Sec Form 4 Filing - Singer Eric @ A10 Networks, Inc. - 2022-05-05

FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

OMB APPROVAL OMB Number: 3235-0287 Expires: November 30, 2011 Estimated average burden hours per response... 0.5

1. Name and Address of Reporting Person Singer Eric 2. Issuer Name and Ticker or Trading Symbol A10 Networks, Inc. [ ATEN] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) X __ Director _____ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) C/O A10 NETWORKS, INC., 2300 ORCHARD PARKWAY 3. Date of Earliest Transaction (MM/DD/YY) 05/05/2022 (Street) SAN JOSE, CA95131 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) _____ Form filed by One Reporting Person __ X __ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Stock, par value $0.00001 05/05/2022 S 116,535 D $ 15.0876( 3 ) 135,139 D( 1 )( 2 ) Common Stock, par value $0.00001 05/06/2022 S 62,000 D $ 14.9356( 4 ) 73,139 D( 1 )( 2 ) Common Stock, par value $0.00001 05/05/2022 S 150,000 D $ 15.4483( 7 ) 495,541 I By Viex Opportunities Fund, LP - Series One( 1 )( 2 )( 5 ) Common Stock, par value $0.00001 05/06/2022 S 90,000 D $ 15.0693( 8 ) 405,541 I By Viex Opportunities Fund, LP - Series One( 1 )( 2 )( 5 ) Common Stock, par value $0.00001 05/09/2022 S 100,000 D $ 14.1582( 9 ) 305,541 I By Viex Opportunities Fund, LP - Series One( 1 )( 2 )( 5 ) Common Stock, par value $0.00001 05/05/2022 S 80,000 D $ 15.4483( 10 ) 103,036 I By Viex Opportunities Fund, LP - Series Two( 1 )( 2 )( 6 )

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities) 1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5) 6. Date Exercisable and Expiration Date (MM/DD/YY) 7. Title and Amount of Underlying Securities (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4) Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Singer Eric C/O A10 NETWORKS, INC. 2300 ORCHARD PARKWAY SAN JOSE, CA95131 X VIEX Opportunities Fund, LP Series One C/O A10 NETWORKS, INC. 2300 ORCHARD PARKWAY SAN JOSE, CA95131 See Explanation of Responses VIEX Opportunities Fund, LP - Series Two C/O A10 NETWORKS, INC. 2300 ORCHARD PARKWAY SAN JOSE, CA95131 See Explanation of Responses Signatures /s/ Eric Singer 05/09/2022 Signature of Reporting Person Date VIEX Opportunities Fund, LP - Series One, By: VIEX GP, LLC, its general partner, By: /s/ Eric Singer, Managing Member 05/09/2022 Signature of Reporting Person Date VIEX Opportunities Fund, LP - Series Two, By: VIEX GP, LLC, its general partner, By: /s/ Eric Singer, Managing Member 05/09/2022 Signature of Reporting Person Date

Explanation of Responses:

( 1 )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 GP, LLC ("VIEX GP"), VIEX Capital Advisors, LLC ("VIEX Capital"), and Eric Singer (collectively, the "Reporting Persons"). ( 2 )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. ( 3 )Represents a weighted average price. These Shares were purchased in multiple transactions at prices ranging from $15.00 to $15.18. The Reporting Persons undertake to provide the Issuer, any security holder of the Issuer or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of Shares purchased at each separate price within the range set forth in this footnote. ( 4 )Represents a weighted average price. These Shares were purchased in multiple transactions at prices ranging from $14.90 to $14.98. The Reporting Persons undertake to provide the Issuer, any security holder of the Issuer or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of Shares purchased at each separate price within the range set forth in this footnote. ( 5 )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 by Series 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 of each of VIEX GP and VIEX Capital, may be deemed the beneficial owner of the securities of the Issuer beneficially owned by Series One. ( 6 )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 by Series 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 member of each of VIEX GP and VIEX Capital, may be deemed the beneficial owner of the securities of the Issuer beneficially owned by Series Two. ( 7 )Represents a weighted average price. These Shares were purchased in multiple transactions at prices ranging from $14.90 to $16.50. The Reporting Persons undertake to provide the Issuer, any security holder of the Issuer or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of Shares purchased at each separate price within the range set forth in this footnote. ( 8 )Represents a weighted average price. These Shares were purchased in multiple transactions at prices ranging from $14.84 to $15.46. The Reporting Persons undertake to provide the Issuer, any security holder of the Issuer or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of Shares purchased at each separate price within the range set forth in this footnote. ( 9 )Represents a weighted average price. These Shares were purchased in multiple transactions at prices ranging from $13.79 to $14.66. The Reporting Persons undertake to provide the Issuer, any security holder of the Issuer or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of Shares purchased at each separate price within the range set forth in this footnote. ( 10 )Represents a weighted average price. These Shares were purchased in multiple transactions at prices ranging from $14.90 to $16.50. The Reporting Persons undertake to provide the Issuer, any security holder of the Issuer or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of Shares purchased at each separate price within the range set forth in this footnote.

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).

** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).

Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.