WARRANT TO PURCHASE STOCK

Exhibit 10.20

THIS WARRANT AND THE SHARES ISSUABLE HEREUNDER HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE “ACT”), OR THE SECURITIES LAWS OF ANY STATE AND, EXCEPT AND PURSUANT TO THE PROVISIONS OF ARTICLE 5 BELOW, MAY NOT BE OFFERED, SOLD OR OTHERWISE TRANSFERRED, PLEDGED OR HYPOTHECATED UNLESS AND UNTIL REGISTERED UNDER SAID ACT AND APPLICABLE STATE SECURITIES LAW OR, IN THE OPINION OF LEGAL COUNSEL IN FORM AND SUBSTANCE SATISFACTORY TO THE ISSUER OF THESE SECURITIES, SUCH OFFER, SALE OR TRANSFER, PLEDGE OR HYPOTHECATION IS EXEMPT FROM REGISTRATION.

WARRANT TO PURCHASE STOCK

THIS WARRANT CERTIFIES THAT, for good and valuable consideration, GOLD HILL VENTURE LENDING 03, LP (Gold Hill Venture Lending 03, LP, together with any registered holder from time to time of this Warrant or any holder of the shares issuable or issued upon exercise of this Warrant, “Holder”) is entitled to purchase the number of fully paid and nonassessable shares of the class of securities (the “Shares”) of the Company at the Warrant Price, all as set forth above and as adjusted pursuant to Article 2 of this Warrant, subject to the provisions and upon the terms and conditions set forth in this Warrant.

ARTICLE 1. EXERCISE

1.1. Method of Exercise. Holder may exercise this Warrant by delivering a duly executed Notice of Exercise in substantially the form attached as Appendix 1 to the principal office of the Company. Unless Holder Is exercising the conversion right set forth in Article 1.2, Holder shall also deliver to the Company a check, wire transfer (to an account designated by the Company), or other form of payment acceptable to the Company for the aggregate Warrant Price for the Shares being purchased.

1.2. Conversion Right. In lieu of exercising this Warrant as specified in Article 1.1, Holder may from time to time convert this Warrant, in whole or in part, into a number of Shares determined by dividing (a) the aggregate fair market value of the Shares or other securities otherwise issuable upon exercise of this Warrant (or, if only a portion of the Warrant is being converted, the aggregate fair market value of the portion of the Warrant being converted) minus the aggregate Warrant Price of such Shares by (b) the fair market value of one Share. The fair market value of the Shares shall be determined pursuant to Article 1.3.

1.3. Fair Market Value. If the Company’s common stock is traded in a public market and the Shares are common stock, the fair market value of each Share shall be the closing price of a Share reported for the business day immediately before Holder delivers its Notice of Exercise to the Company (or in the instance where the Warrant is exercised immediately prior to the effectiveness of the Company’s initial public offering, the “price to public” per share price specified in the final prospectus relating to such offering). If the Company’s common stock is traded in a public market and the Shares are preferred stock, the fair market value of a Share shall be the closing price of a share of the Company’s common stock reported for the business day immediately before Holder delivers its Notice of Exercise to the Company (or, in the instance where the Warrant Is exercised immediately prior to the effectiveness of the Company’s initial public offering, the initial “price to public” per share price specified in the final prospectus relating to such offering), in both cases, multiplied by the number of shares of the Company’s common stock into which a Share is convertible. If the Company’s common stock is not traded in a public market, the Board of Directors of the Company shall determine fair market value in its reasonable good faith judgment.

1.4. Delivery of Certificate and New Warrant. Promptly after Holder exercises or converts this Warrant and, if applicable, the Company receives payment of the aggregate Warrant Price, the Company shall deliver to Holder certificates for the Shares acquired and, if this Warrant has not been fully exercised or converted and has not expired, a new Warrant representing the Shares not so acquired.

1.5. Replacement of Warrants. On receipt of evidence reasonably satisfactory to the Company of the loss, theft, destruction or mutilation of this Warrant and, in the case of loss, theft or destruction, on delivery of an indemnity agreement reasonably satisfactory in form and amount to the Company or, in the case of mutilation or surrender and cancellation of this Warrant, the Company shall execute and deliver, in lieu of this Warrant, a new warrant of like tenor.

1.6. Treatment of Warrant Upon Acquisition of Company.

1.6.1 “Acquisition”. For the purpose of this Warrant, “Acquisition” means any sale, license, or other disposition of all or substantially all of the assets of the Company, or any reorganization, consolidation, or merger of the Company where the holders of the Company’s securities before the transaction beneficially own less than 50% of the outstanding voting securities of the surviving entity after the transaction.

1.6.2 Treatment of Warrant at Acquisition.

(A) Upon the written request of the Company, Holder agrees that, in the event of an Acquisition that is not an asset sale and in which the sole consideration is cash, either (a) Holder shall exercise its conversion or purchase right under this Warrant and such exercise will be deemed effective immediately prior to the consummation of such Acquisition or (b) if Holder does not exercise the Warrant prior to or in connection with the consummation of such Acquisition, this Warrant will expire upon the consummation of such Acquisition. The Company shall provide Holder with written notice of its request relating to the foregoing (together with such reasonable information as Holder may request in connection with such contemplated Acquisition giving rise to

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such notice), which Is to be delivered to Holder not less than ten (10) days prior to the closing of the proposed Acquisition.

(B) Upon the written request of the Company, Holder agrees that, in the event of an Acquisition that Is an “arms length” safe of all or substantially all of the Company’s assets (and only Its assets) to a third party that Is not an Affiliate (as defined below) of the Company (a “True Asset Sale”), either (a) Holder shall exercise its conversion or purchase right under this Warrant and such exercise will be deemed effective Immediately prior to the consummation of such True Asset Safe or (b) if Holder does not exercise the Warrant prior to or in connection with the consummation of such True Asset Sale, this Warrant will continue until the Expiration Date if the Company continues as a going concern following the closing of any such True Asset Sale. The Company shall provide Holder with written notice of Its request relating to the foregoing (together with such reasonable information as Holder may request in connection with such contemplated Acquisition giving rise to such notice), which Is to be delivered to Holder not less than ten (10) days prior to the closing of the proposed Acquisition.

(C) Upon the written request of the Company, Holder agrees that, in the event of a stock for stock Acquisition of the Company by a publicly traded acquirer if, on the record date for the Acquisition, the fair market value of the Shares (or other securities issuable upon exercise of this Warrant) Is equal to or greater than three (3) times the Warrant Price, the Company may require the Warrant to be deemed automatically exercised and the Holder shall participate in the Acquisition as a holder of the Shares (or other securities Issuable upon exercise of the Warrant) on the same terms as other holders of the same class of securities of the Company.

(D) Upon the closing of any Acquisition other than those particularly described in subsections (A), (B) and (C) above, the successor entity shall assume the obligations of this Warrant, and this Warrant shall be exercisable for the same securities, cash, and property as would be payable for the Shares Issuable upon exercise of the unexercised portion of this Warrant as if such Shares were outstanding on the record date for the Acquisition and subsequent closing. The Warrant Price and/or number of Shares shall be adjusted accordingly.

As used herein “Affiliate” shall mean any person or entity that owns or controls directly or indirectly ten (10) percent or more of the stock of Company, any person or entity that controls or is controlled by or is under common control with such persons or entities, and each of such person’s or entity’s officers, directors, joint venturers or partners, as applicable.

For purposes of clarification, nothing contained in this Article 1.6, shall require the separate consent of the Holder for any Acquisition.

ARTICLE 2. ADJUSTMENTS TO THE SHARES.

2.1. Stock Dividends, Splits, Etc. If the Company declares or pays a dividend on the Shares payable in common stock, or other securities, then upon exercise of this Warrant, for each Share acquired, Holder shall receive, without cost to Holder, the total number and kind of securities to which Holder would have been entitled had Holder owned the Shares of record as of the date the dividend occurred. If the Company subdivides the Shares by reclassification or otherwise into a greater number of shares or takes any other action which increases the amount of stock into which the

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Shares are convertible, the number of shares purchasable hereunder shall be proportionately increased and the Warrant Price shall be proportionately decreased. If the outstanding shares are combined or consolidated, by reclassification or otherwise, into a lesser number of shares, the Warrant Price shall be proportionately increased and the number of Shares shall be proportionately decreased.

2.2. Reclassification, Exchange. Combinations or Substitution. Upon any reclassification, exchange, substitution, or other event that results in a change of the number and/or class of the securities Issuable upon exercise or conversion of this Warrant, Holder shall be entitled to receive, upon exercise or conversion of this Warrant, the number and kind of securities and property that Holder would have received for the Shares if this Warrant had been exercised immediately before such reclassification, exchange, substitution, or other event. Such an event shall include any automatic conversion of the outstanding or Issuable securities of the Company of the same class or series as the Shares to common stock pursuant to the terms of the Company’s Articles or Certificate (as applicable) of Incorporation upon the closing of a registered public offering of the Company’s common stock. The Company or Its successor shall promptly Issue to Holder an amendment to this Warrant setting forth the number and kind of such new securities or other property issuable upon exercise or conversion of this Warrant as a result of such reclassification, exchange, substitution or other event that results in a change of the number and/or class of securities issuable upon exercise or conversion of this Warrant. The amendment to this Warrant shall provide for adjustments which shall be as nearly equivalent as may be practicable to the adjustments provided for in this Article 2 including, without limitation, adjustments to the Warrant Price and to the number of securities or property issuable upon exercise of the new Warrant. The provisions of this Article 2.2 shall similarly apply to successive reclassifications, exchanges, substitutions, or other events.

2.3. Adjustments for Diluting Issuances. The Warrant Price and the number of Shares issuable upon exercise of this Warrant or, if the Shares are preferred stock, the number of shares of common stock issuable upon conversion of the Shares, shall be subject to adjustment, from time to time in the manner set forth in the Company’s Articles or Certificate of Incorporation as if the Shares were issued and outstanding on and as of the date of any such required adjustment. The provisions set forth for the Shares in the Company’s Articles or Certificate (as applicable) of Incorporation relating to the above in effect as of the Issue Date may not be amended, modified or waived, without the prior written consent of Holder unless such amendment, modification or waiver affects the rights associated with the Shares in the same manner as such amendment, modification or waiver affects the rights associated with all other shares of the same series and class as the Shares granted to Holder.

2.4. No Impairment. The Company shall not, by amendment of its Articles or Certificate (as applicable) of Incorporation or through a reorganization, transfer of assets, consolidation, merger, dissolution, issue, or sale of securities or any other voluntary action, avoid or seek to avoid the observance or performance of any of the terms to be observed or performed under this Warrant by the Company, but shall at all times in good faith assist in carrying out of all the provisions of this Article 2 and in taking all such action as may be necessary or appropriate to protect Holder’s rights under this Article against impairment.

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2.5. Fractional Shares. No fractional Shares shall be issuable upon exercise or conversion of this Warrant and the number of Shares to be issued shall be rounded down to the nearest whole Share. If a fractional share interest arises upon any exercise or conversion of the Warrant, the Company shall eliminate such fractional share interest by paying Holder the amount computed by multiplying the fractional interest by the fair market value of a full Share.

2.6. Certificate as to Adjustments. Upon each adjustment of the Warrant Price, the Company shall provide Holder with a Certificate of Adjustment pursuant to Article IV, Section D.5(j) of the Company’s Certificate of Incorporation.

ARTICLE 3. REPRESENTATIONS AND COVENANTS OF THE COMPANY.

3.1. Representations and Warranties. The Company represents and warrants to Holder as follows:

(a) The initial Warrant Price referenced on the first page of this Warrant is the same as the price per share at which the Shares were issued pursuant to the Series 61 Convertible Preferred Stock and Warrant Purchase Agreement dated May 23, 2008.

(b) All Shares which may be issued upon the exercise of the purchase right represented by this Warrant, and all securities, if any, issuable upon conversion of the Shares, shall, upon Issuance, be duly authorized, validly issued, fully paid and nonassessable, and free of any liens and encumbrances except for restrictions on transfer provided for herein or under applicable federal and state securities laws.

(c) The Company’s capitalization table attached hereto as Schedule 1 is true and complete as of the Issue Date.

3.2. Notice of Certain Events. If the Company proposes at any time (a) to declare any dividend or distribution upon any of Its stock, whether in cash, property, stock, or other securities and whether or not a regular cash dividend; (b) to offer for sale any shares of the Company’s capital stock (or other securities convertible into such capital stock), other than (i) pursuant to the Company’s stock option or other compensatory plans, (ii) in connection with commercial credit arrangements or equipment financings, or (iii) in connection with strategic transactions for purposes other than capital raising; (c) to effect any reclassification or recapitalization of any of its stock; (d) to merge or consolidate with or into any other corporation, or sell, lease, license, or convey all or substantially all of its assets, or to liquidate, dissolve or wind up; or (e) offer holders of registration rights the opportunity to participate in an underwritten public offering of the Company’s securities for cash, then, in connection with each such event, the Company shall give Holder: (1) at least 10 days prior written notice of the date on which a record will be taken for such dividend, distribution, or subscription rights (and specifying the date on which the holders of common stock will be entitled thereto) or for determining rights to vote, if any, in respect of the matters referred to in (a) and (b) above; (2) in the case of the matters referred to in (c) and (d) above at least 10 days prior written notice of the date when the same will take place (and specifying the date on which the holders of common stock will be entitled to exchange their common stock for securities or other property deliverable upon the occurrence of such event); and (3) in the case of the matter referred to in (e) above, the same notice as is given to the holders

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of such registration rights. Company will also provide information requested by Holder reasonably necessary to enable Holder to comply with Holder’s accounting or reporting requirements.

3.3. Registration Under Securities Act of 1933. as amended. The Company agrees that the shares of common stock, issuable upon conversion of the Shares, shall have certain “piggyback” and S-3 registration rights pursuant to and as set forth in the Company’s Investor Rights Agreement or similar agreement. Upon the exercise or conversion of this Warrant, Holder agrees to become a party to the Company’s Amended and Restated Investor Rights Agreement, dated May 23, 2008 (the “Investor Rights Agreement”). The provisions set forth in the Company’s Investor Rights Agreement or similar agreement relating to the above in effect as of the Issue Date may not be amended, modified or waived without the prior written consent of Holder unless such amendment, modification or waiver affects the rights associated with the Shares in the same manner as such amendment, modification, or waiver affects the rights associated with all other shares of the same series and class as the Shares granted to Holder.

3.4. No Shareholder Rights. Except as provided in this Warrant, Holder will not have any rights as a shareholder of the Company until the exercise of this Warrant.

ARTICLE 4. REPRESENTATIONS, WARRANTIES OF HOLDER. Holder represents and warrants to the Company as follows:

4.1. Purchase for Own Account. This Warrant and the securities to be acquired upon exercise of this Warrant by Holder will be acquired for investment for Holder’s account, not as a nominee or agent, and not with a view to the public resale or distribution within the meaning of the Act. Holder also represents that Holder has not been formed for the specific purpose of acquiring this Warrant or the Shares.

4.2. Disclosure of Information. Holder has received or has had full access to all the information it considers necessary or appropriate to make an informed investment decision with respect to the acquisition of this Warrant and its underlying securities. Holder further has had an opportunity to ask questions and receive answers from the Company regarding the terms and conditions of the offering of this Warrant and its underlying securities and to obtain additional information (to the extent the Company possessed such information or could acquire it without unreasonable effort or expense) necessary to verify any information furnished to Holder or to which Holder has access.

4.3. Investment Experience. Holder understands that the purchase of this Warrant and its underlying securities involves substantial risk. Holder has experience as an investor in securities of companies in the development stage and acknowledges that Holder can bear the economic risk of such Holder’s investment in this Warrant and its underlying securities and has such knowledge and experience in financial or business matters that Holder Is capable of evaluating the merits and risks of its investment in this Warrant and its underlying securities and/or has a preexisting personal or business relationship with the Company and certain of Its officers, directors or controlling persons of a nature and duration that enables Holder to be aware of the character, business acumen and financial circumstances of such persons.

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4.4. Accredited Investor Status. Holder is an “accredited investor” within the meaning of Regulation D promulgated under the Act.

4.5.The Act. Holder understands that this Warrant and the Shares Issuable upon exercise or conversion hereof have not been registered under the Act in reliance upon a specific exemption therefrom, which exemption depends upon, among other things, the bona fide nature of Holder’s investment intent as expressed herein. Holder understands that this Warrant and the Shares Issued upon any exercise or conversion hereof must be held indefinitely unless subsequently registered under the Act and qualified under applicable state securities laws, or unless exemption from such registration and qualification are otherwise available.

ARTICLE 5. MISCELLANEOUS

5.1. Term. This Warrant is exercisable in whole or in part at any time and from time to time on or before the Expiration Date.

5.2. Legends. The Shares (and the securities Issuable, directly or indirectly, upon conversion of the Shares, if any) shall be imprinted with a legend in substantially the following form:

THE SECURITIES REPRESENTED HEREBY HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933 (THE “ACT) AND MAY NOT BE OFFERED, SOLD OR OTHERWISE TRANSFERRED, ASSIGNED, PLEDGED OR HYPOTHECATED UNLESS AND UNTIL REGISTERED UNDER THE ACT OR UNLESS THE COMPANY HAS RECEIVED AN OPINION OF COUNSEL SATISFACTORY TO THE COMPANY AND ITS COUNSEL THAT SUCH REGISTRATION IS NOT REQUIRED.

THE SALE, PLEDGE, HYPOTHECATION OR TRANSFER OF THE SECURITIES REPRESENTED BY THIS CERTIFICATE IS SUBJECT TO THE TERMS AND CONDITIONS OF AN INVESTOR RIGHTS AGREEMENT BY AND BETWEEN THE STOCKHOLDER AND THE COMPANY, AS AMENDED FROM TIME TO TIME. COPIES OF SUCH AGREEMENT MAY BE OBTAINED UPON WRITTEN REQUEST TO THE SECRETARY OF THE COMPANY.

5.3. Compliance with Securities Laws on Transfer. This Warrant and the Shares Issuable upon exercise of this Warrant (and the securities issuable, directly or indirectly, upon conversion of the Shares, if any) may not be transferred or assigned in whole or in part without compliance with applicable federal and state securities laws by the transferor and the transferee (including, without limitation, the delivery of investment representation letters and legal opinions reasonably satisfactory to the Company, as reasonably requested by the Company). The Company shall not require Holder to provide an opinion of counsel if the transfer is to any affiliate of Holder. Additionally, the Company shall also not require an opinion of counsel if there is no material question as to the availability of current information as referenced in Rule 144(c), Holder represents that it has complied with Rule 144(d) and (e) in reasonable detail, the selling broker represents that it has complied with Rule 144(f), and the Company Is provided with a copy of Holder’s notice of proposed sale.

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5.4. Transfer Procedure. Upon receipt by Holder of the executed Warrant, Holder may transfer all of this Warrant to any Affiliate of Holder by execution of an Assignment substantially in the form of Appendix 2. Subject to the provisions of Section 5.3 and upon providing the Company with written notice, and any subsequent Holder may transfer all or part of this Warrant or the Shares issuable upon exercise of this Warrant (or the Shares issuable directly or indirectly, upon conversion of the Shares, if any) to any transferee, provided, however, that in connection with any such transfer, any subsequent Holder will give the Company notice of the name, address and taxpayer identification number of the transferee, will surrender this Warrant to the Company for reissuance to the transferee(s) and such transferee(s) will agree to be bound by all restrictions set forth herein. The Company may refuse to transfer this Warrant or the Shares to any person who directly competes with the Company, unless, in either case, the stock of the Company is publicly traded.

5.5. Notices. All notices and other communications from the Company to Holder, or vice versa, shall be deemed delivered and effective when given personally or mailed by first-class registered or certified mail, postage prepaid, at such address as may have been furnished to the Company or Holder, as the case may (or on the first business day after transmission by facsimile) be, in writing by the Company or such Holder from time to time. Effective upon receipt of the fully executed Warrant and the initial transfer described in Article 5.4 above, all notices to Holder shall be addressed as follows until the Company receives notice of a change of address in connection with a transfer or otherwise:

Gold Hill Venture Lending 03, LP

Two Newton Executive Park, Suite 203

Newton, Massachusetts 02462

Attn: Frank Tower

Telephone: (617) 243-2626

Facsimile: (617) 243-2601

Notice to the Company shall be addressed as follows until Holder receives notice of a change in address:

Netcordia, Inc.

2431 Solomons Island Road

Suite 302

Annapolis, Maryland 21401

Attn: Patrick McCoy

Telephone: (410) 266-6161 Ext. 312

Facsimile: (410) 573-9774

5.6. Waiver. This Warrant and any term hereof may be changed, waived, discharged or terminated only by an instrument in writing signed by the party against which enfocement of such change, waiver, discharge or termination is sought.

5.7. Attorneys’ Fees. In the event of any dispute between the parties concerning the terms and provisions of this Warrant, the party prevailing in such dispute shall be entitled to collect from the other party all costs incurred in such dispute, including reasonable attorneys’ fees.

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5.8. Automatic Conversion upon Expiration. In the event that, upon the Expiration Date, the fair market value of one Share (or other security Issuable upon the exercise hereof) as determined in accordance with Section 1.3 above is greater than the Warrant Price in effect on such date, then this Warrant shall automatically be deemed on and as of such date to be converted pursuant to Section 1.2 above as to all Shares (or such other securities) for which it shall not previously have been exercised or converted, and the Company shall promptly deliver a certificate representing the Shares (or such other securities) issued upon such conversion to Holder.

5.9. Market Standoff. The Holder hereby agrees to be bound by the “Market Stand-Off” in Section 2.13 of the Investor Rights Agreement (the “Market Stand­ Off Provision”). The Market Stand-Off Provision may not be amended, modified or waived without the prior written consent of Holder unless such amendment, modification or waiver affects the rights associated with the Shares in the same manner as such amendment, modification or waiver affects the rights associated with all other shares of the same series and class as the Shares granted pursuant to this Warrant.

5.10. Counterparts. This Warrant may be executed in counterparts, all of which together shall constitute one and the same agreement.

5.11. Governing Law. This Warrant shall be governed by and construed in accordance with the laws of the State of Delaware, without giving effect to its principles regarding conflicts of law.

[Signature page follows.]

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