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Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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MIC-Info: RSA-MD5,RSA,
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 kvTOHF+o+OSyDgwYmxigzw==

<SEC-DOCUMENT>0001304939-05-000001.txt : 20050613
<SEC-HEADER>0001304939-05-000001.hdr.sgml : 20050611
<ACCEPTANCE-DATETIME>20050613133412
ACCESSION NUMBER:		0001304939-05-000001
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20050609
FILED AS OF DATE:		20050613
DATE AS OF CHANGE:		20050613

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			REDBACK NETWORKS INC
		CENTRAL INDEX KEY:			0001081290
		STANDARD INDUSTRIAL CLASSIFICATION:	SERVICES-COMPUTER INTEGRATED SYSTEMS DESIGN [7373]
		IRS NUMBER:				770438443
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		300 HOLGER WAY
		CITY:			SAN JOSE
		STATE:			CA
		ZIP:			95134
		BUSINESS PHONE:		4087505000

	MAIL ADDRESS:	
		STREET 1:		300 HOLGER WAY
		CITY:			SAN JOSE
		STATE:			CA
		ZIP:			95134

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Marshall Scott W
		CENTRAL INDEX KEY:			0001304939

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-25853
		FILM NUMBER:		05891897

	BUSINESS ADDRESS:	
		BUSINESS PHONE:		408-750-8607

	MAIL ADDRESS:	
		STREET 1:		300 HOLGER WAY
		CITY:			SAN JOSE
		STATE:			CA
		ZIP:			95134
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>primary_doc.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2005-06-09</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001081290</issuerCik>
        <issuerName>REDBACK NETWORKS INC</issuerName>
        <issuerTradingSymbol>RBAK</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001304939</rptOwnerCik>
            <rptOwnerName>Marshall Scott W</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>300 HOLGER WAY</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>SAN JOSE</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>95134</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Sr VP of Prod Mgmt/Engineering</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Non-qualified Stock Option</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>6.32</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2005-06-09</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>65000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <value>2015-06-09</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>65000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>65000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">The shares subject to this option will vest monthly over 48 months from the date of grant.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Susan Marsch as Attorney in Fact for Scott Marshall</signatureName>
        <signatureDate>2005-06-13</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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