable and as it shall deem to be equitable. Unless a different maximum amount of Shares that may be purchased by any Participant during an Offering is determined by the Board prior to the start of an Offering, the maximum amount of Shares that may be purchased by any Participant during an Offering is 10,000 Shares.

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(d) The purchase price of Shares acquired pursuant to Rights granted under the Plan shall be not less than the lesser of:

(i) an amount equal to eighty-five percent (85%) of the fair market value of the Shares on the Offering Date; or

(ii) an amount equal to eighty-five percent (85%) of the fair market value of the Shares on the Purchase Date.

8. PARTICIPATION; WITHDRAWAL; TERMINATION.

(a) An Eligible Employee may become a Participant in the Plan pursuant to an Offering by delivering a participation agreement to the Company within the time specified in the Offering, in such form as the Company provides. Each such agreement shall authorize payroll deductions of up to the maximum percentage specified by the Board of such Employee’s Earnings during the Offering (as defined in each Offering). The payroll deductions made for each Participant shall be credited to a bookkeeping account for such Participant under the Plan and either may be deposited with the general funds of the Company or may be deposited in a separate account in the name of, and for the benefit of, such Participant with a financial institution designated by the Company. To the extent provided in the Offering, a Participant may reduce (including to zero) or increase such payroll deductions. To the extent provided in the Offering, a Participant may begin such payroll deductions after the beginning of the Offering. A Participant may make additional payments into his or her account only if specifically provided for in the Offering and only if the Participant has not already had the maximum permitted amount withheld during the Offering.

(b) At any time during an Offering, a Participant may terminate his or her payroll deductions under the Plan and withdraw from the Offering by delivering to the Company a notice of withdrawal in such form as the Company provides. Such withdrawal may be elected at any time prior to the end of the Offering except as provided by the Board in the Offering. Upon such withdrawal from the Offering by a Participant, the Company shall distribute to such Participant all of his or her accumulated payroll deductions (reduced to the extent, if any, such deductions have been used to acquire Shares for the Participant) under the Offering, without interest unless otherwise specified in the Offering, and such Participant’s interest in that Offering shall be automatically terminated. A Participant’s withdrawal from an Offering will have no effect upon such Participant’s eligibility to participate in any other Offerings under the Plan but such Participant will be required to deliver a new participation agreement in order to participate in subsequent Offerings under the Plan.

(c) Rights granted pursuant to any Offering under the Plan shall terminate immediately upon cessation of any participating Employee’s employment with the Company or a designated Affiliate for any reason (subject to any post-employment participation period required by law) or other lack of eligibility. The Company shall distribute to such terminated Employee

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all of his or her accumulated payroll deductions (reduced to the extent, if any, such deductions have been used to acquire Shares for the terminated Employee) under the Offering, without interest unless otherwise specified in the Offering. If the accumulated payroll deductions have been deposited with the Company’s general funds, then the distribution shall be made from the general funds of the Company, without interest. If the accumulated payroll deductions have been deposited in a separate account with a financial institution as provided in subparagraph 8(a), then the distribution shall be made from the separate account, without interest unless otherwise specified in the Offering.

(d) Rights granted under the Plan shall not be transferable by a Participant otherwise than by will or the laws of descent and distribution and, otherwise during his or her lifetime, shall be exercisable only by the person to whom such Rights are granted.

9. EXERCISE.

(a) On each Purchase Date specified therefor in the relevant Offering, each Participant’s accumulated payroll deductions and other additional payments specifically provided for in the Offering (without any increase for interest) will be applied to the purchase of Shares up to the maximum amount of Shares permitted pursuant to the terms of the Plan and the applicable Offering, at the purchase price specified in the Offering. No fractional Shares shall be issued upon the exercise of Rights granted under the Plan unless specifically provided for in the Offering.

(b) Unless otherwise specifically provided in the Offering, the amount, if any, of accumulated payroll deductions remaining in any Participant’s account after the purchase of Shares that is equal to the amount required to purchase one or more whole Shares on the final Purchase Date of the Offering shall be distributed in full to the Participant at the end of the Offering, without interest. If the accumulated payroll deductions have been deposited with the Company’s general funds, then the distribution shall be made from the general funds of the Company, without interest. If the accumulated payroll deductions have been deposited in a separate account with a financial institution as provided in subparagraph 8(a), then the distribution shall be made from the separate account, without interest unless otherwise specified in the Offering.

(c) No Rights granted under the Plan may be exercised to any extent unless the Shares to be issued upon such exercise under the Plan (including Rights granted thereunder) are covered by an effective registration statement pursuant to the Securities Act and the Plan is in material compliance with all applicable state, foreign and other securities and other laws applicable to the Plan. If on a Purchase Date in any Offering hereunder the Plan is not so registered or in such compliance, no Rights granted under the Plan or any Offering shall be exercised on such Purchase Date, and the Purchase Date shall be delayed until the Plan is subject to such an effective registration statement and such compliance, except that the Purchase Date shall not be delayed more than twelve (12) months and the Purchase Date shall in no event be more than twenty-seven (27) months from the Offering Date. If, on the Purchase Date of any Offering hereunder, as delayed to the maximum extent permissible, the Plan is not registered and in such compliance, no Rights granted under the Plan or any Offering shall be exercised and all payroll deductions accumulated during the Offering (reduced to the extent, if any, such

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deductions have been used to acquire Shares) shall be distributed to the Participants, without interest unless otherwise specified in the Offering. If the accumulated payroll deductions have been deposited with the Company’s general funds, then the distribution shall be made from the general funds of the Company, without interest. If the accumulated payroll deductions have been deposited in a separate account with a financial institution as provided in subparagraph 8(a), then the distribution shall be made from the separate account, without interest unless otherwise specified in the Offering.

10. ISSUANCE OF SHARES.

(a) If on a given Purchase Date, the number of Shares with respect to which Rights are to be exercised exceeds the number of Shares then available under the Plan, the Board shall make a pro rata allocation of the Shares remaining available under the Plan in as nearly a uniform manner as shall be practical and as it shall determine to be equitable.

(b) If the Company is unable to obtain from any regulatory commission or agency the authority which counsel for the Company deems necessary for the lawful issuance and sale of Shares under the Plan, the Company shall be relieved from any liability for failure to issue and sell Shares upon exercise of such Rights unless and until such authority is obtained.

11. USE OF PROCEEDS FROM SHARES.

Proceeds from the sale of Shares pursuant to Rights granted under the Plan shall constitute general funds of the Company.

12. RIGHTS AS A SHAREHOLDER.

A Participant shall not be deemed to be the holder of, or to have any of the rights of a holder with respect to, Shares subject to Rights granted under the Plan unless and until the Participant’s Shares acquired upon exercise of Rights under the Plan are issued. No adjustment will be made for dividends or other rights for which the record date is prior to the date of issuance.

13. ADJUSTMENTS UPON CHANGES IN SECURITIES.

(a) If any change is made in the Shares subject to the Plan, or subject to any Right, without the receipt of consideration by the Company (through merger, consolidation, reorganization, recapitalization, reincorporation, stock dividend, dividend in property other than cash, stock split, liquidating dividend, combination of shares, exchange of shares, change in corporate structure or other transaction not involving the receipt of consideration by the Company), the Plan will be appropriately adjusted in the class(es) and maximum number of Shares subject to the Plan pursuant to subparagraph 4(a), and the outstanding Rights will be appropriately adjusted in the class(es), number of Shares and purchase limits of such outstanding Rights. The Board shall make such adjustments, and its determination shall be final, binding and conclusive. (The conversion of any convertible securities of the Company shall not be treated as a transaction that does not involve the receipt of consideration by the Company.)

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(b) In the event of: (i) a dissolution, liquidation, or sale of all or substantially all of the assets of the Company; (ii) a merger or consolidation in which the Company is not the surviving corporation; or (iii) a reverse merger in which the Company is the surviving corporation but the Shares outstanding immediately preceding the merger are converted by virtue of the merger into other property, whether in the form of securities, cash or otherwise, then: (1) any surviving or acquiring corporation shall assume Rights outstanding under the Plan or shall substitute similar rights (including a right to acquire the same consideration paid to Shareholders in the transaction described in this subparagraph 13(b)) for those outstanding under the Plan, or (2) in the event any surviving or acquiring corporation refuses to assume such Rights or to substitute similar rights for those outstanding under the Plan, then, as determined by the Board in its sole discretion such Rights may continue in full force and effect or the Participants’ accumulated payroll deductions (exclusive of any accumulated interest which cannot be applied toward the purchase of Shares under the terms of the Offering) may be used to purchase Shares immediately prior to the transaction described above under the ongoing Offering and the Participants’ Rights under the ongoing Offering thereafter terminated.

14. AMENDMENT OF THE PLAN.

(a) The Board at any time, and from time to time, may amend the Plan. However, except as provided in paragraph 13 relating to adjustments upon changes in securities and except as to minor amendments to benefit the administration of the Plan, to take account of a change in legislation or to obtain or maintain favorable tax, exchange control or regulatory treatment for Participants or the Company or any Affiliate, no amendment shall be effective unless approved by the shareholders of the Company to the extent shareholder approval is necessary for the Plan to satisfy the requirements of Section 423 of the Code and any Nasdaq or other securities exchange listing requirements. Currently under the Code, shareholder approval within twelve (12) months before or after the adoption of the amendment is required where the amendment will:

(i) Increase the amount of Shares reserved for Rights under the Plan;

(ii) Modify the provisions as to eligibility for participation in the Plan to the extent such modification requires shareholder approval in order for the Plan to obtain employee stock purchase plan treatment under Section 423 of the Code; or

(iii) Modify the Plan in any other way if such modification requires shareholder approval in order for the Plan to obtain employee stock purchase plan treatment under Section 423 of the Code.

(b) It is expressly contemplated that the Board may amend the Plan in any respect the Board deems necessary or advisable to provide Employees with the maximum benefits provided or to be provided under the provisions of the Code and the regulations promulgated thereunder relating to Employee Stock Purchase Plans and/or to bring the Plan and/or Rights granted under it into compliance therewith.

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(c) Rights and obligations under any Rights granted before amendment of the Plan shall not be impaired by any amendment of the Plan, except with the consent of the person to whom such Rights were granted, or except as necessary to comply with any laws or governmental regulations, or except as necessary to ensure that the Plan and/or Rights granted under the Plan comply with the requirements of Section 423 of the Code or are exempt from or comply with the requirements of Section 409A of the Code.

15. TERMINATION OR SUSPENSION OF THE PLAN.

(a) The Board in its discretion may suspend or terminate the Plan at any time. Unless sooner terminated, the Plan shall terminate at the time that all of the Shares subject to the Plan’s reserve, as increased and/or adjusted from time to time, have been issued under the terms of the Plan. No Rights may be granted under the Plan while the Plan is suspended or after it is terminated.

(b) Rights and obligations under any Rights granted while the Plan is in effect shall not be impaired by suspension or termination of the Plan, except as expressly provided in the Plan or with the consent of the person to whom such Rights were granted, or except as necessary to comply with any laws or governmental regulation, or except as necessary to ensure that the Plan and/or Rights granted under the Plan comply with the requirements of Section 423 of the Code.

16. TREATMENT OF ELIGIBLE EMPLOYEES OUTSIDE OF THE UNITED STATES.

Eligible Employees who are paid in foreign currency, and who contribute foreign currency to the Plan through contributions or payroll deductions will have such amounts converted to U.S. dollars. The exchange rate and method for such conversion will be determined as prescribed by the Board or Committee. In no event will any procedure implemented for dealing with exchange rate fluctuations that may occur during an Offering result in a purchase price below the purchase price permitted under subparagraph 6(d) of the Plan. Each Eligible Employee shall bear the risk of any currency exchange fluctuations (if applicable) between the date on which any Eligible Employee amounts are converted to U.S. dollars and the Purchase Date.

17. WITHHOLDING.

The Employer shall have the power and the right to (a) deduct, withhold or cause the sale of Shares purchased pursuant to an Offering under the Plan to obtain, (b) deduct or withhold from any other compensation to the Participant, or (c) require a Participant to remit to the Employer, an amount sufficient to satisfy Federal, state and local taxes, domestic or foreign, required by law or regulation to be withheld with respect to any taxable event arising as a result of the Plan.

18. SECTION 409A.

Rights under the Plan are intended to be exempt from the application of Section 409A of the Code and the Plan is intended to be interpreted consistent with such intention. Notwithstanding the foregoing, neither the Company nor the Board shall have any liability to any Participant or any other party if the Rights under the Plan are not exempt from or compliant with Section 409A of the Code.

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19. NO RIGHT OF EMPLOYMENT.

Neither the grant nor the exercise of any Right under the Plan nor anything in this Plan shall impose upon the Company or any other Employer any obligation to employ or continue to employ any Eligible Employee. The right of the Company or any other Employer to terminate any Employee shall not be diminished or affected because any Rights have been granted to such Employee.

20. OBLIGATION TO MAINTAIN SHARES WITH BROKER.

Without limitation on the Participant’s or former Participant’s ability to sell, transfer, or otherwise makes a disposition of Shares purchased pursuant to an Offering under the Plan and without limitation on paragraph 3, Participants and former Participants must maintain any Shares purchased pursuant to an Offering under the Plan at the broker designated by the Committee unless the Committee determines otherwise.

21. EFFECTIVE DATE AND HISTORY OF PLAN.

The 1999 Employee Stock Purchase Plan was originally adopted by the Board and approved by shareholders in 1999 and subsequently amended as set forth on Appendix II. The 2011 Employee Stock Purchase Plan is an amendment and restatement of the 1999 Employee Stock Purchase Plan, as amended.

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APPENDIX I

DEFINITIONS

(a) “Affiliate” means any parent corporation or subsidiary corporation, whether now or hereafter existing, as those terms are defined in Sections 424(e) and (f), respectively, of the Code.

(b) “Board” means the Board of Directors of the Company.

(c) “Code” means the United States Internal Revenue Code of 1986, as amended.

(d) “Committee” means a Committee appointed by the Board in accordance with subparagraph 3(d) of the Plan.

(e) “Company” means F5 Networks, Inc., a Washington corporation.

(f) “Director” means a member of the Board.

(g) “Earnings” means, unless otherwise determined by the Board, cash compensation actually paid to an Eligible Employee during the specified period.

(h) “Eligible Employee” means an Employee who meets the requirements set forth in the Offering for eligibility to participate in the Offering.

(i) “Employee” means any person, including Officers and Directors, employed by the Company or an Affiliate of the Company. Neither service as a Director nor payment of a director’s fee shall be sufficient to constitute “employment” by the Company or the Affiliate.

(j) “Employee Stock Purchase Plan” means a plan that grants rights intended to be options issued under an “employee stock purchase plan,” as that term is defined in Section 423(b) of the Code.

(k) “Employer” means the Company and the Affiliates designated from time to time pursuant to subparagraph 3(b) of the plan to participate in the Plan.

(l) “Exchange Act” means the United States Securities Exchange Act of 1934, as amended.

(m) “Fair Market Value” means the value of a security, as determined in good faith by the Board. If the security is listed on any established stock exchange, then, except as otherwise provided in the Offering, the Fair Market Value of the security shall be the closing sales price (rounded up where necessary to the nearest whole cent) for such security (or the closing bid, if no sales were reported) as quoted on such exchange or market (or the exchange or market with the greatest volume of trading in the relevant security of the Company) on the trading day prior to the relevant determination date, as reported in The Wall Street Journal or such other source as the Board deems reliable.

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(n) “Non-Employee Director” means a Director who either (i) is not a current Employee or Officer of the Company or its parent or subsidiary, does not receive compensation (directly or indirectly) from the Company or its parent or subsidiary for services rendered as a consultant or in any capacity other than as a Director (except for an amount as to which disclosure would not be required under Item 404(a) of Regulation S K promulgated pursuant to the Securities Act (“Regulation S-K”)) and does not possess an interest in any other transaction as to which disclosure would be required under Item 404(a) of Regulation S-K; or (ii) is otherwise considered a “non-employee director” for purposes of Rule 16b-3.

(o) “Offering” means the grant of Rights to purchase Shares under the Plan to Eligible Employees.

(p) “Offering Date” means a date selected by the Board for an Offering to commence.

(q) “Outside Director” means a Director who either (i) is not a current employee of the Company or an “affiliated corporation” (within the meaning of the Treasury regulations promulgated under Section 162(m) of the Code), is not a former employee of the Company or an “affiliated corporation” receiving compensation for prior services (other than benefits under a tax qualified pension plan), was not an officer of the Company or an “affiliated corporation” at any time, and is not currently receiving direct or indirect remuneration from the Company or an “affiliated corporation” for services in any capacity other than as a Director, or (ii) is otherwise considered an “outside director” for purposes of Section 162(m) of the Code.

(r) “Participant” means an Eligible Employee who holds an outstanding Right granted pursuant to the Plan or, if applicable, such other person who holds an outstanding Right granted under the Plan.

(s) “Plan” means this F5 Networks, Inc. 2011 Employee Stock Purchase Plan.

(t) “Purchase Date” means one or more dates established by the Board during an Offering on which Rights granted under the Plan shall be exercised and purchases of Shares carried out in accordance with such Offering.

(u) “Right” means an option to purchase Shares granted pursuant to the Plan.

(v) “Rule 16b-3” means Rule 16b-3 of the Exchange Act or any successor to Rule 16b-3 as in effect with respect to the Company at the time discretion is being exercised regarding the Plan.

(w) “Securities Act” means the United States Securities Act of 1933, as amended.

(x) “Share” means a share of the common stock of the Company.

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APPENDIX II

HISTORY: ORIGINALLY ADOPTED BY BOARD OF DIRECTORS APRIL 5, 1999 ORIGINALLY APPROVED BY SHAREHOLDERS MAY, 1999 AMENDMENT ADOPTED BY BOARD OF DIRECTORS JANUARY 26, 2004 AMENDMENT ADOPTED BY SHAREHOLDERS APRIL 29, 2004 SECOND AMENDMENT ADOPTED BY BOARD OF DIRECTORS JANUARY 7, 2009 SECOND AMENDMENT ADOPTED BY SHAREHOLDERS MARCH 12, 2009 AMENDMENT ADOPTED BY BOARD OF DIRECTORS SEPTEMBER 9, 2010 AMENDMENT AND RESTATEMENT ADOPTED BY BOARD OF DIRECTORS JULY 14, 2011

TERMINATION DATE: NONE

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EX-21.1

Exhibit 21.1

SUBSIDIARIES OF THE REGISTRANT

Name	Jurisdiction of Organization
F5 Networks Australia Pty. Ltd.	Australia
FCINCO REPRESENTAÇÕES DO BRASIL LTDA	Brazil
F5 Networks SARL	France
F5 Networks GmbH	Germany
F5 Networks Hong Kong Ltd.	Hong Kong
F5 Networks SRL	Italy
F5 Networks Japan K.K.	Japan
F5 Networks Korea Ltd.	Korea
F5 Networks Benelux B.V.	Netherlands
F5 Networks New Zealand Ltd.	New Zealand
F5 Networks China	People’s Republic of China
F5 Networks Singapore Pte. Ltd.	Singapore
F5 Networks Iberia SL	Spain
F5 Networks Ltd.	United Kingdom
F5 RO, Inc.	Washington, U.S.A.
MagniFire Websystems, Inc.	Delaware, U.S.A.
Swan Labs Corporation	Delaware, U.S.A.
Acopia Networks, Inc.	Delaware, U.S.A.

The names of other subsidiaries are omitted. Such subsidiaries would not, if considered in the aggregate as a single subsidiary, constitute a significant subsidiary within the meaning of Item 601(b)(21)(ii) of Regulation S-K.

EX-23.1

Exhibit 23.1

CONSENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

We hereby consent to the incorporation by reference in the Registration Statement on Form S-8 (No. No. 333-80177, 333-82249, 333-34570, 333-51878, 333-76272, 333-87618, 333-102434, 333-104169, 333-109895, 333-112022, 333-116187, 333-122054, 333-124092, 333-142709, 333-146195 and 333-160321) and Form S-3 (No. 333-108826) of F5 Networks, Inc. of our report dated November 22, 2011 relating to the consolidated financial statements and the effectiveness of internal control over financial reporting, which appears in this Form 10-K.

/s/ PricewaterhouseCoopers LLP

PricewaterhouseCoopers LLP

Seattle, WA

November 22, 2011

EX-31.1

Exhibit 31.1

CERTIFICATIONS

I, John McAdam, certify that:

1) I have reviewed this Annual Report on Form 10-K of F5 Networks, Inc.;

2) Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report;

3) Based on my knowledge, the financial statements, and other financial information included in this report, fairly present in all material respects the financial condition, results of operations and cash flows of the registrant as of, and for, the periods presented in this report;

4) The registrant’s other certifying officer and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) and internal control over financial reporting (as defined in Exchange Act Rules 13a-15(f) and 15d-15(f)) for the registrant and have:

a. Designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, to ensure that material information relating to the registrant, including its consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this report is being prepared;

b. Designed such internal control over financial reporting, or caused such internal control over financial reporting to be designed under our supervision, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles;

c. Evaluated the effectiveness of the registrant’s disclosure controls and procedures and presented in this report our conclusions about the effectiveness of the disclosure controls and procedures, as of the end of the period covered by this report based on such evaluation; and

d. Disclosed in this report any change in the registrant’s internal controls over financial reporting that occurred during the registrant’s most recent fiscal quarter (the registrant’s fourth quarter in the case of an annual report) that has materially affected, or is reasonably likely to materially affect, the registrant’s internal controls over financial reporting; and

5) The registrant’s other certifying officer and I have disclosed, based on our most recent evaluation of internal control over financial reporting, to the registrant’s auditors and the audit committee of the registrant’s board of directors (or persons performing the equivalent functions):

a. All significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting, which are reasonably likely to adversely affect the registrant’s ability to record, process, summarize and report financial information; and

b. Any fraud, whether or not material, that involves management or other employees who have a significant role in the registrant’s internal control over financial reporting.

Date: November 22, 2011

/s/ JOHN MCADAM

John McAdam

Chief Executive Officer and President

EX-31.2

Exhibit 31.2

CERTIFICATIONS

I, John Rodriguez, certify that:

1) I have reviewed this Annual Report on Form 10-K of F5 Networks, Inc.;

2) Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report;

3) Based on my knowledge, the financial statements, and other financial information included in this report, fairly present in all material respects the financial condition, results of operations and cash flows of the registrant as of, and for, the periods presented in this report;

4) The registrant’s other certifying officer and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) and internal control over financial reporting (as defined in Exchange Act Rules 13a-15(f) and 15d-15(f)) for the registrant and have:

a. Designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, to ensure that material information relating to the registrant, including its consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this report is being prepared;

b. Designed such internal control over financial reporting, or caused such internal control over financial reporting to be designed under our supervision, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles;

c. Evaluated the effectiveness of the registrant’s disclosure controls and procedures and presented in this report our conclusions about the effectiveness of the disclosure controls and procedures, as of the end of the period covered by this report based on such evaluation; and

d. Disclosed in this report any change in the registrant’s internal controls over financial reporting that occurred during the registrant’s most recent fiscal quarter (the registrant’s fourth quarter in the case of an annual report) that has materially affected, or is reasonably likely to materially affect, the registrant’s internal controls over financial reporting; and

5) The registrant’s other certifying officer and I have disclosed, based on our most recent evaluation of internal control over financial reporting, to the registrant’s auditors and the audit committee of the registrant’s board of directors (or persons performing the equivalent functions):

a. All significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting, which are reasonably likely to adversely affect the registrant’s ability to record, process, summarize and report financial information; and

b. Any fraud, whether or not material, that involves management or other employees who have a significant role in the registrant’s internal control over financial reporting.

Date: November 22, 2011

/s/ JOHN RODRIGUEZ

John Rodriguez

Senior Vice President, Chief Accounting Officer

(principal financial officer)

EX-32.1

Exhibit 32.1

CERTIFICATION PURSUANT TO

18 U.S.C. SECTION 1350,

AS ADOPTED PURSUANT TO

SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

In connection with the Annual Report of F5 Networks, Inc. (the “Company”) on Form 10-K for the period ended September 30, 2011 as filed with the Securities and Exchange Commission on the date hereof (the “Report”), we, John McAdam, President and Chief Executive Officer and John Rodriguez, Senior Vice President and Chief Accounting Officer (principal financial officer) of the Company, certify, pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, that:

(1) The Report fully complies with the requirements of section 13(a) or 15(d) of the Securities Exchange Act of 1934; and

(2) The information contained in the Report fairly presents, in all material respects, the financial condition and result of operations of the Company.

Date: November 22, 2011

/s/ JOHN MCADAM

John McAdam

Chief Executive Officer and President

/s/ JOHN RODRIGUEZ

John Rodriguez

Senior Vice President and Chief Accounting Officer

(principal financial officer)

A signed original of this written statement required by Section 906, or other document authenticating, acknowledging, or otherwise adopting the signature that appears in typed form within the electronic version of this written statement required by Section 906, has been provided to F5 Networks, Inc., and will be retained by F5 Networks, Inc., and furnished to the Securities and Exchange Commission or its staff upon request.

XML

Balance Sheet Details (Schedule Of Intangible Assets) (Details) (USD $) In Thousands	Sep. 30, 2011	Sep. 30, 2010
Acquired And Developed Technology And Software Development Cost [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 39,109	$ 33,474
Accumulated Amortization	(30,589)	(27,100)
Net Carrying Amount	8,520	6,374
Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	2,699	2,699
Accumulated Amortization	(2,314)	(1,894)
Net Carrying Amount	385	805
Patents And Trademarks [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	3,044	2,964
Accumulated Amortization	(2,214)	(1,832)
Net Carrying Amount	830	1,132
Trade Names [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	200	200
Accumulated Amortization	(163)	(123)
Net Carrying Amount	37	77
Non-Compete Covenants [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	200	200
Accumulated Amortization	(200)	(200)
Intangible Assets, Total [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	45,252	39,537
Accumulated Amortization	(35,480)	(31,149)
Net Carrying Amount	$ 9,772	$ 8,388

XML

Commitments And Contingencies (Narrative) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended			1 Months Ended	12 Months Ended	1 Months Ended	12 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2009	Oct. 31, 2006 333 Elliott West [Member]	Sep. 30, 2008 333 Elliott West [Member]	Mar. 31, 2010 Second Sublease [Member]	Sep. 30, 2011 Second Sublease [Member]	Sep. 30, 2011 Partially Subleased [Member]	Sep. 30, 2008 One Sublease [Member]
Commitments And Contingencies [Line Items]
Office space occupied under lease agreement				137,000
Area of building subject to sublease agreement					112,500
Expanded area under amended second sublease						11,700
Rent expense under non-cancelable operating leases	$ 19.0	$ 17.5	$ 15.6
Contract manufacturers' purchase obligations	$ 13.6
Year lease expires	2022			2018			2018	2012	2013

XML

Income Taxes (Schedule Of Reconciliation Of Beginning And Ending Amount Of Unrecognized Tax Benefits) (Details) (USD $) In Thousands	12 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2009
Income Taxes [Abstract]
Balance, beginning of period	$ 6,568	$ 5,841	$ 4,075
Gross increases related to prior period tax positions	1,198	442	642
Gross increases related to current period tax positions	1,659	432	1,124
Decreases relating to settlements with tax authorities	(243)
Reductions due to lapses of statute of limitations	(3,230)	(147)
Balance, end of period	$ 5,952	$ 6,568	$ 5,841

XML

Commitments And Contingencies (Schedule Of Future Minimum Operating Lease Payments, Net Of Sublease Income) (Details) (USD $) In Thousands	Sep. 30, 2011
Commitments And Contingencies [Abstract]
Gross Lease Payments, in year 2012	$ 42,317
Gross Lease Payments, in year 2013	17,673
Gross Lease Payments, in year 2014	16,185
Gross Lease Payments, in year 2015	15,786
Gross Lease Payments, in year 2016	15,072
Gross Lease Payments, Thereafter	65,370
Gross Lease Payments, Total	172,403
Sublease Income, in, year 2012	4,321
Sublease Income, in, year 2013	2,611
Sublease Income, in, year 2014	338
Sublease Income, in, year 2015	85
Sublease Income, Total	7,355
Net Lease Payments, in year 2012	37,996
Net Lease Payments, in year 2013	15,062
Net Lease Payments, in year 2014	15,847
Net Lease Payments, in year 2015	15,701
Net Lease Payments, in year 2016	15,072
Net Lease Payments, Thereafter	65,370
Net Lease Payments, Total	$ 165,048

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Income Taxes (Schedule Of Effective Tax Rate Differs From The U.S. Federal Statutory Rate) (Details) (USD $) In Thousands	12 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2009
Income Taxes [Abstract]
Income tax provision at statutory rate	$ 126,263	$ 83,170	$ 46,075
State taxes, net of federal benefit	5,999	2,871	2,121
Impact of foreign income taxes	(892)	915	(1,262)
Research and development and other credits	(5,486)	(2,124)	(5,954)
Domestic manufacturing deduction	(9,844)	(3,766)	(3,346)
Impact of stock compensation	5,310	2,825	2,411
Other	(1,996)	2,583	68
Income taxes (benefit)	$ 119,354	$ 86,474	$ 40,113

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Fair Value Measurements (Schedule Of Financial Assets Measured At Fair Value On A Recurring Basis) (Details) (USD $) In Thousands	Sep. 30, 2011	Sep. 30, 2010
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Cash equivalents, fair value	$ 33,740	$ 26,987
Investments, fair value	795,969
Financial assets measured at fair value on a recurring basis, total	829,709	720,299
Short-Term Investments [Member] | Corporate Bonds And Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Investments, fair value	137,156	120,124
Short-Term Investments [Member] | Corporate Bonds And Notes [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Investments, fair value	137,156	120,124
Short-Term Investments [Member] | Municipal Bonds And Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Investments, fair value	82,715	77,063
Short-Term Investments [Member] | Municipal Bonds And Notes [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Investments, fair value	82,715	77,063
Short-Term Investments [Member] | U.S. Government Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Investments, fair value	799
Short-Term Investments [Member] | U.S. Government Securities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Investments, fair value	799
Short-Term Investments [Member] | U.S. Government Agency Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Investments, fair value	105,096	62,555
Short-Term Investments [Member] | U.S. Government Agency Securities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Investments, fair value	105,096	62,555
Long-Term Investments [Member] | Corporate Bonds And Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Investments, fair value	141,150	174,053
Long-Term Investments [Member] | Corporate Bonds And Notes [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Investments, fair value	141,150	174,053
Long-Term Investments [Member] | Municipal Bonds And Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Investments, fair value	30,714	22,094
Long-Term Investments [Member] | Municipal Bonds And Notes [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Investments, fair value	30,714	22,094
Long-Term Investments [Member] | U.S. Government Agency Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Investments, fair value	285,329	221,380
Long-Term Investments [Member] | U.S. Government Agency Securities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Investments, fair value	285,329	221,380
Long-Term Investments [Member] | Auction Rate Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Investments, fair value	13,010	16,043
Long-Term Investments [Member] | Auction Rate Securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Investments, fair value	13,010	16,043
Quoted Prices In Active Markets For Identical Securities (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Cash equivalents, fair value	33,740	26,987
Financial assets measured at fair value on a recurring basis, total	33,740	26,987
Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Financial assets measured at fair value on a recurring basis, total	782,959	677,269
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Financial assets measured at fair value on a recurring basis, total	$ 13,010	$ 16,043

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Employee Benefit Plans (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2009
Employee Benefit Plans [Abstract]
Contributions by the Company to the plan	$ 4.7	$ 3.8	$ 3.3
Vesting period, in years	4

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Commitment And Contingencies (Tables)

12 Months Ended

Sep. 30, 2011

Commitments And Contingencies [Abstract]

Schedule Of Future Minimum Operating Lease Payments, Net Of Sublease Income

	Gross  Lease Payments		Sublease Income		Net Lease Payments
2012		42,317		4,321		37,996
	Gross  Lease Payments		Sublease Income		Net Lease Payments
2013		17,673		2,611		15,062
2014		16,185		338		15,847
2015		15,786		85		15,701
2016		15,072		-		15,072
Thereafter		65,370		-		65,370
	$	172,403	$	7,355	$	165,048

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Stock-Based Compensation (Schedule Of Summary Of Restricted Stock Unit Activity) (Details) (USD $)	1 Months Ended	12 Months Ended
	Aug. 31, 2009	Sep. 30, 2011 Restricted Stock Unit [Member]
Schedule Of Summary Of Restricted Stock Unit Activity [Line Items]
Outstanding Stock Units, Beginning balance		1,985,325
Outstanding Stock Units, Units granted	420,000	908,757
Outstanding Stock Units, Units vested		(1,316,253)
Outstanding Stock Units, Units cancelled		(121,143)
Outstanding Stock Units, Ending balance		1,456,686
Weighted Average Grant Date Fair Value, Beginning balance		$ 62.52
Weighted average grant date fair value, Units granted		$ 94.99
Weighted Average Grant Date Fair Value, Units vested		$ 105.59
Weighted Average Grant Date Fair Value, Units cancelled		$ 56.04
Weighted Average Grant Date Fair Value, Ending balance		$ 44.40

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Balance Sheet Details (Schedule Of Other Long Term Liabilities) (Details) (USD $) In Thousands	Sep. 30, 2011	Sep. 30, 2010
Balance Sheet Details [Abstract]
Income tax accrual	$ 5,675	$ 7,029
Deferred rent and other	12,713	9,124
Total other long-term liabilities	$ 18,388	$ 16,153

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Short-Term And Long-Term Investments (Schedule Of Investments That Have Been In A Continuous Unrealized Loss Position) (Details) (USD $) In Thousands	12 Months Ended
	Sep. 30, 2011
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Continuous Loss Position, Unrealized Loss, Less Than 12 Months	$ 329,278
Fair Value, Continuous Loss Position, Unrealized Loss, 12 Months or Greater	19,572
Fair Value, Continuous Loss Position, Unrealized Loss, Total	348,850
Gross Unrealized Losses, Continuous Loss Position, Less Than 12 Months	(967)
Gross Unrealized Losses, Continuous Loss Position, 12 Months or Greater	(2,009)
Gross Unrealized Losses, Continuous Loss Position, Total	(2,976)
Liquidity days for the securities provided by auction process, minimum	7
Liquidity days for the securities provided by auction process, maximum	35
Corporate Bonds And Notes [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Continuous Loss Position, Unrealized Loss, Less Than 12 Months	133,752
Fair Value, Continuous Loss Position, Unrealized Loss, 12 Months or Greater	4,019
Fair Value, Continuous Loss Position, Unrealized Loss, Total	137,771
Gross Unrealized Losses, Continuous Loss Position, Less Than 12 Months	(751)
Gross Unrealized Losses, Continuous Loss Position, 12 Months or Greater	(11)
Gross Unrealized Losses, Continuous Loss Position, Total	(762)
Municipal Bonds And Notes [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Continuous Loss Position, Unrealized Loss, Less Than 12 Months	24,304
Fair Value, Continuous Loss Position, Unrealized Loss, 12 Months or Greater	2,543
Fair Value, Continuous Loss Position, Unrealized Loss, Total	26,847
Gross Unrealized Losses, Continuous Loss Position, Less Than 12 Months	(38)
Gross Unrealized Losses, Continuous Loss Position, 12 Months or Greater	(8)
Gross Unrealized Losses, Continuous Loss Position, Total	(46)
Auction Rate Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Continuous Loss Position, Unrealized Loss, 12 Months or Greater	13,010
Fair Value, Continuous Loss Position, Unrealized Loss, Total	13,010
Gross Unrealized Losses, Continuous Loss Position, 12 Months or Greater	(1,990)
Gross Unrealized Losses, Continuous Loss Position, Total	(1,990)
U.S. Government Agency Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Continuous Loss Position, Unrealized Loss, Less Than 12 Months	171,222
Fair Value, Continuous Loss Position, Unrealized Loss, Total	171,222
Gross Unrealized Losses, Continuous Loss Position, Less Than 12 Months	(178)
Gross Unrealized Losses, Continuous Loss Position, Total	$ (178)

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Stock-Based Compensation (Schedule Of Outstanding Stock Options Currently Exercisable, Vested And Expected To Vest) (Details) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Sep. 30, 2011		Sep. 30, 2010
Stock-Based Compensation [Abstract]
Stock options outstanding	331,424		483,040
Stock options outstanding, Weighted Average Remaining Contractual Life (in Years)	2.31
Stock options outstanding, Weighted Average Exercise Price per Share	$ 12.66		$ 13.51
Stock options outstanding, Aggregate Intrinsic Value	$ 19,353	[1]
Exercisable, Number of Shares	331,424
Exercisable, Weighted Average Remaining Contractual Life (in Years)	2.31
Exercisable, Weighted Average Exercise Price per Share	$ 12.66
Exercisable, Aggregate Intrinsic Value	19,353	[1]
Vested and expected to vest, Number of Shares	331,424
Vested and expected to vest, Weighted Average Remaining Contractual Life (in Years)	2.31
Vested and expected to vest, Weighted Average Exercise Price per Share	$ 12.66
Vested and expected to vest, Aggregate Intrinsic Value	$ 19,353	[1]

[1] Aggregate intrinsic value represents the difference between the fair value of the Company's common stock underlying these options at September 30, 2011 and the related exercise prices.

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Income Taxes (Schedule Of Tax Effects To Deferred Tax Assets And Liabilities) (Details) (USD $) In Thousands	Sep. 30, 2011	Sep. 30, 2010
Income Taxes [Abstract]
Net operating loss carry-forwards	$ 452	$ 5,672
Allowance for doubtful accounts	898	1,644
Accrued compensation and benefits	4,879	4,003
Inventories and related reserves	1,564	2,063
Stock-based compensation	8,969	6,247
Deferred revenue	19,400	16,260
Other accruals and reserves	9,629	7,829
Depreciation	1,403	5,239
Tax credit carry-forwards	1,657	4,065
Total deferred tax assets before deferred liabilities	48,851	53,022
Deferred tax liabilities, Purchased intangibles and other	(5,698)	(6,391)
Net deferred tax assets	$ 43,153	$ 46,631

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Short-Term And Long-Term Investments

12 Months Ended

Sep. 30, 2011

Short-Term And Long-Term Investments [Abstract]

Short-Term And Long-Term Investments

3.  Short-Term and Long-Term Investments

Short-term investments consist of the following (in thousands):

	Cost or Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
September 30, 2011
Corporate bonds and notes	$	137,087	$	251	$	(182	)	$	137,156
Municipal bonds and notes		82,687		62		(34	)		82,715
U.S. government securities		799		—		—			799
U.S. government agency securities		105,050		55		(9	)		105,096
	$	325,623	$	368	$	(225	)	$	325,766

	Cost or Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
September 30, 2010
Corporate bonds and notes	$	119,829	$	318	$	(23	)	$	120,124
Municipal bonds and notes		76,886		182		(5	)		77,063
U.S. government agency securities		62,390		165		—			62,555
	$	259,105	$	665	$	(28	)	$	259,742

Long-term investments consist of the following (in thousands):

	Cost or Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
September 30, 2011
Corporate bonds and notes	$	141,315	$	415	$	(580	)	$	141,150
Municipal bonds and notes		30,575		151		(12	)		30,714
Auction rate securities		15,000		—		(1,990	)		13,010
U.S. government agency securities		285,334		164		(169	)		285,329
	$	472,224	$	730	$	(2,751	)	$	470,203

	Cost or Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
September 30, 2010
Corporate bonds and notes	$	172,493	$	1,582	$	(22	)	$	174,053
Municipal bonds and notes		22,045		67		(18	)		22,094
Auction rate securities		19,000		—		(2,957	)		16,043
U.S. government agency securities		221,262		200		(82	)		221,380
	$	434,800	$	1,849	$	(3,079	)	$	433,570

The amortized cost and fair value of fixed maturities at September 30, 2011, by contractual years-to-maturity, are presented below (in thousands):

	Cost or Amortized Cost		Fair Value
One year or less	$	325,623	$	325,766
Over one year		472,224		470,203
	$	797,847	$	795,969

The cost or amortized cost values of the Company's fixed maturities include $15.0 million and $19.0 million of available-for-sale ARS as of September 30, 2011 and 2010, respectively.

The following table summarizes investments that have been in a continuous unrealized loss position for less than 12 months and those that have been in a continuous unrealized loss position for more than 12 months as of September 30, 2011 (in thousands):

	Less Than 12 Months					12 Months or Greater					Total
	Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses
September 30, 2011
Corporate bonds and notes	$	133,752	$	(751	)	$	4,019	$	(11	)	$	137,771	$	(762	)
Municipal bonds and notes		24,304		(38	)		2,543		(8	)		26,847		(46	)
Auction rate securities		—		—			13,010		(1,990	)		13,010		(1,990	)
U.S. government agency securities		171,222		(178	)		—		—			171,222		(178	)
Total	$	329,278	$	(967	)	$	19,572	$	(2,009	)	$	348,850	$	(2,976	)

The Company invests in securities that are rated investment grade or better. The unrealized losses on investments for fiscal year 2011 were primarily caused by reductions in the values of the ARS due to the illiquid markets and were partially offset by unrealized gains related to interest rate decreases.

ARS are variable-rate debt securities. The Company limits its investments in ARS to securities that carry an AAA/A- (or equivalent) rating from recognized rating agencies and limits the amount of credit exposure to any one issuer. At the time of the Company's initial investment and at the date of this report, all ARS were in compliance with the Company's investment policy. In the past, the auction process allowed investors to obtain immediate liquidity if so desired by selling the securities at their face amounts. Liquidity for these securities has historically been provided by an auction process that resets interest rates on these investments on average every 7-35 days. However, as has been reported in the financial press, the disruptions in the credit markets adversely affected the auction market for these types of securities.

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Income Taxes (Narrative) (Details) (USD $)	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2009
Tax Credit Carryforward [Line Items]
Undistributed earnings from international subsidiaries	$ 28,700,000
Unrecognized tax benefits, interest expenses accrued	283,000,000	390,000,000	193,000,000
Unrecognized tax benefits, penalties accrued	0	0	0
U.S. [Member]
Tax Credit Carryforward [Line Items]
Operating loss carry-forwards, net	$ 1,200,000

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Summary Of Significant Accounting Policies (Schedule Of Inventories) (Details) (USD $) In Thousands	Sep. 30, 2011	Sep. 30, 2010
Summary Of Significant Accounting Policies [Abstract]
Finished goods	$ 12,917	$ 14,949
Raw materials	4,232	3,866
Inventories, Total	$ 17,149	$ 18,815

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Summary Of Significant Accounting Policies (Narrative) (Details) (USD $)	1 Months Ended			12 Months Ended					12 Months Ended														1 Months Ended				1 Months Ended	12 Months Ended
	Aug. 31, 2011	Aug. 31, 2010	Aug. 31, 2009	Sep. 30, 2011 years	Sep. 30, 2010	Sep. 30, 2009	Sep. 30, 2007 Acopia [Member] Acquired Technology [Member]	Sep. 30, 2006 Swan Labs [Member] Acquired Technology [Member]	Sep. 30, 2011 Acquired Technology [Member]	Sep. 30, 2010 Acquired Technology [Member]	Sep. 30, 2009 Acquired Technology [Member]	Sep. 30, 2011 Customer Relationships, Patents And Trademarks [Member]	Sep. 30, 2010 Customer Relationships, Patents And Trademarks [Member]	Sep. 30, 2009 Customer Relationships, Patents And Trademarks [Member]	Sep. 30, 2011 Avnet Technology Solutions [Member]	Sep. 30, 2010 Avnet Technology Solutions [Member]	Sep. 30, 2011 Ingram Micro, Inc. [Member]	Sep. 30, 2010 Ingram Micro, Inc. [Member]	Sep. 30, 2010 Tech Data [Member]	Sep. 30, 2011 Minimum [Member]	Sep. 30, 2011 Maximum [Member]	Sep. 30, 2011 Restricted Stock Unit [Member]	Nov. 30, 2011 Annual Equity Program [Member]	Aug. 31, 2011 Annual Equity Program [Member]	Aug. 31, 2010 Annual Equity Program [Member]	Sep. 30, 2011 Annual Equity Program [Member]	Aug. 31, 2010 Retention Awards Program [Member]	Sep. 30, 2011 Executive Officers And Board Of Directors [Member]	Sep. 30, 2011 Other Employees [Member]
Schedule Of Summary Of Significant Accounting Policies [Line Items]
Accounts receivable from major customers, percentage															15.00%	13.20%	14.50%	13.20%	11.80%
Estimated useful lives of the assets, minimum, in years				2
Estimated useful lives of the assets, maximum, in years				5
Depreciation and amortization				$ 16,600,000	$ 17,800,000	$ 18,400,000
Capitalized software development costs				0	0	0
Acquired and developed technology and customer relationship assets estimated useful lives				5
Acquired technology in connection with the acquisitions							15,000,000	8,000,000
Amortization expense related to acquired technology									3,100,000	4,600,000	5,300,000
Amortization expense of all other intangible assets												0	0	0
Domestic accounts receivable terms of payment																				30	45
International accounts receivable terms of payment																				30	120
Range of VSOE to median sales price				15.00%
Advertising costs				2,200,000	2,100,000	1,300,000
Stock-based compensation				89,747,000	70,773,000	56,064,000
Unrecognized stock-based compensation cost				$ 105,500,000
Unrecognized stock-based compensation cost, period for recognition, years				2
Rate for grant awarded																												3.00%	9.00%
Stock options granted				0	0	0
Approved RSUs to employees and executive officers by compensation committee				1,718,042																						833,739
Approved RSUs to employees and executive officers pursuant to the Company's annual equity awards program			420,000																			908,757	82,968	170,390	181,334		83,000
Annual equity awards program vesting period			two years	two-year	two-year	two-year																		three years	three years
RSU vesting date for annual equity and retention awards programs		August 1, 2013	August 1, 2011
Percentage of quarterly performance stock grant based on achieving quarterly revenue goal	50.00%	50.00%	50.00%
Percentage of quarterly performance stock grant based on achieving EBITDA goal	50.00%	50.00%	50.00%
Percentage of quarterly revenue goal to be achieved for performance stock grant	80.00%	80.00%	80.00%
Percentage of achievement threshold to which the goals are entitled	80.00%	80.00%	80.00%
Percentage of over-achievement threshold to which the goals are entitled	100.00%	100.00%	100.00%
Percentage of annual equity awards RSU grant subject to performance based vesting	33.33%	33.33%
Percentage of annual equity awards RSU grant subject to performance based vesting in each period	16.66%	16.66%
Percentage of the aggregate number of RSUs granted that vest in equal quarterly increments	50.00%	50.00%	50.00%
Annual equity awards RSU grant subject to achieving specified quarterly revenue and EBITDA goal			twenty-five percent

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Restructuring Charges (Details) (USD $) In Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2009	Sep. 30, 2009
Restructuring Charges [Abstract]
Restructuring charge	$ 4,300	$ 4,329

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Income Taxes (Components Of Income Before Income Taxes) (Details) (USD $) In Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2009	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2009
Income Taxes [Abstract]
United States									$ 342,741	$ 225,698	$ 128,537
International									18,010	11,929	3,111
Income before income taxes	$ 103,418	$ 90,150	$ 84,782	$ 82,401	$ 76,371	$ 63,690	$ 52,149	$ 45,417	$ 360,751	$ 237,627	$ 131,648

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Summary Of Significant Accounting Policies (Schedule Of Property And Equipment) (Details) (USD $) In Thousands	Sep. 30, 2011	Sep. 30, 2010
Summary Of Significant Accounting Policies [Abstract]
Computer equipment	$ 77,899	$ 59,557
Office furniture and equipment	11,243	9,793
Leasehold improvements	41,344	36,462
Property and equipment, gross	130,486	105,812
Accumulated depreciation and amortization	(82,488)	(71,655)
Property and equipment, net	$ 47,998	$ 34,157

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Summary Of Significant Accounting Policies (Schedule Of Assumptions In Determining The Fair Value Of Shares Issued Under The Employee Stock Purchase Plan) (Details)	12 Months Ended
	Sep. 30, 2011 years	Sep. 30, 2010 years	Sep. 30, 2009 years
Summary Of Significant Accounting Policies [Abstract]
Risk-free interest rate	0.10%	0.25%	0.31%
Expected term	0.5	0.5	0.5
Expected volatility	53.87%	41.04%	47.00%

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Fair Value Measurements

12 Months Ended

Sep. 30, 2011

Fair Value Measurements [Abstract]

Fair Value Measurements

2.  Fair Value Measurements

In accordance with the authoritative guidance on fair value measurements and disclosure under GAAP, the Company determines fair value using a fair value hierarchy that distinguishes between market participant assumptions developed based on market data obtained from sources independent of the reporting entity, and the reporting entity's own assumptions about market participant assumptions developed based on the best information available in the circumstances and expands disclosure about fair value measurements.

Fair value is the price that would be received to sell an asset or paid to transfer a liability in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants at the measurement date, essentially the exit price.

The levels of fair value hierarchy are:

Level 1: Quoted prices in active markets for identical assets and liabilities at the measurement date.

Level 2: Observable inputs other than quoted prices included in Level 1, such as quoted prices for similar assets and liabilities in active markets; quoted prices for identical or similar assets and liabilities in markets that are not active; or other inputs that are observable or can be corroborated by observable market data.

Level 3: Unobservable inputs for which there is little or no market data available. These inputs reflect management's assumptions of what market participants would use in pricing the asset or liability.

Level 1 investments are valued based on quoted market prices in active markets and include the Company's cash equivalent investments. Level 2 investments, which include investments that are valued based on quoted prices in markets that are not active, broker or dealer quotations, actual trade data, benchmark yields or alternative pricing sources with reasonable levels of price transparency, include the Company's corporate bonds and notes, municipal bonds and notes, U.S. government securities and U.S. government agency securities. Fair values for the Company's level 2 investments are based on similar assets without applying significant judgments. In addition, all of the Company's level 2 investments have a sufficient level of trading volume to demonstrate that the fair values used are appropriate for these investments.

A financial instrument's level within the fair value hierarchy is based upon the lowest level of any input that is significant to the fair value measurement. However, the determination of what constitutes "observable" requires significant judgment by the Company. The Company considers observable data to be market data which is readily available, regularly distributed or updated, reliable and verifiable, not proprietary, and provided by independent sources that are actively involved in the relevant market.

The Company's financial assets measured at fair value on a recurring basis subject to the disclosure requirements at September 30, 2011, were as follows (in thousands):

	Fair Value Measurements at Reporting Date Using
	Quoted Prices  in Active Markets for Identical Securities (Level 1)		Significant Other  Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Fair Value at September 30, 2011
Cash equivalents	$	33,740	$	—	$	—	$	33,740
Short-term investments
Available-for-sale securities — corporate bonds and notes		—		137,156		—		137,156
Available-for-sale securities — municipal bonds and notes		—		82,715		—		82,715
Available-for-sale securities — U.S. government securities		—		799		—		799
Available-for-sale securities — U.S. government agency securities		—		105,096		—		105,096
Long-term investments
Available-for-sale securities — corporate bonds and notes		—		141,150		—		141,150
Available-for-sale securities — municipal bonds and notes		—		30,714		—		30,714
Available-for-sale securities — U.S. government agency securities		—		285,329		—		285,329
Available-for-sale securities — auction rate securities		—		—		13,010		13,010
Total	$	33,740	$	782,959	$	13,010	$	829,709

The Company's financial assets measured at fair value on a recurring basis subject to the disclosure requirements at September 30, 2010, were as follows (in thousands):

	Fair Value Measurements at Reporting Date Using
	Quoted Prices in Active Markets for Identical Securities (Level 1)		Significant Other  Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Fair Value at September 30, 2010
Cash equivalents	$	26,987	$	—	$	—	$	26,987
Short-term investments
Available-for-sale securities — corporate bonds and notes		—		120,124		—		120,124
Available-for-sale securities — municipal bonds and notes		—		77,063		—		77,063
Available-for-sale securities — U.S. government agency securities		—		62,555		—		62,555
Long-term investments
Available-for-sale securities — corporate bonds and notes		—		174,053		—		174,053
Available-for-sale securities — municipal bonds and notes		—		22,094		—		22,094
Available-for-sale securities — U.S. government agency securities		—		221,380		—		221,380
Available-for-sale securities — auction rate securities		—		—		16,043		16,043
Total	$	26,987	$	677,269	$	16,043	$	720,299

Due to the auction failures of the Company's auction rate securities (ARS) that began in the second quarter of fiscal year 2008, there are still no quoted prices in active markets for similar assets as of September 30, 2011. Therefore, the Company has classified its ARS as level 3 financial assets. The following table provides a reconciliation between the beginning and ending balances of items measured at fair value on a recurring basis in the tables above that used significant unobservable inputs (Level 3) (in thousands):

	2011			2010
Balance, beginning of period	$	16,043		$	41,595
Total gains realized or unrealized:
Included in earnings (other income, net)		—			1,491
Included in other comprehensive income		967			498
Recognition of put option to earnings		—			(1,491	)
Settlements		(4,000	)		(26,050	)
Transfers into and/or out of level 3		—			—
Balance, end of period	$	13,010		$	16,043
Gains attributable to assets still held as of the end of the period		967			498

Financial assets are considered Level 3 when their fair values are determined using pricing models, discounted cash flow methodologies or similar techniques and at least one significant model assumption or input is unobservable or there is limited market activity such that the determination of fair value requires significant judgment or estimation. Level 3 investment securities primarily include certain ARS for which there was a decrease in the observation of market pricing. At September 30, 2011, the values of these securities were estimated primarily using discounted cash flow analysis that incorporated transaction details such as contractual terms, maturity, timing and amount of future cash flows, as well as assumptions about liquidity and credit valuation adjustments of marketplace participants at September 30, 2011.

The Company uses the fair value hierarchy for financial assets and liabilities. The Company's non-financial assets and liabilities, which include goodwill, intangible assets, and long-lived assets, are not required to be carried at fair value on a recurring basis. These non-financial assets and liabilities are measured at fair value on a non-recurring basis when there is an indicator of impairment, and they are recorded at fair value only when impairment is recognized. The Company reviews goodwill and intangible assets for impairment annually, during the second quarter of each fiscal year, or as circumstances indicate the possibility of impairment. The Company monitors the carrying value of long-lived assets for impairment whenever events or changes in circumstances indicate its carrying amount may not be recoverable. During the year ended September 30, 2011, the Company did not recognize any impairment charges related to goodwill, intangible assets, or long-lived assets.

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Summary Of Significant Accounting Policies (Schedule Of Computation Of Basic And Diluted Net Income Per Share) (Details) (USD $) In Thousands, except Per Share data	3 Months Ended								12 Months Ended
	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2009	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2009
Summary Of Significant Accounting Policies [Abstract]
Net income	$ 67,610	$ 62,549	$ 55,575	$ 55,663	$ 48,235	$ 40,495	$ 33,144	$ 29,279	$ 241,397	$ 151,153	$ 91,535
Weighted average shares outstanding - basic	80,317	80,866	80,809	80,644	80,268	79,864	79,394	78,906	80,658	79,609	78,842
Dilutive effect of common shares from stock options and restricted stock units									824	1,440	1,231
Weighted average shares outstanding - diluted	80,766	81,497	81,622	81,648	81,253	81,031	80,737	80,333	81,482	81,049	80,073
Basic net income per share	$ 0.84	$ 0.77	$ 0.69	$ 0.69	$ 0.60	$ 0.51	$ 0.42	$ 0.37	$ 2.99	$ 1.90	$ 1.16
Diluted net income per share	$ 0.84	$ 0.77	$ 0.68	$ 0.68	$ 0.59	$ 0.50	$ 0.41	$ 0.36	$ 2.96	$ 1.86	$ 1.14

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Balance Sheet Details (Schedule Of Estimated Amortization Expense For Intangible Assets) (Details) (USD $) In Thousands	12 Months Ended
	Sep. 30, 2011
Balance Sheet Details [Abstract]
2012	$ 4,428
2013	934
2014	867
2015	867
2016	867
Total estimated amortization expense, intangible assets	$ 7,963

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Stock-Based Compensation (Schedule Of Equity Based Awards (Including Stock Options And Restricted Stock Units)) (Details)	1 Months Ended	12 Months Ended
	Aug. 31, 2009	Sep. 30, 2011 Equity Based Awards [Member]
Schedule Of Equity Based Awards Including Stock Options And Restricted Stock Units [Line Items]
Awards Available for Grant, Beginning balance		4,289,200
Awards Available for Grant, Granted	(420,000)	(908,757)
Awards Available for Grant, Cancelled		125,156
Additional shares reserved (terminated), net		(4,013)
Awards Available for Grant, Ending balance		3,501,586

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Consolidated Balance Sheets (USD $) In Thousands	Sep. 30, 2011	Sep. 30, 2010
ASSETS
Cash and cash equivalents	$ 216,784	$ 168,754
Short-term investments	325,766	259,742
Accounts receivable, net of allowances of $2,898 and $4,319	165,676	112,132
Inventories	17,149	18,815
Deferred tax assets	8,391	8,767
Other current assets	29,907	37,745
Total current assets	763,673	605,955
Property and equipment, net	47,998	34,157
Long-term investments	470,203	433,570
Deferred tax assets	34,762	37,864
Goodwill	234,691	234,700
Other assets, net	17,222	15,946
Total assets	1,568,549	1,362,192
LIABILITIES AND SHAREHOLDERS' EQUITY
Accounts payable	33,525	21,180
Accrued liabilities	67,902	61,768
Deferred revenue	270,880	204,137
Total current liabilities	372,307	287,085
Other long-term liabilities	18,388	16,153
Deferred revenue, long-term	72,418	55,256
Total long-term liabilities	90,806	71,409
Commitments and contingencies (Note 7)
Shareholders' equity
Preferred stock, no par value; 10,000 shares authorized, no shares outstanding
Common stock, no par value; 200,000 shares authorized, 79,145 and 80,355 shares issued and outstanding	380,737	517,215
Accumulated other comprehensive loss	(6,422)	(3,241)
Retained earnings	731,121	489,724
Total shareholders' equity	1,105,436	1,003,698
Total liabilities and shareholders' equity	$ 1,568,549	$ 1,362,192

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Income Taxes (Schedule Of Provision For Income Taxes (Benefit)) (Details) (USD $) In Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2009	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2009
Income Taxes [Abstract]
Current, U.S. federal									$ 103,620	$ 79,802	$ 41,948
Current, State									7,397	4,722	1,631
Current, Foreign									5,743	3,230	1,790
Current, income taxes (benefit)									116,760	87,754	45,369
Deferred, U.S. federal									3,070	(2,049)	(3,317)
Deferred, State									(144)	(1,091)	25
Deferred, Foreign									(332)	1,860	(1,964)
Deferred, income taxes (benefit)									2,594	(1,280)	(5,256)
Income taxes (benefit)	$ 35,808	$ 27,601	$ 29,207	$ 26,738	$ 28,136	$ 23,195	$ 19,005	$ 16,138	$ 119,354	$ 86,474	$ 40,113

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Consolidated Statements Of Cash Flows (USD $) In Thousands	12 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2009
Operating activities
Net income	$ 241,397	$ 151,153	$ 91,535
Adjustments to reconcile net income to net cash provided by operating activities:
Realized gain on disposition of assets and investments	(163)	(125)	(9)
Stock-based compensation	89,747	70,773	56,064
Provisions for doubtful accounts and sales returns	982	1,206	2,638
Depreciation and amortization	20,887	23,833	26,407
Deferred income taxes	4,487	8,243	(6,057)
Gain on auction rate securities put option		(1,491)	(3,901)
Loss on trading auction rate securities		1,491	3,901
Changes in operating assets and liabilities, net of amounts acquired:
Accounts receivable	(54,526)	(6,365)	(12,555)
Inventories	1,666	(4,996)	(3,671)
Other current assets	8,000	(17,064)	(523)
Other assets	81	(1,466)	(226)
Accounts payable and accrued liabilities	20,476	12,157	10,248
Deferred revenue	83,904	76,263	38,130
Net cash provided by operating activities	416,938	313,612	201,981
Investing activities
Purchases of investments	(979,597)	(877,003)	(414,857)
Maturities of investments	812,042	603,825	315,110
Sales of investments	63,977	45,050	13,000
Decrease in restricted cash	19	2,530	13
Acquisition of intangible assets	(5,715)		(706)
Purchases of property and equipment	(30,445)	(12,625)	(11,669)
Net cash used in investing activities	(139,719)	(238,223)	(99,109)
Financing activities
Excess tax benefit (loss) from stock-based compensation	23,623	26,532	(1,958)
Proceeds from the exercise of stock options and purchases of stock under employee stock purchase plan	21,239	31,670	18,688
Repurchase of common stock	(271,526)	(75,000)	(87,436)
Net cash used in financing activities	(226,664)	(16,798)	(70,706)
Net increase in cash and cash equivalents	50,555	58,591	32,166
Effect of exchange rate changes on cash and cash equivalents	(2,525)	(674)	368
Cash and cash equivalents, beginning of year	168,754	110,837	78,303
Cash and cash equivalents, end of year	216,784	168,754	110,837
Supplemental Information
Cash paid for taxes	$ 84,753	$ 67,120	$ 48,586

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Quarterly Results Of Operations (Schedule Of Quarterly Results Of Operations) (Details) (USD $) In Thousands, except Per Share data	3 Months Ended								12 Months Ended
	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2009	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2009
Quarterly Results Of Operations [Abstract]
Products	$ 197,446	$ 179,327	$ 173,710	$ 171,492	$ 164,972	$ 147,393	$ 129,559	$ 119,218	$ 721,975	$ 561,142	$ 406,529
Services	117,169	111,386	103,862	97,442	89,302	83,081	76,509	71,938	429,859	320,830	246,550
Total	314,615	290,713	277,572	268,934	254,274	230,474	206,068	191,156	1,151,834	881,972	653,079
Products	34,485	31,803	31,423	31,614	31,045	29,328	27,419	26,042	129,325	113,834	95,209
Services	21,435	20,645	19,250	17,349	15,783	15,251	13,997	13,087	78,679	58,118	47,517
Total	55,920	52,448	50,673	48,963	46,828	44,579	41,416	39,129	208,004	171,952	142,726
Gross profit	258,695	238,265	226,899	219,971	207,446	185,895	164,652	152,027	943,830	710,020	510,353
Sales and marketing	100,945	93,633	89,332	86,825	80,696	77,219	69,644	65,642	370,735	293,201	225,193
Research and development	36,552	35,245	34,507	32,606	31,571	30,889	29,134	26,720	138,910	118,314	103,664
General and administrative	21,867	21,126	19,846	20,684	18,876	17,658	16,016	15,953	83,523	68,503	55,243
Total	159,364	150,004	143,685	140,115	131,143	125,766	114,794	108,315	593,168	480,018	388,429
Income from operations	99,331	88,261	83,214	79,856	76,303	60,129	49,858	43,712	350,662	230,002	121,924
Other income, net	4,087	1,889	1,568	2,545	68	3,561	2,291	1,705	10,089	7,625	9,724
Income before income taxes	103,418	90,150	84,782	82,401	76,371	63,690	52,149	45,417	360,751	237,627	131,648
Provision for income taxes	35,808	27,601	29,207	26,738	28,136	23,195	19,005	16,138	119,354	86,474	40,113
Net income	$ 67,610	$ 62,549	$ 55,575	$ 55,663	$ 48,235	$ 40,495	$ 33,144	$ 29,279	$ 241,397	$ 151,153	$ 91,535
Net income per share - basic	$ 0.84	$ 0.77	$ 0.69	$ 0.69	$ 0.60	$ 0.51	$ 0.42	$ 0.37	$ 2.99	$ 1.90	$ 1.16
Weighted average shares - basic	80,317	80,866	80,809	80,644	80,268	79,864	79,394	78,906	80,658	79,609	78,842
Net income per share - diluted	$ 0.84	$ 0.77	$ 0.68	$ 0.68	$ 0.59	$ 0.50	$ 0.41	$ 0.36	$ 2.96	$ 1.86	$ 1.14
Weighted average shares outstanding - diluted	80,766	81,497	81,622	81,648	81,253	81,031	80,737	80,333	81,482	81,049	80,073

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Short-Term And Long-Term Investments (Schedule Of Short-Term And Long-Term Investments) (Details) (USD $) In Thousands	Sep. 30, 2011	Sep. 30, 2010
Schedule of Investments [Line Items]
Cost or Amortized Cost	$ 797,847
Fair Value	795,969
Short-Term Investments [Member] | Corporate Bonds And Notes [Member]
Schedule of Investments [Line Items]
Cost or Amortized Cost	137,087	119,829
Gross Unrealized Gains	251	318
Gross Unrealized Losses	(182)	(23)
Fair Value	137,156	120,124
Long-Term Investments [Member] | Corporate Bonds And Notes [Member]
Schedule of Investments [Line Items]
Cost or Amortized Cost	141,315	172,493
Gross Unrealized Gains	415	1,582
Gross Unrealized Losses	(580)	(22)
Fair Value	141,150	174,053
Short-Term Investments [Member] | Municipal Bonds And Notes [Member]
Schedule of Investments [Line Items]
Cost or Amortized Cost	82,687	76,886
Gross Unrealized Gains	62	182
Gross Unrealized Losses	(34)	(5)
Fair Value	82,715	77,063
Long-Term Investments [Member] | Municipal Bonds And Notes [Member]
Schedule of Investments [Line Items]
Cost or Amortized Cost	30,575	22,045
Gross Unrealized Gains	151	67
Gross Unrealized Losses	(12)	(18)
Fair Value	30,714	22,094
Long-Term Investments [Member] | Auction Rate Securities [Member]
Schedule of Investments [Line Items]
Cost or Amortized Cost	15,000	19,000
Gross Unrealized Losses	(1,990)	(2,957)
Fair Value	13,010	16,043
Short-Term Investments [Member] | U.S. Government Securities [Member]
Schedule of Investments [Line Items]
Cost or Amortized Cost	799
Fair Value	799
Short-Term Investments [Member] | U.S. Government Agency Securities [Member]
Schedule of Investments [Line Items]
Cost or Amortized Cost	105,050	62,390
Gross Unrealized Gains	55	165
Gross Unrealized Losses	(9)
Fair Value	105,096	62,555
Long-Term Investments [Member] | U.S. Government Agency Securities [Member]
Schedule of Investments [Line Items]
Cost or Amortized Cost	285,334	221,262
Gross Unrealized Gains	164	200
Gross Unrealized Losses	(169)	(82)
Fair Value	285,329	221,380
Short-Term Investments [Member]
Schedule of Investments [Line Items]
Cost or Amortized Cost	325,623	259,105
Gross Unrealized Gains	368	665
Gross Unrealized Losses	(225)	(28)
Fair Value	325,766	259,742
Long-Term Investments [Member]
Schedule of Investments [Line Items]
Cost or Amortized Cost	472,224	434,800
Gross Unrealized Gains	730	1,849
Gross Unrealized Losses	(2,751)	(3,079)
Fair Value	$ 470,203	$ 433,570

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Balance Sheet Details (Tables)

12 Months Ended

Sep. 30, 2011

Balance Sheet Details [Abstract]

Schedule Of Other Assets

	Years Ended September 30,
	2011		2010
Acquired and developed technology and software development cost	$	8,520	$	6,374
Deposits and other		8,540		9,377
Restricted cash		162		195
	$	17,222	$	15,946

Schedule Of Intangible Assets

	2011							2010
	Gross Carrying Amount		Accumulated Amortization			Net Carrying Amount		Gross Carrying Amount		Accumulated Amortization			Net Carrying Amount
Acquired and developed technology and software development cost	$	39,109	$	(30,589	)	$	8,520	$	33,474	$	(27,100	)	$	6,374
Customer relationships		2,699		(2,314	)		385		2,699		(1,894	)		805
Patents and trademarks		3,044		(2,214	)		830		2,964		(1,832	)		1,132
Trade names		200		(163	)		37		200		(123	)		77
Non-compete covenants		200		(200	)		—		200		(200	)		—
	$	45,252	$	(35,480	)	$	9,772	$	39,537	$	(31,149	)	$	8,388

Schedule Of Estimated Amortization Expense For Intangible Assets

2012	$	4,428
2013		934
2014		867
2015		867
2016		867
	$	7,963

Schedule Of Accrued Liabilities

	Years Ended September 30,
	2011		2010
Payroll and benefits	$	47,824	$	40,904
Sales and marketing		5,062		2,522
Income tax accruals		4,860		2,458
Other		10,156		15,884
	$	67,902	$	61,768

Schedule Of Other Long Term Liabilities

	Years Ended September 30,
	2011		2010
Income tax accrual	$	5,675	$	7,029
Deferred rent and other		12,713		9,124
	$	18,388	$	16,153

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Short-Term And Long-Term Investments (Schedule Of Amortized Cost And Fair Value Of Fixed Maturities By Contractual Years-To-Maturity) (Details) (USD $)	Sep. 30, 2011	Sep. 30, 2010
Short-Term And Long-Term Investments [Abstract]
Cost or Amortized Cost, Fixed Maturities, One year or less	$ 325,623,000
Cost or Amortized Cost, Fixed Maturities, Over one year	472,224,000
Cost or Amortized Cost	797,847,000
Fair Value, Fixed Maturities, One year or less	325,766,000
Fair Value, Fixed Maturities, Over one year	470,203,000
Fair Value	795,969,000
Cost or amortized cost value of fixed maturities available-for-sale ARS	$ 15,000,000	$ 19,000,000

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Stock-Based Compensation (Tables)

12 Months Ended

Sep. 30, 2011

Stock-Based Compensation [Abstract]

Schedule Of Summary Of Restricted Stock Unit Activity

	Outstanding Stock Units			Weighted Average Grant Date Fair Value
Balance, September 30, 2010		1,985,325		$	62.52
Units granted		908,757			94.99
Units vested		(1,316,253	)		105.59
Units cancelled		(121,143	)		56.04
Balance, September 30, 2011		1,456,686		$	44.40

Schedule Of Stock Option Activity

	Options Outstanding
	Number of Shares			Weighted Average Exercise Price per Share
Balance, September 30, 2010		483,040		$	13.51
Options exercised		(150,416	)		15.24
Options cancelled		(1,200	)		33.92
Balance, September 30, 2011		331,424		$	12.66

Schedule Of Outstanding Stock Options Currently Exercisable, Vested And Expected To Vest

	Number of Shares		Weighted Average Remaining Contractual Life (in Years)		Weighted Average Exercise Price per Share		Aggregate Intrinsic Value(1)
	(In thousands)
Stock options outstanding		331,424		2.31	$	12.66	$	19,353
Exercisable		331,424		2.31	$	12.66	$	19,353
Vested and expected to vest		331,424		2.31	$	12.66	$	19,353

(1) Aggregate intrinsic value represents the difference between the fair value of the Company's common stock underlying these options at September 30, 2011 and the related exercise prices.

Schedule Of Equity Based Awards (Including Stock Options And Restricted Stock Units)

	Awards Available for Grant
Balance, September 30, 2010		4,289,200
Granted		(908,757	)
Cancelled		125,156
Additional shares reserved (terminated), net		(4,013	)
Balance, September 30, 2011		3,501,586

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Summary Of Significant Accounting Policies

12 Months Ended

Sep. 30, 2011

Summary Of Significant Accounting Policies [Abstract]

Summary Of Significant Accounting Policies

1.  Summary of Significant Accounting Policies

The Company

F5 Networks, Inc. (the "Company") provides products and services to help companies manage their Internet Protocol (IP) traffic and file storage infrastructure efficiently and securely. The Company's application delivery networking products improve the performance, availability and security of applications on Internet-based networks. Internet traffic between network-based applications and clients passes through these devices where the content is inspected to ensure that it is safe and modified as necessary to ensure that it is delivered securely and in a way that optimizes the performance of both the network and the applications. The Company's storage virtualization products simplify and reduce the cost of managing files and file storage devices, and ensure fast, secure, easy access to files for users and applications. The Company also offers a broad range of services that include consulting, training, maintenance and other technical support services.

Accounting Principles

The Company's consolidated financial statements and accompanying notes are prepared on the accrual basis of accounting in accordance with generally accepted accounting principles in the United States of America (GAAP).

Principles of Consolidation

The consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries. All intercompany accounts and transactions have been eliminated in consolidation.

Reclassifications

Certain reclassifications have been made to prior year balances to conform to the current period presentation. Such reclassifications did not affect total revenues, operating income or net income.

Use of Estimates

The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosures of contingent assets and liabilities as of the date of the financial statements, and the reported amounts of revenues and expenses during the reporting period. Estimates are used in accounting for revenue recognition, reserves for doubtful accounts, product returns, obsolete and excess inventory and valuation allowances on deferred tax assets. Actual results could differ from those estimates.

Cash and Cash Equivalents

The Company considers all highly liquid investments with original maturities of three months or less to be cash equivalents. The Company invests its cash and cash equivalents in deposits with four major financial institutions, which, at times, exceed federally insured limits. The Company has not experienced any losses on its cash and cash equivalents.

Investments

The Company classifies its investment securities as available-for-sale. Investment securities, consisting of corporate and municipal bonds and notes and United States government and agency securities, are reported at fair value with the related unrealized gains and losses included as a component of accumulated other comprehensive income (loss) in shareholders' equity. Realized gains and losses and declines in value of securities judged to be other than temporary are included in other income (expense). The cost of investments for purposes of computing realized and unrealized gains and losses is based on the specific identification method. Investments in securities with maturities of less than one year or where management's intent is to use the investments to fund current operations are classified as short-term investments. Investments with maturities of greater than one year, as well as certain auction rate securities (ARS) that the Company believes it will not be able to liquidate in the next twelve months, are classified as long-term investments.

The Company has ARS that are classified as available-for-sale securities and are reported as long-term. The Company has no intent to sell, won't be required to sell, and believes it will hold these securities until recovery. The Company uses the income approach to estimate the fair value of ARS. The assumptions the Company used in preparing the discounted cash flow model include estimates for interest rates; estimates for discount rates using yields of comparable traded instruments adjusted for illiquidity and other risk factors, amount of anticipated future cash flows and expected holding periods for the ARS.

Concentration of Credit Risk

The Company extends credit to customers and is therefore subject to credit risk. The Company performs initial and ongoing credit evaluations of its customers' financial condition and does not require collateral. An allowance for doubtful accounts is recorded to account for potential bad debts. Estimates are used in determining the allowance for doubtful accounts and are based upon an assessment of selected accounts and as a percentage of remaining accounts receivable by aging category. In determining these percentages, the Company evaluates historical write-offs, and current trends in customer credit quality, as well as changes in credit policies. At September 30, 2011, Avnet Technology Solutions and Ingram Micro, Inc. accounted for 15.0% and 14.5% of the Company's accounts receivable, respectively. At September 30, 2010, Avnet Technology Solutions, Ingram Micro, Inc. and Tech Data accounted for 13.2%, 13.2% and 11.8% of the Company's accounts receivable, respectively.

The Company maintains its cash and investment balances with high credit quality financial institutions. Included within the Company's investment portfolio are investments in ARS. The Company's ARS investments are currently not liquid as a result of continued auction failures. If the issuers are not able to meet their payment obligations or if the Company sells its ARS investments before they recover, the Company may lose some or all of its principal invested or may be required to further reduce the carrying value.

Fair Value of Financial Instruments

Short-term and long-term investments are recorded at fair value as the underlying securities are classified as available-for-sale with any unrealized gain or loss being recorded to other comprehensive income. The fair value for securities held is determined using quoted market prices, broker or dealer quotations, or alternative pricing sources with reasonable levels of price transparency with the exception of ARS, which fair market value is estimated using a discounted cash flow model.

Inventories

The Company outsources the manufacturing of its pre-configured hardware platforms to contract manufacturers, who assemble each product to the Company's specifications. As protection against component shortages and to provide replacement parts for its service teams, the Company also stocks limited supplies of certain key product components. The Company reduces inventory to net realizable value based on excess and obsolete inventories determined primarily by historical usage and forecasted demand. Inventories consist of hardware and related component parts and are recorded at the lower of cost or market (as determined by the first-in, first-out method).

Inventories consist of the following (in thousands):

	Years Ended September 30,
	2011		2010
Finished goods	$	12,917	$	14,949
Raw materials		4,232		3,866
	$	17,149	$	18,815

Property and Equipment

Property and equipment is stated at cost. Depreciation of property and equipment are provided using the straight-line method over the estimated useful lives of the assets, ranging from two to five years. Leasehold improvements are amortized over the lesser of the lease term or the estimated useful life of the improvements. The cost of normal maintenance and repairs is charged to expense as incurred and expenditures for major improvements are capitalized at cost. Gains or losses on the disposition of assets are reflected in the income statements at the time of disposal.

Property and equipment consist of the following (in thousands):

	Years Ended September 30,
	2011			2010
Computer equipment	$	77,899		$	59,557
Office furniture and equipment		11,243			9,793
Leasehold improvements		41,344			36,462
		130,486			105,812
Accumulated depreciation and amortization		(82,488	)		(71,655	)
	$	47,998		$	34,157

Depreciation and amortization expense totaled approximately $16.6 million, $17.8 million, and $18.4 million for the fiscal years ended September 30, 2011, 2010 and 2009, respectively.

Goodwill

Goodwill represents the excess purchase price over the estimated fair value of net assets acquired as of the acquisition date. The Company tests goodwill for impairment on an annual basis and between annual tests when impairment indicators are identified, and goodwill is written down when impaired. Goodwill was recorded in connection with the acquisition of Acopia Networks, Inc. in fiscal year 2007, Swan Labs, Inc. in fiscal year 2006, MagniFire Websystems, Inc. in fiscal year 2004 and uRoam, Inc. in fiscal year 2003.

The Company performs its annual goodwill impairment test during the second fiscal quarter, or whenever events or changes in circumstances indicate that the carrying amount of goodwill may not be recoverable. The first step of the test identifies whether potential impairment may have occurred, while the second step of the test measures the amount of the impairment, if any. Impairment is recognized when the carrying amount of goodwill exceeds its fair value. For its annual goodwill impairment analysis, the Company operates under one reporting unit. The Company determined the fair value of its reporting unit based on the Company's enterprise value. In March 2011, the Company completed its annual impairment test and concluded there was no impairment of goodwill. The Company also considered potential impairment indicators at September 30, 2011 and noted no indicators of impairment.

Other Assets

Other assets primarily consist of software development costs, acquired and developed technology and customer relationships.

Software development costs are charged to research and development expense in the period incurred until technological feasibility is established. Thereafter, until the product is released for sale, software development costs are capitalized and reported at the lower of unamortized cost or net realizable value of each product. Capitalized software development costs are amortized over the remaining estimated economic life of the product. The establishment of technological feasibility and the ongoing assessment of recoverability of costs require considerable judgment by the Company with respect to certain internal and external factors, including, but not limited to, anticipated future gross product revenues, estimated economic life and changes in hardware and software technology. The Company did not capitalize any software development costs in fiscal years 2011, 2010 and 2009. Amortization expense related to capitalized software development was immaterial for fiscal years 2011, 2010, and 2009.

Acquired and developed technology and customer relationship assets are recorded at cost and amortized over their estimated useful lives of five years. The estimated useful life of these assets is assessed and evaluated for reasonableness periodically. Acquired technology of $15.0 million in fiscal 2007 and $8.0 million in fiscal 2006 was recorded in connection with the acquisitions of Acopia and Swan Labs, respectively. Amortization expense related to acquired technology, which is charged to cost of product revenues, totaled $3.1 million, $4.6 million and $5.3 million during the fiscal years 2011, 2010 and 2009, respectively.

Amortization expense of all other intangible assets, including customer relationships, patents and trademarks was not material during the fiscal years 2011, 2010 and 2009.

Impairment of Long-Lived Assets

The Company assesses the impairment of long-lived assets whenever events or changes in business circumstances indicate that the carrying amount of an asset may not be recoverable. When such events occur, management determines whether there has been impairment by comparing the anticipated undiscounted net future cash flows to the related asset's carrying value. If impairment exists, the asset is written down to its estimated fair value. No impairment of long-lived assets was noted as of and for the year ended September 30, 2011.

Revenue Recognition

The Company sells products through distributors, resellers, and directly to end users. Revenue is recognized provided that all of the following criteria have been met:

• Persuasive evidence of an arrangement exists. Evidence of an arrangement generally consists of a purchase order issued pursuant to the terms and conditions of a distributor, reseller or end user agreement.

• Delivery has occurred. The Company uses shipping or related documents, or written evidence of customer acceptance, when applicable, to verify delivery or completion of any performance terms.

• The sales price is fixed or determinable. The Company assesses whether the sales price is fixed or determinable based on payment terms associated with the transaction and whether the sales price is subject to refund or adjustment.

• Collectability is reasonably assured. The Company assesses collectability primarily based on the creditworthiness of the customer as determined by credit checks and related analysis, as well as the Customer's payment history.

In certain regions where the Company does not have the ability to reasonably estimate returns, the Company defers revenue on sales to its distributors until they have received information from the channel partner indicating that the product has been sold to the end-user customer. Payment terms to domestic customers are generally net 30 days to net 45 days. Payment terms to international customers range from net 30 days to net 120 days based on normal and customary trade practices in the individual markets. The Company offers extended payment terms to certain customers, in which case, revenue is recognized when payments are due.

Whenever product, training services and post-contract customer support (PCS) elements are sold together, a portion of the sales price is allocated to each element based on their respective fair values as determined when the individual elements are sold separately. Revenue from the sale of products is recognized when the product has been shipped and the customer is obligated to pay for the product. When rights of return are present and the Company cannot estimate returns, it recognizes revenue when such rights of return lapse. Revenues for PCS are recognized on a straight-line basis over the service contract term. PCS includes a limited period of telephone support updates, repair or replacement of any failed product or component that fails during the term of the agreement, bug fixes and rights to upgrades, when and if available. Consulting services are customarily billed at fixed hourly rates, plus out-of-pocket expenses, and revenues are recognized when the consulting has been completed. Training revenue is recognized when the training has been completed.

In October 2009, the Financial Accounting Standards Board (FASB) amended the accounting standards for revenue recognition to remove from the scope of industry-specific software revenue recognition guidance any tangible products containing software components and non-software components that operate together to deliver the products essential functionality. In addition, the FASB amended the accounting standards for certain multiple element revenue arrangements to:

• Provide updated guidance on whether multiple elements exist, how the elements in an arrangement should be separated, and how the arrangement consideration should be allocated to the separate elements;

• Require an entity to allocate arrangement consideration to each element based on a selling price hierarchy, where the selling price for an element is based on vendor-specific objective evidence (VSOE), if available, third-party evidence (TPE), if available and VSOE is not available; or the best estimate of selling price (BESP), if neither VSOE or TPE is available; and

• Eliminate the use of the residual method and require an entity to allocate arrangement consideration using the selling price hierarchy.

The Company adopted this guidance in the first quarter of fiscal year 2011 on a prospective basis for applicable arrangements originating or materially modified after October 1, 2010. The impact of this adoption was not material to the Company's financial position and results of operations for the fiscal year ended September 30, 2011.

The majority of the Company's products are hardware appliances which contain software essential to the overall functionality of the products. Accordingly, the Company no longer recognizes revenue on sales of these products in accordance with the industry-specific software revenue recognition guidance.

For all transactions entered into prior to the first quarter of fiscal year 2011 and for sales of nonessential and stand-alone software after October 1, 2010, the Company allocates revenue for arrangements with multiple elements based on the software revenue recognition guidance. Software revenue recognition guidance requires revenue earned on software arrangements involving multiple elements to be allocated to each element based on the relative fair values of those elements. The fair value of an element must be based on VSOE. Where fair value of certain elements is not available, revenue is recognized on the "residual method" based on the fair value of undelivered elements. If evidence of the fair value of one or more undelivered elements does not exist, all revenue is deferred and recognized at the earlier of the delivery of those elements or the establishment of fair value of the remaining undelivered elements.

For transactions entered into subsequent to the adoption of the amended revenue recognition standards that are multiple-element arrangements, the arrangement consideration is allocated to each element based on the relative selling prices of all of the elements in the arrangement using the fair value hierarchy in the amended revenue recognition guidance.

Consistent with the methodology used under the previous accounting guidance, the Company establishes VSOE for its products, training services, PCS and consulting services based on the sales price charged for each element when sold separately. The sales price is discounted from the applicable list price based on various factors including the type of customer, volume of sales, geographic region and program level. The Company's list prices are generally not fair value as discounts may be given based on the factors enumerated above. The Company believes that the fair value of its consulting services is represented by the billable consulting rate per hour, based on the rates they charge customers when they purchase standalone consulting services. The price of consulting services is not based on the type of customer, volume of sales, geographic region or program level.

The Company uses historical sales transactions to determine whether VSOE can be established for each of the elements. In most instances, VSOE is the sales price of actual standalone (unbundled) transactions within the past 12 month period that are priced within a reasonable range, which the Company has determined to be plus or minus 15% of the median sales price of each respective price list.

VSOE of PCS is based on standalone sales since the Company does not provide stated renewal rates to its customers. In accordance with the Company's PCS pricing practice (supported by standalone renewal sales), renewal contracts are priced as a percentage of the undiscounted product list price. The PCS renewal percentages may vary, depending on the type and length of PCS purchased. The Company offers standard and premium PCS, and the term generally ranges from one to three years. The Company employs a bell-shaped-curve approach in evaluating VSOE of fair value of PCS. Under this approach, the Company considers VSOE of the fair value of PCS to exist when a substantial majority of its standalone PCS sales fall within a narrow range of pricing.

The Company is typically not able to determine TPE for its products or services. TPE is based on competitor prices for similar elements when sold separately. Generally, the Company's go-to-market strategy differs from that of other competitive products or services in its markets and the Company's offerings contain a significant level of differentiation such that the comparable pricing of products with similar functionality cannot be obtained. Furthermore, the Company is unable to reliably determine the selling prices on a stand-alone basis of similar products offered by its competitors.

When the Company is unable to establish the selling price of its non-software elements using VSOE or TPE, the Company uses BESP in its allocation of arrangement consideration. The objective of BESP is to determine the price at which the Company would transact a sale if the product or service were sold on a stand-alone basis. The Company is generally not able to establish VSOE for non-software product sales. Under software revenue recognition guidance, these product sales were accounted for utilizing the residual method. With the adoption of the new revenue recognition guidance, the Company has been able to establish BESP for non-software product sales through the list price, less a discount deemed appropriate to maintain a reasonable gross margin. Management regularly reviews the gross margin information. Non-software product BESP is determined through our review of historical sales transactions within the past 12 month period. Additional factors considered in determining an appropriate BESP include, but are not limited to, cost of products, pricing practices, geographies, customer classes, and distribution channels.

The Company has established and regularly validates the VSOE of fair value and BESP for elements in its multiple element arrangements. The Company accounts for taxes collected from customers and remitted to governmental authorities on a net basis and excluded from revenues.

Shipping and Handling

Shipping and handling fees charged to the Company's customers are recognized as product revenue in the period shipped and the related costs for providing these services are recorded as a cost of sale.

Guarantees and Product Warranties

In the normal course of business to facilitate sales of its products, the Company indemnifies other parties, including customers, resellers, lessors, and parties to other transactions with the Company, with respect to certain matters. The Company has agreed to hold the other party harmless against losses arising from a breach of representations or covenants, or out of intellectual property infringement or other claims made against certain parties. These agreements may limit the time within which an indemnification claim can be made and the amount of the claim. The Company has entered into indemnification agreements with its officers and directors, and the Company's bylaws contain similar indemnification obligations to the Company's agents. It is not possible to determine the maximum potential amount under these indemnification agreements due to the limited history of prior indemnification claims and the unique facts and circumstances involved in each particular agreement.

The Company offers warranties of one year for hardware for those customers without service contracts, with the option of purchasing additional warranty coverage in yearly increments. The Company accrues for warranty costs as part of its cost of sales based on associated material product costs and technical support labor costs. Accrued warranty costs as of September 30, 2011, 2010 and 2009 were not considered material.

Research and Development

Research and development expenses consist of salaries and related benefits of product development personnel, prototype materials and expenses related to the development of new and improved products, and an allocation of facilities and depreciation expense. Research and development expenses are reflected in the statements of income as incurred.

Advertising

Advertising costs are expensed as incurred. The Company incurred $2.2 million, $2.1 million and $1.3 million in advertising costs during the fiscal years 2011, 2010 and 2009, respectively.

Income Taxes

Deferred income tax assets and liabilities are determined based upon differences between the financial statement and income tax bases of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. The realization of deferred tax assets is based on historical tax positions and estimates of future taxable income. A valuation allowance is recorded when it is more likely than not that some of the deferred tax assets will not be realized.

The Company assesses whether tax benefits claimed or expected to be claimed on a tax return should be recorded in the financial statements. The Company may recognize the tax benefit from an uncertain tax position only if it is more likely than not that the tax position will be sustained on examination by the taxing authorities, including resolution of any related appeals or litigation processes, based on the technical merits of the position. The tax benefits to be recognized in the financial statements from such a position is measured as the largest amount of benefit that has a greater than fifty percent likelihood of being realized upon ultimate settlement. The new guidance also provides guidance on de-recognition, classification, interest and penalties on income taxes, accounting in interim periods and requires increased disclosures.

Foreign Currency

The functional currency for the Company's foreign subsidiaries is the local currency in which the respective entity is located, with the exception of F5 Networks, Ltd., in the United Kingdom that uses the U.S. dollar as its functional currency. An entity's functional currency is determined by the currency of the economic environment in which the majority of cash is generated and expended by the entity. The financial statements of all majority-owned subsidiaries and related entities, with a functional currency other than the U.S. dollar, have been translated into U.S. dollars. All assets and liabilities of the respective entities are translated at year-end exchange rates and all revenues and expenses are translated at average rates during the respective period. Translation adjustments are reported as a separate component of accumulated other comprehensive income (loss) in shareholders' equity.

Foreign currency transaction gains and losses are a result of the effect of exchange rate changes on transactions denominated in currencies other than the functional currency, including U.S. dollars. Gains and losses on those foreign currency transactions are included in determining net income or loss for the period of exchange. The net effect of foreign currency gains and losses was not significant during the fiscal years ended September 30, 2011, 2010 and 2009.

Segments

Management has determined that the Company was organized as, and operated in, one reportable operating segment for fiscal year 2011 and prior years: the development, marketing and sale of application delivery networking products that optimize the security, performance and availability of network applications, servers and storage systems.

Stock-Based Compensation

The Company accounts for stock-based compensation using the straight-line attribution method for recognizing compensation expense. The Company recognized $89.7 million, $70.8 million and $56.1 million of stock-based compensation expense for the fiscal years ended September 30, 2011, 2010 and 2009, respectively. As of September 30, 2011, there was $105.5 million of total unrecognized stock-based compensation cost, the majority of which will be recognized over the next two years. Going forward, stock-based compensation expenses may increase as the Company issues additional equity-based awards to continue to attract and retain key employees.

The Company issues incentive awards to its employees through stock-based compensation consisting of restricted stock units (RSUs). On July 29, 2011, the Company's Compensation Committee approved 833,739 RSUs to employees and executive officers pursuant to the Company's annual equity awards program. The value of RSUs is determined using the fair value method, which in this case, is based on the number of shares granted and the quoted price of the Company's common stock on the date of grant. No stock options were granted in fiscal years 2011, 2010 and 2009. In determining the fair value of shares issued under the Employee Stock Purchase Plan (ESPP), the Company uses the Black-Scholes option pricing model that employs the following key assumptions.

	Employee Stock Purchase Plan Years Ended September 30,
	2011			2010			2009
Risk-free interest rate		0.10	%		0.25	%		0.31	%
Expected dividend		—			—			—
Expected term		0.5 years			0.5 years			0.5 years
Expected volatility		53.87	%		41.04	%		47.00	%

The risk-free rate is based on the U.S. Treasury yield curve in effect at the time of grant. The Company does not anticipate declaring dividends in the foreseeable future. Expected volatility is based on the annualized daily historical volatility of the Company's stock price commensurate with the expected life of the ESPP option. Expected term of the ESPP option is based on an offering period of six months. The assumptions above are based on management's best estimates at that time, which impact the fair value of the ESPP option calculated under the Black-Scholes methodology and, ultimately, the expense that will be recognized over the life of the ESPP option.

The Company recognizes compensation expense for only the portion of restricted stock units that are expected to vest. Therefore, the Company applies estimated forfeiture rates that are derived from historical employee termination behavior. Based on historical differences with forfeitures of stock-based awards granted to the Company's executive officers and Board of Directors versus grants awarded to all other employees, the Company has developed separate forfeiture expectations for these two groups. The estimated forfeiture rate for grants awarded to the Company's executive officers and Board of Directors was approximately 3% and the estimated forfeiture rate for grants awarded to all other employees was approximately 9% in fiscal 2011. If the actual number of forfeitures differs from those estimated by management, additional adjustments to compensation expense may be required in future periods.

In August 2011, the Company granted 170,390 RSUs to certain current executive officers as part of the annual equity awards program. Fifty percent of the aggregate number of RSUs granted as part of the annual equity awards program vest in equal quarterly increments over three years, until such portion of the grant is fully vested on August 1, 2014. One-sixth of the annual equity awards RSU grant, or a portion thereof, is subject to the Company achieving specified quarterly revenue and EBITDA goals during the period beginning in the fourth quarter of fiscal year 2011 through the third quarter of fiscal year 2012. In each case, 50% of the quarterly performance stock grant is based on achieving at least 80% of the quarterly revenue goal and the other 50% is based on achieving at least 80% of the quarterly EBITDA goal. The quarterly performance stock grant is paid linearly above 80% of the targeted goals. At least 100% of both goals must be attained in order for the quarterly performance stock grant to be awarded over 100%. Each goal is evaluated individually and subject to the 80% achievement threshold and 100% over-achievement threshold. The remaining 33.33% of this annual equity awards RSU grant shall be subject to performance based vesting for each of the four quarter periods beginning with the fourth quarters of fiscal years 2012 and 2013 (16.66% in each period). The Compensation Committee of the Board of Directors will set applicable performance targets and vesting formulas for each of these periods.

In August 2010, the Company granted 181,334 and 83,000 RSUs to certain current executive officers as part of the annual equity and retention awards programs, respectively. Fifty percent of the aggregate number of RSUs granted as part of the annual equity awards program vest in equal quarterly increments over three years, until such portion of the grant is fully vested on August 1, 2013. One-sixth of the annual equity awards RSU grant, or a portion thereof, was subject to the Company achieving specified quarterly revenue and EBITDA goals during the period beginning in the fourth quarter of fiscal year 2010 through the third quarter of fiscal year 2011. In each case, 50% of the quarterly performance stock grant is based on achieving at least 80% of the quarterly revenue goal and the other 50% is based on achieving at least 80% of the quarterly EBITDA goal. The quarterly performance stock grant is paid linearly above 80% of the targeted goals. At least 100% of both goals must be attained in order for the quarterly performance stock grant to be awarded over 100%. Each goal is evaluated individually and subject to the 80% achievement threshold and 100% over-achievement threshold. The remaining 33.33% of this annual equity awards RSU grant shall be subject to performance based vesting for each of the four quarter periods beginning with the fourth quarters of fiscal years 2011 and 2012 (16.66% in each period). The Compensation Committee of the Board of Directors will set applicable performance targets and vesting formulas for each of these periods. All RSUs granted as part of the retention awards program fully vest on August 1, 2013.

In August 2009, the Company granted 420,000 RSUs to certain current executive officers. Fifty percent of the aggregate number of RSUs granted at such time vest in equal quarterly increments over two years, until such portion of the grant is fully vested on August 1, 2011. Twenty-five percent of the RSU grant, or a portion thereof, was subject to the Company achieving specified quarterly revenue and EBITDA goals during the period beginning in the fourth quarter of fiscal year 2009 through the third quarter of fiscal year 2010 and the remaining twenty-five percent was subject to the Company achieving specified quarterly revenue and EBITDA goals during the period beginning in the fourth quarter of fiscal year 2010 through the third quarter of fiscal year 2011. In each case, 50% of the quarterly performance stock grant is based on achieving at least 80% of the quarterly revenue goal and the other 50% is based on achieving at least 80% of the quarterly EBITDA goal. The quarterly performance stock grant is paid linearly above 80% of the targeted goals. At least 100% of both goals must be attained in order for the quarterly performance stock grant to be awarded over 100%. Each goal is evaluated individually and subject to the 80% achievement threshold and 100% over-achievement threshold.

The Company recognizes compensation costs for awards with performance conditions when it concludes it is probable that the performance condition will be achieved. The Company reassesses the probability of vesting at each balance sheet date and adjusts compensation costs based on the probability assessment.

In November 2011, as part of the annual review of executive compensation by the Compensation Committee of the Board of Directors and a change in the grant date for the Company's annual equity awards program for the executive officers, the Company granted 82,968 RSUs to certain current executive officers.

Earnings Per Share

Basic net income per share is computed by dividing net income by the weighted average number of common shares outstanding during the period. Diluted net income per share is computed by dividing net income by the weighted average number of common and dilutive common stock equivalent shares outstanding during the period. The Company's nonvested restricted stock awards and restricted stock units do not have nonforfeitable rights to dividends or dividend equivalents.

The following table sets forth the computation of basic and diluted net income per share (in thousands, except per share data):

	Years Ended September 30,
	2011		2010		2009
Numerator
Net income	$	241,397	$	151,153	$	91,535
Denominator
Weighted average shares outstanding — basic		80,658		79,609		78,842
Dilutive effect of common shares from stock options and restricted stock units		824		1,440		1,231
Weighted average shares outstanding — diluted		81,482		81,049		80,073
Basic net income per share	$	2.99	$	1.90	$	1.16
Diluted net income per share	$	2.96	$	1.86	$	1.14

An immaterial amount of common shares potentially issuable from stock options for the years ended September 30, 2011, 2010 and 2009 are excluded from the calculation of diluted earnings per share because the exercise price was greater than the average market price of common stock for the respective period. 

Recent Accounting Pronouncements

In May 2011, the FASB issued ASU 2011-04, Amendments to Achieve Common Fair Value Measurement and Disclosure Requirements in U.S. GAAP and IFRS (ASU 2011-04), which amends current fair value measurement and disclosure guidance to converge with International Financial Reporting Standards (IFRS) and provides increased transparency around valuation inputs and investment categorization. The amendments in this standard are effective for fiscal years, and interim periods within those years beginning after December 15, 2011. The Company will adopt ASU 2011-04 in the first quarter of fiscal 2013 and does not expect the adoption of this standard to have an impact on its consolidated financial statements.

In June 2011, the FASB issued ASU 2011-05, Comprehensive Income, Presentation of Comprehensive Income (ASU 2011-05), which eliminates the option of presenting other comprehensive income as part of the statement of changes in stockholders' equity and instead requires the entity to present other comprehensive income as either a single statement of comprehensive income combined with net income or as two separate but continuous statements. The amendments in this standard are to be applied retrospectively and are effective for fiscal years, and interim periods within those years beginning after December 15, 2011. The Company will adopt ASU 2011-05 in the first quarter of fiscal 2013 and does not expect the adoption of this standard to have an impact on its consolidated financial statements.

In September 2011, the FASB issued ASU 2011-08, Intangibles – Goodwill and Other, Testing Goodwill for Impairment (ASU 2011-08), which simplifies how an entity tests goodwill for impairment by allowing the entity to first assess qualitative factors to determine whether it is necessary to perform the two-step quantitative goodwill impairment test. If an entity determines, as a result of its qualitative assessment, that it is more-likely-than-not that the fair value of a reporting unit is less than its carrying amount, the quantitative impairment test is required. Otherwise, no further testing is required. ASU 2011-08 is effective for annual and interim goodwill impairment tests performed for fiscal years beginning after December 15, 2011, with early adoption permitted. The Company is likely to early adopt this standard for the goodwill impairment test to be performed in fiscal 2012. This standard will impact how the Company assesses goodwill for impairment but will not change the measurement or recognition of a potential goodwill impairment charge.

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Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Per Share data	Sep. 30, 2011	Sep. 30, 2010
Consolidated Balance Sheets [Abstract]
Accounts receivable, allowances	$ 2,898	$ 4,319
Preferred stock, par value	$ 0	$ 0
Preferred stock, shares authorized	10,000	10,000
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0	$ 0
Common stock, shares authorized	200,000	200,000
Common stock, shares issued	79,145	80,355
Common stock, shares outstanding	79,145	80,355

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Quarterly Results Of Operations

12 Months Ended

Sep. 30, 2011

Quarterly Results Of Operations [Abstract]

Quarterly Results Of Operations

11. Quarterly Results of Operations

The following presents the Company's unaudited quarterly results of operations for the eight quarters ended September 30, 2011. The information should be read in conjunction with the Company's financial statements and related notes included elsewhere in this report. This unaudited information has been prepared on the same basis as the audited financial statements and includes all adjustments, consisting only of normal recurring adjustments that were considered necessary for a fair statement of the Company's operating results for the quarters presented.

	Three Months Ended
	Sept. 30, 2011		June 30, 2011		March 31, 2011		Dec. 31, 2010		Sept. 30, 2010		June 30, 2010		March 31, 2010		Dec. 31, 2009
	(Unaudited and in thousands, except per share data)
Net revenues
Products	$	197,446	$	179,327	$	173,710	$	171,492	$	164,972	$	147,393	$	129,559	$	119,218
Services		117,169		111,386		103,862		97,442		89,302		83,081		76,509		71,938
Total		314,615		290,713		277,572		268,934		254,274		230,474		206,068		191,156
Cost of net revenues
Products		34,485		31,803		31,423		31,614		31,045		29,328		27,419		26,042
Services		21,435		20,645		19,250		17,349		15,783		15,251		13,997		13,087
Total		55,920		52,448		50,673		48,963		46,828		44,579		41,416		39,129
Gross profit		258,695		238,265		226,899		219,971		207,446		185,895		164,652		152,027
Operating expenses
Sales and marketing		100,945		93,633		89,332		86,825		80,696		77,219		69,644		65,642
Research and development		36,552		35,245		34,507		32,606		31,571		30,889		29,134		26,720
General and administrative		21,867		21,126		19,846		20,684		18,876		17,658		16,016		15,953
Total operating expenses		159,364		150,004		143,685		140,115		131,143		125,766		114,794		108,315
Income from operations		99,331		88,261		83,214		79,856		76,303		60,129		49,858		43,712
Other income, net		4,087		1,889		1,568		2,545		68		3,561		2,291		1,705
Income before income taxes		103,418		90,150		84,782		82,401		76,371		63,690		52,149		45,417
Provision for income taxes		35,808		27,601		29,207		26,738		28,136		23,195		19,005		16,138
Net income	$	67,610	$	62,549	$	55,575	$	55,663	$	48,235	$	40,495	$	33,144	$	29,279
Net income per share — basic	$	0.84	$	0.77	$	0.69	$	0.69	$	0.60	$	0.51	$	0.42	$	0.37
Weighted average shares — basic		80,317		80,866		80,809		80,644		80,268		79,864		79,394		78,906
Net income per share — diluted	$	0.84	$	0.77	$	0.68	$	0.68	$	0.59	$	0.50	$	0.41	$	0.36
Weighted average shares — diluted		80,766		81,497		81,622		81,648		81,253		81,031		80,737		80,333

XML

Document And Entity Information (USD $)	12 Months Ended
	Sep. 30, 2011	Nov. 17, 2011	Mar. 31, 2011
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Sep. 30, 2011
Document Fiscal Year Focus	2011
Document Fiscal Period Focus	FY
Entity Registrant Name	F5 NETWORKS INC
Entity Central Index Key	0001048695
Current Fiscal Year End Date	--09-30
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Public Float			$ 8,230,608,207
Entity Common Stock, Shares Outstanding		79,484,124

XML

Summary Of Significant Accounting Policies (Policy)

12 Months Ended

Sep. 30, 2011

Summary Of Significant Accounting Policies [Abstract]

Principles Of Consolidation

Principles of Consolidation

The consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries. All intercompany accounts and transactions have been eliminated in consolidation.

Reclassifications

Reclassifications

Certain reclassifications have been made to prior year balances to conform to the current period presentation. Such reclassifications did not affect total revenues, operating income or net income.

Use Of Estimates

Use of Estimates

The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosures of contingent assets and liabilities as of the date of the financial statements, and the reported amounts of revenues and expenses during the reporting period. Estimates are used in accounting for revenue recognition, reserves for doubtful accounts, product returns, obsolete and excess inventory and valuation allowances on deferred tax assets. Actual results could differ from those estimates.

Cash And Cash Equivalents

Cash and Cash Equivalents

The Company considers all highly liquid investments with original maturities of three months or less to be cash equivalents. The Company invests its cash and cash equivalents in deposits with four major financial institutions, which, at times, exceed federally insured limits. The Company has not experienced any losses on its cash and cash equivalents.

Investments

Investments

The Company classifies its investment securities as available-for-sale. Investment securities, consisting of corporate and municipal bonds and notes and United States government and agency securities, are reported at fair value with the related unrealized gains and losses included as a component of accumulated other comprehensive income (loss) in shareholders' equity. Realized gains and losses and declines in value of securities judged to be other than temporary are included in other income (expense). The cost of investments for purposes of computing realized and unrealized gains and losses is based on the specific identification method. Investments in securities with maturities of less than one year or where management's intent is to use the investments to fund current operations are classified as short-term investments. Investments with maturities of greater than one year, as well as certain auction rate securities (ARS) that the Company believes it will not be able to liquidate in the next twelve months, are classified as long-term investments.

The Company has ARS that are classified as available-for-sale securities and are reported as long-term. The Company has no intent to sell, won't be required to sell, and believes it will hold these securities until recovery. The Company uses the income approach to estimate the fair value of ARS. The assumptions the Company used in preparing the discounted cash flow model include estimates for interest rates; estimates for discount rates using yields of comparable traded instruments adjusted for illiquidity and other risk factors, amount of anticipated future cash flows and expected holding periods for the ARS.

Concentration Of Credit Risk

Concentration of Credit Risk

The Company extends credit to customers and is therefore subject to credit risk. The Company performs initial and ongoing credit evaluations of its customers' financial condition and does not require collateral. An allowance for doubtful accounts is recorded to account for potential bad debts. Estimates are used in determining the allowance for doubtful accounts and are based upon an assessment of selected accounts and as a percentage of remaining accounts receivable by aging category. In determining these percentages, the Company evaluates historical write-offs, and current trends in customer credit quality, as well as changes in credit policies. At September 30, 2011, Avnet Technology Solutions and Ingram Micro, Inc. accounted for 15.0% and 14.5% of the Company's accounts receivable, respectively. At September 30, 2010, Avnet Technology Solutions, Ingram Micro, Inc. and Tech Data accounted for 13.2%, 13.2% and 11.8% of the Company's accounts receivable, respectively.

The Company maintains its cash and investment balances with high credit quality financial institutions. Included within the Company's investment portfolio are investments in ARS. The Company's ARS investments are currently not liquid as a result of continued auction failures. If the issuers are not able to meet their payment obligations or if the Company sells its ARS investments before they recover, the Company may lose some or all of its principal invested or may be required to further reduce the carrying value.

Fair Value Of Financial Instruments

Fair Value of Financial Instruments

Short-term and long-term investments are recorded at fair value as the underlying securities are classified as available-for-sale with any unrealized gain or loss being recorded to other comprehensive income. The fair value for securities held is determined using quoted market prices, broker or dealer quotations, or alternative pricing sources with reasonable levels of price transparency with the exception of ARS, which fair market value is estimated using a discounted cash flow model.

Inventories

Inventories

The Company outsources the manufacturing of its pre-configured hardware platforms to contract manufacturers, who assemble each product to the Company's specifications. As protection against component shortages and to provide replacement parts for its service teams, the Company also stocks limited supplies of certain key product components. The Company reduces inventory to net realizable value based on excess and obsolete inventories determined primarily by historical usage and forecasted demand. Inventories consist of hardware and related component parts and are recorded at the lower of cost or market (as determined by the first-in, first-out method).

Inventories consist of the following (in thousands):

	Years Ended September 30,
	2011		2010
Finished goods	$	12,917	$	14,949
Raw materials		4,232		3,866
	$	17,149	$	18,815

Property And Equipment

Property and Equipment

Property and equipment is stated at cost. Depreciation of property and equipment are provided using the straight-line method over the estimated useful lives of the assets, ranging from two to five years. Leasehold improvements are amortized over the lesser of the lease term or the estimated useful life of the improvements. The cost of normal maintenance and repairs is charged to expense as incurred and expenditures for major improvements are capitalized at cost. Gains or losses on the disposition of assets are reflected in the income statements at the time of disposal.

Property and equipment consist of the following (in thousands):

	Years Ended September 30,
	2011			2010
Computer equipment	$	77,899		$	59,557
Office furniture and equipment		11,243			9,793
Leasehold improvements		41,344			36,462
		130,486			105,812
Accumulated depreciation and amortization		(82,488	)		(71,655	)
	$	47,998		$	34,157

Depreciation and amortization expense totaled approximately $16.6 million, $17.8 million, and $18.4 million for the fiscal years ended September 30, 2011, 2010 and 2009, respectively.

Goodwill

Goodwill

Goodwill represents the excess purchase price over the estimated fair value of net assets acquired as of the acquisition date. The Company tests goodwill for impairment on an annual basis and between annual tests when impairment indicators are identified, and goodwill is written down when impaired. Goodwill was recorded in connection with the acquisition of Acopia Networks, Inc. in fiscal year 2007, Swan Labs, Inc. in fiscal year 2006, MagniFire Websystems, Inc. in fiscal year 2004 and uRoam, Inc. in fiscal year 2003.

The Company performs its annual goodwill impairment test during the second fiscal quarter, or whenever events or changes in circumstances indicate that the carrying amount of goodwill may not be recoverable. The first step of the test identifies whether potential impairment may have occurred, while the second step of the test measures the amount of the impairment, if any. Impairment is recognized when the carrying amount of goodwill exceeds its fair value. For its annual goodwill impairment analysis, the Company operates under one reporting unit. The Company determined the fair value of its reporting unit based on the Company's enterprise value. In March 2011, the Company completed its annual impairment test and concluded there was no impairment of goodwill. The Company also considered potential impairment indicators at September 30, 2011 and noted no indicators of impairment.

Other Assets

Other Assets

Other assets primarily consist of software development costs, acquired and developed technology and customer relationships.

Software development costs are charged to research and development expense in the period incurred until technological feasibility is established. Thereafter, until the product is released for sale, software development costs are capitalized and reported at the lower of unamortized cost or net realizable value of each product. Capitalized software development costs are amortized over the remaining estimated economic life of the product. The establishment of technological feasibility and the ongoing assessment of recoverability of costs require considerable judgment by the Company with respect to certain internal and external factors, including, but not limited to, anticipated future gross product revenues, estimated economic life and changes in hardware and software technology. The Company did not capitalize any software development costs in fiscal years 2011, 2010 and 2009. Amortization expense related to capitalized software development was immaterial for fiscal years 2011, 2010, and 2009.

Acquired and developed technology and customer relationship assets are recorded at cost and amortized over their estimated useful lives of five years. The estimated useful life of these assets is assessed and evaluated for reasonableness periodically. Acquired technology of $15.0 million in fiscal 2007 and $8.0 million in fiscal 2006 was recorded in connection with the acquisitions of Acopia and Swan Labs, respectively. Amortization expense related to acquired technology, which is charged to cost of product revenues, totaled $3.1 million, $4.6 million and $5.3 million during the fiscal years 2011, 2010 and 2009, respectively.

Amortization expense of all other intangible assets, including customer relationships, patents and trademarks was not material during the fiscal years 2011, 2010 and 2009.

Impairment Of Long-Lived Assets

Impairment of Long-Lived Assets

The Company assesses the impairment of long-lived assets whenever events or changes in business circumstances indicate that the carrying amount of an asset may not be recoverable. When such events occur, management determines whether there has been impairment by comparing the anticipated undiscounted net future cash flows to the related asset's carrying value. If impairment exists, the asset is written down to its estimated fair value. No impairment of long-lived assets was noted as of and for the year ended September 30, 2011.

Revenue Recognition

Revenue Recognition

The Company sells products through distributors, resellers, and directly to end users. Revenue is recognized provided that all of the following criteria have been met:

• Persuasive evidence of an arrangement exists. Evidence of an arrangement generally consists of a purchase order issued pursuant to the terms and conditions of a distributor, reseller or end user agreement.

• Delivery has occurred. The Company uses shipping or related documents, or written evidence of customer acceptance, when applicable, to verify delivery or completion of any performance terms.

• The sales price is fixed or determinable. The Company assesses whether the sales price is fixed or determinable based on payment terms associated with the transaction and whether the sales price is subject to refund or adjustment.

• Collectability is reasonably assured. The Company assesses collectability primarily based on the creditworthiness of the customer as determined by credit checks and related analysis, as well as the Customer's payment history.

In certain regions where the Company does not have the ability to reasonably estimate returns, the Company defers revenue on sales to its distributors until they have received information from the channel partner indicating that the product has been sold to the end-user customer. Payment terms to domestic customers are generally net 30 days to net 45 days. Payment terms to international customers range from net 30 days to net 120 days based on normal and customary trade practices in the individual markets. The Company offers extended payment terms to certain customers, in which case, revenue is recognized when payments are due.

Whenever product, training services and post-contract customer support (PCS) elements are sold together, a portion of the sales price is allocated to each element based on their respective fair values as determined when the individual elements are sold separately. Revenue from the sale of products is recognized when the product has been shipped and the customer is obligated to pay for the product. When rights of return are present and the Company cannot estimate returns, it recognizes revenue when such rights of return lapse. Revenues for PCS are recognized on a straight-line basis over the service contract term. PCS includes a limited period of telephone support updates, repair or replacement of any failed product or component that fails during the term of the agreement, bug fixes and rights to upgrades, when and if available. Consulting services are customarily billed at fixed hourly rates, plus out-of-pocket expenses, and revenues are recognized when the consulting has been completed. Training revenue is recognized when the training has been completed.

In October 2009, the Financial Accounting Standards Board (FASB) amended the accounting standards for revenue recognition to remove from the scope of industry-specific software revenue recognition guidance any tangible products containing software components and non-software components that operate together to deliver the products essential functionality. In addition, the FASB amended the accounting standards for certain multiple element revenue arrangements to:

• Provide updated guidance on whether multiple elements exist, how the elements in an arrangement should be separated, and how the arrangement consideration should be allocated to the separate elements;

• Require an entity to allocate arrangement consideration to each element based on a selling price hierarchy, where the selling price for an element is based on vendor-specific objective evidence (VSOE), if available, third-party evidence (TPE), if available and VSOE is not available; or the best estimate of selling price (BESP), if neither VSOE or TPE is available; and

• Eliminate the use of the residual method and require an entity to allocate arrangement consideration using the selling price hierarchy.

The Company adopted this guidance in the first quarter of fiscal year 2011 on a prospective basis for applicable arrangements originating or materially modified after October 1, 2010. The impact of this adoption was not material to the Company's financial position and results of operations for the fiscal year ended September 30, 2011.

The majority of the Company's products are hardware appliances which contain software essential to the overall functionality of the products. Accordingly, the Company no longer recognizes revenue on sales of these products in accordance with the industry-specific software revenue recognition guidance.

For all transactions entered into prior to the first quarter of fiscal year 2011 and for sales of nonessential and stand-alone software after October 1, 2010, the Company allocates revenue for arrangements with multiple elements based on the software revenue recognition guidance. Software revenue recognition guidance requires revenue earned on software arrangements involving multiple elements to be allocated to each element based on the relative fair values of those elements. The fair value of an element must be based on VSOE. Where fair value of certain elements is not available, revenue is recognized on the "residual method" based on the fair value of undelivered elements. If evidence of the fair value of one or more undelivered elements does not exist, all revenue is deferred and recognized at the earlier of the delivery of those elements or the establishment of fair value of the remaining undelivered elements.

For transactions entered into subsequent to the adoption of the amended revenue recognition standards that are multiple-element arrangements, the arrangement consideration is allocated to each element based on the relative selling prices of all of the elements in the arrangement using the fair value hierarchy in the amended revenue recognition guidance.

Consistent with the methodology used under the previous accounting guidance, the Company establishes VSOE for its products, training services, PCS and consulting services based on the sales price charged for each element when sold separately. The sales price is discounted from the applicable list price based on various factors including the type of customer, volume of sales, geographic region and program level. The Company's list prices are generally not fair value as discounts may be given based on the factors enumerated above. The Company believes that the fair value of its consulting services is represented by the billable consulting rate per hour, based on the rates they charge customers when they purchase standalone consulting services. The price of consulting services is not based on the type of customer, volume of sales, geographic region or program level.

The Company uses historical sales transactions to determine whether VSOE can be established for each of the elements. In most instances, VSOE is the sales price of actual standalone (unbundled) transactions within the past 12 month period that are priced within a reasonable range, which the Company has determined to be plus or minus 15% of the median sales price of each respective price list.

VSOE of PCS is based on standalone sales since the Company does not provide stated renewal rates to its customers. In accordance with the Company's PCS pricing practice (supported by standalone renewal sales), renewal contracts are priced as a percentage of the undiscounted product list price. The PCS renewal percentages may vary, depending on the type and length of PCS purchased. The Company offers standard and premium PCS, and the term generally ranges from one to three years. The Company employs a bell-shaped-curve approach in evaluating VSOE of fair value of PCS. Under this approach, the Company considers VSOE of the fair value of PCS to exist when a substantial majority of its standalone PCS sales fall within a narrow range of pricing.

The Company is typically not able to determine TPE for its products or services. TPE is based on competitor prices for similar elements when sold separately. Generally, the Company's go-to-market strategy differs from that of other competitive products or services in its markets and the Company's offerings contain a significant level of differentiation such that the comparable pricing of products with similar functionality cannot be obtained. Furthermore, the Company is unable to reliably determine the selling prices on a stand-alone basis of similar products offered by its competitors.

When the Company is unable to establish the selling price of its non-software elements using VSOE or TPE, the Company uses BESP in its allocation of arrangement consideration. The objective of BESP is to determine the price at which the Company would transact a sale if the product or service were sold on a stand-alone basis. The Company is generally not able to establish VSOE for non-software product sales. Under software revenue recognition guidance, these product sales were accounted for utilizing the residual method. With the adoption of the new revenue recognition guidance, the Company has been able to establish BESP for non-software product sales through the list price, less a discount deemed appropriate to maintain a reasonable gross margin. Management regularly reviews the gross margin information. Non-software product BESP is determined through our review of historical sales transactions within the past 12 month period. Additional factors considered in determining an appropriate BESP include, but are not limited to, cost of products, pricing practices, geographies, customer classes, and distribution channels.

The Company has established and regularly validates the VSOE of fair value and BESP for elements in its multiple element arrangements. The Company accounts for taxes collected from customers and remitted to governmental authorities on a net basis and excluded from revenues.

Shipping And Handling

Shipping and Handling

Shipping and handling fees charged to the Company's customers are recognized as product revenue in the period shipped and the related costs for providing these services are recorded as a cost of sale.

Guarantees And Product Warranties

Guarantees and Product Warranties

In the normal course of business to facilitate sales of its products, the Company indemnifies other parties, including customers, resellers, lessors, and parties to other transactions with the Company, with respect to certain matters. The Company has agreed to hold the other party harmless against losses arising from a breach of representations or covenants, or out of intellectual property infringement or other claims made against certain parties. These agreements may limit the time within which an indemnification claim can be made and the amount of the claim. The Company has entered into indemnification agreements with its officers and directors, and the Company's bylaws contain similar indemnification obligations to the Company's agents. It is not possible to determine the maximum potential amount under these indemnification agreements due to the limited history of prior indemnification claims and the unique facts and circumstances involved in each particular agreement.

The Company offers warranties of one year for hardware for those customers without service contracts, with the option of purchasing additional warranty coverage in yearly increments. The Company accrues for warranty costs as part of its cost of sales based on associated material product costs and technical support labor costs. Accrued warranty costs as of September 30, 2011, 2010 and 2009 were not considered material.

Research And Development

Research and Development

Research and development expenses consist of salaries and related benefits of product development personnel, prototype materials and expenses related to the development of new and improved products, and an allocation of facilities and depreciation expense. Research and development expenses are reflected in the statements of income as incurred.

Advertising

Advertising

Advertising costs are expensed as incurred. The Company incurred $2.2 million, $2.1 million and $1.3 million in advertising costs during the fiscal years 2011, 2010 and 2009, respectively.

Income Taxes

Income Taxes

Deferred income tax assets and liabilities are determined based upon differences between the financial statement and income tax bases of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. The realization of deferred tax assets is based on historical tax positions and estimates of future taxable income. A valuation allowance is recorded when it is more likely than not that some of the deferred tax assets will not be realized.

The Company assesses whether tax benefits claimed or expected to be claimed on a tax return should be recorded in the financial statements. The Company may recognize the tax benefit from an uncertain tax position only if it is more likely than not that the tax position will be sustained on examination by the taxing authorities, including resolution of any related appeals or litigation processes, based on the technical merits of the position. The tax benefits to be recognized in the financial statements from such a position is measured as the largest amount of benefit that has a greater than fifty percent likelihood of being realized upon ultimate settlement. The new guidance also provides guidance on de-recognition, classification, interest and penalties on income taxes, accounting in interim periods and requires increased disclosures.

Foreign Currency

Foreign Currency

The functional currency for the Company's foreign subsidiaries is the local currency in which the respective entity is located, with the exception of F5 Networks, Ltd., in the United Kingdom that uses the U.S. dollar as its functional currency. An entity's functional currency is determined by the currency of the economic environment in which the majority of cash is generated and expended by the entity. The financial statements of all majority-owned subsidiaries and related entities, with a functional currency other than the U.S. dollar, have been translated into U.S. dollars. All assets and liabilities of the respective entities are translated at year-end exchange rates and all revenues and expenses are translated at average rates during the respective period. Translation adjustments are reported as a separate component of accumulated other comprehensive income (loss) in shareholders' equity.

Foreign currency transaction gains and losses are a result of the effect of exchange rate changes on transactions denominated in currencies other than the functional currency, including U.S. dollars. Gains and losses on those foreign currency transactions are included in determining net income or loss for the period of exchange. The net effect of foreign currency gains and losses was not significant during the fiscal years ended September 30, 2011, 2010 and 2009.

Segments

Segments

Management has determined that the Company was organized as, and operated in, one reportable operating segment for fiscal year 2011 and prior years: the development, marketing and sale of application delivery networking products that optimize the security, performance and availability of network applications, servers and storage systems.

Stock-Based Compensation

Stock-Based Compensation

The Company accounts for stock-based compensation using the straight-line attribution method for recognizing compensation expense. The Company recognized $89.7 million, $70.8 million and $56.1 million of stock-based compensation expense for the fiscal years ended September 30, 2011, 2010 and 2009, respectively. As of September 30, 2011, there was $105.5 million of total unrecognized stock-based compensation cost, the majority of which will be recognized over the next two years. Going forward, stock-based compensation expenses may increase as the Company issues additional equity-based awards to continue to attract and retain key employees.

The Company issues incentive awards to its employees through stock-based compensation consisting of restricted stock units (RSUs). On July 29, 2011, the Company's Compensation Committee approved 833,739 RSUs to employees and executive officers pursuant to the Company's annual equity awards program. The value of RSUs is determined using the fair value method, which in this case, is based on the number of shares granted and the quoted price of the Company's common stock on the date of grant. No stock options were granted in fiscal years 2011, 2010 and 2009. In determining the fair value of shares issued under the Employee Stock Purchase Plan (ESPP), the Company uses the Black-Scholes option pricing model that employs the following key assumptions.

	Employee Stock Purchase Plan Years Ended September 30,
	2011			2010			2009
Risk-free interest rate		0.10	%		0.25	%		0.31	%
Expected dividend		—			—			—
Expected term		0.5 years			0.5 years			0.5 years
Expected volatility		53.87	%		41.04	%		47.00	%

The risk-free rate is based on the U.S. Treasury yield curve in effect at the time of grant. The Company does not anticipate declaring dividends in the foreseeable future. Expected volatility is based on the annualized daily historical volatility of the Company's stock price commensurate with the expected life of the ESPP option. Expected term of the ESPP option is based on an offering period of six months. The assumptions above are based on management's best estimates at that time, which impact the fair value of the ESPP option calculated under the Black-Scholes methodology and, ultimately, the expense that will be recognized over the life of the ESPP option.

The Company recognizes compensation expense for only the portion of restricted stock units that are expected to vest. Therefore, the Company applies estimated forfeiture rates that are derived from historical employee termination behavior. Based on historical differences with forfeitures of stock-based awards granted to the Company's executive officers and Board of Directors versus grants awarded to all other employees, the Company has developed separate forfeiture expectations for these two groups. The estimated forfeiture rate for grants awarded to the Company's executive officers and Board of Directors was approximately 3% and the estimated forfeiture rate for grants awarded to all other employees was approximately 9% in fiscal 2011. If the actual number of forfeitures differs from those estimated by management, additional adjustments to compensation expense may be required in future periods.

In August 2011, the Company granted 170,390 RSUs to certain current executive officers as part of the annual equity awards program. Fifty percent of the aggregate number of RSUs granted as part of the annual equity awards program vest in equal quarterly increments over three years, until such portion of the grant is fully vested on August 1, 2014. One-sixth of the annual equity awards RSU grant, or a portion thereof, is subject to the Company achieving specified quarterly revenue and EBITDA goals during the period beginning in the fourth quarter of fiscal year 2011 through the third quarter of fiscal year 2012. In each case, 50% of the quarterly performance stock grant is based on achieving at least 80% of the quarterly revenue goal and the other 50% is based on achieving at least 80% of the quarterly EBITDA goal. The quarterly performance stock grant is paid linearly above 80% of the targeted goals. At least 100% of both goals must be attained in order for the quarterly performance stock grant to be awarded over 100%. Each goal is evaluated individually and subject to the 80% achievement threshold and 100% over-achievement threshold. The remaining 33.33% of this annual equity awards RSU grant shall be subject to performance based vesting for each of the four quarter periods beginning with the fourth quarters of fiscal years 2012 and 2013 (16.66% in each period). The Compensation Committee of the Board of Directors will set applicable performance targets and vesting formulas for each of these periods.

In August 2010, the Company granted 181,334 and 83,000 RSUs to certain current executive officers as part of the annual equity and retention awards programs, respectively. Fifty percent of the aggregate number of RSUs granted as part of the annual equity awards program vest in equal quarterly increments over three years, until such portion of the grant is fully vested on August 1, 2013. One-sixth of the annual equity awards RSU grant, or a portion thereof, was subject to the Company achieving specified quarterly revenue and EBITDA goals during the period beginning in the fourth quarter of fiscal year 2010 through the third quarter of fiscal year 2011. In each case, 50% of the quarterly performance stock grant is based on achieving at least 80% of the quarterly revenue goal and the other 50% is based on achieving at least 80% of the quarterly EBITDA goal. The quarterly performance stock grant is paid linearly above 80% of the targeted goals. At least 100% of both goals must be attained in order for the quarterly performance stock grant to be awarded over 100%. Each goal is evaluated individually and subject to the 80% achievement threshold and 100% over-achievement threshold. The remaining 33.33% of this annual equity awards RSU grant shall be subject to performance based vesting for each of the four quarter periods beginning with the fourth quarters of fiscal years 2011 and 2012 (16.66% in each period). The Compensation Committee of the Board of Directors will set applicable performance targets and vesting formulas for each of these periods. All RSUs granted as part of the retention awards program fully vest on August 1, 2013.

In August 2009, the Company granted 420,000 RSUs to certain current executive officers. Fifty percent of the aggregate number of RSUs granted at such time vest in equal quarterly increments over two years, until such portion of the grant is fully vested on August 1, 2011. Twenty-five percent of the RSU grant, or a portion thereof, was subject to the Company achieving specified quarterly revenue and EBITDA goals during the period beginning in the fourth quarter of fiscal year 2009 through the third quarter of fiscal year 2010 and the remaining twenty-five percent was subject to the Company achieving specified quarterly revenue and EBITDA goals during the period beginning in the fourth quarter of fiscal year 2010 through the third quarter of fiscal year 2011. In each case, 50% of the quarterly performance stock grant is based on achieving at least 80% of the quarterly revenue goal and the other 50% is based on achieving at least 80% of the quarterly EBITDA goal. The quarterly performance stock grant is paid linearly above 80% of the targeted goals. At least 100% of both goals must be attained in order for the quarterly performance stock grant to be awarded over 100%. Each goal is evaluated individually and subject to the 80% achievement threshold and 100% over-achievement threshold.

The Company recognizes compensation costs for awards with performance conditions when it concludes it is probable that the performance condition will be achieved. The Company reassesses the probability of vesting at each balance sheet date and adjusts compensation costs based on the probability assessment.

In November 2011, as part of the annual review of executive compensation by the Compensation Committee of the Board of Directors and a change in the grant date for the Company's annual equity awards program for the executive officers, the Company granted 82,968 RSUs to certain current executive officers.

Earnings Per Share

Earnings Per Share

Basic net income per share is computed by dividing net income by the weighted average number of common shares outstanding during the period. Diluted net income per share is computed by dividing net income by the weighted average number of common and dilutive common stock equivalent shares outstanding during the period. The Company's nonvested restricted stock awards and restricted stock units do not have nonforfeitable rights to dividends or dividend equivalents.

The following table sets forth the computation of basic and diluted net income per share (in thousands, except per share data):

	Years Ended September 30,
	2011		2010		2009
Numerator
Net income	$	241,397	$	151,153	$	91,535
Denominator
Weighted average shares outstanding — basic		80,658		79,609		78,842
Dilutive effect of common shares from stock options and restricted stock units		824		1,440		1,231
Weighted average shares outstanding — diluted		81,482		81,049		80,073
Basic net income per share	$	2.99	$	1.90	$	1.16
Diluted net income per share	$	2.96	$	1.86	$	1.14

An immaterial amount of common shares potentially issuable from stock options for the years ended September 30, 2011, 2010 and 2009 are excluded from the calculation of diluted earnings per share because the exercise price was greater than the average market price of common stock for the respective period. 

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Consolidated Income Statements (USD $) In Thousands, except Per Share data	3 Months Ended									12 Months Ended
	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2009	Mar. 31, 2009	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2009
Net revenues
Products	$ 197,446	$ 179,327	$ 173,710	$ 171,492	$ 164,972	$ 147,393	$ 129,559	$ 119,218		$ 721,975	$ 561,142	$ 406,529
Services	117,169	111,386	103,862	97,442	89,302	83,081	76,509	71,938		429,859	320,830	246,550
Total	314,615	290,713	277,572	268,934	254,274	230,474	206,068	191,156		1,151,834	881,972	653,079
Cost of net revenues
Products	34,485	31,803	31,423	31,614	31,045	29,328	27,419	26,042		129,325	113,834	95,209
Services	21,435	20,645	19,250	17,349	15,783	15,251	13,997	13,087		78,679	58,118	47,517
Total	55,920	52,448	50,673	48,963	46,828	44,579	41,416	39,129		208,004	171,952	142,726
Gross profit	258,695	238,265	226,899	219,971	207,446	185,895	164,652	152,027		943,830	710,020	510,353
Operating expenses
Sales and marketing	100,945	93,633	89,332	86,825	80,696	77,219	69,644	65,642		370,735	293,201	225,193
Research and development	36,552	35,245	34,507	32,606	31,571	30,889	29,134	26,720		138,910	118,314	103,664
General and administrative	21,867	21,126	19,846	20,684	18,876	17,658	16,016	15,953		83,523	68,503	55,243
Restructuring charges									4,300			4,329
Total	159,364	150,004	143,685	140,115	131,143	125,766	114,794	108,315		593,168	480,018	388,429
Income from operations	99,331	88,261	83,214	79,856	76,303	60,129	49,858	43,712		350,662	230,002	121,924
Other income, net	4,087	1,889	1,568	2,545	68	3,561	2,291	1,705		10,089	7,625	9,724
Income before income taxes	103,418	90,150	84,782	82,401	76,371	63,690	52,149	45,417		360,751	237,627	131,648
Provision for income taxes	35,808	27,601	29,207	26,738	28,136	23,195	19,005	16,138		119,354	86,474	40,113
Net income	$ 67,610	$ 62,549	$ 55,575	$ 55,663	$ 48,235	$ 40,495	$ 33,144	$ 29,279		$ 241,397	$ 151,153	$ 91,535
Net income per share - basic	$ 0.84	$ 0.77	$ 0.69	$ 0.69	$ 0.60	$ 0.51	$ 0.42	$ 0.37		$ 2.99	$ 1.90	$ 1.16
Weighted average shares - basic	80,317	80,866	80,809	80,644	80,268	79,864	79,394	78,906		80,658	79,609	78,842
Net income per share - diluted	$ 0.84	$ 0.77	$ 0.68	$ 0.68	$ 0.59	$ 0.50	$ 0.41	$ 0.36		$ 2.96	$ 1.86	$ 1.14
Weighted average shares - diluted	80,766	81,497	81,622	81,648	81,253	81,031	80,737	80,333		81,482	81,049	80,073

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Stock-Based Compensation

12 Months Ended

Sep. 30, 2011

Stock-Based Compensation [Abstract]

Stock-Based Compensation

6.  Stock-based Compensation

The majority of awards consist of restricted stock units and to a lesser degree, stock options. Employees vest in restricted stock units and stock options ratably over the corresponding service term, generally one to four years. The Company's stock options expire 10 years from the date of grant. Restricted stock units are payable in shares of the Company's common stock as the periodic vesting requirements are satisfied. The value of a restricted stock unit is based upon the fair market value of the Company's common stock on the date of grant. The value of restricted stock units is determined using the intrinsic value method and is based on the number of shares granted and the quoted price of the Company's common stock on the date of grant. Alternatively, the Company used the Black-Scholes option pricing model to determine the fair value of its stock options. Compensation expense related to restricted stock units and stock options is recognized over the vesting period. The Company has adopted a number of stock-based compensation plans as discussed below.

1998 Equity Incentive Plan. In November 1998, the Company adopted the 1998 Equity Incentive Plan, or the 1998 Plan, which provided for discretionary grants of non-qualified and incentive stock options, stock purchase awards and stock bonuses for employees and other service providers. The 1998 Plan expired on November 11, 2008 and no shares remain available for awards under the 1998 Plan. Upon certain changes in control of the Company, all outstanding and unvested options or stock awards under the 1998 Plan will vest at the rate of 50%, unless assumed or substituted by the acquiring entity. During the fiscal years 2011 and 2010, the Company issued no stock options, stock purchase awards or stock bonuses under this plan. As of September 30, 2011, there were options to purchase 132,459 shares outstanding under the 1998 Plan.

2011 Employee Stock Purchase Plan. In July 2011, the board of directors amended and restated the Company's 1999 Employee Stock Purchase Plan, or the Employee Stock Purchase Plan. A total of 6,000,000 shares of common stock have been reserved for issuance under the Employee Stock Purchase Plan. The Employee Stock Purchase Plan permits eligible employees to acquire shares of the Company's common stock through periodic payroll deductions of up to 15% of base compensation. No employee may purchase more than $25,000 worth of stock, determined at the fair market value of the shares at the time such option is granted, in one calendar year. The Employee Stock Purchase Plan has been implemented in a series of offering periods, each 6 months in duration. The price at which the common stock may be purchased is 85% of the lesser of the fair market value of the Company's common stock on the first day of the applicable offering period or on the last day of the respective purchase period. As of September 30, 2011 there were 1,718,042 shares available for awards under the Employee Stock Purchase Plan.

2000 Equity Incentive Plan. In July 2000, the Company adopted the 2000 Employee Equity Incentive Plan, or the 2000 Plan, which provides for discretionary grants of non-qualified stock options, stock purchase awards and stock bonuses for non-executive employees and other service providers. A total of 7,000,000 shares of common stock were reserved for issuance under the 2000 Plan. Upon certain changes in control of the Company, all outstanding and unvested options or stock awards under the 2000 Plan will vest at the rate of 50%, unless assumed or substituted by the acquiring entity. As of September 30, 2011, there were options to purchase 165,088 shares outstanding and no shares available for awards under the 2000 Plan. The Company terminated the 2000 Plan effective November 1, 2008 and no additional shares may be issued from the 2000 Plan.

Acquisition Incentive Plans. In connection with the Company's acquisition of Acopia, the Company assumed the Acopia 2001 Stock Incentive Plan, or the Acopia Plan. Unvested options to acquire Acopia's common stock were converted into options to acquire the Company's common stock in connection with the acquisition. A total of 2,230,703 shares of common stock were reserved for issuance under the Acopia Plan. The plan provides for discretionary grants of non-qualified and incentive stock options, restricted stock awards and other stock-based awards to persons who were employees, officers, directors, consultants or advisors to Acopia on or prior to September 12, 2007. During the fiscal year 2011, the Company issued no stock options or restricted stock units under the Acopia Plan. As of September 30, 2011, there were options to purchase 26,287 shares outstanding and no shares available for awards under the Acopia Plan. The Company terminated the Acopia Plan effective November 1, 2008 and no additional shares may be issued from the Acopia Plan.

2005 Equity Incentive Plan. In December 2004, the Company adopted the 2005 Equity Incentive Plan, or the 2005 Plan, which provides for discretionary grants of non-statutory stock options and stock units for employees, including officers, and other service providers. A total of 12,400,000 shares of common stock have been reserved for issuance under the 2005 Plan. Upon certain changes in control of the Company, all outstanding and unvested options or stock awards under the 2005 Plan will vest at the rate of 50%, unless assumed or substituted by the acquiring entity. During the fiscal year 2011, the Company issued no stock options and 908,757 restricted stock units under the 2005 Plan. As of September 30, 2011, there were no options outstanding and 3,501,586 shares available for new awards under the 2005 Plan.

A majority of the restricted stock units granted in fiscal years 2011, 2010 and 2009 vest quarterly over a two-year period. The restricted stock units were granted during fiscal years 2011, 2010 and 2009 with a per-share weighted average fair value of $94.99, $86.32 and $36.31, respectively. The fair value of restricted stock vested during fiscal years 2011, 2010 and 2009 was $145.0 million, $116.4 million and $41.0 million, respectively.

A summary of restricted stock unit activity under the 2005 Plan is as follows:

	Outstanding Stock Units			Weighted Average Grant Date Fair Value
Balance, September 30, 2010		1,985,325		$	62.52
Units granted		908,757			94.99
Units vested		(1,316,253	)		105.59
Units cancelled		(121,143	)		56.04
Balance, September 30, 2011		1,456,686		$	44.40

A summary of stock option activity under all of the Company's plans is as follows:

	Options Outstanding
	Number of Shares			Weighted Average Exercise Price per Share
Balance, September 30, 2010		483,040		$	13.51
Options exercised		(150,416	)		15.24
Options cancelled		(1,200	)		33.92
Balance, September 30, 2011		331,424		$	12.66

No stock options were granted in fiscal years 2011, 2010 and 2009.

The total intrinsic value of options exercised during fiscal 2011, 2010 and 2009 was $15.2 million, $36.6 million and $8.4 million, respectively.

	Number of Shares		Weighted Average Remaining Contractual Life (in Years)		Weighted Average Exercise Price per Share		Aggregate Intrinsic Value(1)
	(In thousands)
Stock options outstanding		331,424		2.31	$	12.66	$	19,353
Exercisable		331,424		2.31	$	12.66	$	19,353
Vested and expected to vest		331,424		2.31	$	12.66	$	19,353

(1) Aggregate intrinsic value represents the difference between the fair value of the Company's common stock underlying these options at September 30, 2011 and the related exercise prices.

As of September 30, 2011, equity based awards (including stock options and restricted stock units) are available for future issuance as follows:

	Awards Available for Grant
Balance, September 30, 2010		4,289,200
Granted		(908,757	)
Cancelled		125,156
Additional shares reserved (terminated), net		(4,013	)
Balance, September 30, 2011		3,501,586

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Income Taxes

12 Months Ended

Sep. 30, 2011

Income Taxes [Abstract]

Income Taxes

5.  Income Taxes

The United States and international components of income before income taxes are as follows (in thousands):

	Years Ended September 30,
	2011		2010		2009
United States	$	342,741	$	225,698	$	128,537
International		18,010		11,929		3,111
	$	360,751	$	237,627	$	131,648

The provision for income taxes (benefit) consists of the following (in thousands):

	Years Ended September 30,
	2011			2010			2009
Current
U.S. federal	$	103,620		$	79,802		$	41,948
State		7,397			4,722			1,631
Foreign		5,743			3,230			1,790
Total		116,760			87,754			45,369
Deferred
U.S. federal		3,070			(2,049	)		(3,317	)
State		(144	)		(1,091	)		25
Foreign		(332	)		1,860			(1,964	)
Total		2,594			(1,280	)		(5,256	)
	$	119,354		$	86,474		$	40,113

The effective tax rate differs from the U.S. federal statutory rate as follows (in thousands):

	Years Ended September 30,
	2011			2010			2009
Income tax provision at statutory rate	$	126,263		$	83,170		$	46,075
State taxes, net of federal benefit		5,999			2,871			2,121
Impact of foreign income taxes		(892	)		915			(1,262	)
Research and development and other credits		(5,486	)		(2,124	)		(5,954	)
Domestic manufacturing deduction		(9,844	)		(3,766	)		(3,346	)
Impact of stock compensation		5,310			2,825			2,411
Other		(1,996	)		2,583			68
	$	119,354		$	86,474		$	40,113

The tax effects of the temporary differences that give rise to the deferred tax assets and liabilities are as follows (in thousands):

	Years Ended September 30,
	2011			2010
Deferred tax assets
Net operating loss carry-forwards	$	452		$	5,672
Allowance for doubtful accounts		898			1,644
Accrued compensation and benefits		4,879			4,003
Inventories and related reserves		1,564			2,063
Stock-based compensation		8,969			6,247
Deferred revenue		19,400			16,260
Other accruals and reserves		9,629			7,829
Depreciation		1,403			5,239
Tax credit carry-forwards		1,657			4,065
		48,851			53,022
Deferred tax liabilities
Purchased intangibles and other		(5,698	)		(6,391	)
Net deferred tax assets	$	43,153		$	46,631

At September 30, 2011, the Company had U.S. net operating loss carry-forwards of approximately $1.2 million. All U.S. net operating loss carry-forwards relate to entities acquired by the Company and are limited in use by I.R.C. Sec. 382.

United States income and foreign withholding taxes have not been provided on approximately $28.7 million of undistributed earnings from the Company's international subsidiaries. The Company has not recognized a deferred tax liability for the undistributed earnings of its foreign subsidiaries because the Company currently does not expect to remit those earnings in the foreseeable future. Determination of the amount of unrecognized deferred tax liability related to undistributed earnings of foreign subsidiaries is not practicable because such liability, if any, is dependent on circumstances existing if and when remittance occurs.

The decrease in the effective tax rate from fiscal year 2010 to fiscal year 2011 was primarily due to an increased benefit resulting from the United States Domestic Production Activities Deduction, the reinstatement of the federal research and development credit on December 17, 2010 and a change in the Company's uncertain tax positions as a result of the settlement of audits and expiration of statutes of limitation in various jurisdictions.

The Company recognizes the financial statement impact of a tax position only after determining that the relevant tax authority would more likely than not sustain the position following an audit. For tax positions meeting the more-likely-than-not threshold, the amount recognized in the financial statements is the largest impact that has a greater than fifty percent likelihood of being realized upon ultimate settlement with the relevant tax authority.

The following table provides a reconciliation of the beginning and ending amount of unrecognized tax benefits in fiscal years 2011, 2010 and 2009:

	2011			2010			2009
Balance, beginning of period	$	6,568		$	5,841		$	4,075
Gross increases related to prior period tax positions		1,198			442			642
Gross increases related to current period tax positions		1,659			432			1,124
Decreases relating to settlements with tax authorities		(243	)		—			—
Reductions due to lapses of statute of limitations		(3,230	)		(147	)		—
Balance, end of period	$	5,952		$	6,568		$	5,841

The Company recognizes interest and, if applicable, penalties (not included in the "unrecognized tax benefits" table above) for any uncertain tax positions. This interest and penalty expense will be a component of income tax expense. In the years ended September 30, 2011, 2010 and 2009 the Company accrued approximately $283,000, $390,000 and $193,000, respectively, of interest expense related to its liability for unrecognized tax benefits. No penalties were recognized in fiscal years 2011, 2010 and 2009 or accrued for at September 30, 2011, 2010 and 2009.

All unrecognized tax benefits, if recognized, would affect the effective tax rate. The Company does not anticipate that total unrecognized tax benefits will significantly change within the next twelve months.

The Company and its subsidiaries are subject to U.S. federal income tax as well as the income tax of multiple state and foreign jurisdictions. The Company has concluded all U.S. federal income tax matters for fiscal years through September 30, 2007. Major jurisdictions where there are wholly owned subsidiaries of F5 Networks, Inc. which require income tax filings include the United Kingdom, Japan, Australia and Germany. The earliest periods open for review by local taxing authorities are fiscal years 2010, 2010, 2007 and 2007 for the United Kingdom, Japan, Australia and Germany, respectively. Within the next four fiscal quarters, the statute of limitations will begin to close on the fiscal years ended 2007 and 2008 tax returns filed in various states and the fiscal year ended 2008 federal income tax return.

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Income Taxes (Tables)

12 Months Ended

Sep. 30, 2011

Income Taxes [Abstract]

Components Of Income Before Income Taxes

	Years Ended September 30,
	2011		2010		2009
United States	$	342,741	$	225,698	$	128,537
International		18,010		11,929		3,111
	$	360,751	$	237,627	$	131,648

Schedule Of Provision For Income Taxes (Benefit)

	Years Ended September 30,
	2011			2010			2009
Current
U.S. federal	$	103,620		$	79,802		$	41,948
State		7,397			4,722			1,631
Foreign		5,743			3,230			1,790
Total		116,760			87,754			45,369
Deferred
U.S. federal		3,070			(2,049	)		(3,317	)
State		(144	)		(1,091	)		25
Foreign		(332	)		1,860			(1,964	)
Total		2,594			(1,280	)		(5,256	)
	$	119,354		$	86,474		$	40,113

Schedule Of Effective Tax Rate Differs From The U.S. Federal Statutory Rate

	Years Ended September 30,
	2011			2010			2009
Income tax provision at statutory rate	$	126,263		$	83,170		$	46,075
State taxes, net of federal benefit		5,999			2,871			2,121
Impact of foreign income taxes		(892	)		915			(1,262	)
Research and development and other credits		(5,486	)		(2,124	)		(5,954	)
Domestic manufacturing deduction		(9,844	)		(3,766	)		(3,346	)
Impact of stock compensation		5,310			2,825			2,411
Other		(1,996	)		2,583			68
	$	119,354		$	86,474		$	40,113

Schedule Of Tax Effects To Deferred Tax Assets And Liabilities

	Years Ended September 30,
	2011			2010
Deferred tax assets
Net operating loss carry-forwards	$	452		$	5,672
Allowance for doubtful accounts		898			1,644
Accrued compensation and benefits		4,879			4,003
Inventories and related reserves		1,564			2,063
Stock-based compensation		8,969			6,247
Deferred revenue		19,400			16,260
Other accruals and reserves		9,629			7,829
Depreciation		1,403			5,239
Tax credit carry-forwards		1,657			4,065
		48,851			53,022
Deferred tax liabilities
Purchased intangibles and other		(5,698	)		(6,391	)
Net deferred tax assets	$	43,153		$	46,631

Schedule Of Reconciliation Of Beginning And Ending Amount Of Unrecognized Tax Benefits

	2011			2010			2009
Balance, beginning of period	$	6,568		$	5,841		$	4,075
Gross increases related to prior period tax positions		1,198			442			642
Gross increases related to current period tax positions		1,659			432			1,124
Decreases relating to settlements with tax authorities		(243	)		—			—
Reductions due to lapses of statute of limitations		(3,230	)		(147	)		—
Balance, end of period	$	5,952		$	6,568		$	5,841

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Summary Of Significant Accounting Policies (Tables)

12 Months Ended

Sep. 30, 2011

Summary Of Significant Accounting Policies [Abstract]

Schedule Of Inventories

	Years Ended September 30,
	2011		2010
Finished goods	$	12,917	$	14,949
Raw materials		4,232		3,866
	$	17,149	$	18,815

Schedule Of Property And Equipment

	Years Ended September 30,
	2011			2010
Computer equipment	$	77,899		$	59,557
Office furniture and equipment		11,243			9,793
Leasehold improvements		41,344			36,462
		130,486			105,812
Accumulated depreciation and amortization		(82,488	)		(71,655	)
	$	47,998		$	34,157

Schedule Of Assumptions In Determining The Fair Value Of Shares Issued Under The Employee Stock Purchase Plan

	Employee Stock Purchase Plan Years Ended September 30,
	2011			2010			2009
Risk-free interest rate		0.10	%		0.25	%		0.31	%
Expected dividend		—			—			—
Expected term		0.5 years			0.5 years			0.5 years
Expected volatility		53.87	%		41.04	%		47.00	%

Schedule Of Computation Of Basic And Diluted Net Income Per Share

	Years Ended September 30,
	2011		2010		2009
Numerator
Net income	$	241,397	$	151,153	$	91,535
Denominator
Weighted average shares outstanding — basic		80,658		79,609		78,842
Dilutive effect of common shares from stock options and restricted stock units		824		1,440		1,231
Weighted average shares outstanding — diluted		81,482		81,049		80,073
Basic net income per share	$	2.99	$	1.90	$	1.16
Diluted net income per share	$	2.96	$	1.86	$	1.14

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Employee Benefit Plans

12 Months Ended

Sep. 30, 2011

Employee Benefit Plans [Abstract]

Employee Benefit Plans

9. Employee Benefit Plans

The Company has a 401(k) savings plan whereby eligible employees may voluntarily contribute a percentage of their compensation. The Company may, at its discretion, match a portion of the employees' eligible contributions. Contributions by the Company to the plan during the years ended September 30, 2011, 2010, and 2009 were approximately $4.7 million, $3.8 million and $3.3 million, respectively. Contributions made by the Company vest over four years.

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Commitments And Contingencies

12 Months Ended

Sep. 30, 2011

Commitments And Contingencies [Abstract]

Commitments And Contingencies

7. Commitments and Contingencies

Operating Leases

The majority of the Company's operating lease payments relate to the Company's three building corporate headquarters in Seattle, Washington. The lease for all three buildings was amended and restated in April of 2010. This lease will now expire in 2022 with an option for renewal. One of the buildings has been partially subleased through 2012. The Company also leases additional office space for product development and sales and support personnel in the United States and internationally.

In October 2006, the Company entered into an agreement to lease a total of approximately 137,000 square feet of office space in a building known as 333 Elliott West, which is adjacent to the three buildings that serve as the Company's corporate headquarters. The lease expires in 2018. During 2008, the Company entered into two separate sublease agreements to sublease approximately 112,500 square feet of building 333 Elliott West. One sublease will expire in 2013. In March 2010, the Company amended the second sublease, which expanded the subleased space by approximately 11,700 square feet and extended the term of the sublease to 2018.

Future minimum operating lease payments, net of sublease income, are as follows (in thousands):

	Gross  Lease Payments		Sublease Income		Net Lease Payments
2012		42,317		4,321		37,996
	Gross  Lease Payments		Sublease Income		Net Lease Payments
2013		17,673		2,611		15,062
2014		16,185		338		15,847
2015		15,786		85		15,701
2016		15,072		-		15,072
Thereafter		65,370		-		65,370
	$	172,403	$	7,355	$	165,048

Rent expense under non-cancelable operating leases amounted to approximately $19.0 million, $17.5 million, and $15.6 million for the fiscal years ended September 30, 2011, 2010, and 2009, respectively.

Purchase Obligations

Purchase obligations are comprised of purchase commitments with the Company's contract manufacturers. The agreement with the Company's primary contract manufacturer allows them to procure component inventory on the Company's behalf based on the Company's production forecast. The Company is obligated to purchase component inventory that the contract manufacturer procures in accordance with the forecast, unless cancellation is given within applicable lead times. As of September 30, 2011, the Company's purchase obligations were $13.6 million.

Litigation

The Company is not aware of any pending legal proceedings that, individually or in the aggregate, are reasonably possible to have a material adverse effect on the Company's business, operating results, or financial condition. The Company may in the future be party to litigation arising in the ordinary course of business, including claims that we allegedly infringe upon third-party intellectual property rights. Such claims, even if not meritorious, could result in the expenditure of significant financial and managerial resources.

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Restructuring Charges

12 Months Ended

Sep. 30, 2011

Restructuring Charges [Abstract]

Restructuring Charges

8. Restructuring Charges

In January 2009, the Company initiated a restructuring plan to reduce its operating expenses which included the consolidation of facilities, accelerated depreciation on tenant improvements and a reduction in workforce. These initiatives are intended to conserve or generate cash in response to the uncertainties associated with the recent deterioration in the global economy. As a result of these initiatives, the Company recorded a restructuring charge of $4.3 million in the second quarter of fiscal 2009. All accrued restructuring costs had been incurred as of September 30, 2011.

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Geographic Sales And Significant Customers

12 Months Ended

Sep. 30, 2011

Geographic Sales And Significant Customers [Abstract]

Geographic Sales And Significant Customers

10. Geographic Sales and Significant Customers

Operating segments are defined as components of an enterprise for which separate financial information is available and evaluated regularly by the chief operating decision-maker, or decision-making group, in deciding how to allocate resources and in assessing performance. The Company does business in four main geographic regions: the Americas (primarily the United States); Europe, the Middle East, and Africa (EMEA); Japan; and the Asia Pacific region (APAC). The Company's chief operating decision-making group reviews financial information presented on a consolidated basis accompanied by information about revenues by geographic region. The Company's foreign offices conduct sales, marketing and support activities. Revenues are attributed by geographic location based on the location of the customer. The Company's assets are primarily located in the United States and not allocated to any specific region. Therefore, geographic information is presented only for net revenue.

The following presents revenues by geographic region (in thousands):

	Years Ended September 30,
	2011		2010		2009
Americas	$	676,868	$	517,269	$	361,230
EMEA		240,453		201,259		150,776
Japan		74,824		59,151		56,792
Asia Pacific		159,689		104,293		84,281
	$	1,151,834	$	881,972	$	653,079

One worldwide distributor accounted for 18.1%, 14.5% and 15.4% of total net revenues in fiscal years 2011, 2010 and 2009, respectively. Another worldwide distributor accounted for 10.7% of total net revenues in fiscal year 2011. Another worldwide distributor accounted for 10.2% of total net revenues in fiscal year 2010.

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Fair Value Measurements (Schedule Of Reconciliation Of Items Measured At Fair Value On A Recurring Basis That Used Significant Unobservable Inputs (Level 3)) (Details) (USD $) In Thousands	12 Months Ended
	Sep. 30, 2011	Sep. 30, 2010
Fair Value Measurements [Abstract]
Balance, beginning of period	$ 16,043	$ 41,595
Total gains realized or unrealized: Included in earnings (other income, net)		1,491
Total gains realized or unrealized: Included in other comprehensive income	967	498
Recognition of put option to earnings		(1,491)
Settlements	(4,000)	(26,050)
Balance, end of period	13,010	16,043
Gains attributable to assets still held as of the end of the period	$ 967	$ 498

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Stock-Based Compensation (Schedule Of Stock Option Activity) (Details) (USD $)	12 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2009
Stock-Based Compensation [Abstract]
Number of Shares, Beginning balance	483,040
Number of Shares, Options exercised	(150,416)
Number of Shares, Options cancelled	(1,200)
Number of Shares, Ending balance	331,424	483,040
Weighted Average Exercise Price per Share, Beginning balance	$ 13.51
Weighted Average Exercise Price per Share, Options exercised	$ 15.24
Weighted Average Exercise Price per Share, Options cancelled	$ 33.92
Weighted Average Exercise Price per Share, Ending balance	$ 12.66	$ 13.51
Number of Shares, Options granted	0	0	0

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Short-Term And Long-Term Investments (Tables)

12 Months Ended

Sep. 30, 2011

Sep. 30, 2010

Schedule of Investments [Line Items]

Schedule Of Amortized Cost And Fair Value Of Fixed Maturities By Contractual Years-To-Maturity

	Cost or Amortized Cost		Fair Value
One year or less	$	325,623	$	325,766
Over one year		472,224		470,203
	$	797,847	$	795,969

Schedule Of Investments That Have Been In A Continuous Unrealized Loss Position

	Less Than 12 Months					12 Months or Greater					Total
	Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses
September 30, 2011
Corporate bonds and notes	$	133,752	$	(751	)	$	4,019	$	(11	)	$	137,771	$	(762	)
Municipal bonds and notes		24,304		(38	)		2,543		(8	)		26,847		(46	)
Auction rate securities		—		—			13,010		(1,990	)		13,010		(1,990	)
U.S. government agency securities		171,222		(178	)		—		—			171,222		(178	)
Total	$	329,278	$	(967	)	$	19,572	$	(2,009	)	$	348,850	$	(2,976	)

Short-Term Investments [Member]

Schedule of Investments [Line Items]

Schedule Of Short-Term And Long-Term Investments

	Cost or Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
September 30, 2011
Corporate bonds and notes	$	137,087	$	251	$	(182	)	$	137,156
Municipal bonds and notes		82,687		62		(34	)		82,715
U.S. government securities		799		—		—			799
U.S. government agency securities		105,050		55		(9	)		105,096
	$	325,623	$	368	$	(225	)	$	325,766

	Cost or Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
September 30, 2010
Corporate bonds and notes	$	119,829	$	318	$	(23	)	$	120,124
Municipal bonds and notes		76,886		182		(5	)		77,063
U.S. government agency securities		62,390		165		—			62,555
	$	259,105	$	665	$	(28	)	$	259,742

Long-Term Investments [Member]

Schedule of Investments [Line Items]

Schedule Of Short-Term And Long-Term Investments

	Cost or Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
September 30, 2011
Corporate bonds and notes	$	141,315	$	415	$	(580	)	$	141,150
Municipal bonds and notes		30,575		151		(12	)		30,714
Auction rate securities		15,000		—		(1,990	)		13,010
U.S. government agency securities		285,334		164		(169	)		285,329
	$	472,224	$	730	$	(2,751	)	$	470,203

	Cost or Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
September 30, 2010
Corporate bonds and notes	$	172,493	$	1,582	$	(22	)	$	174,053
Municipal bonds and notes		22,045		67		(18	)		22,094
Auction rate securities		19,000		—		(2,957	)		16,043
U.S. government agency securities		221,262		200		(82	)		221,380
	$	434,800	$	1,849	$	(3,079	)	$	433,570

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Geographic Sales And Significant Customers (Tables)

12 Months Ended

Sep. 30, 2011

Geographic Sales And Significant Customers [Abstract]

Schedule Of Revenues By Geographic Region

	Years Ended September 30,
	2011		2010		2009
Americas	$	676,868	$	517,269	$	361,230
EMEA		240,453		201,259		150,776
Japan		74,824		59,151		56,792
Asia Pacific		159,689		104,293		84,281
	$	1,151,834	$	881,972	$	653,079

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Stock-Based Compensation (Narrative) (Details) (USD $)	1 Months Ended	12 Months Ended						12 Months Ended				12 Months Ended
	Aug. 31, 2009	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2009	Sep. 30, 2011 1998 Equity Incentive Plan [Member]	Sep. 30, 2011 2011 Employee Stock Purchase Plan [Member]	May 31, 1999 2011 Employee Stock Purchase Plan [Member]	Sep. 30, 2011 2000 Equity Incentive Plan [Member]	Sep. 30, 2011 2005 Equity Incentive Plan [Member]	Dec. 31, 2004 2005 Equity Incentive Plan [Member]	Sep. 30, 2011 Acopia Plan [Member]	Sep. 30, 2011 Stock Options [Member]	Sep. 30, 2011 Restricted Stock Unit [Member]	Sep. 30, 2010 Restricted Stock Unit [Member]	Sep. 30, 2009 Restricted Stock Unit [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock units and stock options vesting period in years, minimum		one
Restricted stock units and stock options vesting period in years, maximum		four
Restricted stock units vesting period in years	two years	two-year	two-year	two-year
Stock option expiration period from date of grant												10 years
Vesting rate of stock options and awards upon certain changes in ownership control					50.00%			50.00%	50.00%
Shares available for award		1,718,042						0	3,501,586		0
Shares available for purchase under stock option plan					132,459			165,088	0		26,287
Common stock reserved for issuance							6,000,000	7,000,000		12,400,000	2,230,703
Percentage of base compensation for which employees can acquire shares of common stock						15.00%
Maximum aggregate fair value of stock that an employee may purchase						$ 25,000
Percentage of common stock lesser of the fair market value						85.00%
Restricted stock units issued									908,757
Weighted average fair value of restricted stock units granted													$ 94.99	$ 86.32	$ 36.31
Fair market value of restricted stock vested													145,000,000	116,400,000	41,000,000
Total intrinsic value of options exercised		$ 15,200,000	$ 36,600,000	$ 8,400,000

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Balance Sheet Details (Schedule Of Accrued Liabilities) (Details) (USD $) In Thousands	Sep. 30, 2011	Sep. 30, 2010
Balance Sheet Details [Abstract]
Payroll and benefits	$ 47,824	$ 40,904
Sales and marketing	5,062	2,522
Income tax accruals	4,860	2,458
Other	10,156	15,884
Total accrued liabilities	$ 67,902	$ 61,768

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Consolidated Statements Of Shareholders' Equity And Comprehensive Income (USD $) In Thousands, except Share data	Common Stock [Member]	Accumulated Other Comprehensive Income/(Loss) [Member]	Retained Earnings [Member]	Total Shareholders' Equity [Member]	Total
Balance at Sep. 30, 2008	$ 477,299	$ (6,076)	$ 247,036	$ 718,259
Balance, shares at Sep. 30, 2008	79,094,000
Exercise of employee stock options	7,243			7,243
Exercise of employee stock options, shares	498,000
Issuance of stock under employee stock purchase plan	11,574			11,574
Issuance of stock under employee stock purchase plan, shares	561,000
Issuance of restricted stock, shares	1,516,000
Repurchase of common stock	(87,436)			(87,436)
Repurchase of common stock, shares	(3,344,000)
Tax benefit (loss) from employee stock transactions	(1,958)			(1,958)
Stock-based compensation	56,064			56,064
Net income			91,535		91,535
Foreign currency translation adjustment		387
Unrealized gain (loss) on securities, net of tax		3,352
Comprehensive income				95,274
Balance at Sep. 30, 2009	462,786	(2,337)	338,571	799,020
Balance, shares at Sep. 30, 2009	78,325,000
Exercise of employee stock options	17,618			17,618
Exercise of employee stock options, shares	911,000
Issuance of stock under employee stock purchase plan	13,936			13,936
Issuance of stock under employee stock purchase plan, shares	458,000
Issuance of restricted stock, shares	1,849,000
Repurchase of common stock	(75,000)			(75,000)
Repurchase of common stock, shares	(1,188,000)
Tax benefit (loss) from employee stock transactions	27,102			27,102
Stock-based compensation	70,773			70,773
Net income			151,153		151,153
Foreign currency translation adjustment		(771)
Unrealized gain (loss) on securities, net of tax		(133)
Comprehensive income				150,249
Balance at Sep. 30, 2010	517,215	(3,241)	489,724	1,003,698	1,003,698
Balance, shares at Sep. 30, 2010	80,355,000				80,355,000
Exercise of employee stock options	2,293			2,293
Exercise of employee stock options, shares	150,000				150,416
Issuance of stock under employee stock purchase plan	18,932			18,932
Issuance of stock under employee stock purchase plan, shares	257,000
Issuance of restricted stock, shares	1,370,000
Repurchase of common stock	(271,526)			(271,526)
Repurchase of common stock, shares	(2,987,000)
Tax benefit (loss) from employee stock transactions	24,076			24,076
Stock-based compensation	89,747			89,747
Net income			241,397		241,397
Foreign currency translation adjustment		(2,366)
Unrealized gain (loss) on securities, net of tax		(815)
Comprehensive income				238,216
Balance at Sep. 30, 2011	$ 380,737	$ (6,422)	$ 731,121	$ 1,105,436	$ 1,105,436
Balance, shares at Sep. 30, 2011	79,145,000				79,145,000

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Balance Sheet Details

12 Months Ended

Sep. 30, 2011

Balance Sheet Details [Abstract]

Balance Sheet Details

4.  Balance Sheet Details

Other Assets

Other assets consist of the following (in thousands):

	Years Ended September 30,
	2011		2010
Acquired and developed technology and software development cost	$	8,520	$	6,374
Deposits and other		8,540		9,377
Restricted cash		162		195
	$	17,222	$	15,946

Amortization expense related to other assets was approximately $4.3 million, $6.0 million, and $6.7 million for the fiscal years ended September 30, 2011, 2010 and 2009, respectively.

Intangible assets consist of the following (in thousands):

	2011							2010
	Gross Carrying Amount		Accumulated Amortization			Net Carrying Amount		Gross Carrying Amount		Accumulated Amortization			Net Carrying Amount
Acquired and developed technology and software development cost	$	39,109	$	(30,589	)	$	8,520	$	33,474	$	(27,100	)	$	6,374
Customer relationships		2,699		(2,314	)		385		2,699		(1,894	)		805
Patents and trademarks		3,044		(2,214	)		830		2,964		(1,832	)		1,132
Trade names		200		(163	)		37		200		(123	)		77
Non-compete covenants		200		(200	)		—		200		(200	)		—
	$	45,252	$	(35,480	)	$	9,772	$	39,537	$	(31,149	)	$	8,388

Estimated amortization expense for intangible assets for the five succeeding fiscal years is as follows (in thousands):

2012	$	4,428
2013		934
2014		867
2015		867
2016		867
	$	7,963

Accrued Liabilities

Accrued liabilities consist of the following (in thousands):

	Years Ended September 30,
	2011		2010
Payroll and benefits	$	47,824	$	40,904
Sales and marketing		5,062		2,522
Income tax accruals		4,860		2,458
Other		10,156		15,884
	$	67,902	$	61,768

Other Long Term Liabilities

Other long term liabilities consist of the following (in thousands):

	Years Ended September 30,
	2011		2010
Income tax accrual	$	5,675	$	7,029
Deferred rent and other		12,713		9,124
	$	18,388	$	16,153

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Geographic Sales And Significant Customers (Schedule Of Revenues By Geographic Region) (Details) (USD $)	3 Months Ended								12 Months Ended
	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2009	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2009
Segment Reporting Information [Line Items]
Sales Revenue, Net	$ 314,615,000	$ 290,713,000	$ 277,572,000	$ 268,934,000	$ 254,274,000	$ 230,474,000	$ 206,068,000	$ 191,156,000	$ 1,151,834,000	$ 881,972,000	$ 653,079,000
Worldwide Distributor 1 [Member]
Segment Reporting Information [Line Items]
Net revenues from worldwide distributor, percent									18.10%	14.50%	15.40%
Worldwide Distributor 2 [Member]
Segment Reporting Information [Line Items]
Net revenues from worldwide distributor, percent									10.70%
Worldwide Distributor 3 [Member]
Segment Reporting Information [Line Items]
Net revenues from worldwide distributor, percent										10.20%
Americas [Member]
Segment Reporting Information [Line Items]
Sales Revenue, Net									676,868	517,269	361,230
EMEA [Member]
Segment Reporting Information [Line Items]
Sales Revenue, Net									240,453	201,259	150,776
Japan [Member]
Segment Reporting Information [Line Items]
Sales Revenue, Net									74,824	59,151	56,792
Asia Pacific [Member]
Segment Reporting Information [Line Items]
Sales Revenue, Net									$ 159,689	$ 104,293	$ 84,281

XML

Quarterly Results Of Operations (Tables)

12 Months Ended

Sep. 30, 2011

Quarterly Results Of Operations [Abstract]

Schedule Of Quarterly Results Of Operations

	Three Months Ended
	Sept. 30, 2011		June 30, 2011		March 31, 2011		Dec. 31, 2010		Sept. 30, 2010		June 30, 2010		March 31, 2010		Dec. 31, 2009
	(Unaudited and in thousands, except per share data)
Net revenues
Products	$	197,446	$	179,327	$	173,710	$	171,492	$	164,972	$	147,393	$	129,559	$	119,218
Services		117,169		111,386		103,862		97,442		89,302		83,081		76,509		71,938
Total		314,615		290,713		277,572		268,934		254,274		230,474		206,068		191,156
Cost of net revenues
Products		34,485		31,803		31,423		31,614		31,045		29,328		27,419		26,042
Services		21,435		20,645		19,250		17,349		15,783		15,251		13,997		13,087
Total		55,920		52,448		50,673		48,963		46,828		44,579		41,416		39,129
Gross profit		258,695		238,265		226,899		219,971		207,446		185,895		164,652		152,027
Operating expenses
Sales and marketing		100,945		93,633		89,332		86,825		80,696		77,219		69,644		65,642
Research and development		36,552		35,245		34,507		32,606		31,571		30,889		29,134		26,720
General and administrative		21,867		21,126		19,846		20,684		18,876		17,658		16,016		15,953
Total operating expenses		159,364		150,004		143,685		140,115		131,143		125,766		114,794		108,315
Income from operations		99,331		88,261		83,214		79,856		76,303		60,129		49,858		43,712
Other income, net		4,087		1,889		1,568		2,545		68		3,561		2,291		1,705
Income before income taxes		103,418		90,150		84,782		82,401		76,371		63,690		52,149		45,417
Provision for income taxes		35,808		27,601		29,207		26,738		28,136		23,195		19,005		16,138
Net income	$	67,610	$	62,549	$	55,575	$	55,663	$	48,235	$	40,495	$	33,144	$	29,279
Net income per share — basic	$	0.84	$	0.77	$	0.69	$	0.69	$	0.60	$	0.51	$	0.42	$	0.37
Weighted average shares — basic		80,317		80,866		80,809		80,644		80,268		79,864		79,394		78,906
Net income per share — diluted	$	0.84	$	0.77	$	0.68	$	0.68	$	0.59	$	0.50	$	0.41	$	0.36
Weighted average shares — diluted		80,766		81,497		81,622		81,648		81,253		81,031		80,737		80,333

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Balance Sheet Details (Schedule Of Other Assets) (Details) (USD $)	12 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2009
Balance Sheet Details [Abstract]
Acquired and developed technology and software development cost	$ 8,520,000	$ 6,374,000
Deposits and other	8,540,000	9,377,000
Restricted cash	162,000	195,000
Other assets	17,222,000	15,946,000
Amortization expense related to other assets	$ 4,300,000	$ 6,000,000	$ 6,700,000

XML

Fair Value Measurements (Tables)

12 Months Ended

Sep. 30, 2011

Sep. 30, 2010

Fair Value Measurements [Abstract]

Schedule Of Financial Assets Measured At Fair Value on A Recurring Basis

	Fair Value Measurements at Reporting Date Using
	Quoted Prices  in Active Markets for Identical Securities (Level 1)		Significant Other  Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Fair Value at September 30, 2011
Cash equivalents	$	33,740	$	—	$	—	$	33,740
Short-term investments
Available-for-sale securities — corporate bonds and notes		—		137,156		—		137,156
Available-for-sale securities — municipal bonds and notes		—		82,715		—		82,715
Available-for-sale securities — U.S. government securities		—		799		—		799
Available-for-sale securities — U.S. government agency securities		—		105,096		—		105,096
Long-term investments
Available-for-sale securities — corporate bonds and notes		—		141,150		—		141,150
Available-for-sale securities — municipal bonds and notes		—		30,714		—		30,714
Available-for-sale securities — U.S. government agency securities		—		285,329		—		285,329
Available-for-sale securities — auction rate securities		—		—		13,010		13,010
Total	$	33,740	$	782,959	$	13,010	$	829,709

	Fair Value Measurements at Reporting Date Using
	Quoted Prices in Active Markets for Identical Securities (Level 1)		Significant Other  Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Fair Value at September 30, 2010
Cash equivalents	$	26,987	$	—	$	—	$	26,987
Short-term investments
Available-for-sale securities — corporate bonds and notes		—		120,124		—		120,124
Available-for-sale securities — municipal bonds and notes		—		77,063		—		77,063
Available-for-sale securities — U.S. government agency securities		—		62,555		—		62,555
Long-term investments
Available-for-sale securities — corporate bonds and notes		—		174,053		—		174,053
Available-for-sale securities — municipal bonds and notes		—		22,094		—		22,094
Available-for-sale securities — U.S. government agency securities		—		221,380		—		221,380
Available-for-sale securities — auction rate securities		—		—		16,043		16,043
Total	$	26,987	$	677,269	$	16,043	$	720,299

Schedule Of Reconciliation Of Items Measured At Fair Value On A Recurring Basis That Used Significant Unobservable Inputs (Level 3)

	2011			2010
Balance, beginning of period	$	16,043		$	41,595
Total gains realized or unrealized:
Included in earnings (other income, net)		—			1,491
Included in other comprehensive income		967			498
Recognition of put option to earnings		—			(1,491	)
Settlements		(4,000	)		(26,050	)
Transfers into and/or out of level 3		—			—
Balance, end of period	$	13,010		$	16,043
Gains attributable to assets still held as of the end of the period		967			498