A10 Networks, Inc. — Director's Dealing 2021

May 3, 2021

SEC Form 4 — Statement of Changes in Beneficial Ownership

Issuer: A10 Networks, Inc. (ATEN)
CIK: 0001580808
Period of Report: 2021-04-29

Reporting Person: Singer Eric (Director, 10% Owner)
Reporting Person: VIEX Opportunities Fund, LP Series One (10% Owner)
Reporting Person: VIEX Opportunities Fund, LP - Series Two (10% Owner)
Reporting Person: VIEX Special Opportunities Fund II, LP (10% Owner)
Reporting Person: VIEX Special Opportunities Fund III, LP (10% Owner)

Non-Derivative Transactions

Date	Security	Code	Shares	Price	A/D	Holdings After	Ownership
2021-04-29	Common Stock, par value $0.00001	A	16949	—	Acquired	73139	Direct

Holdings (Non-Derivative)

Security	Shares	Ownership
Common Stock, par value $0.00001	1465781	Indirect
Common Stock, par value $0.00001	482877	Indirect
Common Stock, par value $0.00001	5255022	Indirect
Common Stock, par value $0.00001	487416	Indirect

Footnotes

F1: Each share is represented by a Restricted Stock Unit ("RSU"). The RSUs will vest 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 as of such date.

F2: This Form 4 is filed jointly by VIEX Opportunities Fund, LP - Series One ("Series One"), a series of VIEX Opportunities Fund, LP, VIEX Opportunities Fund, LP - Series Two ("Series Two"), a series of VIEX Opportunities Fund, LP, VIEX Special Opportunities Fund II, LP ("VSO II"), Viex Special Opportunities Fund III, LP ("VSO III"), VIEX GP, LLC ("VIEX GP"), VIEX Special Opportunities GP II, LLC ("VSO GP II"), Viex Special Opportunities GP III, LLC ("VSO GP III"), VIEX Capital Advisors, LLC ("VIEX Capital"), and Eric Singer (collectively, the "Reporting Persons").

F3: Each Reporting Person disclaims beneficial ownership of the securities of the Issuer reported herein except to the extent of his or its pecuniary interest therein, and this report shall not be deemed to be an admission that any Reporting Person is the beneficial owner of such securities for purposes of Section 16 or any other purpose.

F4: Securities of the Issuer beneficially owned directly by Series One. VIEX GP, as the general partner of Series One, may be deemed the beneficial owner of the securities of the Issuer beneficially owned bySeries One. VIEX Capital, as the investment manager of Series One, may be deemed the beneficial owner of the securities of the Issuer beneficially owned by Series One. Mr. Singer, as the managing member ofeach of VIEX GP and VIEX Capital, may be deemed the beneficial owner of the securities of the Issuer beneficially owned by Series One.

F5: Securities of the Issuer beneficially owned directly by Series Two. VIEX GP, as the general partner of Series Two, may be deemed the beneficial owner of the securities of the Issuer beneficially owned bySeries Two. VIEX Capital, as the investment manager of Series Two, may be deemed the beneficial owner of the securities of the Issuer beneficially owned by Series Two. Mr. Singer, as the managing memberof each of VIEX GP and VIEX Capital, may be deemed the beneficial owner of the securities of the Issuer beneficially owned by Series Two.

F6: Securities of the Issuer beneficially owned directly by VSO II. VSO GP II, as the general partner of VSO II, may be deemed the beneficial owner of the securities of the Issuer beneficially owned by VSO II.VIEX Capital, as the investment manager of VSO II, may be deemed the beneficial owner of the securities of the Issuer beneficially owned by VSO II. Mr. Singer, as the managing member of each of VSO GP IIand VIEX Capital, may be deemed the beneficial owner of the securities of the Issuer beneficially owned by VSO II.

F7: Securities of the Issuer beneficially owned directly by VSO III. VSO GP III, as the general partner of VSO III, may be deemed the beneficial owner of the securities of the Issuer beneficially owned by VSOIII. VIEX Capital, as the investment manager of VSO III, may be deemed the beneficial owner of the securities of the Issuer beneficially owned by VSO III. Mr. Singer, as the managing member of each of VSOGP III and VIEX Capital, may be deemed the beneficial owner of the securities of the Issuer beneficially owned by VSO III.