Sec Form 4 Filing - CHEN LEE @ A10 Networks, Inc. - 2020-05-18

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

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1. Name and Address of Reporting Person CHEN LEE 2. Issuer Name and Ticker or Trading Symbol A10 Networks, Inc. [ ATEN] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director X __ 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) 05/18/2020 (Street) SAN JOSE, CA95131 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) __ X __ Form filed by One Reporting Person _____ 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 05/18/2020 S 2,200,000 D $ 6 ( 1 ) 7,670,224 D Common Stock 3,200 I See footnote ( 2 )

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 Employee Stock Option (right to buy) ( 3 ) $ 5.52 05/18/2020 S( 4 ) 282,500 03/12/2016( 4 ) 05/31/2020( 5 ) Common Stock 282,500 $ 0 0 D

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other CHEN LEE C/O A10 NETWORKS, INC, 2300 ORCHARD PARKWAY SAN JOSE, CA95131 X Signatures /s/ Lee Chen 05/20/2020 Signature of Reporting Person Date

Explanation of Responses:

( 1 )The Issuer and Reporting Person entered into a Common Stock Repurchase and Option Exchange Agreement (the "Repurchase Agreement") for the purchase by the Issuer, and sale by the Reporting Person, of 2,200,000 shares of the Issuer's common stock in a privately-negotiated transaction for an aggregate purchase price of $13,200,000. ( 2 )Shares held of record by the U/A DTD 07/25/2000 Lee Chen Family Trust, for which the Reporting Person serves as a trustee. ( 3 )Represents fully vested stock options. ( 4 )Pursuant to the Repurchase Agreement, in addition to the purchase and sale of common stock referenced in footnote 1, the Reporting Person agreed to cancel such options in exchange for the payment by the Issuer to the Reporting Person of $135,600. ( 5 )Following Reporting Person's separation from service, the stock options expire if not exercised by May 31, 2020.

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).

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