UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d)

of the Securities Exchange Act of 1934

Date of report (Date of earliest event reported): July 26, 2019

A10 NETWORKS, INC.

(Exact Name of Registrant as Specified in its Charter)

3 West Plumeria Drive

San Jose, CA 95134

(Address of Principal Executive Offices, including zip code)

(408) 325-8668

(Registrant’s telephone number including area code)

Not Applicable

(Former Name or Address, if Changed Since Last Report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

Securities registered pursuant to Section 12(b) of the Act:

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter).

Emerging growth company  ☒

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act.  ☐

On July 26, 2019, A10 Networks, Inc. (the “Company”) entered into a letter agreement (the “Agreement”) with VIEX Capital Advisors, LLC (“VIEX”), VIEX Opportunities Fund, LP – Series One, VIEX Opportunities Fund, LP – Series Two, VIEX GP, LLC, VIEX Special Opportunities Fund II, LP, VIEX Special Opportunities GP II, LLC, VIEX Special Opportunities Fund III, LP, VIEX Special Opportunities GP III, LLC and Eric Singer (collectively, the “VIEX Group”). Among other things, the Agreement provides that:

The foregoing summary of the Agreement does not purport to be complete and is subject to, and qualified in its entirety by, the full text of the Agreement, which is attached as Exhibit 10.1 and incorporated herein by reference.

On July 30, 2019, the Company issued a press release regarding financial results for the quarter ended June 30, 2019. The Company also posted on its website (www.a10networks.com) slides with accompanying prepared remarks regarding such financial results. Copies of the press release and slides with accompanying prepared remarks by the Company are attached as Exhibits 99.1 and 99.2, respectively, and the information in Exhibits 99.1 and 99.2 are incorporated herein by reference.

The information in this Item 2.02 and Exhibits 99.1 and 99.2 attached hereto shall not be deemed “filed” for the purposes of Section 18 of the Securities Exchange Act of 1934, as amended, or otherwise subject to the liabilities of that Section, nor shall it be deemed incorporated by reference into any filing under the Securities Act of 1933, as amended, or the Securities Exchange Act of 1934, as amended.

(b) Departure of Directors or Certain Officers

On July 30, 2019, the Company announced the planned retirement of Lee Chen, the Company’s president and chief executive officer. The Board has formed a search committee and retained an executive search firm for the purpose of recruiting and exploring potential CEO candidates. Upon the appointment of a successor, Mr. Chen will resign as president and chief executive officer.

(d) Election of Director

In connection with the Agreement, the Board increased the size of the Board to six directors and appointed Mr. Singer to serve as a director, effective July 26, 2019. Mr. Singer was also appointed to the Board’s Compensation Committee, Nominating and Corporate Governance Committee and Strategy Committee.

Following this, the Board’s standing committees are composed of:

Other than as described in Item 1.01, there are no arrangements or understandings between Mr. Singer, on the one hand, and the Company or any other persons, on the other hand, pursuant to which Mr. Singer was selected as a director. There are no related party transactions between the Company and Mr. Singer (or any of his immediate family members) requiring disclosure under Item 404(a) of Regulation S-K. Mr. Singer does not have any family relationships with any of the Company’s directors or executive officers.

Mr. Singer will participate in the director benefits arrangements applicable to non-employee directors as described in the Company’s Annual Report on Form 10-K/A filed with the Securities and Exchange Commission on April 26, 2019. In addition, the Company will enter into its standard form of indemnification agreement with Mr. Singer.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

Date:    July 30, 2019

Exhibit 10.1

A10 Networks, Inc.

3 West Plumeria Drive

San Jose, CA 95134

July 26, 2019

VIEX Capital Advisors, LLC

745 Boylston Street, 3rd Floor

Boston, MA 02116

Attn:    Eric Singer

Gentlemen:

This letter (this “Agreement”) constitutes the agreement between (a) A10 Networks, Inc. (“Company”) and (b) VIEX Capital Advisors, LLC (“VIEX”) and each of the other related Persons (as defined below) set forth on the signature pages to this Agreement (collectively with VIEX, the “VIEX Group”). The VIEX Group and each of its Affiliates (as defined below) and Associates (as defined below) are collectively referred to as the “Investors.” Company and the VIEX Group are collectively the “Parties.”

1.    Appointment of New Director. Contingent upon and immediately following the execution of this Agreement, Company’s Board of Directors (the “Board”) will take all action necessary to increase the size of the Board by one and appoint Eric Singer (the “Designee”) as a director with a term expiring at Company’s 2019 Annual Meeting of Stockholders (the “2019 Annual Meeting”).

2.    Replacement Director. During the Restricted Period (as defined below), if (a) the Designee ceases to be a member of the Board for any reason and (b) at such time the VIEX Group beneficially owns shares (which shares are determined to be Net Long Shares (as defined below)) representing in the aggregate at least two percent of Company’s then-outstanding common stock, then VIEX will have the right to recommend (and the Board will promptly appoint) another person (a “Successor Director”) to serve as a director in place of the Designee. Any Successor Director must (a) be qualified to serve as a member of the Board under all applicable corporate governance policies or guidelines of Company and the Board and applicable legal, regulatory and stock market requirements; and (b) meet the independence requirements with respect to Company of the listing rules of The New York Stock Exchange. Upon becoming a member of the Board, the Successor Director will succeed to all of the rights and privileges, and will be bound by the terms and conditions, of the Designee under this Agreement.

3.    Additional New Director. After August 25, 2019, and prior to the expiration of the Restricted Period, VIEX will have the right to recommend one independent director (the “Additional Designee”) for appointment to the Board. The Additional Designee must (a) be qualified to serve as a member of the Board under all applicable corporate governance policies or guidelines of Company and the Board and applicable legal, regulatory and stock market

requirements; and (b) meet the independence requirements with respect to Company of the listing rules of The New York Stock Exchange. No later than 15 days after being identified to Company, Company will take all action necessary to cause (a) the resignation of Phillip J. Salsbury from the Board; and (b) the appointment of the Additional Designee to the Board.

4.    Board Size. Except for the increase to the size of the Board contemplated by paragraph 1, during the Restricted Period a unanimous vote of all directors then-serving on the Board will be required to increase the size of the Board beyond six members.

5.    2019 Annual Meeting. Company agrees to nominate the Designee and Tor R. Braham (together, the “VIEX Designees”) for election as directors at the 2019 Annual Meeting with terms expiring at Company’s 2020 Annual Meeting of Stockholders (the “2020 Annual Meeting”). Company will recommend that Company’s stockholders vote, and will solicit proxies, in favor of the election of the VIEX Designees at the 2019 Annual Meeting and otherwise support the VIEX Designees for election in a manner no less rigorous and favorable than the manner in which Company supports its other director nominees at the 2019 Annual Meeting.

6.    Committee Assignments. Concurrent with the appointment of the Designee to the Board, the Board will appoint the Designee to the Board’s strategy committee (the “Strategy Committee”), compensation committee and nominating and corporate governance committee. The other members of the Strategy Committee are Mr. Braham and Peter Chung. The size of the Strategy Committee will be fixed at three directors during the Restricted Period.

7.    Compliance with Laws and Company Policies. The Investors acknowledge that Company may request the Designee and any Additional Designee to agree in writing, during the term of service as a director of Company, to (a) comply with all laws, policies, procedures, processes, codes, rules, standards and guidelines applicable to members of the Board, including Company’s code of conduct, insider trading policy, Regulation FD policy, related party transactions policy and corporate governance guidelines, in each case as amended from time to time; and (b) keep confidential all confidential information of Company and not disclose to any third party (including the Investors) any discussions or matters considered in meetings of the Board and its committees (unless such discussion or matters have been previously disclosed publicly by Company).

8.    No Fiduciary Restriction. Notwithstanding anything to the contrary in this Agreement, the Investors acknowledge that the Designee and any Additional Designee, during such director’s service as a director of Company, will not be prohibited from acting in such director’s capacity as a director or from complying with such director’s fiduciary duties as a director of Company (including voting on any matter submitted for consideration by the Board, participating in deliberations or discussions of the Board, and making suggestions or raising any issues or recommendations to the Board).

9.    Director Benefits. The Designee and any Additional Designee will be entitled to the same director benefits as other members of the Board, including (a) compensation for such director’s service as a director and reimbursement for such director’s expenses on the same basis as all other non-employee directors of Company; (b) equity-based compensation grants and other benefits, if

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any, on the same basis as all other non-employee directors of Company; and (c) the same rights of indemnification and directors’ and officers’ liability insurance coverage as the other non-employee directors of Company as such rights may exist from time to time.

10.    Voting Commitment. During the Restricted Period, at each annual or special meeting of Company’s stockholders or action by written consent, the Investors will (a) cause all Voting Securities (as defined below) that are beneficially owned by them to be present for quorum purposes, if applicable; and (b) vote, or cause to be voted, all Voting Securities beneficially owned by them in a manner consistent with the recommendation of the Board. Notwithstanding the prior sentence, (i) if, as of the date of the 2019 Annual Meeting, Institutional Shareholder Services Inc. (“ISS”) and Glass Lewis & Co., LLC (“Glass Lewis”) both recommend a vote “against” or “abstain” on any proposal presented at the 2019 Annual Meeting (other than any proposal relating to the election or removal of directors), then the Investors will be permitted to vote in accordance with the ISS and Glass Lewis recommendations on that proposal; and (ii) the Investors will have the right to vote in their sole discretion with respect to any merger, acquisition, recapitalization, restructuring, disposition, distribution, spin-off, asset sale, joint venture or other business combination involving Company.

11.    Standstill. During the Restricted Period, none of the Investors will, and VIEX will cause the principals, directors, general partners, officers, employees, agents and representatives of each Investor not to, in any way, directly or indirectly (in each case, except as expressly permitted by this Agreement):

(a)    with respect to Company or the Voting Securities, (i) make, participate in or encourage any “solicitation” (as such term is used in the proxy rules of Securities and Exchange Commission (the “SEC”)) of proxies or consents with respect to the election or removal of directors or any other matter or proposal; (ii) become a “participant” (as such term is used in the proxy rules of the SEC) in any such solicitation of proxies or consents; (iii) seek to advise, encourage or influence any Person with respect to the voting or disposition of any Voting Securities; or (iv) initiate, encourage or participate, directly or indirectly, in any “vote no,” “withhold” or similar campaign;

(b)    initiate, propose or otherwise “solicit” (as such term is used in the proxy rules of the SEC) Company’s stockholders for the approval of any shareholder proposal, whether made pursuant to Rule 14a-4 or Rule 14a-8 promulgated under the Securities Exchange Act of 1934 (the “Exchange Act”), or otherwise, or cause or encourage any Person to initiate or submit any such shareholder proposal;

(c)    with respect to Company or the Voting Securities, (i) communicate with Company’s stockholders or others pursuant to Rule 14a-1(l)(2)(iv) pursuant to the Exchange Act; (ii) participate in, or take any action pursuant to, or encourage any Person to take any action pursuant to, any type of “proxy access”; or (iii) conduct any nonbinding referendum or hold a “stockholder forum”;

(d)    (i) seek, alone or in concert with others, election or appointment to, or representation on, the Board; (ii) nominate or propose the nomination of, or recommend the

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nomination of, or encourage any Person to nominate or propose the nomination of or recommend the nomination of, any candidate to the Board; or (iii) seek, alone or in concert with others, or encourage any Person to seek, the removal of any member of the Board;

(e)    (i) call or seek to call a special meeting of stockholders, or encourage any Person to call a special meeting of stockholders; (ii) act or seek to act by written consent of stockholders; or (iii) make a request for any stockholder list or other similar Company records;

(f)    other than solely with other Investors and their Affiliates with respect to Voting Securities now or subsequently owned by them, (i) form, join (whether or not in writing), encourage, influence, advise or participate in a partnership, limited partnership, syndicate or other group, including a “group” as defined pursuant to Section 13(d) of the Exchange Act, with respect to any Voting Securities (other than any group comprised solely of Investors and their Affiliates); (ii) deposit any Voting Securities into a voting trust, arrangement or agreement; or (iii) subject any Voting Securities to any voting trust, arrangement or agreement;

(g)    (i) make any offer or proposal (with or without conditions) with respect to any merger, acquisition, recapitalization, restructuring, disposition or other business combination involving any Investor and Company; (ii) solicit a third party to, on an unsolicited basis, make an offer or proposal (with or without conditions) with respect to any merger, acquisition, recapitalization, restructuring, disposition or other business combination involving Company, or publicly encourage, initiate or support any third party in making such an offer or proposal; or (iii) publicly comment on any proposal regarding any merger, acquisition, recapitalization, restructuring, disposition or other business combination with respect to Company by a third party prior to such proposal becoming public;

(h)    other than through non-public communications with Company that would not reasonably be expected to trigger public disclosure obligations for any Party, make or disclose any statement regarding any intent, purpose, plan or proposal with respect to the Board, Company or its management, policies, affairs or assets, or the Voting Securities or this Agreement, that is inconsistent with the provisions of this Agreement, including any intent, purpose, plan or proposal that is conditioned on, or would require, the waiver, amendment, nullification or invalidation of any provision of this Agreement, or take any action that could require Company to make any public disclosure relating to any such intent, purpose, plan, proposal or condition;

(i)    institute, solicit, assist or join, as a party, any litigation, arbitration or other proceedings against or involving Company or any of its current or former directors or officers (including derivative actions) based upon facts publicly known as of the date of this Agreement, other than (i) litigation by the Investors enforce the provisions of this Agreement; (ii) counterclaims with respect to any proceeding initiated by, or on behalf of, Company or any of its Affiliates against the Investors; and (iii) the exercise of statutory appraisal rights;

(j)    take any action in support of, or, other than through non-public communications, make any proposal or request that constitutes: (i) controlling, changing or influencing Company’s management, business or corporate structure; (ii) seeking to have Company waive or make amendments or modifications to its certificate of incorporation or bylaws;

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(iii) causing a class of securities of Company to be delisted from, or to cease to be authorized to be quoted on, any securities exchange; or (iv) causing a class of securities of Company to become eligible for termination of registration pursuant to Section 12(g)(4) of the Exchange Act;

(k)    sell, offer or agree to sell to any third party, through swap or hedging transactions, derivative agreements or otherwise, any voting rights decoupled from the underlying Voting Securities held by the Investors;

(l)    acquire, offer, agree or propose to acquire, whether by purchase, tender or exchange offer, through the acquisition of control of another Person, by joining a partnership, limited partnership, syndicate or other group, including a “group” as defined pursuant to Section 13(d) of the Exchange Act, through swap or hedging transactions, or otherwise, any securities of Company or any rights decoupled from the underlying securities of Company that would result in the Investors in the aggregate beneficially owning more than 9.9 percent of the then-outstanding Voting Securities; or

(m)    other than through open market broker sale transactions where the identity of the purchaser is not known and in underwritten widely dispersed public offerings, sell, offer or agree to sell, through swap or hedging transactions or otherwise, the securities of Company to any Person not a Party (a “Third Party”) that, to VIEX’s knowledge (after due inquiry in connection with a private, non-open market transaction, it being understood that such knowledge will be deemed to exist with respect to any publicly available information, including information in documents filed with the SEC), would result in such Third Party, together with its Affiliates and Associates, owning, controlling or otherwise having any beneficial or other ownership interest of more than 4.9 percent of the then-outstanding Voting Securities or that would increase the beneficial or other ownership interest of any Third Party who, together with its Affiliates and Associates, has a beneficial or other ownership interest of more than 4.9 percent of the then-outstanding Voting Securities.

12.    Permitted Actions. Notwithstanding paragraph 11, nothing in this Agreement will prohibit or restrict the Investors from: (a) communicating privately with the Board or any officer or director of Company regarding any matter, so long as such communications are not intended to, and would not reasonably be expected to, require any public disclosure of such communications, subject in any case to any confidentiality obligations to Company of any such director or officer; (b) taking any action necessary to comply with any law, rule or regulation or any action required by any governmental or regulatory authority or stock exchange that has, or may have, jurisdiction over the Investors or any of their respective Affiliates or Associates, but only if a breach by the Investors of this Agreement is not the cause of the applicable requirement; or (c) privately communicating to any of their investors or potential investors factual information regarding Company, but only if such communications are subject to reasonable confidentiality obligations and are not otherwise reasonably expected to be publicly disclosed. For the avoidance of doubt, subject to applicable law, the Investors will not be prohibited from communicating privately with stockholders of Company and others in a manner that does not otherwise violate paragraph 11.

13.    Non-Disparagement. Subject to applicable law, each of the Parties covenants and agrees that, during the Restricted Period, it and its respective Affiliates, Associates, subsidiaries, officers, key employees, general partners and directors will not in any way publicly disparage, call

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into disrepute or otherwise defame or slander the other Party or such other Party’s Affiliates, Associates, subsidiaries, successors, assigns, officers (including any current or former officer of such other Party or its subsidiaries), directors (including any current or former director of such other Party or its subsidiaries), employees, stockholders, agents, attorneys or representatives, or any of their businesses, products or services, in any manner that would reasonably be expected to damage the business or reputation of such other Party or its businesses, products or services, subsidiaries, Affiliates, successors, assigns, officers (or former officers), directors (or former directors), employees, stockholders, agents, attorneys or representatives. This paragraph 13 will not apply to any statement made in connection with any action to enforce this Agreement.

14.    No Compensation Arrangements. The Investors will not, directly or indirectly, compensate or agree to compensate the Designee for his service as a director of Company with any cash, securities (including any rights or options convertible into or exercisable for or exchangeable into securities or any profit-sharing agreement or arrangement) or other form of compensation directly or indirectly related to Company or its securities.

15.    Compliance with this Agreement. VIEX will cause the other Investors to comply with the terms of this Agreement and will be responsible for any breach of the terms of this Agreement by any Investor, in each case even if such Investor is not a party to this Agreement.

16.    Expense Reimbursement. Within five business days of the receipt of appropriate documentation, Company will reimburse the Investors for their reasonable and documented out-of-pocket fees and expenses (including legal expenses) (up to a maximum of $25,000) incurred by the Investors in connection with the negotiation and execution of this Agreement.

17.    Public Disclosure.

(a)    Press Release. No later than 5:00 p.m., Eastern time, on July 30, 2019, Company will issue a press release in the form attached as Exhibit A (the “Press Release”). Neither Company nor the Investors will make any public statements with respect to the matters covered by this Agreement (including in the Schedule 13D or in any other filing with the SEC, any other regulatory or governmental agency, any stock exchange or in any materials that would reasonably be expected to be filed with the SEC) that are inconsistent with, or otherwise contrary to, the statements in the Press Release.

(b)    Form 8-K. Company will promptly prepare and file (but not before the issuance of the Press Release) with the SEC a Current Report on Form 8-K (the “Form 8-K”) reporting the entry into this Agreement. All disclosure in the Form 8-K will be consistent with this Agreement. Company will provide VIEX and its counsel with a reasonable opportunity to review and comment on the Form 8-K prior to filing, and will consider in good faith any changes proposed by VIEX or its counsel.

(c)    Amended Schedule 13D. The VIEX Group will promptly prepare and file (but not before the issuance of the Press Release) with the SEC an amendment to its Schedule 13D (the “Amended Schedule 13D”) with respect to Company reporting the entry into this Agreement. All disclosure in the Amended Schedule 13D will be consistent with this Agreement. The VIEX Group

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will provide Company and its counsel with reasonable opportunity to review and comment on the Amended Schedule 13D prior to filing, and will consider in good faith any changes proposed by Company or its counsel.

18.    Definitions. As used in this Agreement, the term (a) “Person” will be interpreted broadly to include, among others, any individual, general or limited partnership, corporation, limited liability or unlimited liability company, joint venture, estate, trust, group, association or other entity of any kind or structure; (b) “Affiliate” has the meaning set forth in Rule 12b-2 promulgated under the Exchange Act and will include Persons who become Affiliates of any Person after the date of this Agreement; (c) “Associate” has the meaning set forth in Rule 12b-2 promulgated under the Exchange Act and will include Persons who become Associates of any Person after the date of this Agreement, but will exclude any Person not controlled by or under common control with the related Person; (d) “beneficially own,” “beneficially owned” and “beneficial ownership” has the meaning set forth in Rule 13d-3 promulgated under the Exchange Act; (e) “business day” means any day other than a Saturday, Sunday or a day on which the Federal Reserve Bank of San Francisco is closed; (f) “Net Long Shares” will be limited to the number of shares of Company’s common stock beneficially owned by any Person that constitute such Person’s net long position as defined in Rule 14e-4 under the Exchange Act (except that for purposes of such definition, the date that the tender offer is first announced will instead be the date for determining or documenting such Person’s Net Long Shares and the reference to the highest tender price will refer to the market price on such date) and, to the extent not covered by such definition, reduced by any shares as to which such Person does not have the right to vote or direct the vote as of the date for determining or documenting or as to which such Person has entered into a derivative or other agreement, arrangement or understanding that hedges or transfers, in whole or in part, directly or indirectly, any of the economic consequences of ownership of such shares, it being understood that whether shares constitute Net Long Shares will be decided by the Board in its reasonable determination; (g) “Restricted Period” means the period from the date of this Agreement until 11:59 p.m., Pacific time, on the day that is 15 business days prior to the deadline for the submission of stockholder nominations of directors and business proposals for 2020 Annual Meeting as set forth in Company’s bylaws as in effect on the date of this Agreement (it being understood that Company will not advance or delay the dates of the 2019 Annual Meeting or 2020 Annual Meeting by more than 30 days from the date of the previous year’s annual meeting); and (h) “Voting Securities” means the shares of Company’s common stock and any other securities of Company entitled to vote in the election of directors, or securities convertible into, or exercisable or exchangeable for, such shares or other securities, whether or not subject to the passage of time or other contingencies.

19.    Interpretations. The words “include,” “includes” and “including” will be deemed to be followed by the words “without limitation.” The word “or” is not exclusive. The definitions contained in this Agreement are applicable to the singular as well as the plural forms of such terms. Any agreement, instrument, law, rule or statute defined or referred to in this Agreement means, unless otherwise indicated, such agreement, instrument, law, rule or statute as from time to time amended, modified or supplemented. The measure of a period of one month or year for purposes of this Agreement will be the day of the following month or year corresponding to the starting date. If no corresponding date exists, then the end date of such period being measured will be the next actual day of the following month or year (for example, one month following February 18 is March 18 and one month following March 31 is May 1).

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20.    Representations of the VIEX Group. Each member of the VIEX Group, severally and not jointly, represents that (a) its authorized signatory set forth on the signature page to this Agreement has the power and authority to execute this Agreement and any other documents or agreements to be entered into in connection with this Agreement and to bind such member; (b) this Agreement has been duly authorized, executed and delivered by it and is a valid and binding obligation of such member, enforceable against it in accordance with its terms, except as enforcement thereof may be limited by applicable bankruptcy, insolvency, reorganization, moratorium, fraudulent conveyance or similar laws generally affecting the rights of creditors and subject to general equity principles; (c) this Agreement does not and will not violate any law, any order of any court or other agency of government, its organizational documents or any provision of any agreement or other instrument to which such member or any of its properties or assets is bound, or conflict with, result in a breach of or constitute (with due notice or lapse of time or both) a default under any such agreement or other instrument, or result in the creation or imposition of, or give rise to, any material lien, charge, restriction, claim, encumbrance or adverse penalty of any nature whatsoever; and (d) as of the date of this Agreement, it has not, directly or indirectly, compensated or agreed to compensate the Designee for his service as a director of Company with any cash, securities (including any rights or options convertible into or exercisable for or exchangeable into securities or any profit sharing agreement or arrangement) or other form of compensation directly or indirectly related to Company or its securities. The VIEX Group represents and warrants that as of the date of this Agreement, it is the beneficial owner of an aggregate of 6,315,775 shares of Company’s common stock, including 523,100 shares underlying call options that are currently exercisable. The VIEX Group is also party to various put options covering an aggregate of 1,679,600 shares of Company’s common stock.

21.    Representations of Company. Company represents that this Agreement (a) has been duly authorized, executed and delivered by it and is a valid and binding obligation of Company, enforceable against Company in accordance with its terms, except as enforcement thereof may be limited by applicable bankruptcy, insolvency, reorganization, moratorium, fraudulent conveyance or similar laws generally affecting the rights of creditors and subject to general equity principles; (b) does not require the approval of the stockholders of Company; and (c) does not and will not violate any law, any order of any court or other agency of government, Company’s certificate of incorporation or bylaws, each as amended from time to time, or any provision of any agreement or other instrument to which Company or any of its properties or assets is bound, or conflict with, result in a breach of or constitute (with due notice or lapse of time or both) a default under any such agreement or other instrument, or result in the creation or imposition of, or give rise to, any material lien, charge, restriction, claim, encumbrance or adverse penalty of any nature whatsoever.

22.    Specific Performance. Each Party acknowledges and agrees that money damages would not be a sufficient remedy for any breach (or threatened breach) of this Agreement by it and that, in the event of any breach or threatened breach of this Agreement, (a) the Party seeking specific performance will be entitled to injunctive and other equitable relief, without proof of actual damages; (b) the Party against whom specific performance is sought will not plead in defense that there would be an adequate remedy at law; and (c) the Party against whom specific performance is sought agrees to waive any applicable right or requirement that a bond be posted. Such remedies will not be the exclusive remedies for a breach of this Agreement, but will be in addition to all other remedies available at law or in equity.

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23.    Entire Agreement; Binding Nature; Assignment; Waiver. This Agreement constitutes the only agreement between the Parties with respect to the subject matter of this Agreement and it supersedes all prior agreements, understandings, negotiations and discussions, whether oral or written (including the letter agreement between the Parties dated March 13, 2018). This Agreement binds, and will inure to the benefit of, the Parties and their respective successors and permitted assigns. No Party may assign or otherwise transfer either this Agreement or any of its rights, interests, or obligations under this Agreement without the prior written approval of the other Party. Any purported transfer requiring consent without such consent is void. No amendment, modification, supplement or waiver of any provision of this Agreement will be effective unless it is in writing and signed by the affected Party, and then only in the specific instance and for the specific purpose stated in such writing. Any waiver by any Party of a breach of any provision of this Agreement will not operate as or be construed to be a waiver of any other breach of such provision or of any breach of any other provision of this Agreement. The failure of a Party to insist upon strict adherence to any term of this Agreement on one or more occasions will not be considered a waiver or deprive that Party of the right to insist upon strict adherence to that term or any other term of this Agreement in the future.

24.    Severability. If any provision of this Agreement is held invalid or unenforceable by any court of competent jurisdiction, then the other provisions of this Agreement will remain in full force and effect. Any provision of this Agreement that is held invalid or unenforceable only in part or degree will remain in full force and effect to the extent not held invalid or unenforceable, and this Agreement will otherwise be construed so as to effectuate the original intention of the Parties reflected in this Agreement. The Parties further agree to replace such invalid or unenforceable provision of this Agreement with a valid and enforceable provision that will achieve, to the extent possible, the purposes of such invalid or unenforceable provision.

25.    Governing Law; Forum. This Agreement is governed by and will be construed in accordance with the laws of the State of Delaware. Each of the Parties (a) irrevocably and unconditionally consents to the exclusive personal jurisdiction and venue of the Court of Chancery of the State of Delaware and any appellate court thereof (unless the federal courts have exclusive jurisdiction over the matter, in which case the United States District Court for the District of Delaware and any appellate court thereof will have exclusive personal jurisdiction); (b) agrees that it will not attempt to deny or defeat such personal jurisdiction by motion or other request for leave from any such court; (c) agrees that it will not bring any action relating to this Agreement or otherwise in any court other than the such courts; and (d) waives any claim of improper venue or any claim that those courts are an inconvenient forum. The Parties agree that mailing of process or other papers in connection with any such action or proceeding in the manner provided in paragraph 28 or in such other manner as may be permitted by applicable law, will be valid and sufficient service thereof.

26.    Waiver of Jury Trial. EACH OF THE PARTIES, AFTER CONSULTING OR HAVING HAD THE OPPORTUNITY TO CONSULT WITH COUNSEL, KNOWINGLY, VOLUNTARILY AND INTENTIONALLY WAIVES ANY RIGHT THAT SUCH PARTY MAY HAVE TO A TRIAL BY JURY IN ANY LITIGATION BASED UPON OR ARISING OUT OF THIS AGREEMENT OR ANY RELATED INSTRUMENT OR AGREEMENT, OR ANY OF THE TRANSACTIONS CONTEMPLATED THEREBY, OR ANY COURSE OF CONDUCT,

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DEALING, STATEMENTS (WHETHER ORAL OR WRITTEN), OR ACTIONS OF ANY OF THEM. No Party will seek to consolidate, by counterclaim or otherwise, any action in which a jury trial has been waived with any other action in which a jury trial cannot be or has not been waived.

27.    Third Party Beneficiaries. This Agreement is solely for the benefit of the Parties and is not enforceable by any other Person.

28.    Notices. All notices, consents, requests, instructions, approvals and other communications provided for in, and all legal process in regard to, this Agreement will be in writing and will be deemed validly given, made or served (i) upon receipt, when delivered personally; (ii) upon confirmation of receipt, when sent by email (but only if such confirmation is not automatically generated); or (iii) one business day after deposit with a nationally recognized overnight delivery service. The addresses for such communications are as follows. At any time, any Party may, by notice given in accordance with this paragraph 28 to the other Parties, provide updated information for notices pursuant to this Agreement.

A10 Networks, Inc.

3 West Plumeria Drive

San Jose, CA 95134

Attn:      General Counsel

Email:    [email protected]

with a copy (which will not constitute notice) to:

Wilson Sonsini Goodrich & Rosati

Professional Corporation

650 Page Mill Road

Palo Alto, CA 94304

Attn:      Herbert P. Fockler

              Mark B. Baudler

              David J. Berger

              Douglas K. Schnell

Fax:      (650) 493-6811

Email:   [email protected], [email protected], [email protected], [email protected]

VIEX Capital Advisors, LLC

745 Boylston Street, 3rd Floor

Boston, MA 02116

Attn:      Eric Singer

Email:    [email protected]

-10-

with a copy (which will not constitute notice) to:

Olshan Frome Wolosky LLP

1325 Avenue of the Americas

New York, NY 10019

Attn:      Steve Wolosky

              Elizabeth Gonzalez-Sussman

Fax:       (212) 451-2222

Email:   [email protected], [email protected]

29.    Representation by Counsel. Each of the Parties acknowledges that it has been represented by counsel of its choice throughout all negotiations that have preceded the execution of this Agreement, and that it has executed this Agreement with the advice of such counsel. Each Party and its counsel cooperated and participated in the drafting and preparation of this Agreement, and any and all drafts of this Agreement exchanged among the Parties will be deemed the work product of all of the Parties and may not be construed against any Party by reason of its drafting or preparation. Accordingly, any rule of law or any legal decision that would require interpretation of any ambiguities in this Agreement against any Party that drafted or prepared it is of no application and is expressly waived by each of the Parties, and any controversy over interpretations of this Agreement will be decided without regard to events of drafting or preparation.

30.    Counterparts. This Agreement and any amendments to this Agreement may be executed in one or more textually-identical counterparts, all of which will be considered one and the same agreement and will become effective when one or more counterparts have been signed by each of the Parties and delivered to the other Parties, it being understood that all Parties need not sign the same counterpart. Any such counterpart, to the extent delivered by fax or .pdf, .tif, .gif, .jpg or similar attachment to electronic mail (any such delivery, an “Electronic Delivery”), will be treated in all manner and respects as an original executed counterpart and will be considered to have the same binding legal effect as if it were the original signed version thereof delivered in person. No Party may raise the use of an Electronic Delivery to deliver a signature, or the fact that any signature or agreement or instrument was transmitted or communicated through the use of an Electronic Delivery, as a defense to the formation of a contract, and each Party forever waives any such defense, except to the extent such defense relates to lack of authenticity.

31.    Headings. The headings set forth in this Agreement are for convenience of reference purposes only and will not affect or be deemed to affect in any way the meaning or interpretation of this Agreement or any term or provision of this Agreement.

[Signature page follows.]

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[Signature Page to Letter Agreement]

[Signature Page to Letter Agreement]

Exhibit 99.1

DRAFT_NOT FOR RELEASE

A10 Networks Reports Second Quarter 2019 Financial Results and Company Update

Announces Election of Eric Singer to the Board of Directors

Announces Formation of Strategy Committee and Review of Strategic Alternatives

Announces Search Committee Directed at Supporting CEO Succession

SAN JOSE, Calif., July 30, 2019 — A10 Networks (NYSE: ATEN), a provider of intelligent and automated cybersecurity solutions, today announced financial results for its second quarter ended June 30, 2019.

Second Quarter 2019 Financial Summary

A reconciliation between GAAP and non-GAAP information is contained in the financial statements below.

“Second quarter revenue came in below our guidance as a number of large deals in our pipeline pushed into future quarters or were downsized. These deals were primarily in North America and within the service provider and web giant verticals where opportunities can be large but the timing is difficult to predict,” said Lee Chen, president and chief executive officer of A10 Networks. “Outside of North America, all of our major geographies met or exceeded our Q2 expectations, and we continued to make progress on our strategic initiatives in security, 5G and multi-cloud.”

Third Quarter 2019 Business Outlook (+)

For the third quarter of 2019, the company currently expects:

Company Update

Election of Eric Singer to the Board of Directors, effective immediately

The Board of Directors welcomes Eric Singer, Founder and Managing Member of VIEX Capital Advisors, to the Board. In addition to a long track record as a successful investor in technology companies, Singer has substantial experience serving on public boards and in assisting them in creating and expanding shareholder value. Singer is currently a director of Quantum Corporation and previously served on the boards of directors of Numerex Corp., YuMe, Inc., Support.com, Meru Networks, PLX Technology, Inc., and Sigma Designs, Inc., among other companies.

Singer joins the Board in connection with the company’s entry into a letter agreement with VIEX Capital Advisors and its affiliates, in which the company has agreed to fix the size of the Board at six and renominate Singer and Tor R. Braham for election at the 2019 annual meeting of stockholders. Pursuant to the agreement, VIEX Capital Advisors has also been granted the right to identify, and A10 Networks will appoint within 15 days thereafter, an additional director to the Board, with Phillip J. Salsbury agreeing to resign from the Board in such event.

Formation of Strategy Committee of the Board and review of Strategic Alternatives

As part of the election of Singer, the company has formed a Strategy Committee, which consists of Singer, existing director Peter Chung and existing director Tor Braham. The Strategy Committee is tasked and empowered with overseeing and executing specific activities directed to increasing shareholder value. In furtherance of these activities, the company has retained Bank of America Merrill Lynch to advise the company and the Board on strategic matters, including a near term exploration of a potential sale or change of control transaction. No assurance can be given that such a transaction will be consummated in the near term or at all.

Formation of Search Committee of the Board directed at supporting CEO succession

The Board of Directors has also formed a Search Committee, which is tasked with developing near term plans for CEO succession. The Search Committee has retained a leading executive search firm for the purpose of recruiting and exploring potential candidates for the chief executive officer position. This search is under-way and the company is optimistic that this search can be completed with the announcement of a new CEO during the third quarter of 2019.

A10 Networks also announced today the planned retirement of Lee Chen, president and chief executive officer of A10 Networks, to take place upon the appointment of a successor. Chen commented, “A10’s future remains bright and I continue to be very excited about the innovations we have brought to market and our position in security, 5G and multi-cloud. However, I have decided that now is the appropriate time for me to transition the company to a new leader. I will work closely with the Board and management team to help ensure a smooth transition.”

“The A10 Board of Directors wishes to thank Lee for his leadership, entrepreneurial dedication and years of service in building A10’s business with vision and integrity”, said Phil Salsbury, lead independent director of the A10 Board.

Prepared Materials and Conference Call Information

A10 Networks has made available a presentation with management’s prepared remarks on its second quarter 2019 financial results. These materials are accessible from the “Investor Relations” section of the A10 Networks website at investors.a10networks.com.

A10 Networks will host a conference call today at 4:30 p.m. Eastern time / 1:30 p.m. Pacific time for analysts and investors to discuss its second quarter 2019 financial results and outlook for its third quarter 2019. Open to the public, investors may access the call by dialing +1-844-792-3728 or +1-412-317-5105. A live audio webcast of the conference call will be accessible from the “Investor Relations” section of the A10 Networks website at investors.a10networks.com. The webcast will be archived for a period of one year. A telephonic replay of the conference call will be available two hours after the call, will run for five business days, and may be accessed by dialing +1-877-344-7529 or +1-412-317-0088 and entering the passcode 10133387. The press release and supplemental financials will be accessible from the “Investor Relations” section of the A10 Networks website prior to the commencement of the conference call.

Forward-Looking Statements

This press release contains “forward-looking statements,” including statements regarding our pipeline; projections for our future operating results, including our anticipation that we will achieve sequential revenue growth in the fourth quarter of 2019; the size of opportunities in North America and within the service provider and web giant verticals; progress on our strategic initiatives; our position in security, 5G and multi-cloud; our plans to explore strategic alternatives, including a potential sale or change of control transaction; and the timing of completing a search for a CEO successor. Forward-looking statements are subject to known and unknown risks and uncertainties and are based on assumptions that may prove to be incorrect, which could cause actual results to differ materially from those expected or implied by the forward-looking statements. Factors that may cause actual results to differ include execution risks related to closing key deals and improving our execution, the continued market adoption of our products, our ability to successfully anticipate market needs and opportunities, our timely development of new products and features, our ability to achieve or maintain profitability, any loss or delay of expected purchases by our largest end-customers, our ability to maintain or improve our competitive position, competitive and execution risks related to cloud-based computing trends, our ability to attract and retain new end-customers and our largest end-consumers, our ability to maintain and enhance our brand and reputation, changes demanded by our customers in the deployment and payment model for our products, continued growth in markets relating to network security, the success of any future acquisitions or investments in complementary companies, products, services or technologies, the ability of our sales team to execute well, our ability to shorten our close cycles, the ability of our channel partners to sell our products, variations in product mix or geographic locations of our sales, risks associated with our presence in international markets, weaknesses or deficiencies in our internal control over financial reporting, and our ability to timely file periodic reports required to be filed under the Securities Exchange Act of 1934.

Non-GAAP Financial Measures

In addition to disclosing financial measures prepared in accordance with U.S. generally accepted accounting principles (GAAP), this press release and the accompanying table contain certain non-GAAP financial measures, including non-GAAP net income (loss), non-GAAP gross profit and non-GAAP operating income (loss). Non-GAAP financial measures do not have any standardized meaning and are therefore unlikely to be comparable to similarly titled measures presented by other companies.

A10 Networks considers these non-GAAP financial measures to be important because they provide useful measures of the operating performance of the company, exclusive of unusual events or factors that do not directly affect what we consider to be our core operating performance, and are used by the company’s management for that purpose. We define non-GAAP net income (loss) as our GAAP net income (loss) excluding: (i) stock-based compensation and related payroll tax, (ii) amortization expense related to acquisition and (iii) non-recurring expenses associated with the litigation settlement expense and internal investigation. We define non-GAAP gross profit as our GAAP gross profit excluding stock-based compensation and related payroll tax. We define non-GAAP operating income (loss) as our GAAP income (loss) from operations excluding (i) stock-based compensation and related payroll tax, (ii) amortization expense related to acquisition and (iii) non-recurring expenses associated with the litigation settlement expense and internal investigation.

We have included our non-GAAP net income (loss), non-GAAP gross profit and non-GAAP operating income (loss) in this press release. Non-GAAP financial measures are presented for supplemental informational purposes only for understanding the company’s operating results. The non-GAAP financial measures should not be considered a substitute for financial information presented in accordance with GAAP, and may be different from non-GAAP financial measures presented by other companies. Please see the reconciliation of non-GAAP financial measures to the most directly comparable GAAP measure attached to this release. A reconciliation of non-GAAP guidance measures to corresponding GAAP measures on a forward-looking basis is not available due to high variability and low visibility with respect to the charges which are excluded from these non-GAAP measures.

About A10 Networks

A10 Networks (NYSE: ATEN) provides Reliable Security Always^™, with a range of high-performance application networking solutions that help organizations ensure that their data center applications and networks remain highly available, accelerated and secure. Founded in 2004, A10 Networks is based in San Jose, Calif., and serves customers globally with offices worldwide. For more information, visit: www.a10networks.com and @A10Networks.

The A10 logo and A10 Networks are trademarks or registered trademarks of A10 Networks, Inc. in the United States and other countries. All other trademarks are the property of their respective owners.

Investor Contact:

Maria Riley & Chris Mammone

The Blueshirt Group

415-217-7722

[email protected]

A10 NETWORKS, INC.

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS

(unaudited, in thousands, except per share amounts)

A10 NETWORKS, INC.

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (Continued)

(unaudited, in thousands, except per share amounts)

A10 NETWORKS, INC.

CONDENSED CONSOLIDATED BALANCE SHEETS

(unaudited, in thousands)

A10 NETWORKS, INC.

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS

(unaudited, in thousands)

A10 NETWORKS, INC.

RECONCILIATION OF GAAP GROSS PROFIT TO NON-GAAP GROSS PROFIT

(unaudited, in thousands, except percentages)

RECONCILIATION OF GAAP LOSS FROM OPERATIONS TO NON-GAAP OPERATING INCOME (LOSS)

(unaudited, in thousands, except percentages)

Exhibit 99.2

Reliable Security Always Q2 2019 FINANCIAL RESULTS & COMMENTARY July 30, 2019 ATEN ?Q2 2019 Financial Results Conference Call ?Tuesday, July 30, 2019 1| Page

Agenda Introduction Maria Riley, Investor Relations Results Overview Lee Chen, CEO, President and Founder Market Overview Chris White, EVP WW Sales Q2 2019 Financial Results & Business Outlook Tom Constantino, CFO Q&A: Lee Chen, Tom Constantino, and Chris White 2 2. CONFIDENTIAL | DO NOT DISTRIBUTE Maria Thank you all for joining us today. This call is being recorded and webcast live and may be accessed for one year via the A10 Networks website, www.a10networks.com. Members of A10’s management team joining me today are, Lee Chen, Founder & CEO; Chris White, EVP of worldwide sales; and Tom Constantino, CFO. Before we begin,I would like to remind you that shortly after the market closed today, A10 Networks issued a press release announcing its second quarter 2019 financial results. Additionally, A10 published a presentation along with its prepared comments for this call and supplemental trended financial statements. You may access the press release, presentation with prepared comments, and trended financial statements on the investor relations section of the company?s website. ATEN ?Q2 2019 Financial Results Conference Call ?Tuesday, July 30, 2019 2| Page

CAUTIONARY STATEMENTS & DISCLOSURES This presentation and the accompanying oral presentation contain ?forward-looking? statements that are based on our management?s beliefs and assumptions, including statements regarding our projections for our future operating results, our ability to transform our sales team, our expectations regarding future opportunities and our ability to execute on those opportunities, our commitment to innovation and bringing new solutions to market, our expectations for future revenue and market growth, the development and performance of our products, our current and future strategies, our beliefs relating to our competitive advantages, our expectations with respect to the 5G market and products related to 5G, responses to new security threats, our partnerships with key technology providers and sales partnerships, our priorities to drive growth, the adoption of our products, our ability to penetrate certain markets, anticipated customer benefits from use of our products, the refining of our go to market engine, improvements in productivity, growth in our security solutions, expected product launches and the general growth of our business. Forward-looking statements are subject to known and unknown risks, uncertainties, assumptions and other factors that could cause our actual results to differ materially from those anticipated or implied by our forward-looking statements. These factors include, but are not limited to, successfully executing our strategies, market adoption of our products, successfully anticipating market needs and opportunities, timely development of new products and features, achieving or maintaining profitability, loss or delay of expected purchases, attracting and retaining new end-customers, maintaining and enhancing our brand and reputation, growth in markets relating to network security, the success of any future acquisitions or investments, the success of our partnerships with technology providers, our ability to shorten our close cycle, the ability of our channel partners to sell our products, our presence in international markets, and other factors described in our quarterly reports on Form 10-Q, annual reports on Form 10-K and other filings made with the Securities and Exchange Commission, to which your attention is directed. We assume no responsibility for the accuracy and completeness of the forward-looking statements and disclaim any obligation to update information contained in these forward-looking statements. This presentation and the accompanying oral presentation also include certain non-GAAP financial measures. Non-GAAP financial measures have limitations as analytical tools and you should not consider them in isolation or as a substitute for an analysis of our results under U.S. GAAP. Definitions of our non-GAAP financial measures and a reconciliation between GAAP and non-GAAP financial measures can be found in the appendix to this document and in the accompanying financial results press release. A reconciliation of non-GAAP guidance measures to corresponding GAAP measures on a forward-looking basis is not available due to high variability and low visibility with respect to the charges which are excluded from these non-GAAP measures. 3 3. CONFIDENTIAL | DO NOT DISTRIBUTE During the course of today?s call, management will make forward-looking statements, including statements regarding our projections for our future operating results, the capabilities of our sales team, our expectations regarding future opportunities and our ability to execute on those opportunities, our commitment to innovation and bringing new solutions to market, our expectations for future revenue and market growth, the development and performance of our products, our current and future strategies, our beliefs relating to our competitive advantages, our expectations with respect to the 5G market, responses to new security threats, our partnerships with key technology providers and sales partnerships, our ability to penetrate certain markets, anticipated customer benefits from use of our products, the refining of our marketing engine, improvements in productivity, our priorities relating to 5G, growth in our security solutions, expected product launches and adoption of recent new product or software releases, the general growth of our business, and our ability to incrementally grow operating margin annually and timeline to achieve our target operating margin. These statements are based on current expectations and beliefs as of today, July 30th, 2019. These forward-looking statements involve a number of risks and uncertainties, some of which are beyond our control that could cause actual results to differ materially and you should not rely on them as predictions of future events. A10 disclaims any obligation to update information contained in these forward-looking statements whether as a result of new information, future events, or otherwise. For a more detailed description of these risks and uncertainties, please refer to our most recent 10-Q and 10-K. ATEN ?Q2 2019 Financial Results Conference Call ?Tuesday, July 30, 2019 3| Page

CAUTIONARY STATEMENTS & DISCLOSURES This presentation and the accompanying oral presentation contain ?forward-looking? statements that are based on our management?s beliefs and assumptions, including statements regarding our projections for our future operating results, our ability to transform our sales team, our expectations regarding future opportunities and our ability to execute on those opportunities, our commitment to innovation and bringing new solutions to market, our expectations for future revenue and market growth, the development and performance of our products, our current and future strategies, our beliefs relating to our competitive advantages, our expectations with respect to the 5G market and products related to 5G, responses to new security threats, our partnerships with key technology providers and sales partnerships, our priorities to drive growth, the adoption of our products, our ability to penetrate certain markets, anticipated customer benefits from use of our products, the refining of our go to market engine, improvements in productivity, growth in our security solutions, expected product launches and the general growth of our business. Forward-looking statements are subject to known and unknown risks, uncertainties, assumptions and other factors that could cause our actual results to differ materially from those anticipated or implied by our forward-looking statements. These factors include, but are not limited to, successfully executing our strategies, market adoption of our products, successfully anticipating market needs and opportunities, timely development of new products and features, achieving or maintaining profitability, loss or delay of expected purchases, attracting and retaining new end-customers, maintaining and enhancing our brand and reputation, growth in markets relating to network security, the success of any future acquisitions or investments, the success of our partnerships with technology providers, our ability to shorten our close cycle, the ability of our channel partners to sell our products, our presence in international markets, and other factors described in our quarterly reports on Form 10-Q, annual reports on Form 10-K and other filings made with the Securities and Exchange Commission, to which your attention is directed. We assume no responsibility for the accuracy and completeness of the forward-looking statements and disclaim any obligation to update information contained in these forward-looking statements. This presentation and the accompanying oral presentation also include certain non-GAAP financial measures. Non-GAAP financial measures have limitations as analytical tools and you should not consider them in isolation or as a substitute for an analysis of our results under U.S. GAAP. Definitions of our non-GAAP financial measures and a reconciliation between GAAP and non-GAAP financial measures can be found in the appendix to this document and in the accompanying financial results press release. A reconciliation of non-GAAP guidance measures to corresponding GAAP measures on a forward-looking basis is not available due to high variability and low visibility with respect to the charges which are excluded from these non-GAAP measures. 4 4. CONFIDENTIAL | DO NOT DISTRIBUTE Please note that with the exception of revenue, financial measures discussed today are on a non-GAAP basis and have been adjusted to exclude certain charges. The non-GAAP financial measures are not intended to be considered in isolation or as a substitute for results prepared in accordance with GAAP, and may be different from non-GAAP financial measures presented by other companies. A reconciliation between GAAP and non-GAAP measures can be found in the press release issued today and on the trended quarterly financial statements posted on the company?s website. We will provide our current expectations for the third quarter of 2019 on a non-GAAP basis. However, we are unable to make available a reconciliation of non-GAAP guidance measures to corresponding GAAP measures on a forward-looking basis due to high variability and low visibility with respect to the charges, which are excluded from these non-GAAP measures. Now I would like to turn the call over to Lee Chen, Founder and CEO of A10 Networks. ATEN ?Q2 2019 Financial Results Conference Call ?Tuesday, July 30, 2019 4| Page

Lee Chen CEO, President and Founder ATEN ?Q2 2019 Financial Results Conference Call ?Tuesday, July 30, 2019 5| Page

A10: Well-Positioned in 5G A10?s proven strength in hyper-scalability, low latency, security and CGN consolidation, and AI-driven automation Strong anti-DDoS attack solutions and integrated security and CGN analytics platform High-end hardware and SDN/NFV/container solutions Strong presence with global service providers Partners are important. Ericsson & NEC are strong partners Scale, performance, low latency, security, extreme reliability and automation Lee Chen, Founder & CEO Thank you, Maria and thank you all for joining us today. Before we begin, I would first like to address the news of my planned retirement, which we announced today. I am very excited about A10’s future, the innovations we have brought to market and our position in security, 5G and multi-cloud. Additionally, while our subscription revenue remains small, it is a rapidly growing part of A10?s business. Subscription was 8 percent of product revenue for Q2, and on a year-over-year basis, it grew over 80 percent. This brings us to nearly $100 million in annualized run-rate of recurring maintenance and subscription revenue. This revenue is high margin, creates customer loyalty and affords improved visibility not present in hardware product sales. We continue to see early success in 5G as we secured follow-on 5G orders during the quarter. Additionally, we are pleased with the level of engagement we see with several service providers across the globe as they prepare and ready their networks for 5G. ATEN ?Q2 2019 Financial Results Conference Call ?Tuesday, July 30, 2019 6| Page

Company Update Lee Chen, CEO President and Founder announces planned retirement Chen will resign from role as CEO once a newly appointed CEO begins Search Committee has been formed for a new CEO Eric Singer, Managing Partner of Viex Capital Advisors, joins A10 Board of Directors Strategy Committee has been formed to help drive shareholder value 7 7. CONFIDENTIAL | DO NOT DISTRIBUTE However, I have decided that now is the appropriate time for me to transition the company to a new leader. I have reached agreement with the Board that I will resign from my role as CEO of A10 once a newly appointed CEO begins. The Board has formed a search committee for my replacement and I will work closely with the team to help ensure a smooth transition. The search has been focused on a strong leader who will bring a different perspective and industry expertise. I would also like to take a moment to welcome Eric Singer of ViexCapital Advisors to A10?s Board of Directors. Eric is one of our largest shareholders and we have had an ongoing constructive dialogue with him for more than a year. He brings deep strategic insight to the Board and we look forward to the continued collaboration. As part of the election of Eric, the company has formed a StrategyCommittee, which consists of Eric and existing directors Peter Chung and Tor Braham. The Strategy committee is tasked and empowered with overseeing and executing specific activities to increasing shareholder value. Please note that we will not make any further comments on this matter. ATEN ?Q2 2019 Financial Results Conference Call ?Tuesday, July 30, 2019 7| Page

ZERO-DAY AUTOMATED PROTECTION (ZAP) FOR DDOS Zero-Day Attack Pattern Recognition (ZAPR) technology Packet Filtering Request Spoofed Distinct Content Reflector 01000 111 Pattern Ma g Distinct Content Content Pattern Detection DDoS Bot Pattern Legitimate Normal Content User Protected Thunder TPS Service Unsupervised Machine Learning Automatic DDoS Threat Detection & Mitigation @ Hyperscale 8 Moving to our Q2 performance. We delivered revenue of 49.2 million dollars, non-GAAP gross margin of 78.0 percent and reached breakeven on a non-GAAP per share basis. Revenue came in below our guidance as a number of large deals in our pipeline pushed into future quarters or were downsized. These deals were primarily in North America and within the service provider and web giant verticals, and we continue to see this dynamic in Q3. Outside of North America, all of our major geographies met or exceeded expectations for Q2. One of the reasons for this divergence is that spending and deployment on 5G infrastructure is ahead in certain international markets as compared to U.S. markets. Thus, we are seeing earlier and faster uplift in spending in Japan, South Korea and the Middle East in comparison to the U.S. We believe that we are well positioned to participate as U.S. customers move further into the 5G deployment phase. Chris will discuss the market dynamics, customer wins and go-to-market efforts in more detail. We continued to make progress on our major initiatives in security, 5G and multi-cloud. On the solution front, we continue to innovate and execute on our roadmap for this year. In June, we announced the addition of zero-day automated protection, or ZAP capabilities, to our Thunder TPS family of DDoS defense solutions. The ZAP capabilities automatically recognize the characteristics of DDoS attacks and apply mitigation filters without advanced configuration or manual intervention. In today?s climate with the dramatic increase in multi-vector attacks coupled with the chronic shortage of qualified security professionals, organizations need intelligent, automated defenses that can accomplish tasks automatically. A significant portion of the R&D investments we have made over the past couple of years have been focused on solving these critical problems for customers through behavior analysis, machine learning and automation. This new A10 solution is already gaining strong industry recognition, including Best of Show in the security category at Interop Tokyo, which is the premier industry event in Japan. ATEN ?Q2 2019 Financial Results Conference Call ?Tuesday, July 30, 2019 8| Page

THUNDER CONTAINERS Visibility, Analytics and Management Platform ADC CGNAT/IPv6 DC Firewall Gi, GTP Firewall Ultra-High Performance ?Up to 200Gbps Throughput per Thunder Container Application Delivery, Carrier Grade NAT, Data Center Firewall Elastic, Portable & Scalable for 5G & Multi Cloud 9 During the quarter, we also announced our cloud-ready, light-weight set of container-based solutions. A10?s Thunder Containers will be available starting this quarter and will offer the industry?s highest performing container solutions with up to 200 Gbps of throughput for Thunder ADC, CGN, and CFW solutions. The addition of Thunder Containers extends the company?s multi-cloud portfolio and increases the performance, security and availability of applications, enabling customers to confidently run their critical workloads in multi-cloud environments at hyperscale. This new A10 solution also shined at Interop Tokyo, taking the Grand Prize in the NFV/SDI category. ATEN ?Q2 2019 Financial Results Conference Call ?Tuesday, July 30, 2019 9| Page

STRATEGIC PARTNERSHIP EXPANSION A10 vThunder ADC and Harmony Controller Executed a global reseller agreement to become available in the Oracle Cloud Marketplace an Extended Global Technology Partner First virtual ADC available in OCI Dell EMC to resell full product line of A10 multi-cloud and 5G security solutions First cloud native controller for ADC available in OCI Joint GTM strategies under development Highly flexible capacity based licensing model A10 and Dell EMC to develop jointly integrated solutions for virtualized infrastructure Easy migration to cloud based load balancing transformations via OCI 10 On the partner front, we entered into two new important engagements with industry leaders to help extend our go-to-market leverage ?one is a global reseller agreement with Dell EMC and the second partnership is joining the Oracle Cloud Marketplace. Chris will provide the details of these new partnerships in a moment. Overall, while our revenue was below our guidance in Q2, we continue to make progress on our top priorities for 2019, which include driving growth and innovation in security, 5G and multi-cloud. This is an exciting time for A10 and the company is in a strong position to extend its leadership and expand its addressable market to help further position the company for success. With that, I will turn the call over to Chris. ATEN ?Q2 2019 Financial Results Conference Call ?Tuesday, July 30, 2019 10| Page

Chris White EVP, WW Sales 11 11. CONFIDENTIAL | DO NOT DISTRIBUTE ATEN ?Q2 2019 Financial Results Conference Call ?Tuesday, July 30, 2019 11| Page

Market Summary North America Large deals among Service Provider and Web Giant Customers were delayed or downsized Win rate remains high & majority of deals remain in pipeline International Double-digit year-over-year product revenue growth in Japan, EMEA and Latin America Triple-digit year-over-year product revenue growth in South Korea driven by our installed base of 5G wins 215 new customers added in Q2 12 12. CONFIDENTIAL | DO NOT DISTRIBUTE Chris White, EVP of worldwide sales Thank you, Lee. In looking at the dynamics within the quarter, demand from our largest installed base in North America slowed as large deals were pushed into future quarters or downsized, which impacted our Q2 revenue performance. These deals were primarily in our service provider and web giant verticals, where deals can be large and can fluctuate from quarter to quarter. I would like to emphasize that that our win rate remained high and the majority of these opportunities remain in our pipeline. We are pleased with our international performance this quarter, where we delivered double-digit quarter-over-quarter growth in product bookings. On a year-over-year basis, we delivered strong double-digit product revenue growth in Japan, EMEA and Latin America. We also saw strong triple-digit year-over-year product revenue growth in South Korea driven by our installed base of 5G wins. Moving to our go-to-market. As we discussed at the start of the year, we implemented several changes designed to incentivize the sales team to drive new product sales with both new and existing accounts, as well as launched two important go-to-market changes in North America. This included a new partnership with Arrow Electronics and the move to a two-tier channel structure. We are also working with a third party to help us expand our lead-gen efforts in North America, which went into effect in Q1. While we believe these programs are the right course to help drive sales, they take time to ramp. We continue to expect to see the benefit of these new relationships as we progress throughout the year. ATEN ?Q2 2019 Financial Results Conference Call ?Tuesday, July 30, 2019 12| Page

STRATEGIC PARTNERSHIP EXPANSION A10 vThunder ADC and Harmony Controller Executed a global reseller agreement to become available in the Oracle Cloud Marketplace an Extended Global Technology Partner First virtual ADC available in OCI Dell EMC to resell full product line of A10 multi-cloud and 5G security solutions First cloud native controller for ADC available in OCI Joint GTM strategies under development Highly flexible capacity based licensing model A10 and Dell EMC to develop jointly integrated solutions for virtualized infrastructure Easy migration to cloud based load balancing transformations via OCI 13 Additionally, as Lee mentioned, we expect to extend our leverage with the new go-to-market engagements that we entered into with Dell EMC and Oracle Cloud. Our new partnership with Dell is in the form of a global reseller agreement to become an Extended Global Technology Partner. The Dell relationship is a validation of our product architecture, as Dell partners with A10 to transition from its previous global ADC vendor. This agreement enables Dell EMC to resell our full product line of multi-cloud and 5G security solutions, including our vThunderADC, CGN, CFW, and SSL Insight as well as the A10 Harmony Controller. Dell customers will have the flexibility and choice to run A10 Networks solutions in a private, hybrid, or public cloud with modern analytics and centralized management necessary for these complex environments. It also allows customers to prepare their infrastructures for 5G and multi-cloud demands with security and analytics across multiple points in the network. Second, as we announced in a press release in May, our vThunderADC and Harmony controller are now available in the Oracle Cloud Marketplace. A10 solutions running on Oracle Cloud provide Oracle?s customers with agile application delivery controller capabilities focused on secure and efficient application support. Additionally, our leading application traffic analytics, centralized management and orchestration dashboard provide Oracle Cloud customers with actionable intelligence through a single pane of glass for operational efficiency. While both of these new partnerships will take time to ramp, we have already closed our first deals and we are excited by the opportunities they could ultimately bring to A10. ATEN ?Q2 2019 Financial Results Conference Call ?Tuesday, July 30, 2019 13| Page

CUSTOMER SUCCESS During the quarter, we added 215 new customers, which is our highest level in fourteen quarters. In addition to the number of new logos, we were also pleased with the expansions we generated with our existing customers. I will highlight a few recent customer engagements: One of the largest banks in Latin America selected our CFW-ADC solution. Key features in A10?s Harmony Controller were a significant differentiator and selling point in this competitive win against an incumbent. This was a relationship our sales team worked very hard to cultivate and won with determination and can-do attitude. We replaced an incumbent at a mobile provider in the Asia Pacific with our Thunder CGN Solution. We won this new A10 customer based on our CGN features, ease of use and automation through APIs, as well as strong technical engagement through the sales process. Winning new service provider customers across the globe, like this one, is a key initiative for the sales team, and we are pleased to see our international progress in Q2. We also secured follow-on CGN business with a leading mobile provider in EMEA. Demonstrating our high-performance prowess, A10 was the only vendor that could meet this customer?s throughput requirements. Additionally, we secured follow-on 5G orders with leading mobile providers in South Korea. While we are making progress on our broader go-to-market initiatives and forging new partner relationships, we recognize we have work ahead to ramp and enable our teams and new partners to capitalize on the fast-growing areas of our market. Our product portfolio is strong, our win rate remains high and we are committed to innovating and refining our go-to-market engine. We have a very clear vision, and our team is energized about the market opportunity for our solutions. With that, I?d like to turn the call over to Tom to review the details of our second quarter financial performance and third quarter guidance. Tom? ATEN ?Q2 2019 Financial Results Conference Call ?Tuesday, July 30, 2019 14| Page

Tom Constantino CFO 15 15. CONFIDENTIAL | DO NOT DISTRIBUTE ATEN ?Q2 2019 Financial Results Conference Call ?Tuesday, July 30, 2019 15| Page

REVENUE $Millions Q2’19 Revenue: $49M 19% y/y $227 $235 $232 $196 $180 2014 2015 2016 2017 2018 16 16. The company CONFIDENTIAL adopted ASC | 606 DO accounting NOT DISTRIBUTE standard effective January 1, 2018, all prior periods are based on ASC 605 standard. Tom Constantino, CFO Thank you, Chris. Second quarter revenue was 49.2 million dollars, a 19 percent decrease when compared with 60.7 million dollars in the same period last year, driven by a decline in bookings from our largest web giant account in North America. ATEN ?Q2 2019 Financial Results Conference Call ?Tuesday, July 30, 2019 16| Page

PRODUCT AND SERVICE REVENUE $Millions $235 $232 $227 2Q 2019 $196 $49 million $180 33% 36% 38% 31% 25% 46% 67% 64% 62% 75% 69% 54% 2014 2015 2016 2017 2018 Product Service 17 17. The company CONFIDENTIAL adopted ASC | 606 DO accounting NOT DISTRIBUTE standard effective January 1, 2018, all prior periods are based on ASC 605 standard. Second quarter product revenue was 26.8 million dollars representing 54 percent of total revenue. Service revenue was 22.4 million dollars, or 46 percent of total revenue. Security product revenue grew 8 percent over last year to reach 34 percent of total product revenue in Q2. ATEN ?Q2 2019 Financial Results Conference Call ?Tuesday, July 30, 2019 17| Page

REVENUE BY GEOGRAPHY $Millions $235 $232 $227 2Q 2019 $196 2% 3% 4% $49 million 10% 12% 12% $180 3% 13% 14% 16% 4% 14% 11% 7% 12% 11% 23% 22% 24% 13% 31% 25% 18% $56 19% 53% 51% 49% 45% 48% 30% 2014 2015 2016 2017 2018 United States Japan APAC ex Japan EMEA Other 18 18. The company CONFIDENTIAL adopted ASC | 606 DO accounting NOT DISTRIBUTE standard effective January 1, 2018, all prior periods are based on ASC 605 standard. Moving to our revenue from a geographic standpoint, for the second quarter revenue from North America decreased 50 percent year-over-year to 15.3 million dollars, compared with 30.4 million dollars in the same period last year. In Japan, revenue was 14.9 million dollars, up 26 percent year-over-year. Revenue from APAC, excluding Japan, was 9.2 million dollars, compared with a record 10.7 million in Q2 of last year. In EMEA, revenue was 6.6 million dollars, an increase of 21 percent when compared with 5.4 million dollars last year. Revenue from LATAM continued to grow and came in at 3.2 million dollars, compared with 2.3 million dollars last year. ATEN ?Q2 2019 Financial Results Conference Call ?Tuesday, July 30, 2019 18| Page

REVENUE BY CUSTOMER VERTICAL $Millions $235 $232 $227 $196 11% 14% 2Q 2019 18% $49 million $180 10% 8% 41% 39% 39% 16% 45% 43% 39% 48% 47% 43% 45% 50% 46% 2014 2015 2016 2017 2018 SP Enterprise Web Giant 19 19. The company CONFIDENTIAL adopted ASC | 606 DO accounting NOT DISTRIBUTE standard effective January 1, 2018, all prior periods are based on ASC 605 standard. Service provider revenue in the quarter was 39 percent of total revenue, enterprise revenue was 45 percent and web giant revenue was 16 percent. As we move beyond revenue, all further metrics discussed on this call are on a non-GAAP basis, unless stated otherwise. ATEN ?Q2 2019 Financial Results Conference Call ?Tuesday, July 30, 2019 19| Page

FINANCIAL PERFORMANCE HIGHLIGHTS $ Millions (except EPS) Income Statement Summary: Q2?19 Q2?18 Revenue $49.2 $60.7 Gross Margin % 78.0% 78.6% Operating Margin % (1.9)% 4.0% EPS ($0.00) $0.02 Balance Sheet & Cash Flow Summary: Q2?19 Q2?18 Cash & Marketable Security $119.3 $127.4 Accounts Receivable $45.3 $50.4 Deferred Revenue $97.8 $98.1 Debt —Free Cash Flow ($5.9) ($2.4) Numbers may not sum due to rounding. Please refer to the supplemental financials posted the ?Investor Relations? section of the A10 Networks website at investors.a10networks.comGross 20 20. Margin, Operating CONFIDENTIAL Margin and | EPS DO are NOT Non-GAAP DISTRIBUTE Financial Measures. See Appendix for reconciliation to most comparable GAAP financial measures. The company adopted ASC 606 accounting standard effective January 1, 2018, all prior periods are based on ASC 605 standard. We delivered second quarter total gross margin of 78.0 percent, an increase of 175 basis points from last quarter and a decrease of 57 basis points from Q2 of last year. Second quarter product gross margin was 74.4 percent, compared with 73.5 percent last quarter and 76.9 percent in Q2 of 2018. Our product gross margin was negatively impacted by geographic mix in the quarter. Services gross margin in the quarter came in at 82.4 percent, compared to 79.9 percent last quarter and 81.8 percent in Q2 of 2018. We ended the quarter with headcount of 862 compared with 834 at the end of last quarter. The incremental headcount reflects our strategy to expand technical talent in lower cost locations. Non-GAAP operating expenses in Q2 came in at 39.3 million dollars, compared with 44.3 million dollars in the prior quarter. A reduction in variable compensation expenses, due to the weaker revenue performance, was the primary contributor to this quarterly decline. Non-GAAP operating loss was just under one million dollars, compared with operating loss of 5.9 million dollars in the prior quarter. Non-GAAP net loss for the quarter was approximately 300,000 dollars, or breakeven on a per share basis, compared with an income of 1.6 million dollars, or 2 cents per basic share in Q2 of last year. Diluted and basic weighted shares used for computing non-GAAP EPS for the second quarter were approximately 75.7 million shares. Moving to the balance sheet, average days sales outstanding were 84 days, compared with 80 days in the prior quarter. At June 30, 2019, we had 119.3 million dollars in total cash and marketable securities, compared with 122.8 million dollars at the end of March. ATEN ?Q2 2019 Financial Results Conference Call ?Tuesday, July 30, 2019 20| Page

Business Outlook Q3 2019 Revenue in the range of $50.0 million to $54.0 million Non-GAAP gross margin in the range of 76.0 percent to 78.0 percent Non-GAAP operating expenses in the range of $40.0 million to $41.0 million Non-GAAP earnings per share to be between a loss of $0.04 and income of $0.03 using approximately 76.5 million basic and 79.5 million diluted shares Q4 2019 Sequential revenue growth versus Q3 2019 We are unable to make available a reconciliation of non-GAAP guidance measures to corresponding GAAP measures on a forward-looking basis due to high variability and low visibility with 21 21. respect toCONFIDENTIAL the charges, which |areDO excluded NOT DISTRIBUTE from these non-GAAP measures. Moving on to our outlook for the third quarter. We currently expect third quarter revenue to be in the range of 50 million to 54 million dollars. We also currently expect that we will achieve sequential revenue growth in the fourth quarter of 2019 over the level expected in the third quarter. We expect third quarter gross margin to be in the 76 to 78 percent range and operating expenses to be between 40 million and 41 million dollars. We expect our third quarter non-GAAP bottom line results to be between a loss of 4 cents and income of 3 cents on a per share basis using a share count of approximately 76.5 million basic and 79.5 million diluted shares. ATEN ?Q2 2019 Financial Results Conference Call ?Tuesday, July 30, 2019 21| Page

QUESTION & ANSWER SESSION Lee Chen Tom Constantino Chris White Founder & CEO CFO EVP, WW Sales 22 22. CONFIDENTIAL | DO NOT DISTRIBUTE Operator, you can now open the call up for questions. ATEN ?Q2 2019 Financial Results Conference Call ?Tuesday, July 30, 2019 22| Page

APPENDIX 23 23. CONFIDENTIAL | DO NOT DISTRIBUTE ATEN ?Q2 2019 Financial Results Conference Call ?Tuesday, July 30, 2019 23| Page

GAAP to NON-GAAP % of Revenue except EPS Q1’19 Q2’19 Q2’19 YTD Q1’18 Q2’18 Q2’18 YTD Gross Margin %—GAAP 75.6 % 77.1 % 76.4 % 75.8 % 78.3 % 77.2 % Stock-based Compensation 0.6 % 0.9 % 0.8 % 1.9 % 0.3 % 1.0 % Gross Margin %—Non-GAAP 76.3 % 78.0 % 77.2 % 77.7 % 78.6 % 78.2 % EPS $—GAAP $ (0.16) $ (0.08) $ (0.24) $ (0.27) $ (0.06) $ (0.33) Stock-based compensation $ 0.05 $ 0.08 $ 0.12 $ 0.11 $ 0.04 $ 0.15 Litigation and investigation expense (benefit) $ 0.01 $ 0.00 $ 0.01 $ 0.06 $ 0.05 $ 0.10 Amortization expense related to acquisition $ 0.00 $ 0.00 $ 0.01 $ 0.00 $ 0.00 $ 0.01 EPS $—Non-GAAP $ (0.10) $ (0.00) $ (0.10) $ (0.10) $ 0.02 $ (0.08) Numbers may not sum due to rounding. EPS data is presented on a basic and diluted basis. Please refer to the supplemental financials posted the ?Investor Relations? section of the A10 24 24. CONFIDENTIAL | DO NOT DISTRIBUTE Networks website at investors.a10networks.com The company adopted ASC 606 accounting standard effective January 1, 2018, all prior periods are based on ASC 605 standard. ATEN ?Q2 2019 Financial Results Conference Call ?Tuesday, July 30, 2019 24| Page

GAAP to NON-GAAP $ Millions Q1’19 Q2’19 Q2’19 YTD Q1’18 Q2’18 Q2’18 YTD Total operating expenses $—GAAP $ 49.0 $ 44.3 $ 93.3 $ 57.3 $ 51.2 $ 108.5 Stock-based compensation (3.6) (4.6) (8.2) (7.3) (2.4) (9.6) Litigation and investigation expense (benefit) (0.9) (0.2) (1.0) (4.2) (3.3) (7.5) Amortization expense related to acquisition (0.3) (0.3) (0.5) (0.3) (0.3) (0.5) Total operating expenses $—Non-GAAP $ 44.3 $ 39.3 $ 83.6 $ 45.6 $ 45.3 $ 90.9 % of Revenue Total operating expenses %—GAAP 97 % 90 % 94 % 116 % 84 % 99 % Stock-based compensation (7)% (9)% (8)% (15)% (4)% (9)% Litigation and investigation expense (benefit) (2)% (0)% (1)% (9)% (5)% (7)% Amortization expense related to acquisition (1)% (1)% (1)% (1)% (0)% (0)% Total operating expenses %—Non-GAAP 88 % 80 % 84 % 93 % 75 % 83 % 25. NumbersCONFIDENTIAL may not sum due to| rounding. DO NOT Please DISTRIBUTE refer to the supplemental financials posted the ?Investor Relations? section of the A10 Networks website at investors.a10networks.com 25 The company adopted ASC 606 accounting standard effective January 1, 2018, all prior periods are based on ASC 605 standard. ATEN ?Q2 2019 Financial Results Conference Call ?Tuesday, July 30, 2019 25| Page

GAAP to NON-GAAP $ Millions Q1’19 Q2’19 Q2’19 YTD Q1’18 Q2’18 Q2’18 YTD Loss from operations $—GAAP $ (11.0) $ (6.4) $ (17.4) $ (20.0) $ (3.7) $ (23.7) Stock-based compensation 3.9 5.0 8.9 8.2 2.6 10.7 Litigation and investigation expense (benefit) 0.9 0.2 1.0 4.2 3.3 7.5 Amortization expense related to acquisition 0.3 0.3 0.5 0.3 0.3 0.5 Loss from operations $—Non-GAAP $ (5.9) $ (0.9) $ (6.9) $ (7.4) $ 2.4 $ (5.0) % of Revenue Loss from operations %—GAAP (22)% (13)% (17)% (41)% (6)% (22)% Stock-based compensation 8 % 10 % 9 % 17 % 4 % 10 % Litigation and investigation expense (benefit) 2 % 0 % 1 % 9 % 5 % 7 % Amortization expense related to acquisition 1 % 1 % 1 % 1 % 0 % 0 % Loss from operations %—Non-GAAP (12)% (2)% (7)% (15)% 4 % (5)% 26. NumbersCONFIDENTIAL may not sum due to| rounding. DO NOT Please DISTRIBUTE refer to the supplemental financials posted the ?Investor Relations? section of the A10 Networks website at investors.a10networks.com 26 The company adopted ASC 606 accounting standard effective January 1, 2018, all prior periods are based on ASC 605 standard. ATEN ?Q2 2019 Financial Results Conference Call ?Tuesday, July 30, 2019 26| Page

THANK YOU ATEN ?Q2 2019 Financial Results Conference Call ?Tuesday, July 30, 2019 27| Page