X0306 4 2018-11-07 0 0001580808 A10 Networks, Inc. ATEN 0000830588 SUMMIT PARTNERS L P 222 BERKELEY STREET 18TH FLOOR BOSTON MA 02116 1 0 1 1 Manager of GP of 10% owner 0001627278 SUMMIT MASTER COMPANY, LLC 222 BERKELEY STREET, 18TH FLOOR BOSTON MA 02116 1 0 0 1 Manager of Manager of 10% owne 0001593029 SUMMIT PARTNERS GE VIII, L.P. 222 BERKELEY STREET, 18TH FLOOR BOSTON MA 02116 1 0 0 1 GP of 10% owner 0001593948 Summit Partners GE VIII, LLC 222 BERKELEY STREET, 18TH FLOOR BOSTON MA 02116 1 0 0 1 GP of 10% owner 0001514386 Summit Partners Growth Equity Fund VIII-A, L.P. 222 BERKELEY STREET, 18TH FLOOR BOSTON MA 02116 1 0 1 0 0001514388 Summit Partners Growth Equity Fund VIII-B, L.P. 222 BERKELEY STREET, 18TH FLOOR BOSTON MA 02116 1 0 1 0 0001507545 Summit Investors Management, LLC 222 BERKELEY STREET, 18TH FLOOR BOSTON MA 02116 1 0 0 1 Manager and GP of 10% Owner 0001435565 Summit Investors I, LLC 222 BERKELEY STREET, 18TH FLOOR BOSTON MA 02116 1 0 1 0 0001494616 Summit Investors I (UK), L.P. 222 BERKELEY STREET, 18TH FLOOR BOSTON MA 02116 1 0 1 0 0001018067 MANNION MARTIN J C/O SUMMIT PARTNERS 222 BERKELEY STREET, 18TH FLOOR BOSTON MA 02116 1 0 1 0 Common Stock 2018-11-07 4 A 0 23112 0 A 9515529 I See Footnotes. Represents restricted stock units granted to Mr. Chung as part of the director compensation program. The restricted stock units will settle solely by delivery of an equal number of shares of Common Stock on the earlier of the first anniversary of the grant date or the date of the Issuer's next Annual Meeting, subject to the Reporting Person's continued service on the board of directors as of such date. Mr. Chung holds any restricted stock units for the benefit of Summit Partners, L.P., which he has empowered to determine when the underlying shares will be sold and which is entitled to the proceeds of any such sales. The Common Stock is held as follows: 6,873,136 shares in the name of Summit Partners Growth Equity Fund VIII-A, L.P.; 2,510,989 shares in the name of Summit Partners Growth Equity Fund VIII-B, L.P.; 40,186 shares in the name of Summit Investors I, LLC; 3,535 shares in the name of Summit Investors I (UK), L.P.; 87,683 shares and restricted stock units in the name of Peter Y. Chung, which are held for the benefit of Summit Partners, L.P. Summit Partners, L.P. is the managing member of Summit Partners GE VIII, LLC, which is the general partner of Summit Partners GE VIII, L.P., which is the general partner of each of Summit Partners Growth Equity Fund VIII-A, L.P. and Summit Partners Growth Equity Fund VIII-B, L.P. Summit Master Company, LLC is the managing member of Summit Investors Management, LLC, which is the manager of Summit Investors I, LLC and the general partner of Summit Investors I (UK), L.P. Summit Master Company, LLC, as the managing member of Summit Investors Management, LLC has delegated investment decisions, including voting and dispositive power, to Summit Partners, L.P. and its Investment Committee responsible for voting and investment decisions with respect to the Issuer. Summit Partners, L.P., through a two-person Investment Committee responsible for voting and investment decisions with respect to the Issuer, currently composed of Martin J. Mannion and Peter Y. Chung, has voting and dispositive authority over the shares held by each of these entities and therefore may be deemed to beneficially own such shares. In addition, Mr. Chung is a member of Summit Master Company, LLC. Each of the Summit entities mentioned herein, Summit Partners, L.P., Summit Master Company, LLC, Mr. Mannion and Mr. Chung disclaims beneficial ownership of the shares of Common Stock and the restricted stock units, except to the extent of their pecuniary interest therein. Form 2 of 2 Summit Partners, L.P., by Summit Master Company, LLC, its GP, by /s/ Robin W. Devereux, Member 2018-11-09 Summit Master Company, LLC, by Robin W. Devereux, Member 2018-11-09 Summit Partners GE VIII, L.P., by Summit Partners GE VIII, LLC, its General Partner, by Summit Partners, L.P., its Manager, by Summit Master Company, LLC, its General Partner, by /s/ Robin W. Devereux, Member 2018-11-09 Summit Partners GE VIII, LLC, by Summit Partners, L.P., its Manager, by Summit Master Company, LLC, its General Partner, by /s/ Robin W. Devereux, Member 2018-11-09 Summit Partners Growth Equity Fund VIII-A, L.P., by Summit Partners GE VIII, L.P., its GP, by Summit Partners GE VIII, LLC, its GP, by Summit Partners, L.P., its Manager, by Summit Master Company, LLC, its GP, by /s/ Robin W. Devereux, Member 2018-11-09 Summit Partners Growth Equity Fund VIII-B, L.P., by Summit Partners GE VIII, L.P., its GP, by Summit Partners GE VIII, LLC, its GP, by Summit Partners, L.P., its Manager, by Summit Master Company, LLC, its GP, by /s/ Robin W. Devereux, Member 2018-11-09 Summit Investors Management, LLC, by Summit Master Company, LLC, its Managing Member, by Robin W. Devereux, Member 2018-11-09 Summit Investors I, LLC, by Summit Investors Management, LLC, its Manager, by Summit Master Company, LLC, its Managing Member, by Robin W. Devereux, Member 2018-11-09 Summit Investors I (UK), L.P., by Summit Investors Management, LLC, its General Partner, by Summit Master Company, LLC, its Managing Member, by Robin W. Devereux, Member 2018-11-09 Robin W. Devereux, POA for Martin J. Mannion 2018-11-09