Exhibit 10.13

LOGO

BUSINESS LOAN AGREEMENT



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|Borrower: |  | Opnet Technologies, Inc. 7255 Woodmont Avenue
Bethesda, MD 20814 |  | Lender: |  | Bank of America, N.A. CCS-Commercial Banking
NC1-014-13-05 10 Light Street Baltimore, MD 21202-1435

THIS BUSINESS LOAN AGREEMENT dated June 20, 2005, is made and executed between Opnet Technologies, Inc.
(Borrower) and Bank of America, N.A. (Lender) on the following terms and conditions. Borrower has received prior commercial loans from Lender or has applied to Lender for a commercial loan or loans or other financial
accommodations, including those which may be described on any exhibit or schedule attached to this Agreement (Loan). Borrower understands and agrees that: (A) in granting, renewing, or extending any Loan, Lender is relying upon
Borrowers representations, warranties, and agreements as set forth in this Agreement; (B) the granting, renewing, or extending of any Loan by Lender at all times shall be subject to Lenders sole judgment and discretion; and
(C) all such Loans shall be and remain subject to the terms and conditions of this Agreement.

TERM. This Agreement shall be effective as of
June 10, 2005, and shall continue in full force and effect until such time as all of Borrowers Loans in favor of Lender have been paid in full, including principal, interest, costs, expenses, attorneys fees, and other fees and
charges, or until such time as the parties may agree in writing to terminate this Agreement.

CONDITIONS PRECEDENT TO EACH ADVANCE. Lenders
obligation to make the initial Advance and each subsequent Advance under this Agreement shall be subject to the fulfillment to Lenders satisfaction of all of the conditions set forth in this Agreement and in the Related Documents.

Loan Documents. Borrower shall provide to Lender the following documents for the Loan: (1) the Note; (2) together with all such
Related Documents as Lender may require for the Loan; all in form and substance satisfactory to Lender and Lenders counsel.

Borrowers Authorization. Borrower shall have provided in form and substance satisfactory to Lender properly certified resolutions, duly authorizing the execution and delivery of this Agreement, the Note and the Related
Documents. In addition, Borrower shall have provided such other resolutions, authorizations, documents and instruments as Lender or its counsel, may require.

Payment of Fees and Expenses. Borrower shall have paid to Lender all fees, charges, and other expenses which are then due and payable as specified in this Agreement or any Related Document.

Representations and Warranties. The representations and warranties set forth in this Agreement, in the Related Documents, and in any document or
certificate delivered to Lender under this Agreement are true and correct.

No Event of Default. There shall not exist at the time of
any Advance a condition which would constitute an Event of Default under this Agreement or under any Related Document.

REPRESENTATIONS AND
WARRANTIES. Borrower represents and warrants to Lender, as of the date of this Agreement, as of the date of each disbursement of loan proceeds, as of the date of any renewal, extension or modification of any Loan, and at all times any
indebtedness exists:

Organization. Borrower is a corporation for profit which is, and at all times shall be, duly organized, validly
existing, and in good standing under and by virtue of the laws of the State of Maryland Borrower has the full power and authority to own its properties and to transact the business in which it is presently engaged or presently proposes to engage.
Borrower maintains an office at 7255 Woodmont Avenue, Bethesda, MD 20814. Unless Borrower has designated otherwise in writing, the principal office is the office at which Borrower keeps its books and records including its records concerning the
Collateral. Borrower will notify Lender prior to any change in the location of Borrowers state of organization or any change in Borrowers name. Borrower shall do all things necessary to preserve and to keep in full force and effect its
existence, rights and privileges, and shall comply with all regulations, rules, ordinances, statutes, orders and decrees of any governmental or quasi-governmental authority or court applicable to Borrower and Borrowers business activities.

Assumed Business Names. Borrower has filed or recorded all documents or filings required by law relating to all assumed business
names used by Borrower. Excluding the name of Borrower, the following is a complete list of all assumed business names under which Borrower does business:



|                         |  |                                    |  |                 |  |     
|------------------------ |  | ---------------------------------- |  | --------------- |  | ----
|Borrower                 |  | Assumed Business Name              |  | Filing Location |  | Date
|Opnet Technologies, Inc. |  | on file with lender, if applicable |  |                 |  |     

Authorization. Borrowers execution, delivery, and performance of this Agreement and all the Related
Documents have been duly authorized by all necessary action by Borrower and do not conflict with, result in a violation of, or constitute a default under (1) any provision of (a) Borrowers articles of incorporation or organization,
or bylaws, or (b) any agreement or other instrument binding upon Borrower or (2) any law, governmental regulation, court decree, or order applicable to Borrower or to Borrowers properties.

Financial Information. Each of Borrowers financial statements supplied to Lender truly and completely disclosed Borrowers financial condition as of
the date of the statement, and there has been no material adverse change in Borrowers financial condition subsequent to the date of the most recent financial statement supplied to Lender. Borrower has no material contingent obligations except
as disclosed in such financial statements.

Legal Effect. This Agreement constitutes, and any instrument or agreement Borrower is required to give
under this Agreement when delivered will constitute legal, valid, and binding obligations of Borrower enforceable against Borrower in accordance with their respective terms.

Properties. Except as contemplated by this Agreement or as previously disclosed in Borrowers financial statements or in writing to Lender and as accepted by Lender, and except for property tax liens for
taxes not presently due and payable, Borrower owns and has good title to all of Borrowers properties free and clear of all Security Interests, and has not executed any security documents or financing statements relating to such properties. All
of Borrowers properties are titled in Borrowers legal name, and Borrower has not used or filed a financing statement under any other name for at least the last five (5) years.

Hazardous Substances. Except as disclosed to and acknowledged by Lender in writing, Borrower represents and warrants that: (1) During the period of
Borrowers ownership of the Collateral, there has been no use, generation, manufacture, storage, treatment, disposal, release or threatened release of any Hazardous Substance by any person on, under, about or from any of the Collateral.
(2) Borrower has no



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|Loan No: 41/567249/Cc |  | (Continued)             |  | Page 2

knowledge of, or reason to believe that there has been (a) any breach or violation of any
Environmental Laws: (b) any use, generation, manufacture, storage, treatment, disposal, release or threatened release of any Hazardous Substance on, under, about or from the Collateral by any prior owners or occupants of any of the Collateral;
or (c) any actual or threatened litigation or claims of any kind by any person relating to such matters. (3) Neither Borrower nor any tenant, contractor, agent or other authorized user of any of the Collateral shall use, generate, manufacture,
store, treat, dispose of or release any Hazardous Substance on, under, about or from any of the Collateral; and any such activity shall be conducted in compliance with all applicable federal, state, and local laws, regulations, and ordinances,
including without limitation all Environmental Laws. Borrower authorizes Lender and its agents to enter upon the Collateral to make such inspections and tests as Lender may deem appropriate to determine compliance of the Collateral with this section
of the Agreement. Any inspections or tests made by Lender shall be at Borrowers expense and for Lenders purposes only and shall not be construed to create any responsibility or liability on the part of Lender to Borrower or to any other
person. The representations and warranties contained herein are based on Borrowers due diligence in Investigating the Collateral for hazardous waste and Hazardous Substances. Borrower hereby (1) releases and waives any future claims
against Lender for indemnity or contribution in the event Borrower becomes liable for cleanup or other costs under any such laws, and (2) agrees to indemnify and hold harmless Lender against any and all claims, losses, liabilities, damages,
penalties, and expenses which Lender may directly or indirectly sustain or suffer resulting from a breach of this section of the Agreement or as a consequence of any use, generation, manufacture, storage, disposal, release or threatened release of a
hazardous waste or substance on the Collateral. The provisions of this section of the Agreement, including the obligation to indemnify, shall survive the payment of the Indebtedness and the termination, expiration or satisfaction of this Agreement
and shall not be affected by Lenders acquisition of any interest in any of the Collateral, whether by foreclosure or otherwise.

Litigation and Claims. No litigation, claim, investigation, administrative proceeding or similar action (including those for unpaid taxes) against Borrower is pending or threatened, and no other event has occurred which may
materially adversely affect Borrowers financial condition or properties, other than litigation, claims, or other events, if any, that have been disclosed to and acknowledged by Lender in writing.

Taxes. To the best of Borrowers knowledge, all of Borrowers tax returns and reports that are or were required to be filed, have been
filed, and all taxes, assessments and other governmental charges have been paid in full, except those presently being or to be contested by Borrower in good faith in the ordinary course of business and for which adequate reserves have been provided.

Lien Priority. Unless otherwise previously disclosed to Lender in writing, Borrower has not entered into or granted any Security
Agreements, or permitted the filing or attachment of any Security Interests on or affecting any of the Collateral directly or indirectly securing repayment of Borrowers Loan and Note, that would be prior or that may in any way be superior to
Lenders Security Interests and rights in and to such Collateral.

Binding Effect. This Agreement, the Note, all Security
Agreements (if any), and all Related Documents are binding upon the signers thereof, as well as upon their successors, representatives and assigns, and are legally enforceable in accordance with their respective terms.

AFFIRMATIVE COVENANTS. Borrower covenants and agrees with Lender that, so long as this Agreement remains in effect, Borrower will:

Notices of Claims and Litigation. Promptly inform Lender in writing of (1) all material adverse changes in Borrowers financial
condition, and (2) all existing and all threatened litigation, claims, investigations, administrative proceedings or similar actions affecting Borrower or any Guarantor which could materially affect the financial condition of Borrower or the
financial condition of any Guarantor.

Financial Records. Maintain its books and records in accordance with GAAP, applied on a
consistent basis, and permit Lender to examine and audit Borrowers books and records at all reasonable times.

Financial
Statements. Furnish Lender with the following:

Annual Statements. As soon as available, but in no event later than
one-hundred-twenty (120) days after the end of each fiscal year, Borrowers balance sheet and income statement for the year ended, audited by a certified public accountant satisfactory to Lender.

Additional Requirements.

Basis of
Financial Statements. The financial statements required by this Agreement shall be prepared on a consolidated basis.

Accounts
Receivable Agings. A detailed aging of Borrowers receivables by invoice or a summary aging by account debtor, as specified by Lender, within 120 days after the end of fiscal year.

Borrower covenants and agrees with Lender that, so long as this Agreement remains in effect, Borrower will deliver to Lender within 120 days following the
end of each fiscal year, a certificate substantially in the form of the Borrower Compliance Certificate attached hereto signed by Borrower, or if Borrower is a business entity, an authorized financial officer of Borrower, setting forth (i) the
information and computations (in sufficient detail) to establish that Borrower is in compliance with all financial covenants at the end of the period covered by the financial statements then being delivered to Lender, and (ii) whether there
existed as of the date of such financial statements and whether there exists as of the date of the certificate, any Event of Default under this Agreement and, if any such default exists, specifying the nature thereof and the action Borrower is
taking and proposes to take with respect thereto.

All financial reports required to be provided under this Agreement shall be prepared in accordance with
GAAP, applied on a consistent basis, and certified by Borrower as being true and correct.

Additional Information. Furnish such additional
information and statements, as Lender may request from time to time.

Insurance. Maintain fire and other risk insurance, public liability insurance,
and such other insurance as Lender may require with respect to Borrowers properties and operations, in form, amounts, coverages and with insurance companies acceptable to Lender. Borrower, upon request of Lender, will deliver to Lender from
time to time the policies or certificates of insurance in form satisfactory to Lender, including stipulations that coverages will not be cancelled or diminished without at least thirty (30) days prior written notice to Lender. Each insurance
policy also shall include an endorsement providing that coverage in favor of Lender will not be impaired in any way by any act, omission or default of Borrower or any other person. In connection with all policies covering assets in which Lender
holds or is offered a security interest for the Loans, Borrower will provide Lender with such lenders loss payable or other endorsements as Lender may require.

Insurance Reports. Furnish to Lender, upon request of Lender, reports on each existing insurance policy showing such information as Lender may reasonably request, including without limitation the following:
(1) the name of the insurer; (2) the risks insured; (3) the amount of the policy; (4) the properties insured; (5) the then current property values on the basis of which insurance has been obtained, and the manner of determining
those values; and (6) the expiration date of the policy. In addition, upon request of Lender (however not more often than annually), Borrower will have an independent appraiser satisfactory to Lender determine, as applicable, the actual cash
value or replacement cost of any Collateral. The cost of such appraisal shall be paid by Borrower.

Other Agreements. Comply with all terms and
conditions of all other agreements, whether now or hereafter existing, between Borrower and any other party and notify Lender immediately in writing of any default in connection with any other such agreements.



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|                      |  | BUSINESS LOAN AGREEMENT |  |       
|Loan No: 41/567249/Cc |  | (Continued)             |  | Page 3

Loan Proceeds. Use all Loan proceeds solely for Borrowers business operations, unless
specifically consented to the contrary by Lender in writing.

Taxes, Charges and Liens. Pay and discharge when due all of its
indebtedness and obligations, including without limitation all assessments, taxes, governmental charges, levies and liens, of every kind and nature, imposed upon Borrower or its properties, income, or profits, prior to the date on which penalties
would attach, and all lawful claims that, if unpaid, might become a lien or charge upon any of Borrowers properties. Income, or profits.

Performance. Perform and comply, in a timely manner, with all terms, conditions, and provisions set forth in this Agreement, in the Related Documents, and in all other instruments and agreements between Borrower and Lender. Borrower
shall notify Lender immediately in writing of any default in connection with any agreement.

Operations. Maintain executive and
management personnel with substantially the same qualifications and experience as the present executive and management personnel; provide written notice to Lender of any change in executive and management personnel; conduct its business affairs in a
reasonable and prudent manner.

Environmental Studies. Promptly conduct and complete, at Borrowers expense, all such
investigations, studies, samplings and testings as may be requested by Lender or any governmental authority relative to any substance, or any waste or by-product of any substance defined as toxic or a hazardous substance under applicable federal,
state, or local law, rule, regulation, order or directive, at or affecting any property or any facility owned, leased or used by Borrower.

Compliance with Governmental Requirements. Comply with all laws, ordinances, and regulations, now or hereafter in effect, of all governmental authorities applicable to the conduct of Borrowers properties, businesses and
operations, and to the use or occupancy of the Collateral, including without limitation, the Americans With Disabilities Act. Borrower may contest in good faith any such law, ordinance, or regulation and withhold compliance during any proceeding,
including appropriate appeals, so long as Borrower has notified Lender in writing prior to doing so and so long as, in Lenders sole opinion, Lenders interests in the Collateral are not jeopardized. Lender may require Borrower to post
adequate security or a surety bond, satisfactory to Lender, to protect Lenders interest.

Inspection. Permit employees or
agents of Lender at any reasonable time to inspect any and all Collateral for the Loan or Loans and Borrowers other properties and to examine or audit Borrowers books, accounts, and records and to make copies and memoranda of
Borrowers books, accounts, and records. If Borrower now or at any time hereafter maintains any records (including without limitation computer generated records and computer software programs for the generation of such records) in the
possession of a third party. Borrower, upon request of Lender, shall notify such party to permit Lender free access to such records at all reasonable times and to provide Lender with copies of any records it may request, all at Borrowers
expense.

Compliance Certificates. Unless waived in writing by Lender, provide Lender within one hundred twenty (120) days after
the end of each fiscal year, with a certificate executed by Borrowers chief financial officer, or other officer or person acceptable to Lender, certifying that the representations and warranties set forth in this Agreement are true and correct
as of the date of the certificate and further certifying that, as of the date of the certificate, no Event of Default exists under this Agreement.

Environmental Compliance and Reports. Borrower shall comply in all respects with any and all Environmental Laws; not cause or permit to exist, as a result of an intentional or unintentional action or omission on Borrowers part
or on the part of any third party, on property owned and/or occupied by Borrower, any environmental activity where damage may result to the environment, unless such environmental activity is pursuant to and in compliance with the conditions of a
permit issued by the appropriate federal, state or local governmental authorities; shall furnish to Lender promptly and in any event within thirty (30) days after receipt thereof a copy of any notice, summons, lien, citation, directive, letter
or other communication from any governmental agency or instrumentality concerning any intentional or unintentional action or omission on Borrowers part in connection with any environmental activity whether or not there is damage to the
environment and/or other natural resources.

Additional Assurances. Make, execute and deliver to Lender such promissory notes,
mortgages, deeds of trust, security agreements, assignments, financing statements, instruments, documents and other agreements as Lender or its attorneys may reasonably request to evidence and secure the Loans and to perfect all Security Interests.

LENDERS EXPENDITURES. If any action or proceeding is commenced that would materially affect Lenders interest in the Collateral or if
Borrower fails to comply with any provision of this Agreement or any Related Documents, Including but not limited to Borrowers failure to discharge or pay when due any amounts Borrower is required to discharge or pay under this Agreement or
any Related Documents, Lender on Borrowers behalf may (but shall not be obligated to) take any action that Lender deems appropriate, including but not limited to discharging or paying all taxes, liens, security interests, encumbrances and
other claims, at any time levied or placed on any Collateral and paying all costs for insuring, maintaining and preserving any Collateral. All such expenditures incurred or paid by Lender for such purposes will then bear interest at the rate charged
under the Note from the date incurred or paid by Lender to the date of repayment by Borrower. All such expenses will become a part of the Indebtedness and, at Lenders option, will (A) be payable on demand; or (B) be added to the
balance of the Note and be apportioned among and be payable with any installment payments to become due during either (1) the term of any applicable insurance policy; or (2) the remaining term of the Note.

NEGATIVE COVENANTS. Borrower covenants and agrees with Lender that while this Agreement is in effect, Borrower shall not, without the prior written consent of
Lender:

Indebtedness and Liens. (1) Except for trade debt incurred in the normal course of business and indebtedness to Lender
contemplated by this Agreement, create, incur or assume additional indebtedness for borrowed money, including capital leases, in excess of the aggregate amount of $500,000,00, (2) sell, transfer, mortgage, assign, pledge, lease, grant a
security interest in, or encumber any of Borrowers assets (except as allowed as Permitted Liens), or (3) sell with recourse any of Borrowers accounts, except to Lender.

Additional Financial Restrictions. Investments. Have any existing, or make any new, investments in, any individual or entity, or make any
capital contributions or other transfers of assets to any individual or entity, except for: investments that do not exceed an aggregate amount of Ten Million 00/100 Dollars ($10,000.00).

Continuity of Operations. (1) Engage in any business activities substantially different than those in which Borrower is presently engaged,
(2) cease operations, liquidate, merge, transfer, acquire or consolidate with any other entity, change its name, dissolve or transfer or sell Collateral out of the ordinary course of business, or (3) pay any dividends on Borrowers
stock (other than dividends payable in its stock), provided, however that notwithstanding the foregoing, but only so long as no Event of Default has occurred and is continuing or would result from the payment of dividends, if Borrower is a
Subchapter S Corporation (as defined in the Internal Revenue Code of 1986, as amended), Borrower may pay cash dividends on its stock to its shareholders from time to time in amounts necessary to enable the shareholders to pay income
taxes and make estimated income tax payments to satisfy their liabilities under federal and state law which arise solely from their status as Shareholders of a Subchapter S Corporation because of their ownership of shares of Borrowers stock,
or purchase or retire any of Borrowers outstanding shares or alter or amend Borrowers capital structure.



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|                      |  | BUSINESS LOAN AGREEMENT |  |       
|Loan No: 41/567249/Cc |  | (Continued)             |  | Page 4

Loans. Acquisitions and Guaranties. (1) Except as expressly stated hereafter, loan,
invest in or advance money or assets to any other person, enterprise or entity, (2) purchase, create or acquire any interest in any other enterprise or entity, or (3) incur any obligation as surety or guarantor other than in the ordinary
course of business. The following exceptions are expressly exempted from the foregoing restrictions; $500,000.00.

Agreements.
Borrower will not enter into any agreement containing any provisions which would be violated or breached by the performance of Borrowers obligations under this Agreement or in connection herewith.

CESSATION OF ADVANCES. If Lender has made any commitment to make any Loan to Borrower, whether under this Agreement or under any other agreement, Lender shall
have no obligation to make Loan Advances or to disburse Loan proceeds if: (A) Borrower or any Guarantor is in default under the terms of this Agreement or any of the Related Documents or any other agreement that Borrower or any Guarantor has
with Lender; (B) Borrower or any Guarantor dies, becomes incompetent or becomes insolvent, files a petition in bankruptcy or similar proceedings, or is adjudged a bankrupt; (C) there occurs a material adverse change in Borrowers
financial condition, in the financial condition of any Guarantor, or in the value of any Collateral securing any Loan; or (D) any Guarantor seeks, claims or otherwise attempts to limit, modify or revoke such Guarantors guaranty of the
Loan or any other loan with Lender; or (E) Lender in good faith deems itself insecure, even though no Event of Default shall have occurred.

RIGHT
OF SETOFF. To the extent permitted by applicable law, Lender reserves a right of setoff in all Borrowers accounts with Lender (whether checking, savings, or some other account). This includes all accounts Borrower holds jointly with
someone else and all accounts Borrower may open in the future. However, this does not include any IRA or Keogh accounts, or any trust accounts for which setoff would be prohibited by law. Borrower authorizes Lender, to the extent permitted by
applicable law, to charge or setoff all sums owing on the debt against any and all such accounts.

DEFAULT. Each of the following shall constitute
an Event of Default under this Agreement:

Payment Default. Borrower fails to make any payment when due under the Loan.

Other Defaults. Borrower fails to comply with or to perform any other term, obligation, covenant or condition contained in this Agreement or in
any of the Related Documents or to comply with or to perform any term, obligation, covenant or condition contained in any other agreement between Lender and Borrower.

Default in Favor of Third Parties. Borrower or any Grantor defaults under any loan, extension of credit, security agreement, purchase or sales agreement, or any other agreement, in favor of any other creditor
or person that may materially affect any of Borrowers or any Grantors property or Borrowers or any Grantors ability to repay the Loans or perform their respective obligations under this Agreement or any of the Related
Documents.

False Statements. Any warranty, representation or statement made or furnished to Lender by Borrower or on Borrowers
behalf under this Agreement or the Related Documents is false or misleading in any material respect, either now or at the time made or furnished or becomes false or misleading at any time thereafter.

Insolvency. The dissolution or termination of Borrowers existence as a going business, or a trustee or receiver is appointed for Borrower or
for all or a substantial portion of the assets of Borrower, or Borrower makes a general assignment for the benefit of Borrowers creditors, or Borrower files for bankruptcy, or an involuntary bankruptcy petition is filed against Borrower and
such involuntary petition remains undismissed for sixty (60) days.

Defective Collateralization. This Agreement or any of the
Related Documents ceases to be in full force and effect (including failure of any collateral document to create a valid and perfected security interest or lien) at any time and for any reason.

Creditor or Forfeiture Proceedings. Commencement of foreclosure or forfeiture proceedings, whether by judicial proceeding, self-help, repossession
or any other method, by any creditor of Borrower or by any governmental agency against any collateral securing the Loan. This includes a garnishment of any of Borrowers accounts, including deposit accounts, with Lender. However, this Event of
Default shall not apply if there is a good faith dispute by Borrower as to the validity or reasonableness of the claim which is the basis of the creditor or forfeiture proceeding and if Borrower gives Lender written notice of the creditor or
forfeiture proceeding and deposits with Lender monies or a surety bond for the creditor or forfeiture proceeding, in an amount determined by Lender, in its sole discretion, as being an adequate reserve or bond for the dispute.

Events Affecting Guarantor. Any of the preceding events occurs with respect to any Guarantor of any of the Indebtedness or any Guarantor dies or
becomes incompetent, or revokes or disputes the validity of, or liability under, any Guaranty of the Indebtedness.

Change in Ownership.Any change in ownership of twenty-five percent (25%) or more of the common stock of Borrower.

Adverse Change. A material
adverse change occurs in Borrowers financial condition, or Lender believes the prospect of payment or performance of the Loan is impaired.

Insecurity. Lender in good faith believes itself insecure.

EFFECT OF AN EVENT OF DEFAULT. If any Event of Default shall occur,
except where otherwise provided in this Agreement or the Related Documents, all commitments and obligations of Lender under this Agreement or the Related Documents or any other agreement immediately will terminate (including any obligation to make
further Loan Advances or disbursements), and, at Lenders option, all sums owing in connection with the Loans, including all principal, interest, and all other fees, costs and charges, if any, will become immediately due and payable, all
without notice of any kind to Borrower, except that in the case of an Event of Default of the type described in the Insolvency subsection above, such acceleration shall be automatic and not optional. In addition, Lender shall have all
the rights and remedies provided in the Related Documents or available at law, in equity, or otherwise. Except as may be prohibited by applicable law, all of Lenders rights and remedies shall be cumulative and may be exercised singularly or
concurrently. Election by Lender to pursue any remedy shall not exclude pursuit of any other remedy, and an election to make expenditures or to take action to perform an obligation of Borrower or of any Grantor shall not affect Lenders right
to declare a default and to exercise its rights and remedies.

ADDITIONAL DEFAULTS. Each of the following shall constitute an event of default
(Event of Default) under this Agreement:

Event of Default Under Related Documents. A default or event of default occurs under the terms
of any Related Document executed by Borrower or any guarantor, pledgor, accommodation party or other obligor.

COUNTERPARTS. This Agreement may be
executed in any number of counterparts, each of which when so executed shall be deemed to be an original and all of which taken together shall constitute one and the same agreement.

AGREEMENTS CUMULATIVE. This Agreement is intended to be cumulative of all other loan agreements between the parties. The terms stated in this Agreement are in addition to, and do not supersede, the terms of any
other loan agreement which is applicable to any extension of credit by Lender to Borrower; provided, however, that this Agreement does supersede the following loan agreements: dated June 10, 2002.



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|                      |  | BUSINESS LOAN AGREEMENT |  |       
|Loan No: 41/567249/Cc |  | (Continued)             |  | Page 5

FINAL AGREEMENT. BY SIGNING THIS DOCUMENT EACH PARTY REPRESENTS AND AGREES THAT: (A) THIS DOCUMENT
REPRESENTS THE FINAL AGREEMENT BETWEEN THE PARTIES WITH RESPECT TO THE SUBJECT MATTER HEREOF, (B) THIS DOCUMENT SUPERSEDES ANY COMMITMENT LETTER, TERM SHEET OR OTHER WRITTEN OUTLINE OF TERMS AND CONDITIONS RELATING TO THE SUBJECT MATTER HEREOF,
UNLESS SUCH COMMITMENT LETTER, TERM SHEET OR OTHER WRITTEN OUTLINE OF TERMS AND CONDITIONS EXPRESSLY PROVIDES TO THE CONTRARY, (C) THERE ARE NO ORAL AGREEMENTS BETWEEN THE PARTIES, AND (D) THIS DOCUMENT MAY NOT BE CONTRADICTED BY EVIDENCE
OF ANY PRIOR, CONTEMPORANEOUS, OR SUBSEQUENT ORAL AGREEMENTS OR UNDERSTANDINGS OF THE PARTIES.

ADDRESS FOR NOTICES. Notwithstanding anything to
the contrary herein, all notices and communications to the Lender shall be directed to the following address:

Bank of
America, N.A.

Charlotte CCS, Attn: Notice Desk

200 South College, 13th Floor

Charlotte, NC 28255.

MISCELLANEOUS PROVISIONS. The following miscellaneous
provisions are a part of this Agreement:

Amendments. This Agreement, together with any Related Documents, constitutes the entire
understanding and agreement of the parties as to the matters set forth in this Agreement. No alteration of or amendment to this Agreement shall be effective unless given in writing and signed by the party or parties sought to be charged or bound by
the alteration or amendment.

Attorneys Fees; Expenses. Borrower agrees that if Lender hires an attorney to help enforce this
Agreement, Borrower will pay, subject to any limits under applicable law, Lenders attorneys fees and all of Lenders other collection expenses, whether or not there is a lawsuit and including without limitation additional legal
expenses for bankruptcy proceedings.

Caption Headings. Caption headings in this Agreement are for convenience purposes only and are
not to be used to interpret or define the provisions of this Agreement.

Consent to Jurisdiction. Borrower irrevocably submits to the
jurisdiction of any state or federal court sitting in the State of Maryland over any suit, action, or proceeding arising out of or relating to this Agreement. Borrower irrevocably waives, to the fullest extent permitted by law, any objection that
Borrower may now or hereafter have to the laying of venue of any such suit, action, or proceeding brought in any such court and any claim that any such suit, action, or proceeding brought in any such court has been brought in an inconvenient forum.
Final judgment in any such suit, action, or proceeding brought in any such court shall be conclusive and binding upon Borrower and may be enforced in any court in which Borrower is subject to jurisdiction by a suit upon such judgment provided that
service of process is effected upon Borrower asprovided in this Agreement or as otherwise permitted by applicable law.

Consent
to Loan Participation. Borrower agrees and consents to Lenders sale or transfer, whether now or later, of one or more participation interests in the Loan to one or more purchasers, whether related or unrelated to Lender. Lender may
provide, without any limitation whatsoever, to any one or more purchasers, or potential purchasers, any information or knowledge Lender may have about Borrower or about any other matter relating to the Loan, and Borrower hereby waives any rights to
privacy Borrower may have with respect to such matters. Borrower additionally waives any and all notices of sale of participation interests, as well as all notices of any repurchase of such participation interests. Borrower also agrees that the
purchasers of any such participation interests will be considered as the absolute owners of such interests in the Loan and will have all the rights granted under the participation agreement or agreements governing the sale of such participation
interests. Borrower further waives all rights of offset or counterclaim that it may have now or later against Lender or against any purchaser of such a participation interest and unconditionally agrees that either Lender or such purchaser may
enforce Borrowers obligation under the Loan irrespective of the failure or insolvency of any holder of any interest in the Loan. Borrower further agrees that the purchaser of any such participation interests may enforce its interests
irrespective of any personal claims or defenses that Borrower may have against lender.

Governing Law. This Agreement will be governed by
federal law applicable to Lender and, to the extent not preempted by federal law, the laws of the State of Maryland without regard to its conflicts of law provisions. This Agreement has been accepted by Lender in the State of Maryland.

Choice of Venue. If there is a lawsuit, Borrower agrees upon Lenders request to submit to the jurisdiction of the courts of
the City of Baltimore, State of Maryland.

JURY WAIVER. LENDER AND BORROWER EACH HEREBY WAIVE TRIAL BY JURY IN ANY ACTION OR PROCEEDING
TO WHICH LENDER OR BORROWER MAY BE PARTIES, ARISING OUT OF, OR IN ANY WAY PERTAINING TO, THIS AGREEMENT. IT IS AGREED THAT THIS WAIVER CONSTITUTES A WAIVER OF TRIAL BY JURY OF ALL CLAIMS AGAINST ALL PARTIES TO SUCH ACTIONS OR PROCEEDINGS. THIS
WAIVER IS KNOWINGLY, WILLINGLY AND VOLUNTARILY MADE BY LENDER AND BORROWER, AND LENDER AND BORROWER EACH HEREBY REPRESENT THAT NO REPRESENTATIONS OF FACT OR OPINION HAVE BEEN MADE BY ANY INDIVIDUAL TO INDUCE THIS WAIVER OF TRIAL BY JURY OR TO IN ANY
WAY MODIFY OR NULLIFY ITS EFFECT. BORROWER FURTHER REPRESENTS THAT BORROWER HAS BEEN REPRESENTED IN THE SIGNING OF THIS AGREEMENT AND IN THE MAKING OF THIS WAIVER BY INDEPENDENT LEGAL COUNSEL, SELECTED OF BORROWERS OWN FREE WILL, AND THAT
BORROWER HAS HAD THE OPPORTUNITY TO DISCUSS THIS WAIVER WITH COUNSEL.

No Waiver by Lender. Lender shall not be deemed to have
waived any rights under this Agreement unless such waiver is given in writing and signed by Lender. No delay or omission on the part of Lender in exercising any right shall operate as a waiver of such right or any other right. A waiver by Lender of
a provision of this Agreement shall not prejudice or constitute a waiver of Lenders right otherwise to demand strict compliance with that provision or any other provision of this Agreement. No prior waiver by Lender, nor any course of dealing
between Lender and Borrower, or between Lender and any Grantor, shall constitute a waiver of any of Lenders rights or of any of Borrowers or any Grantors obligations as to any future transactions. Whenever the consent of Lender is
required under this Agreement, the granting of such consent by Lender in any instance shall not constitute continuing consent to subsequent instances where such consent is required and in all cases such consent may be granted or withheld in the sole
discretion of Lender.

Notices. Any notice required to be given under this Agreement shall be given in writing, and shall be
effective when actually delivered, if hand delivered, when actually received by telefacsimile (unless otherwise required by law), when deposited with a nationally recognized overnight courier, or, if mailed, when deposited in the United States mail,
as first class, certified or registered mail postage prepaid, directed to the addresses shown near the beginning of this Agreement. Any party may change its address for notices under this Agreement by giving formal written notice to the other
parties, specifying that the purpose of the notice is to change the partys address. For notice purposes, Borrower agrees to keep Lender informed at all times of Borrowers current address. Unless otherwise provided or required by law, if
there is more than one Borrower, any notice given by Lender to any Borrower is deemed to be notice given to all Borrowers.



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|--------------------- |  | ----------------------- |  | ------
|                      |  | BUSINESS LOAN AGREEMENT |  |       
|Loan No: 41/567249/Cc |  | (Continued)             |  | Page 6

Severability. If a court of competent jurisdiction finds any provision of this Agreement to
be illegal, invalid, or unenforceable as to any circumstance, that finding shall not make the offending provision illegal, invalid, or unenforceable as to any other circumstance. If feasible, the offending provision shall be considered modified so
that it becomes legal, valid and enforceable. If the offending provision cannot be so modified, it shall be considered deleted from this Agreement. Unless otherwise required by law, the illegality, invalidity, or unenforceability of any provision of
this Agreement shall not affect the legality, validity or enforceability of any other provision of this Agreement.

Subsidiaries and
Affiliates of Borrower. To the extent the context of any provisions of this Agreement makes it appropriate, including without limitation any representation, warranty or covenant, the word Borrower as used in this Agreement shall
include all of Borrowers subsidiaries and affiliates. Notwithstanding the foregoing however, under no circumstances shall this Agreement be construed to require Lender to make any Loan or other financial accommodation to any of Borrowers
subsidiaries or affiliates.

Successors and Assigns. All covenants and agreements by or on behalf of Borrower contained in this
Agreement or any Related Documents shall bind Borrowers successors and assigns and shall inure to the benefit of Lender and its successors and assigns. Borrower shall not, however, have the right to assign Borrowers rights under this
Agreement or any interest therein, without the prior written consent of Lender.

Survival of Representations and Warranties. Borrower
understands and agrees that in extending Loan Advances. Lender is relying on all representations, warranties, and covenants made by Borrower in this Agreement or in any certificate or other instrument delivered by Borrower to Lender under this
Agreement or the Related Documents. Borrower further agrees that regardless of any investigation made by Lender, all such representations, warranties and covenants will survive the extension of Loan Advances and delivery to Lender of the Related
Documents, shall be continuing in nature, shall be deemed made and redated by Borrower at the time each Loan Advance is made, and shall remain in full force and effect until such time as Borrowers indebtedness shall be paid in full, or until
this Agreement shall be terminated in the manner provided above, whichever is the last to occur.

Time is of the Essence. Time is of
the essence in the performance of this Agreement.

DEFINITIONS. The following capitalized words and terms shall have the following meanings when used
in this Agreement. Unless specifically stated to the contrary, all references to dollar amounts shall mean amounts in lawful money of the United States of America. Words and terms used in the singular shall include the plural, and the plural shall
include the singular, as the context may require. Words and terms not otherwise defined in this Agreement shall have the meanings attributed to such terms in the Uniform Commercial Code. Accounting words and terms not otherwise defined in this
Agreement shall have the meanings assigned to them in accordance with generally accepted accounting principles as in effect on the date of this Agreement:

Advance. The word Advance means a disbursement of Loan funds made, or to be made, to Borrower or on Borrowers behalf on a line of credit or multiple advance basis under the terms and
conditions of this Agreement.

Agreement. The word Agreement means this Business Loan Agreement, as this Business Loan
Agreement may be amended or modified from time to time, together with all exhibits and schedules attached to this Business Loan Agreement from time to time.

Borrower. The word Borrower means Opnet Technologies, Inc. and includes all co-signers and co-makers signing the Note.

Collateral. The word Collateral means all property and assets granted as collateral security for a Loan, whether real or personal property, whether granted directly or indirectly, whether granted
now or in the future, and whether granted in the form of a security interest, mortgage, collateral mortgage, deed of trust, assignment, pledge, crop pledge, chattel mortgage, collateral chattel mortgage, chattel trust, factors lien, equipment
trust, conditional sale, trust receipt, lien, charge, lien or title retention contract, lease or consignment intended as a security device, or any other security or lien interest whatsoever, whether created by law, contract, or otherwise.

Environmental Laws. The words Environmental Laws mean any and all state, federal and local statutes, regulations and
ordinances relating to the protection of human health or the environment, including without limitation the Comprehensive Environmental Response, Compensation, and Liability Act of 1980, as amended, 42 U.S.C. Section 9601, et seq.
(CERCLA), the Superfund Amendments and Reauthorization Act of 1986, Pub. L. No. 99-499 (SARA), the Hazardous Materials Transportation Act, 49 U.S.C. Section 1801, et seq., the Resource Conservation and Recovery Act,
42 U.S.C. Section 6901, et seq., or other applicable state or federal laws, rules, or regulations adopted pursuant thereto.

Event
of Default. The words Event of Default mean any of the events of default set forth in this Agreement in the default section of this Agreement.

GAAP. The word GAAP means generally accepted accounting principles.

Grantor. The
word Grantor means each and all of the persons or entities granting a Security Interest in any Collateral for the Loan, and their personal representatives, successors and assigns.

Guarantor. The word Guarantor means any guarantor, surety, or accommodation party of any or all of the Loan.

Guaranty. The word Guaranty means the guaranty from Guarantor to Lender, including without limitation a guaranty of all or part of the
Note.

Hazardous Substances. The words Hazardous Substances mean materials that, because of their quantity, concentration
or physical, chemical or infectious characteristics, may cause or pose a present or potential hazard to human health or the environment when improperly used, treated, stored, disposed of, generated, manufactured, transported or otherwise handled.
The words Hazardous Substances are used in their very broadest sense and include without limitation any and all hazardous or toxic substances, materials or waste as defined by or listed under the Environmental Laws. The term
Hazardous Substances also includes, without limitation, petroleum and petroleum by-products or any fraction thereof and asbestos.

Indebtedness. The word Indebtedness means the indebtedness evidenced by the Note or Related Documents, including all principal and interest together with all other indebtedness and costs and expenses for which Borrower or
Grantor or any other borrower, guarantor, pledger, obligor or accommodation party is responsible under this Agreement or under any of the Related Documents, including any obligations arising under any interest rate, credit, commodity or equity swap,
cap, floor, collar, forward foreign exchange transaction, currency swap, cross currency rate swap, currency option, securities puts, calls, collars, options or forwards or any combination of, or option with respect to, these or similar transactions
now or hereafter entered into between any such party and Lender or any affiliate of Lender.

Lender. The word Lender
means Bank of America, N.A., its successors and assigns.

Loan. The word Loan means any and all loans and financial
accommodations from Lender to Borrower whether now or hereafter existing, and however evidenced, including without limitation those loans and financial accommodations described herein or described on any exhibit or schedule attached to this
Agreement from time to time.



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|--------------------- |  | ----------------------- |  | ------
|                      |  | BUSINESS LOAN AGREEMENT |  |       
|Loan No: 41/567249/Cc |  | (Continued)             |  | Page 7

Note. The word Note means the Note executed by Opnet Technologies, Inc. In the
principal amount of $2,600,000.00 dated June 20, 2005, together with all modifications of and renewals, replacements, and substitutions for the note or credit agreement.

Permitted Liens. The words Permitted Liens mean (1) liens and security interests securing indebtedness owed by Borrower to Lender; (2) liens for taxes, assessments, or similar charges either not yet due or being contested in
good faith; (3) liens of materialmen, mechanics, warehousemen, or carriers, or other like liens arising in the ordinary course of business and securing obligations which are not yet delinquent: (4) purchase money liens or purchase money
security interests upon or in any property acquired or held by Borrower in the ordinary course of business to secure indebtedness outstanding on the date of this Agreement or permitted to be incurred under the paragraph of this Agreement titled
Indebtedness and Liens; (5) liens and security interests which, as of the date of this Agreement, have been disclosed to and approved by the Lender in writing; and (6) those liens and security interests which in the aggregate
constitute an immaterial and insignificant monetary amount with respect to the net value of Borrowers assets.

Related
Documents. The words Related Documents mean all promissory notes, credit agreements, loan agreements, environmental agreements, guaranties, security agreements, mortgages, deeds of trust, security deeds, collateral mortgages, and all
other instruments, agreements and documents, whether now or hereafter existing, executed in connection with the Loan.

Security
Agreement. The words Security Agreement mean and include without limitation any agreements, promises, covenants, arrangements, understandings or other agreements, whether created by law, contract, or otherwise, evidencing, governing,
representing, or creating a Security Interest.

Security Interest. The words Security Interest mean, without limitation,
any and all types of collateral security, present and future, whether in the form of a lien, charge, encumbrance, mortgage, deed of trust, security deed, assignment, pledge, crop pledge, chattel mortgage, collateral chattel mortgage, chattel trust,
factors lien, equipment trust, conditional sale, trust receipt, lien or title retention contract, lease or consignment intended as a security device, or any other security or lien interest whatsoever whether created by law, contract, or
otherwise.

BORROWER ACKNOWLEDGES HAVING READ ALL THE PROVISIONS OF THIS BUSINESS LOAN AGREEMENT AND BORROWER AGREES TO ITS TERMS. THIS BUSINESS LOAN
AGREEMENT IS DATED JUNE 20, 2005.

THIS AGREEMENT IS GIVEN UNDER SEAL AND IT IS INTENDED THAT THIS AGREEMENT IS AND SHALL CONSTITUTE AND HAVE THE
EFFECT OF A SEALED INSTRUMENT ACCORDING TO LAW.

BORROWER:



|                         |  |                                                |  |       
|------------------------ |  | ---------------------------------------------- |  | ------
|OPNET TECHNOLOGIES, INC. |  |                                               
|                         |  |                                               
|By:                      |  | /s/ Marc A. Cohen                              |  | (Seal)
|                         |  | Marc A. Cohen. CEO of Opnet Technologies. Inc.
|                         | 
|LENDER:                  |  |                                               
|                         | 
|BANK OF AMERICA. N.A.    |  |                                               
|                         |  |                                               
|By:                      |  |                                                |  | (Seal)
|                         |  | Authorized Signer                              |  |