X0306 4 2021-12-07 0 0001580808 A10 Networks, Inc. ATEN 0000830588 SUMMIT PARTNERS L P 222 BERKELEY STREET 18TH FLOOR BOSTON MA 02116 0 0 0 1 Manager of GP of 10% owner 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 0001507545 Summit Investors Management, LLC 222 BERKELEY STREET, 18TH FLOOR BOSTON MA 02116 0 0 0 1 Manager and 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 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 2021-12-07 4 S 0 700000 15.05 D 8877890 I See Footnotes. The Common Stock sold as follows: 510,318 shares in the name of Summit Partners Growth Equity Fund VIII-A, L.P.; 186,436 shares in the name of Summit Partners Growth Equity Fund VIII-B, L.P.; 2,984 shares in the name of Summit Investors I, LLC; 262 shares in the name of Summit Investors I (UK), L.P. The Common Stock held as follows: 6,362,818 shares in the name of Summit Partners Growth Equity Fund VIII-A, L.P.; 2,324,553 shares in the name of Summit Partners Growth Equity Fund VIII-B, L.P.; 37,202 shares in the name of Summit Investors I, LLC; 3,273 shares in the name of Summit Investors I (UK), L.P.; 150,044 shares (including shares underlying RSUs) in the name of Mr. 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 Partners GE VIII, LLC, as the general partner of Summit Partners GE VIII, L.P., and Summit Master Company, LLC, as the managing member of Summit Investors Management, LLC has each 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 Company. Summit Partners, L.P., through a two-person Investment Committee responsible for voting and investment decisions with respect to the Company, currently composed of Martin J. Mannion and Mr. Chung, has voting and dispositive authority over the shares of Common Stock held by each of the entities described in the foregoing footnotes (2) and (3) 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, Mr. Mannion and Mr. Chung disclaims beneficial ownership of the shares of Common Stock (including shares underlying RSUs) reported herein, 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 2021-12-09 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 2021-12-09 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 2021-12-09 Summit Investors Management, LLC, by Summit Master Company, LLC, its Managing Member, by Robin W. Devereux, Member 2021-12-09 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 2021-12-09 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 2021-12-09 Summit Investors I, LLC, by Summit Investors Management, LLC, its Manager, by Summit Master Company, LLC, its Managing Member, by Robin W. Devereux, Member 2021-12-09 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 2021-12-09 Robin W. Devereux, POA for Martin J. Mannion 2021-12-09