Sec Form 4 Filing - COCHRAN ROBERT D @ A10 Networks, Inc. - 2021-02-02

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 COCHRAN ROBERT D 2. Issuer Name and Ticker or Trading Symbol A10 Networks, Inc. [ ATEN] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director _____ 10% Owner X __ Officer (give title below) _____ Other (specify below) EVP Legal & Corp Collaboration (Last) (First) (Middle) C/O A10 NETWORKS, 2300 ORCHARD PARKWAY 3. Date of Earliest Transaction (MM/DD/YY) 02/02/2021 (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 02/02/2021 A 14,970 ( 1 ) A $ 0 242,499 D Common Stock 02/02/2021 M 20,467 ( 2 ) A $ 0 262,966 D

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 Performance-based Restricted Stock Units ( 3 ) 02/02/2021 A 34,930 ( 4 ) 02/02/2025 Common Stock 34,930 $ 0 34,930 D Performance-based Restricted Stock Units ( 2 ) 02/02/2021 M 20,467 ( 2 ) 07/02/2024 Common Stock 20,467 $ 0 40,936 D

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other COCHRAN ROBERT D C/O A10 NETWORKS 2300 ORCHARD PARKWAY SAN JOSE, CA95131 EVP Legal & Corp Collaboration Signatures /s/ Robert D. Cochran 02/04/2021 Signature of Reporting Person Date

Explanation of Responses:

( 1 )Each share is represented by a Restricted Stock Unit ("RSU"). One-third (1/3) of the total RSUs will vest on each of the first three (3) anniversaries of the date of grant, provided that the Reporting Person continues to serve through each vesting date. ( 2 )Performance-Based Restricted Stock Units were previously reported on July 7, 2020, each of which represents a contingent right to receive one share of common stock of ATEN, with vesting subject to the achievement of specified levels of the volume weighted average closing prices of a share of ATEN common stock during any one hundred (100) day trading period between July 2, 2020 and July 2, 2024. The first achievement date occurred on January 28, 2021, as certified by the compensation committee of ATEN on February 2, 2021, resulting in 20,467 units meeting the appropriate performance-based conditions. However, these shares remain subject to time-based vesting conditions and will therefore vest as to one-third within thirty (30) days of achievement of the milestone with an additional one-third to vest on each of the first and second anniversaries of achievement of the milestone, subject to continued employment. These shares are reflected on Table I. ( 3 )Each share is represented by a Performance-based Restricted Stock Unit ("PSU") ( 4 )Grant of 34,930 Performance-Based Restricted Stock Units, each of which represents a contingent right to receive one share of common stock of ATEN, with vesting subject to the achievement of specified levels of the volume weighted average closing prices of a share of ATEN common stock during any one hundred (100) day trading period between February 2, 2021 and February 2, 2025 (each, a "Performance Milestone"). Upon achievement of a Performance Milestone, vesting is subject to continued employment with the Company through the applicable vesting date, which occurs in three equal installments with the first vesting to occur within thirty (30) days of achievement of the Performance Milestone and an additional one-third (1/3) on each of the first and second anniversaries of the date of achievement of the corresponding Performance Milestone.

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