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                               BUSINESS LOAN AGREEMENT
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BORROWER: F5 LABS, INC.            LENDER:   SILICON VALLEY BANK, A CALIFORNIA 
          1218 THIRD AVENUE, SUITE 508       CHARTERED BANK
          SEATTLE, WA 98101                  WASHINGTON LOAN PRODUCTION OFFICE
                                             915 118TH AVENUE, S.E., SUITE 250
                                             BELLEVUE, WA 98005
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THIS BUSINESS LOAN AGREEMENT BETWEEN F5 LABS, INC. ("BORROWER") AND SILICON
VALLEY BANK, A CALIFORNIA CHARTERED BANK ("LENDER") IS MADE AND EXECUTED 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 AND OTHER
FINANCIAL ACCOMMODATIONS, INCLUDING THOSE WHICH MAY BE DESCRIBED ON ANY EXHIBIT
OR SCHEDULE ATTACHED TO THIS AGREEMENT. ALL SUCH LOANS AND FINANCIAL
ACCOMMODATIONS, TOGETHER WITH ALL FUTURE LOANS AND FINANCIAL ACCOMMODATIONS FROM
LENDER TO BORROWER, ARE REFERRED TO IN THIS AGREEMENT INDIVIDUALLY AS THE "LOAN"
AND COLLECTIVELY AS THE "LOANS." 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 SHALL REMAIN SUBJECT TO THE FOLLOWING TERMS AND CONDITIONS OF THIS
AGREEMENT.

TERM. This Agreement shall be effective as of OCTOBER 23, 1997, and shall
continue thereafter until all Indebtedness of Borrower to Lender has been
performed in full and the parties terminate this Agreement in writing.

DEFINITIONS. The following words shall have the following meanings when used in
this Agreement. Terms not otherwise defined in this Agreement shall have the
meanings attributed to such terms in the Uniform Commercial Code. All references
to dollar amounts shall mean amounts in lawful money of the United States of
America.

     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 F5 LABS, INC.. The word "Borrower" also
     includes, as applicable, all subsidiaries and affiliates of Borrower as
     provided below in the paragraph titled "Subsidiaries and Affiliates."

     CERCLA. The word "CERCLA" means the Comprehensive Environmental Response,
     Compensation, and Liability Act of 1980, as amended.

     CASH FLOW. The words "Cash Flow" mean net income after taxes, and exclusive
     of extraordinary gains and income, plus depreciation and amortization.

     COLLATERAL. The word "Collateral" means and includes without limitation 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, deed of trust, assignment, pledge, 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.

     DEBT. The word "Debt" means all of Borrower's liabilities excluding
     Subordinated Debt.

     ERISA. The word "ERISA" means the Employee Retirement Income Security Act
     of 1974, as amended.

     EVENT OF DEFAULT. The words "Event of Default" mean and include without
     limitation any of the Events of Default set forth below in the section
     titled "EVENTS OF DEFAULT."

     GRANTOR. The word "Grantor" means and includes without limitation each and
     all of the persons or entities granting a Security Interest in any
     Collateral for the Indebtedness, including without limitation all Borrowers
     granting such a Security Interest.

     GUARANTOR. The word "Guarantor" means and includes without limitation each
     and all of the guarantors, sureties, and accommodation parties in 
     connection with any Indebtedness.

     INDEBTEDNESS. The word "Indebtedness" means and includes indebtedness
     evidenced by any and all notes, letters of credit or credit agreement,
     including all principal and interest, together with all other indebtedness
     and costs and expenses, including, without limitation, attorneys' fees, for
     which Grantor is responsible under this Agreement or under any of the
     Related Documents.

     LENDER. The word "Lender" means Silicon Valley Bank, a California chartered
     bank, its successors and assigns.

     LIQUID ASSETS. The words "Liquid Assets" mean Borrower's cash on hand plus
     Borrower's readily marketable securities.

     LOAN. The word "Loan" or "Loans" means and includes without limitation any
     and all commercial 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.

     NOTE. The word "Note" means and includes without limitation Borrower's
     promissory note or notes, if any, evidencing Borrower's Loan obligations in
     favor of Lender, as well as any substitute, replacement or refinancing note
     or notes therefor.

     PERMITTED LIENS. The words "Permitted Liens" mean: (a) liens and security
     interests securing Indebtedness owed by Borrower to Lender; (b) liens for
     taxes, assessments, or similar charges either not yet due or being
     contested in good faith; (c) 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; (d) 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"; (e) liens and security interests which, as of the date of this
     Agreement, have been disclosed to and approved by the Lender in writing;
     and (f) 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 and include without
     limitation all promissory notes, credit agreements, loan agreements,
     environmental agreements, guaranties, security agreements, mortgages, deeds
     of trust, and all other instruments, agreements and documents, whether now
     or hereafter existing, executed in connection with the Indebtedness.

     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 and include without
     limitation any type of collateral security, whether in the form of a lien,
     charge, mortgage, deed of trust, assignment, pledge, chattel mortgage,
     chattel trust, factor's lien, equipment trust, conditional sale, trust
     receipt,


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                                     (CONTINUED)

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     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.

     SARA. The word "SARA" means the Superfund Amendments and Reauthorization
     Act of 1986 as now or hereafter amended.

     SUBORDINATED DEBT. The words "Subordinated Debt" mean indebtedness and
     liabilities of Borrower which have been subordinated by written agreement
     to indebtedness owed by Borrower to Lender in form and substance acceptable
     to Lender.

     TANGIBLE NET WORTH. The words "Tangible Net Worth" mean Borrower's total
     assets excluding all intangible assets (i.e., goodwill, trademarks,
     patents, copyrights, organizational expenses, and similar intangible items,
     but including leaseholds and leasehold improvements) less total Debt.

     WORKING CAPITAL. The words "Working Capital" mean Borrower's current
     assets, excluding prepaid expenses, less Borrower's current liabilities.

CONDITIONS PRECEDENT TO EACH ADVANCE. Lender's obligation to make the initial 
Loan Advance and each subsequent Loan 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 in form satisfactory to 
      Lender the following documents for the Loan: (a) the Note, (b) Security 
      Agreements granting to Lender security interests in the Collateral, (c) 
      Financing Statements perfecting Lender's Security Interests; (d) 
      evidence of insurance as required below; and (e) any other documents 
      required under this Agreement or by Lender or its 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, and such other authorizations and other 
      documents and instruments as Lender or its counsel, in their sole 
      discretion, 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.

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 which is duly organized, validly 
      existing, and in good standing under the laws of the State of 
      Washington and is validly existing and in good standing in all states 
      in which Borrower is doing business. Borrower has the full power and 
      authority to own its properties and to transact the businesses in which 
      it is presently engaged or presently proposes to engage. Borrower also 
      is duly qualified as a foreign corporation and is in good standing in 
      all states in which the failure to so qualify would have a material 
      adverse effect on its businesses or financial condition.

      AUTHORIZATION. The execution, delivery, and performance of this 
      Agreement and all Related Documents by Borrower, to the extent to be 
      executed, delivered or performed by Borrower, have been duly 
      authorized by all necessary action by Borrower; do not require the 
      consent or approval of any other person, regulatory authority or 
      governmental body; and do not conflict with, result in a violation of, 
      or constitute a default under (a) any provision of its articles of 
      incorporation or organization, or bylaws, or any agreement or other 
      instrument binding upon Borrower or (b) any law, governmental 
      regulation, court decree, or order applicable to Borrower.

      FINANCIAL INFORMATION. Each financial statement of Borrower 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 required hereunder to be given by Borrower 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. The terms "hazardous waste," "hazardous 
      substance," "disposal," "release," and "threatened release," as used in 
      this Agreement, shall have the same meanings as set forth in the 
      "CERCLA," "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 to any of the foregoing. 
      Except as disclosed to and acknowledged by Lender in writing, Borrower 
      represents and warrants that: (a) During the period of Borrower's 
      ownership of the properties, there has been no use, generation, 
      manufacture, storage, treatment, disposal, release or threatened 
      release of any hazardous waste or substance by any person on, under, 
      about or from any of the properties. (b) Borrower has no knowledge of, 
      or reason to believe that there has been (i) any use, generation, 
      manufacture, storage, treatment, disposal, release, or threatened 
      release of any hazardous waste or substance on, under, about or from 
      the properties by any prior owners or occupants of any of the 
      properties, or (ii) any actual or threatened litigation or claims of 
      any kind by any person relating to such matters. (c) Neither Borrower 
      nor any tenant, contractor, agent or other authorized user of any of 
      the properties shall use, generate, manufacture, store, treat, dispose 
      of, or release any hazardous waste or substance on, under, about or 
      from any of the properties; and any such activity shall be conducted in 
      compliance with all applicable federal, state, and local laws, 
      regulations, and ordinances, including without limitation those laws, 
      regulations and ordinances described above. Borrower authorizes Lender 
      and its agents to enter upon the properties to make such inspections 
      and tests as Lender may deem appropriate to determine compliance of the 
      properties 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 properties for hazardous waste and 
      hazardous substances. Borrower hereby (a) 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 (b) 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 occurring prior to Borrower's ownership or interest in the 
      properties, whether or not the same was or should have been known to 
      Borrower. The provisions of this section of the Agreement, including 
      the obligation to indemnify, shall survive the payment of the 
      Indebtedness and the termination or expiration of this Agreement and 
      shall not be affected by Lender's acquisition of any interest in any of 
      the properties, whether by foreclosure or otherwise.

      LITIGATION AND CLAIMS. No litigation, claim, investigation, 
      administrative proceeding or similar action (including those for unpaid 
      taxes) against

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      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 tax returns and reports 
      of Borrower 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 
      directly or indirectly securing repayment of Borrower's Loan and Note 
      and all of the Related Documents are binding upon Borrower as well as 
      upon Borrower's successors, representatives and assigns, and are 
      legally enforceable in accordance with their respective terms.

      COMMERCIAL PURPOSES. Borrower intends to use the Loan proceeds solely 
      for business or commercial related purposes.

      EMPLOYEE BENEFIT PLANS. Each employee benefit plan as to which Borrower 
      may have any liability complies in all material respects with all 
      applicable requirements of law and regulations, and (i) no Reportable 
      Event nor Prohibited Transaction (as defined in ERISA) has occurred 
      with respect to any such plan, (ii) Borrower has not withdrawn from any 
      such plan or initiated steps to do so, (iii) no steps have been taken 
      to terminate any such plan, and (iv) there are no unfunded liabilities 
      other than those previously disclosed to Lender in writing.

      INVESTMENT COMPANY ACT. Borrower is not an "investment company" or a 
      company "controlled" by an "investment company", within the meaning of 
      the Investment Company Act of 1940, as amended.

      PUBLIC UTILITY HOLDING COMPANY ACT. Borrower is not a "holding 
      company", or a "subsidiary company" of a "holding company", or an 
      "affiliate" of a "holding company" or of a "subsidiary company" of a 
      "holding company", within the meaning of the Public Utility Holding 
      Company Act of 1935, as amended.

      REGULATIONS G, T AND U. Borrower is not engaged principally, or as one 
      of its important activities, in the business of extending credit for 
      the purpose of purchasing or carrying margin stock (within the meaning 
      of Regulations G, T and U of the Board of Governors of the Federal 
      Reserve System).

      LOCATION OF BORROWER'S OFFICES AND RECORDS. Borrower's place of 
      business, or Borrower's Chief executive office, if Borrower has more 
      than one place of business, is located at 1218 Third Avenue, Suite 508, 
      Seattle, WA 98101. Unless Borrower has designated otherwise in writing 
      this location is also the office or offices where Borrower keeps its 
      records concerning the Collateral.

      INFORMATION. All information heretofore or contemporaneously herewith 
      furnished by Borrower to Lender for the purposes of or in connection 
      with this Agreement or any transaction contemplated hereby is, and all 
      information hereafter furnished by or on behalf of Borrower to Lender 
      will be, true and accurate in every material respect on the date as of 
      which such information is dated or certified; and none of such 
      information is or will be incomplete by omitting to state any material 
      fact necessary to make such information not misleading.

      CLAIMS AND DEFENSES. There are no defenses or counterclaims, offsets or 
      other adverse claims, demands or actions of any kind, personal or 
      otherwise, that Borrower, Grantor, or any Guarantor could assert with 
      respect to the Note, Loan, Indebtedness, this Agreement, or the Related 
      Documents.

      SURVIVAL OF REPRESENTATIONS AND WARRANTIES. Borrower understands and 
      agrees that Lender, without independent investigation, is relying upon 
      the above representations and warranties in extending Loan Advances to 
      Borrower. Borrower further agrees that the foregoing representations 
      and warranties shall be continuing in nature 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.

AFFIRMATIVE COVENANTS. Borrower covenants and agrees with Lender that, while
this Agreement is in effect, Borrower will:

      LITIGATION. Promptly inform Lender in writing of (a) all material 
      adverse changes in Borrower's financial condition, and (b) 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 
      generally accepted accounting principles, 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, as soon as available, but in 
      no event later than one hundred twenty (120) days after the end of 
      12/31/97, Borrower's balance sheet and income statement for the year 
      ended, audited by a certified public accountant satisfactory to Lender, 
      and, as soon as available, but in no event later than thirty (30) days 
      after the end of each month, Borrower's balance sheet and profit and 
      loss statement for the period ended, prepared and certified as correct 
      to the best knowledge and belief by Borrower's chief financial officer 
      or other officer or person acceptable to Lender. All financial reports 
      required to be provided under this Agreement shall be prepared in 
      accordance with generally accepted accounting principles, applied on a 
      consistent basis, and certified by Borrower as being true and correct.

      ADDITIONAL INFORMATION. Furnish such additional information and 
      statements, lists of assets and liabilities, agings of receivables and 
      payables, inventory schedules, budgets, forecasts, tax returns, and 
      other reports with respect to Borrower's financial condition and 
      business operations as Lender may request from time to time.

      FINANCIAL COVENANTS AND RATIOS. Comply with the following covenants and 
      ratios: Except as provided above, all computations made to determine 
      compliance with the requirements contained in this paragraph shall be 
      made in accordance with generally accepted accounting principles, 
      applied on a consistent basis, and certified by Borrower as being true 
      and correct. Refer to page 5.

      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 reasonably 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 ten (10) 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 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: (a) 
      the name of the insurer; (b) the risks insured; (c) the amount of the 
      policy; (d) the properties insured; (e) the then current property 
      values on the basis of which insurance has been obtained, and the 
      manner of determining those values; and (f) 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

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      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.

      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. Provided however, 
      Borrower will not be required to pay and discharge any such assessment, 
      tax, charge, levy, lien or claim so long as (a) the legality of the 
      same shall be contested in good faith by appropriate proceedings, and 
      (b) Borrower shall have established on its books adequate reserves with 
      respect to such contested assessment, tax, charge, levy, lien, or claim 
      in accordance with generally accepted accounting practices. Borrower, 
      upon demand of Lender, will furnish to Lender evidence of payment of 
      the assessments, taxes, charges, levies, liens and claims and will 
      authorize the appropriate governmental official to deliver to Lender at 
      any time a written statement of any assessments, taxes, charges, 
      levies, liens and claims against Borrower's properties, income, or 
      profits.

      PERFORMANCE. Perform and comply with all terms, conditions, and 
      provisions set forth in this Agreement and in the Related Documents in 
      a timely manner, and promptly notify Lender if Borrower learns of the 
      occurrence of any event which constitutes an Event of Default under 
      this Agreement or under any of the Related Documents.

      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 and in compliance with all 
      applicable federal, state and municipal laws, ordinances, rules and 
      regulations respecting its properties, charters, businesses and 
      operations, including without limitation, compliance with the Americans 
      With Disabilities Act and with all minimum funding standards and other 
      requirements of ERISA and other laws applicable to Borrower's employee 
      benefit plans.

      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 defined as toxic or a hazardous substance under any 
      applicable federal, state, or local law, rule, regulation, order or 
      directive, or any waste or by-product thereof, at or affecting any 
      property or any facility owned, leased or used by Borrower.

      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 CERTIFICATE. Unless waived in writing by Lender, provide 
      Lender MONTHLY WITHIN THIRTY (30) DAYS 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 all environmental protection federal, state and local 
      laws, statutes, regulations and ordinances; not cause or permit to 
      exist, as a result of an intentional or unintentional action or 
      omission on its 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, 
      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.

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. (a) Except for trade debt incurred in the 
      normal course of business and indebtedness to Lender contemplated by 
      this Agreement, create, incur or assume indebtedness for borrowed 
      money, including capital leases, (b) except as allowed as a Permitted 
      Lien, sell, transfer, mortgage, assign, pledge, lease, grant a security 
      interest in, or encumber any of Borrower's assets, or (c) sell with 
      recourse any of Borrower's accounts, except to Lender.

      CONTINUITY OF OPERATIONS. (a) Engage in any business activities 
      substantially different than those in which Borrower is presently 
      engaged, (b) cease operations, liquidate, merge, transfer, acquire or 
      consolidate with any other entity, change ownership, change its name, 
      dissolve or transfer or sell Collateral out of the ordinary course of 
      business, (c) 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 stock of Borrower, 
      or (d) purchase or retire any of Borrower's outstanding shares or alter 
      or amend Borrower's capital structure.

      LOANS, ACQUISITIONS AND GUARANTIES. (a) Loan, invest in or advance 
      money or assets, (b) purchase, create or acquire any interest in any 
      other enterprise or entity, or (c) incur any obligation as surety or 
      guarantor other than in the ordinary course of business.

      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 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.

      FINANCIAL COVENANTS. Borrower shall maintain, on a monthly basis, a 
      positive Tangible Net Worth. 

<PAGE>

10-23-1997                    BUSINESS LOAN AGREEMENT                 PAGE 5
                                     (CONTINUED)

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BORROWING FORMULA. Funds shall be advanced under the line of credit according 
to a Borrowing Base Formula, determined by Lender on a monthly basis, defined 
as follows: the lesser of (i) $250,000.00 or (ii) sixty percent (60%) of 
Eligible Accounts Receivable. Eligible Accounts Receivable shall be defined 
as those accounts that arise in the oridinary course of Borrower's business, 
including those accounts outstanding less than 60 days from the date of 
invoice, but shall exclude foreign, government, contra and intercompany 
accounts, and exclude accounts wherein 50% or more of the account is 
outstanding more than 60 days from the date of invoice. Any account which 
alone exceeds 25% of total accounts will be ineligible to the extent said 
account exceeds 25% of total accounts. Lender shall also deem ineligible any 
credit balances which are aged 30 days, and accounts generated by the sale of 
demonstration or promotional equipment. The standards of eligibility shall be 
fixed from time to time by Lender, in Lender's reasonable judgment upon 
notification to Borrower. Lender reserves the right to exclude any accounts 
the collection of which Lender reasonably determines to be doubtful.

ACCOUNTS RECEIVABLE. Provide Lender of the end of each week, with a borrowing
base certificate and aged list of accounts receivable.

DEFAULT RATE. Following an Event of Default, including failure to pay upon final
maturity, Lender, at its option, may do one or both of the following: (a)
increase the variable interest rate on the Note to five percentage points
(5.00%) over the otherwise effective interest rate payable thereunder, and (b)
add any unpaid accrued interest to principal and such sum will bear interest
therefrom until paid at the interest rate provided in the Note.

LOAN ADVANCES. Lender, in its discretion, will make loans to Borrower, in
amounts determined by Lender, up to the amounts as defined and permitted in this
Agreement and the Related Documents, including but not limited to, any
Promissory Notes, executed by Borrower (the "Credit Limit"). Borrower is
responsible for monitoring the total amount of Loans and Indebtedness
outstanding from time to time, and Borrower shall not permit the same, at any
time to exceed the Credit Limit. If at any time the total outstanding Loans and
Indebtedness exceeds the Credit Limit, Borrower shall immediately pay the amount
in excess to Lender, without notice or demand.

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

      DEFAULT ON INDEBTEDNESS. Failure of Borrower to make any payment when 
      due on the Loans.

      OTHER DEFAULTS. Failure of Borrower or any Grantor to comply with or to 
      perform when due any other term, obligation, covenant or condition 
      contained in this Agreement or in any of the Related Documents, or 
      failure of Borrower to comply with or to perform any other term, 
      obligation, covenant or condition contained in any other agreement 
      between Lender and Borrower.

      DEFAULT IN FAVOR OF THIRD PARTIES. Should Borrower or any Grantor 
      default 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 
      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 or on behalf of Borrower or any Grantor under 
      this Agreement or the Related Documents is false or misleading in any 
      material respect at the time made or furnished, or becomes false or 
      misleading at any time thereafter.

      DEFECTIVE COLLATERALIZATION. This Agreement or any of the Related 
      Documents ceases to be in full force and effect (including failure of 
      any Security Agreement to create a valid and perfected Security 
      Interest) at any time and for any reason.

      INSOLVENCY. The dissolution or termination of Borrower's existence as a 
      going business, the insolvency of Borrower, the appointment of a 
      receiver for any part of Borrower's property, any assignment for the 
      benefit of creditors, any type of creditor workout, or the commencement 
      of any proceeding under any bankruptcy or insolvency laws by or against 
      Borrower.

      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, any 
      creditor of any Grantor against any collateral securing the 
      Indebtedness, or by any governmental agency. This includes a 
      garnishment, attachment, or levy on or of any of Borrower's deposit 
      accounts with Lender.

      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 Indebtedness is impaired.

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
Loan Advances or disbursements), and, at Lender's option, all Indebtedness
immediately will become 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.

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.

      APPLICABLE LAW. THIS AGREEMENT HAS BEEN DELIVERED TO LENDER AND 
      ACCEPTED BY LENDER IN THE STATE OF CALIFORNIA. IF THERE IS A LAWSUIT, 
      BORROWER AGREES UPON LENDER'S REQUEST TO SUBMIT TO THE JURISDICTION OF 
      THE COURTS OF KING COUNTY, THE STATE OF WASHINGTON. LENDER AND BORROWER 
      HEREBY WAIVE THE RIGHT TO ANY JURY TRIAL IN ANY ACTION, PROCEEDING, OR 
      COUNTERCLAIM BROUGHT BY EITHER LENDER OR BORROWER AGAINST THE OTHER. 
      (INITIAL HERE /s/ BD) THIS AGREEMENT SHALL BE GOVERNED BY AND CONSTRUED 
      IN ACCORDANCE WITH THE LAWS OF THE STATE OF WASHINGTON.

      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.

      MULTIPLE PARTIES; CORPORATE AUTHORITY. All obligations of Borrower 
      under this Agreement shall be joint and several, and all references to 
      Borrower shall mean each and every Borrower. This means that each of 
      the persons signing below is responsible for ALL obligations in this 
      Agreement.

      CONSENT TO LOAN PARTICIPATION. Borrower agrees and consents to Lender's 
      sale or transfer, whether now or later, of one or more participation 

<PAGE>

10-23-1997                    BUSINESS LOAN AGREEMENT                 PAGE 6
                                     (CONTINUED)

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      interests in the Loans 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 it 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 Loans 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 Loans irrespective of the failure or 
      insolvency of any holder of any interest in the Loans. 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.

      BORROWER INFORMATION. Borrower consents to the release of information 
      on or about Borrower by Lender in accordance with any court order, law 
      or regulation and in response to credit inquiries concerning Borrower.

      NON-LIABILITY OF LENDER. The relationship between Borrower and Lender 
      is a debtor and creditor relationship and not fiduciary in nature, nor 
      is the relationship to be construed as creating any partnership or 
      joint venture between Lender and Borrower. Borrower is exercising its 
      own judgment with respect to Borrower's business. All information 
      supplied to Lender is for Lender's protection only and no other party is
      entitled to rely on such information. There is no duty for Lender to 
      review, inspect, supervise, or inform Borrower of any matter with 
      respect to Borrower's business. Lender and Borrower intend that Lender 
      may reasonably rely on all information supplied by Borrower to Lender, 
      together with all representations and warranties given by Borrower to 
      Lender, without investigation or confirmation by Lender and that any 
      investigation or failure to investigate will not diminish Lender's 
      right to so rely.

      NOTICE OF LENDER'S BREACH. Borrower must notify Lender in writing of 
      any breach of this Agreement or the Related Documents by Lender and any 
      other claim, cause of action or offset against Lender within thirty 
      (30) days after the occurrence of such breach or after the accrual of 
      such claim, cause of action or offset. Borrower waives any claim, cause 
      of action or offset for which notice is not given in accordance with 
      this paragraph. Lender is entitled to rely on any failure to give such 
      notice.

      BORROWER INDEMNIFICATION. Borrower shall indemnify and hold Lender 
      harmless from and against all claims, costs, expenses, losses, damages, 
      and liabilities of any kind, including but not limited to attorneys' 
      fees and expenses, arising out of any matter relating directly or 
      indirectly to the Indebtedness, whether resulting from internal 
      disputes of the Borrower, disputes between Borrower and any Guarantor, 
      or whether involving any third parties, or out of any other matter 
      whatsoever related to this Agreement or the Related Documents, but 
      excluding any claim or liability which arises as a direct result of 
      Lender's gross negligence or willful misconduct. This indemnity shall 
      survive full repayment and satisfaction of the Indebtedness and 
      termination of this Agreement.

      COUNTERPARTS. This Agreement may be executed in multiple counterparts, 
      each of which, when so executed, shall be deemed an original, but all 
      such counterparts, taken together, shall constitute one and the same 
      Agreement.

      COSTS AND EXPENSES. Borrower agrees to pay upon demand all of Lender's 
      expenses, including without limitation attorneys' fees, incurred in 
      connection with the preparation, execution, enforcement, modification 
      and collection of this Agreement or in connection with the Loans made 
      pursuant to this Agreement. Lender may pay someone else to help collect 
      the Loans and to enforce this Agreement, and Borrower will pay that 
      amount. This includes, subject to any limits under applicable law, 
      Lender's attorneys' fees and Lender's legal expenses, whether or not 
      there is a lawsuit, including attorneys' fees for bankruptcy 
      proceedings (including efforts to modify or vacate any automatic stay 
      or injunction), appeals, and any anticipated post-judgment collection 
      services. Borrower also will pay any court costs, in addition to all 
      other sums provided by law.

      NOTICES. All notices required to be given under this Agreement shall be 
      given in writing, may be sent by telefacsimile (unless otherwise 
      required by law), and shall be effective when actually delivered or 
      when deposited with a nationally recognized overnight courier or 
      deposited in the United States mail, first class, postage prepaid, 
      addressed to the party to whom the notice is to be given at the address 
      shown above. 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. To the extent permitted by applicable law, if there is more 
      than one Borrower, notice to any Borrower will constitute notice to all 
      Borrowers. For notice purposes, Borrower will keep Lender informed at 
      all times of Borrower's current address(es).

      SEVERABILITY. If a court of competent jurisdiction finds any provision 
      of this Agreement to be invalid or unenforceable as to any person or 
      circumstance, such finding shall not render that provision invalid or 
      unenforceable as to any other persons or circumstances. If feasible, 
      any such offending provision shall be deemed to be modified to be 
      within the limits of enforceability or validity; however, if the 
      offending provision cannot be so modified, it shall be stricken and all 
      other provisions of this Agreement in all other respects shall remain 
      valid and enforceable.

      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 herein shall include all subsidiaries and affiliates 
      of Borrower. 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 subsidiary or 
      affiliate of Borrower.

      SUCCESSORS AND ASSIGNS. All covenants and agreements contained by or on 
      behalf of Borrower shall bind its successors and assigns and shall 
      inure to the benefit of Lender, its successors and assigns. Borrower 
      shall not, however, have the right to assign its rights under this 
      Agreement or any interest therein, without the prior written consent of 
      Lender.

      SURVIVAL. All warranties, representations, and covenants made by 
      Borrower in this Agreement or in any certificate or other instrument 
      delivered by Borrower to Lender under this Agreement shall be 
      considered to have been relied upon by Lender and will survive the 
      making of the Loan and delivery to Lender of the Related Documents, 
      regardless of any investigation made by Lender or on Lender's behalf.

      WAIVER. 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 obligations of 
      Borrower or of any Grantor 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 in subsequent instances where such consent is required, and in 
      all cases such consent may be granted or withheld in the sole 
      discretion of Lender.

<PAGE>

10-23-1997                    BUSINESS LOAN AGREEMENT                 PAGE 7
                                     (CONTINUED)

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BORROWER ACKNOWLEDGES HAVING READ ALL THE PROVISIONS OF THIS BUSINESS LOAN
AGREEMENT, AND BORROWER AGREES TO ITS TERMS. THIS AGREEMENT IS DATED AS OF
OCTOBER 23,1997.

BORROWER:

F5 LABS, INC.

BY: /s/ Brian Dixon
   ------------------------
     NAME: Brian Dixon   TITLE: VP Finance
          --------------        --------------


LENDER:

SILICON VALLEY BANK, A CALIFORNIA CHARTERED BANK

BY:
     -----------------------
     AUTHORIZED OFFICER

--------------------------------------------------------------------------------
--------------------------------------------------------------------------------
<PAGE>

                       COMMERCIAL SECURITY AGREEMENT
-------------------------------------------------------------------------------
-------------------------------------------------------------------------------
BORROWER: F5 LABS, INC.            LENDER:   SILICON VALLEY BANK, A CALIFORNIA 
          1218 THIRD AVENUE, SUITE 508       CHARTERED BANK
          SEATTLE, WA 98101                  WASHINGTON LOAN PRODUCTION OFFICE
                                             915 118TH AVENUE, S.E., SUITE 25O
                                             BELLEVUE, WA 98005 
-------------------------------------------------------------------------------
-------------------------------------------------------------------------------

THIS COMMERCIAL SECURITY AGREEMENT IS ENTERED INTO BETWEEN F5 LABS, INC.
(REFERRED TO BELOW AS "GRANTOR"); AND SILICON VALLEY BANK, A CALIFORNIA
CHARTERED BANK (REFERRED TO BELOW AS "LENDER"). FOR VALUABLE CONSIDERATION,
GRANTOR GRANTS TO LENDER A SECURITY INTEREST IN THE COLLATERAL TO SECURE THE
INDEBTEDNESS AND AGREES THAT LENDER SHALL HAVE THE RIGHTS STATED IN THIS
AGREEMENT WITH RESPECT TO THE COLLATERAL, IN ADDITION TO ALL OTHER RIGHTS WHICH
LENDER MAY HAVE BY LAW.

DEFINITIONS. The following words shall have the following meanings when used in
this Agreement. Terms not otherwise defined in this Agreement shall have the
meanings attributed to such terms in the Uniform Commercial Code. All references
to dollar amounts shall mean amounts in lawful money of the United States of
America.

     AGREEMENT. The word "Agreement" means this Commercial Security Agreement,
     as this Commercial Security Agreement may be amended or modified from time
     to time, together with all exhibits and schedules attached to this
     Commercial Security Agreement from time to time.

     COLLATERAL. The word "Collateral" means the following described property of
     Grantor, whether now owned or hereafter acquired, whether now existing or
     hereafter arising, and wherever located:

          INVENTORY, CHATTEL PAPER, INVESTMENT PROPERTY, ACCOUNTS, EQUIPMENT,
          GENERAL INTANGIBLES, FIXTURES, CONTRACT RIGHTS, INSTRUMENTS,
          DOCUMENTS, AND DEPOSIT ACCOUNTS

     In addition, the word "Collateral" includes all the following, whether now
     owned or hereafter acquired, whether now existing or hereafter arising, and
     wherever located:

          (a) All attachments, accessions, accessories, tools, parts, supplies,
          increases, and additions to and all replacements of and substitutions
          for any property described above.

          (b) All products and produce of any of the property described in this
          Collateral section.

          (c) All accounts, general intangibles, instruments, rents, monies,
          payments, and all other rights, arising out of a sale, lease, or other
          disposition of any of the property described in this Collateral
          section.

          (d) All proceeds (including insurance proceeds) from the sale,
          destruction, loss, or other disposition of any of the property
          described in this Collateral section.

          (e) All records and data relating to any of the property described in
          this Collateral section, whether in the form of a writing, photograph,
          microfilm, microfiche, or electronic media, together with all of
          Grantors right, title, and interest in and to all computer software
          required to utilize, create, maintain, and process any such records or
          data on electronic media.

     EVENT OF DEFAULT. The words "Event of Default" mean and include without
     limitation any of the Events of Default set forth below in the section
     titled "Events of Default."

     GRANTOR. The word "Grantor" means F5 LABS, INC., its successors and assigns

     GUARANTOR. The word "Guarantor" means and includes without limitation each
     and all of the guarantors, sureties, and accommodation parties in
     connection with the Indebtedness.

     INDEBTEDNESS. The word "Indebtedness" means indebtedness evidenced by any
     and all notes, letters of credit or credit agreement, including all
     principal and interest, together with all other indebtedness and costs and
     expenses, including, without limitation, attorneys' fees, for which Grantor
     is responsible under this Agreement or under any of the Related Documents.

     LENDER. The word "Lender" means Silicon Valley Bank, a California chartered
     bank, its successors and assigns.

     NOTE. The word "Note" means the notes, letters of credit or credit
     agreements in any principal amount from Borrower to Lender, together with
     all renewals of, extensions of, modifications of, refinancings of,
     consolidations of and substitutions for the notes, letters of credit, or
     credit agreements.

     RELATED DOCUMENTS. The words "Related Documents" mean and include without
     limitation all promissory notes, credit agreements, loan agreements,
     environmental agreements, guaranties, security agreements, mortgages, deeds
     of trust, and all other instruments, agreements and documents, whether now
     or hereafter existing, executed in connection with the Indebtedness.

RIGHT OF SETOFF. Grantor hereby grants Lender a contractual possessory security
interest in and hereby assigns, conveys, delivers, pledges, and transfers all of
Grantor's right, title and interest in and to Grantor's accounts with Lender
(whether checking, savings, or some other account), including all accounts held
jointly with someone else and all accounts Grantor may open in the future,
excluding, however, all IRA and Keogh accounts, and all trust accounts for which
the grant of a security interest would be prohibited by law. Grantor authorizes
Lender, to the extent permitted by applicable law, to charge or setoff all
Indebtedness against any and all such accounts, and, at Lender's option, to
administratively freeze all such accounts to allow Lender to protect Lender's
charge and setoff rights provided in this paragraph.

OBLIGATIONS OF GRANTOR. Grantor warrants and covenants to Lender as follows:

     PERFECTION OF SECURITY INTEREST. Grantor agrees to execute such financing
     statements and to take whatever other actions are requested by Lender to
     perfect and continue Lender's security interest in the Collateral. Upon
     request of Lender, Grantor will deliver to Lender any and all of the
     documents evidencing or constituting the Collateral, and Grantor will note
     Lender's interest upon any and all chattel paper if not delivered to Lender
     for possession by Lender. Grantor hereby appoints Lender as its irrevocable
     attorney-in-fact for the purpose of executing any documents necessary to
     perfect or to continue the security interest granted in this Agreement.
     Lender may at any time, and without further authorization from Grantor,
     file a carbon, photographic or other reproduction of any financing
     statement or of this Agreement for use as a financing statement. Grantor
     will reimburse Lender for all expenses for the perfection and the
     continuation of the perfection of Lender's security interest in the
     Collateral. Grantor promptly will notify Lender before any change in
     Grantor's name including any change to the assumed business names of
     Grantor. THIS IS A CONTINUING SECURITY AGREEMENT AND WILL CONTINUE IN
     EFFECT EVEN THOUGH ALL OR ANY PART OF THE INDEBTEDNESS IS PAID IN FULL AND
     EVEN THOUGH FOR A PERIOD OF TIME GRANTOR MAY NOT BE INDEBTED TO LENDER.

     NO VIOLATION. The execution and delivery of this Agreement will not violate
     any law or agreement governing Grantor or to which Grantor is a party, and
     its certificate or articles of incorporation and bylaws do not prohibit any
     term or condition of this Agreement.

<PAGE>

10-23-1997                COMMERCIAL SECURITY AGREEMENT                  PAGE 2
                                   (CONTINUED)
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     ENFORCEABILITY OF COLLATERAL. To the extent the Collateral consists of 
     accounts, chattel paper, or general intangibles, the Collateral is 
     enforceable in accordance with its terms, is genuine, and complies with 
     applicable laws concerning form, content and manner of preparation and 
     execution, and all persons appearing to be obligated on the Collateral 
     have authority and capacity to contract and are in fact obligated as 
     they appear to be on the Collateral.

     LOCATION OF THE COLLATERAL. Grantor, upon request of Lender, will 
     deliver to Lender in form satisfactory to Lender a schedule of real 
     properties and Collateral locations relating to Grantor's operations, 
     including without limitation the following: (a) all real property owned 
     or being purchased by Grantor; (b) all real property being rented or 
     leased by Grantor; (c) all storage facilities owned, rented, leased, or 
     being used by Grantor; and (d) all other properties where Collateral is 
     or may be located. Except in the ordinary course of its business, 
     Grantor shall not remove the Collateral from its existing locations 
     without the prior written consent of Lender.

     REMOVAL OF COLLATERAL. Grantor shall keep the Collateral (or to the      
     extent the Collateral consists of intangible property such as accounts, 
     the records concerning the Collateral) at Grantor's address shown above, 
     or at such other locations as are acceptable to Lender. Except in the 
     ordinary course of its business, including the sales of inventory, 
     Grantor shall not remove the Collateral from its existing locations 
     without the prior written consent of Lender. To the extent that the 
     Collateral consists of vehicles, or other titled property, Grantor shall 
     not take or permit any action which would require application for 
     certificates of title for the vehicles outside the State of Washington, 
     without the prior written consent of Lender.

     TRANSACTIONS INVOLVING COLLATERAL. Except for inventory sold or accounts 
     collected in the ordinary course of Grantor's business, Grantor shall 
     not sell, offer to sell, or otherwise transfer or dispose of the 
     Collateral. While Grantor is not in default under this Agreement, 
     Grantor may sell inventory, but only in the ordinary course of its 
     business and only to buyers who qualify as a buyer in the ordinary 
     course of business. A sale in the ordinary course of Grantor's business 
     does not include a transfer in partial or total satisfaction of a debt 
     or any bulk sale. Grantor shall not pledge, mortgage, encumber or 
     otherwise permit the Collateral to be subject to any lien, security 
     interest, encumbrance, or charge, other than the security interest 
     provided for in this Agreement, without the prior written consent of 
     Lender. This includes security interests even if junior in right to the 
     security interests granted under this Agreement. Unless waived by 
     Lender, all proceeds from any disposition of the Collateral (for 
     whatever reason) shall be held in trust for Lender and shall not be 
     commingled with any other funds; provided however, this requirement 
     shall not constitute consent by Lender to any sale or other disposition. 
     Upon receipt, Grantor shall immediately deliver any such proceeds to 
     Lender.

     TITLE. Grantor represents and warrants to Lender that it holds good and 
     marketable title to the Collateral, free and clear of all liens and 
     encumbrances except for the lien of this Agreement. No financing 
     statement covering any of the Collateral is on file in any public office 
     other than those which reflect the security interest created by this 
     Agreement or to which Lender has specifically consented. Grantor shall 
     defend Lender's rights in the Collateral against the claims and demands 
     of all other persons.

     COLLATERAL SCHEDULES AND LOCATIONS. Insofar as the Collateral consists 
     of inventory, Grantor shall deliver to Lender, as often as Lender shall 
     require, such lists, descriptions, and designations of such Collateral 
     as Lender may require to identify the nature, extent, and location of 
     such Collateral. Such information shall be submitted for Grantor and 
     each of its subsidiaries or related companies.

     MAINTENANCE AND INSPECTION OF COLLATERAL. Grantor shall maintain all 
     tangible Collateral in good condition and repair. Grantor will not 
     commit or permit damage to or destruction of the Collateral or any part 
     of the Collateral. Lender and its designated representatives and agents 
     shall have the right at all reasonable times to examine, inspect, and 
     audit the Collateral wherever located. Grantor shall immediately notify 
     Lender of all cases involving the return, rejection, repossession, loss 
     or damage of or to any Collateral; of any request for credit or 
     adjustment or of any other dispute arising with respect to the 
     Collateral; and generally of all happenings and events affecting the 
     Collateral or the value or the amount of the Collateral.

     TAXES, ASSESSMENTS AND LIENS. Grantor will pay when due all taxes, 
     assessments and liens upon the Collateral, its use or operation, upon 
     this Agreement, upon any promissory note or notes evidencing the 
     Indebtedness, or upon any of the other Related Documents. Grantor may 
     withhold any such payment or may elect to contest any lien if Grantor is 
     in good faith conducting an appropriate proceeding to contest the 
     obligation to pay and so long as Lender's interest in the Collateral is 
     not jeopardized in Lender's sole opinion. If the Collateral is subjected 
     to a lien which is not discharged within fifteen (15) days, Grantor 
     shall deposit with Lender cash, a sufficient corporate surety bond or 
     other security satisfactory to Lender in an amount adequate to provide 
     for the discharge of the lien plus any interest, costs, attorneys' fees 
     or other charges that could accrue as a result of foreclosure or sale of 
     the Collateral. In any contest Grantor shall defend itself and Lender 
     and shall satisfy any final adverse judgment before enforcement against 
     the Collateral. Grantor shall name Lender as an additional obligee under 
     any surety bond furnished in the contest proceedings.

     COMPLIANCE WITH GOVERNMENTAL REQUIREMENTS. Grantor shall comply promptly 
     with all laws, ordinances, rules and regulations of all governmental 
     authorities, now or hereafter in effect, applicable to the ownership, 
     production, disposition, or use of the Collateral. Grantor may contest 
     in good faith any such law, ordinance or regulation and withhold 
     compliance during any proceeding, including appropriate appeals, so long 
     as Lender's interest in the Collateral, in Lender's opinion, is not 
     jeopardized.

     HAZARDOUS SUBSTANCES. Grantor represents and warrants that the 
     Collateral never has been, and never will be so long as this Agreement 
     remains a lien on the Collateral, used for the generation, manufacture, 
     storage, transportation, treatment, disposal, release or threatened 
     release of any hazardous waste or substance, as those terms are defined 
     in the Comprehensive Environmental Response, Compensation, and Liability 
     Act of 1980, as amended, 42 U.S.C. Section 9601, at 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, at seq., the Resource Conservation and Recovery Act, 42 U.S.C. 
     Section 6901, at seq., or other applicable state or Federal laws, rules, 
     or regulations adopted pursuant to any of the foregoing. The terms 
     "hazardous waste" and "hazardous substance" shall also include, without 
     limitation, petroleum and petroleum by-products or any fraction thereof 
     and asbestos. The representations and warranties contained herein are 
     based on Grantor's due diligence in investigating the Collateral for 
     hazardous wastes and substances. Grantor hereby (a) releases and waives 
     any future claims against Lender for indemnity or contribution in the 
     event Grantor becomes liable for cleanup or other costs under any such 
     laws, and (b) agrees to indemnify and hold harmless Lender against any 
     and all claims and losses resulting from a breach of this provision of 
     this Agreement. This obligation to indemnify shall survive the payment 
     of the Indebtedness and the satisfaction of this Agreement.

     MAINTENANCE OF CASUALTY INSURANCE. Grantor shall procure and maintain 
     all risks insurance, including without limitation fire, theft and 
     liability coverage together with such other insurance as Lender may 
     require with respect to the Collateral, in form, amounts, coverages and 
     basis reasonably acceptable to Lender and issued by a company or 
     companies reasonably acceptable to Lender. Grantor, 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 ten (10) days' prior written notice to Lender and not including 
     any disclaimer of the insurer's liability for failure to give such a 
     notice. 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 Grantor or any other person. In 
     connection with all policies covering assets in which Lender holds or is 
     offered a security interest, Grantor will provide Lender with such loss 
     payable or other endorsements as Lender may require. It Grantor at any 
     time fails to obtain or maintain any insurance as required under this 
     Agreement, Lender may (but shall not be obligated to) obtain such 
     insurance as Lender deems appropriate, including if it so chooses 
     "single interest insurance," which will cover only Lender's interest in 
     the Collateral.

<PAGE>

10-23-1997                COMMERCIAL SECURITY AGREEMENT                 PAGE 3
                                 (CONTINUED)
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     APPLICATION OF INSURANCE PROCEEDS. Grantor shall promptly notify Lender 
     of any loss or damage to the Collateral. Lender may make proof of loss 
     if Grantor fails to do so within fifteen (15) days of the casualty. All 
     proceeds of any insurance on the Collateral, including accrued proceeds 
     thereon, shall be held by Lender as part of the Collateral. If Lender 
     consents to repair or replacement of the damaged or destroyed 
     Collateral, Lender shall, upon satisfactory proof of expenditure, pay or 
     reimburse Grantor from the proceeds for the reasonable cost of repair or 
     restoration. If Lender does not consent to repair or replacement of the 
     Collateral, Lender shall retain a sufficient amount of the proceeds to 
     pay all of the Indebtedness, and shall pay the balance to Grantor. Any 
     proceeds which have not been disbursed within six (6) months after their 
     receipt and which Grantor has not committed to the repair or restoration 
     of the Collateral shall be used to prepay the Indebtedness.

     INSURANCE RESERVES. Lender may require Grantor to maintain with Lender 
     reserves for payment of insurance premiums, which reserves shall be 
     created by monthly payments from Grantor of a sum estimated by Lender to 
     be sufficient to produce, at least fifteen (15) days before the premium 
     due date, amounts at least equal to the insurance premiums to be paid. 
     If fifteen (15) days before payment is due, the reserve funds are 
     insufficient, Grantor shall upon demand pay any deficiency to Lender. 
     The reserve funds shall be held by Lender as a general deposit and shall 
     constitute a non-interest-bearing account which Lender may satisfy by 
     payment of the insurance premiums required to be paid by Grantor as they 
     become due. Lender does not hold the reserve funds in trust for Grantor, 
     and Lender is not the agent of Grantor for payment of the insurance 
     premiums required to be paid by Grantor. The responsibility for the 
     payment of premiums shall remain Grantor's sole responsibility.

     INSURANCE REPORTS. Grantor, upon request of Lender, shall furnish to 
     Lender reports on each existing policy of insurance showing such 
     information as Lender may reasonably request including the following: 
     (a) the name of the insurer; (b) the risks insured; (c) the amount of 
     the policy; (d) the property insured; (e) the then current value on the 
     basis of which insurance has been obtained and the manner of determining 
     that value; and (f) the expiration date of the policy. In addition, 
     Grantor shall upon request by Lender (however not more often than 
     annually) have an independent appraiser satisfactory to Lender 
     determine, as applicable, the cash value or replacement cost of the 
     Collateral.

GRANTOR'S RIGHT TO POSSESSION. Until default, Grantor may have possession of the
tangible personal property and beneficial use of all the Collateral and may use
it in any lawful manner not inconsistent with this Agreement or the Related
Documents, provided that Grantor's right to possession and beneficial use shall
not apply to any Collateral where possession of the Collateral by Lender is
required by law to perfect Lender's security interest in such Collateral. If
Lender at any time has possession of any Collateral, whether before or after an
Event of Default, Lender shall be deemed to have exercised reasonable care in
the custody and preservation of the Collateral if Lender takes such action for
that purpose as Grantor shall request or as Lender, in Lender's sole discretion,
shall deem appropriate under the circumstances, but failure to honor any request
by Grantor shall not of itself be deemed to be a failure to exercise reasonable
care. Lender shall not be required to take any steps necessary to preserve any
rights in the Collateral against prior parties, nor to protect, preserve or
maintain any security interest given to secure the Indebtedness.

EXPENDITURES BY LENDER. If not discharged or paid when due, Lender may (but
shall not be obligated to) discharge or pay any amounts required to be
discharged or paid by Grantor under this Agreement, including without limitation
all taxes, liens, security interests, encumbrances, and other claims, at any
time levied or placed on the Collateral. Lender also may (but shall not be
obligated to) pay all costs for insuring, maintaining and preserving the
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 Grantor. All such
expenses shall become a part of the Indebtedness and, at Lender's option, will
(a) be payable on demand, (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 (i) the term of any applicable insurance policy or (ii) the
remaining term of the Note, or (c) be treated as a balloon payment which will be
due and payable at the Note's maturity. This Agreement also will secure payment
of these amounts. Such right shall be in addition to all other rights and
remedies to which Lender may be entitled upon the occurrence of an Event of
Default.

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

     DEFAULT ON INDEBTEDNESS. Failure of Grantor to make any payment when due 
     on the Indebtedness.

     OTHER DEFAULTS. Failure of Grantor 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 in any other agreement 
     between Lender and Grantor.

     DEFAULT IN FAVOR OF THIRD PARTIES. Should Borrower or any Grantor 
     default 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 
     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 or on behalf of Grantor under this Agreement, the 
     Note or the Related Documents is false or misleading in any material 
     respect, either now or at the time made or furnished.

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

     INSOLVENCY. The dissolution or termination of Grantor's existence as a 
     going business, the insolvency of Grantor, the appointment of a receiver 
     for any part of Grantor's property, any assignment for the benefit of 
     creditors, any type of creditor workout, or the commencement of any 
     proceeding under any bankruptcy or insolvency laws by or against Grantor.

     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 Grantor or by any 
     governmental agency against the Collateral or any other collateral 
     securing the Indebtedness. This includes a garnishment of any of 
     Grantor's deposit accounts with Lender.

     EVENTS AFFECTING GUARANTOR. Any of the preceding events occurs with 
     respect to any Guarantor of any of the Indebtedness or such Guarantor 
     dies or becomes incompetent.

     ADVERSE CHANGE. A material adverse change occurs in Grantor's financial 
     condition, or Lender believes the prospect of payment or performance of 
     the Indebtedness is impaired.

RIGHTS AND REMEDIES ON DEFAULT. If an Event of Default occurs under this
Agreement, at any time thereafter, Lender shall have all the rights of a secured
party under the Washington Uniform Commercial Code. In addition and without
limitation, Lender may exercise any one or more of the following rights and
remedies:

     ACCELERATE INDEBTEDNESS. Lender may declare the entire Indebtedness, 
     including any prepayment penalty which Grantor would be required to pay, 
     immediately due and payable, without notice.

     ASSEMBLE COLLATERAL. Lender may require Grantor to deliver to Lender all 
     or any portion of the Collateral and any and all certificates of title 
     and other documents relating to the Collateral. Lender may require 
     Grantor to assemble the Collateral and make it available to Lender at a 
     place to be designated by Lender. Lender also shall have full power to 
     enter upon the property of Grantor to take possession of and remove the 
     Collateral. If the Collateral contains other goods not covered by this 
     Agreement at the time of repossession, Grantor agrees Lender may take 
     such other goods, provided that Lender makes reasonable efforts to 
     return them to Grantor after repossession.

     SELL THE COLLATERAL. Lender shall have full power to sell, lease, 
     transfer, or otherwise deal with the Collateral or proceeds thereof in 
     its own name or that of Grantor. Lender may sell the Collateral at 
     public auction or private sale. Unless the Collateral threatens to 
     decline speedily in value or

<PAGE>

10-23-1997               COMMERCIAL SECURITY AGREEMENT                   PAGE 4
                                 (CONTINUED)
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     is of a type customarily sold on a recognized market, Lender will give 
     Grantor reasonable notice of the time after which any private sale or 
     any other intended disposition of the Collateral is to be made. The 
     requirements of reasonable notice shall be met if such notice is given 
     at least ten (10) days before the time of the sale or disposition. All 
     expenses relating to the disposition of the Collateral, including 
     without limitation the expenses of retaking, holding, insuring, 
     preparing for sale and selling the Collateral, shall become a part of 
     the Indebtedness secured by this Agreement and shall be payable on 
     demand, with interest at the Note rate from date of expenditure until 
     repaid.

     APPOINT RECEIVER. To the extent permitted by applicable law, Lender 
     shall have the following rights and remedies regarding the appointment 
     of a receiver: (a) Lender may have a receiver appointed as a matter of 
     right, (b) the receiver may be an employee of Lender and may serve 
     without bond, and (c) all fees of the receiver and his or her attorney 
     shall become part of the Indebtedness secured by this Agreement and 
     shall be payable on demand, with interest at the Note rate from date of 
     expenditure until repaid.

     COLLECT REVENUES, APPLY ACCOUNTS. Lender, either itself or through a 
     receiver, may collect the payments, rents, income, and revenues from the 
     Collateral. Lender may at any time in its discretion transfer any 
     Collateral into its own name or that of its nominee and receive the 
     payments, rents, income, and revenues therefrom and hold the same as 
     security for the Indebtedness or apply it to payment of the Indebtedness 
     in such order of preference as Lender may determine. Insofar as the 
     Collateral consists of accounts, general intangibles, insurance 
     policies, instruments, chattel paper, choses in action, or similar 
     property, Lender may demand, collect, receipt for, settle, compromise, 
     adjust, sue for, foreclose, or realize on the Collateral as Lender may 
     determine, whether or not Indebtedness or Collateral is then due. For 
     these purposes, Lender may, on behalf of and in the name of Grantor, 
     receive, open and dispose of mail addressed to Grantor; change any 
     address to which mail and payments are to be sent; and endorse notes, 
     checks, drafts, money orders, documents of title, instruments and items 
     pertaining to payment, shipment, or storage of any Collateral. To 
     facilitate collecton, Lender may notify account debtors and obligors on 
     any Collateral to make payments directly to Lender.

     OBTAIN DEFICIENCY, If Lender chooses to sell any or all of the 
     Collateral, Lender may obtain a judgment against Grantor for any 
     deficiency remaining on the Indebtedness due to Lender after application 
     of all amounts received from the exercise of the rights provided in this 
     Agreement.  Grantor shall be liable for a deficiency even if the 
     transaction described in this subsection is a sale of accounts or 
     chattel paper.

     OTHER RIGHTS AND REMEDIES. Lender shall have all the rights and remedies 
     of a secured creditor under the provisions of the Uniform Commercial 
     Code, as may be amended from time to time. In addition, Lender shall 
     have and may exercise any or all other rights and remedies it may have 
     available at law, in equity, or otherwise.

     CUMULATIVE REMEDIES. All of Lender's rights and remedies, whether 
     evidenced by this Agreement or the Related Documents or by any other 
     writing, 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 Grantor under this Agreement, 
     after Grantor's failure to perform, shall not affect Lender's right to 
     declare a default and to exercise its remedies.

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.

     APPLICABLE LAW. This Agreement has been delivered to Lender and accepted 
     by Lender in the State of California. If there is a lawsuit, Grantor  
     agrees upon Lender's request to submit to the jurisdiction of the courts 
     of King County, the State of Washington. Lender and Grantor hereby waive 
     the right to any jury trial in any action, proceeding, or counterclaim 
     brought by either Lender or Grantor against the other. (INITIAL HERE /s/ 
     BD)  This Agreement shall be governed by and construed in accordance 
     with the laws of the State of Washington.

     ATTORNEYS' FEES; EXPENSES. Grantor agrees to pay upon demand all of 
     Lender's costs and expenses, including attorneys' fees and Lender's 
     legal expenses, incurred in connection with the enforcement of this 
     Agreement. Lender may pay someone else to help enforce this Agreement, 
     and Grantor shall pay the costs and expenses of such enforcement. Costs 
     and expenses include Lender's attorneys' fees and legal expenses whether 
     or not there is a lawsuit, including attorneys' fees and legal expenses 
     for bankruptcy proceedings (and including efforts to modify or vacate 
     any automatic stay or injunction), appeals, and any anticipated 
     post-judgment collection services. Grantor also shall pay all court 
     costs and such additional fees as may be directed by the court.

     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.

     MULTIPLE PARTIES; CORPORATE AUTHORITY. All obligations of Grantor under 
     this Agreement shall be joint and several, and all references to Grantor 
     shall mean each and every Grantor. This means that each of the persons 
     signing below is responsible for ALL obligations in this Agreement.

     NOTICES. All notices required to be given under this Agreement shall be 
     given in writing, may be sent by telefacsimile (unless otherwise 
     required by law), and shall be effective when actually delivered or when 
     deposited with a nationally recognized overnight courier or deposited in 
     the United States mail, first class, postage prepaid, addressed to the 
     party to whom the notice is to be given at the address shown above. 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. To the extent permitted 
     by applicable law, if there is more than one Grantor, notice to any 
     Grantor will constitute notice to all Grantors. For notice purposes, 
     Grantor will keep Lender informed at all times of Grantor's current 
     address(es).

     POWER OF ATTORNEY. Grantor hereby appoints Lender as its true and lawful 
     attorney-in-fact, irrevocably, with full power of substitution to do the 
     following: (a) to demand, collect, receive, receipt for, sue and recover 
     all sums of money or other property which may now or hereafter become 
     due, owing or payable from the Collateral; (b) to execute, sign and 
     endorse any and all claims, instruments, receipts, checks, drafts or 
     warrants issued in payment for the Collateral; (c) to settle or 
     compromise any and all claims arising under the Collateral, and, in the 
     place and stead of Grantor, to execute and deliver its release and 
     settlement for the claim; and (d) to file any claim or claims or to take 
     any action or institute or take part in any proceedings, either in its 
     own name or in the name of Grantor, or otherwise, which in the 
     discretion of Lender may seem to be necessary or advisable. This power 
     is given as security for the Indebtedness, and the authority hereby 
     conferred is and shall be irrevocable and shall remain in full force and 
     effect until renounced by Lender.

     PREFERENCE PAYMENTS. Any monies Lender pays because of an asserted 
     preference claim in Borrower's bankruptcy will become a part of the 
     Indebtedness and, at Lender's option, shall be payable by Borrower as 
     provided above in the "EXPENDITURES BY LENDER" paragraph.

     SEVERABILITY. If a court of competent jurisdiction finds any provision 
     of this Agreement to be invalid or unenforceable as to any person or 
     circumstance, such finding shall not render that provision invalid or 
     unenforceable as to any other persons or circumstances. If feasible, any 
     such offending provision shall be deemed to be modified to be within the 
     limits of enforceability or validity; however, if the offending 
     provision cannot be so modified, it shall be stricken and all other 
     provisions of this Agreement in all other respects shall remain valid 
     and enforceable.

     SUCCESSOR INTERESTS. Subject to the limitations set forth above on 
     transfer of the Collateral, this Agreement shall be binding upon and 
     inure to the benefit of the parties, their successors and assigns. 

     WAIVER. Lender shall not be deemed to have waived any rights under this 
     Agreement unless such waiver is given in writing and signed by


<PAGE>

10-23-1997                COMMERCIAL SECURITY AGREEMENT                 PAGE 5
                                (CONTINUED)
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     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 
     Grantor, shall constitute a waiver of any of Lender's rights or of any 
     of 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.

     WAIVER OF CO-OBLIGOR'S RIGHTS. If more than, one person is obligated for 
     the Indebtedness, Borrower irrevocably waives, disclaims and relinquishs 
     all claims against such other person which Borrower has or would 
     otherwise have by virtue of payment of the Indebtedness or any part 
     thereof, specifically including but not limited to all rights of 
     indemnity, contribution or exoneration.

ADDITIONAL PROVISION. If any law is passed that requires additional action on
the part of Lender, Borrower and/or Grantor shall fully cooperate with Lender in
complying with the law and accordingly, shall reimburse Lender for all costs and
expenses which Lender incurs in compliance with the law.

GRANTOR ACKNOWLEDGES HAVING READ ALL THE PROVISIONS OF THIS COMMERCIAL SECURITY
AGREEMENT, AND GRANTOR AGREES TO ITS TERMS. THIS AGREEMENT IS DATED OCTOBER
23,1997.

GRANTOR:

F5 LABS, INC.

BY: /s/ Brian Dixon
   -----------------------------
  NAME:  Brian Dixon               TITLE: V.P. Finance
        -------------------------         ------------------


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<PAGE>


                              PROMISSORY NOTE
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BORROWER: F5 LABS, INC.               LENDER: SILICON VALLEY BANK, A CALIFORNIA
          1218 THIRD AVENUE, SUITE 508        CHARTERED BANK
          SEATTLE, WA 98101                   WASHINGTON LOAN PRODUCTION OFFICE
                                              915 118TH AVENUE, S.E., SUITE 25O
                                              BELLEVUE, WA 98005
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-------------------------------------------------------------------------------

PRINCIPAL AMOUNT: $250,000.00   INITIAL RATE: 10.500%    DATE OF NOTE: OCTOBER 
23, 1997

PROMISE TO PAY. F5 LABS, INC. ("BORROWER") PROMISES TO PAY TO SILICON VALLEY
BANK, A CALIFORNIA CHARTERED BANK ("LENDER"), OR ORDER, IN LAWFUL MONEY OF THE
UNITED STATES OF AMERICA, THE PRINCIPAL AMOUNT OF TWO HUNDRED FIFTY THOUSAND &
00/100 DOLLARS ($250,000.00) OR SO MUCH AS MAY BE OUTSTANDING, TOGETHER WITH
INTEREST ON THE UNPAID OUTSTANDING PRINCIPAL BALANCE OF EACH ADVANCE. INTEREST
SHALL BE CALCULATED FROM THE DATE OF EACH ADVANCE UNTIL REPAYMENT OF EACH
ADVANCE.

PAYMENT. BORROWER WILL PAY THIS LOAN IN ONE PAYMENT OF ALL OUTSTANDING PRINCIPAL
PLUS ALL ACCRUED UNPAID INTEREST ON DECEMBER 23,1997. IN ADDITION, BORROWER WILL
PAY REGULAR MONTHLY PAYMENTS OF ACCRUED UNPAID INTEREST BEGINNING NOVEMBER 23,
1997, AND ALL SUBSEQUENT INTEREST PAYMENTS ARE DUE ON THE SAME DAY OF EACH MONTH
AFTER THAT. The annual interest rate for this Note is computed on a 365/360
basis; that is, by applying the ratio of the annual interest rate over a year of
360 days, multiplied by the outstanding principal balance, multiplied by the
actual number of days the principal balance is outstanding. Borrower will pay
Lender at Lender's address shown above or at such other place as Lender may
designate in writing. Unless otherwise agreed or required by applicable law,
payments will be applied first to accrued unpaid interest, then to principal,
and any remaining amount to any unpaid collection costs and late charges.

VARIABLE INTEREST RATE. The interest rate on this Note is subject to change from
time to time based on changes in an index which is Lender's Prime Rate (the
"Index"). This is the rate Lender charges, or would charge, on 90-day unsecured
loans to the most creditworthy corporate customers. This rate may or may not be
the lowest rate available from Lender at any given time. Lender will tell
Borrower the current Index rate upon Borrower's request. Borrower understands
that Lender may make loans based on other rates as well. The interest rate
change will not occur more often than each time the prime rate is adjusted by
Silicon Valley Bank. THE INDEX CURRENTLY IS 8.500% PER ANNUM. THE INTEREST RATE
TO BE APPLIED TO THE UNPAID PRINCIPAL BALANCE OF THIS NOTE WILL BE AT A RATE of
2.000 PERCENTAGE POINTS OVER THE INDEX, RESULTING IN AN INITIAL RATE of 10.500%
PER ANNUM. NOTICE: Under no circumstances will the interest rate on this Note be
more than the maximum rate allowed by applicable law.

PREPAYMENT. Borrower agrees that all loan fees and other prepaid finance charges
are earned fully as of the date of the loan and will not be subject to refund
upon early payment (whether voluntary or as a result of default), except as
otherwise required by law. Except for the foregoing. Borrower may pay without
penalty all or a portion of the amount owed earlier than it is cue. Early
payments will not, unless agreed to by Lender in writing, relieve Borrower of
Borrower's obligation to continue to make payments of accrued unpaid interest.
Rather, they will reduce the principal balance due.

DEFAULT. Borrower will be in default if any of the following happens: (a)
Borrower fails to make any payment when due. (b) Borrower breaks any promise
Borrower has made to Lender, or Borrower fails to comply with or to perform when
due any other term, obligation, covenant, or condition contained in this Note or
any agreement related to this Note, or in any other agreement or loan Borrower
has with Lender. (c) Borrower 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 property or Borrower's ability to repay this Note or perform
Borrower's obligations under this Note or any of the Related Documents. (d) Any
representation or statement made or furnished to Lender by Borrower or on
Borrower's behalf is false or misleading in any material respect either now or
at the time made or furnished. (e) Borrower becomes insolvent, a receiver is
appointed for any part of Borrower's property, Borrower makes an assignment for
the benefit of creditors, or any proceeding is commenced either by Borrower or
against Borrower under any bankruptcy or insolvency laws. (f) Any creditor tries
to take any of Borrower's property on or in which Lender has a lien or security
interest. This includes a garnishment of any of Borrower's accounts with Lender.
(g) Any guarantor dies or any of the other events described in this default
section occurs with respect to any guarantor of this Note. (h) A material
adverse change occurs in Borrower's financial condition, or Lender believes the
prospect of payment or performance of the Indebtedness is impaired.

LENDER'S RIGHTS. Upon default, Lender may declare the entire unpaid principal 
balance on this Note and all accrued unpaid interest immediately due, without 
notice, and then Borrower will pay that amount. Upon default, including 
failure to pay upon final maturity, Lender, at its option, may also, if 
permitted under applicable law, increase the variable interest rate on this 
Note to 7.000 percentage points over the Index. The interest rate will not 
exceed the maximum rate permitted by applicable law. Lender may hire or pay 
someone else to help collect this Note if Borrower does not pay. Borrower 
also will pay Lender that amount. This includes, subject to any limits under 
applicable law, Lender's attorneys' fees and Lender's legal expenses whether 
or not there is a lawsuit, including attorneys' fees and legal expenses for 
bankruptcy proceedings (including efforts to modify or vacate any automatic 
stay or injunction), appeals, and any anticipated post-judgment collection 
services. If not prohibited by applicable law, Borrower also will pay any 
court costs, in addition to all other sums provided by law. THIS NOTE HAS 
BEEN DELIVERED TO LENDER AND ACCEPTED BY LENDER IN THE STATE OF CALIFORNIA.  IF
THERE IS A LAWSUIT, BORROWER AGREES UPON LENDER'S REQUEST TO SUBMIT TO THE 
JURISDICTION OF THE COURTS OF KING COUNTY, THE STATE OF WASHINGTON. LENDER 
AND BORROWER HEREBY WAIVE THE RIGHT TO ANY JURY TRIAL IN ANY ACTION, 
PROCEEDING, OR COUNTERCLAIM BROUGHT BY EITHER LENDER OR BORROWER AGAINST THE 
OTHER (INITIAL HERE /s/ BD)  THIS NOTE SHALL BE GOVERNED BY AND CONSTRUED IN 
ACCORDANCE WITH THE LAWS OF THE STATE OF WASHINGTON.

LINE OF CREDIT. This Note evidences a revolving line of credit. Advances 
under this Note, as well as directions for payment from Borrower's accounts, 
may be requested orally or in writing by Borrower or by an authorized person. 
Lender may, but need not, require that all oral requests be confirmed in 
writing. Borrower agrees to be liable for all sums either: (a) advanced in 
accordance with the instructions of an authorized person or (b) credited to 
any of Borrower's accounts with Lender. The unpaid principal balance owing on 
this Note at any time may be evidenced by endorsements on this Note or by 
Lender's internal records, including daily computer print-outs. Lender will 
have no obligation to advance funds under this Note it: (a) Borrower or any 
guarantor is in default under the terms of this Note or any agreement that 
Borrower or any guarantor has with Lender, including any agreement made in 
connection with the signing of this Note; (b) Borrower or any guarantor 
ceases doing business or is insolvent; (c) any guarantor seeks, claims or 
otherwise attempts to limit, modify or revoke such guarantor's guarantee of 
this Note or any other loan with Lender; or (d) Borrower has applied funds 
provided pursuant to this Note for purposes other than those authorized by 
Lender.

REQUEST TO DEBIT ACCOUNTS. Borrower will regularly deposit funds received in 
accounts maintained with Silicon Valley Bank. Borrower hereby requests and 
authorizes Lender to debit any accounts Borrower has with Lender, including, 
without limitation, Account Number 3300108333 for payments of principal and 
interest owing on the loan and any other obligations owing from Borrower to 
Lender. Lender will notify Lender of all debits which Lender makes against 
Borrower's accounts. Any such debits against Borrower's accounts in no way 
shall be deemed a set-off.

LOAN FEE. This Note is subject to a loan fee in the amount of One Thousand and
00/100 Dollars ($1,000.00) (the "Loan Fee"), plus all out-of pocket expenses.

BUSINESS LOAN AGREEMENT. This Note is subject to and shall be governed by all
the terms and conditions of the Business Loan Agreement of even date herewith,
between Borrower and Lender, which Business Loan Agreement is incorporated
herein by reference.

<PAGE>

10-23-1997                 PROMISSORY NOTE                              PAGE 2
                             (CONTINUED)
-------------------------------------------------------------------------------
-------------------------------------------------------------------------------

GENERAL PROVISIONS. Lender may delay or forgo enforcing any of its rights or
remedies under this Note without losing them. Borrower and any other person who
signs, guarantees or endorses this Note, to the extent allowed by law, waive
presentment demand for payment, protest and notice of dishonor. Upon any change
in the terms of this Note, and unless otherwise expressly stated in writing, no
party who signs this Note, whether as maker, guarantor, accommodation maker or
endorser, shall be released from liability. All such parties agree that Lender
may renew or extend (repeatedly and for any length of time) this loan, or
release any party or guarantor or collateral; or impair, fail to realize upon or
perfect Lender's security interest in the collateral; and take any other action
deemed necessary by Lender without the consent of or notes to anyone. All such
parties also agree that Lender may modify this loan without the consent of or
notice to anyone other than the party with whom the modification is made.

PRIOR TO SIGNING THIS NOTE, BORROWER READ AND UNDERSTOOD ALL THE PROVISIONS OF
THIS NOTE, INCLUDING THE VARIABLE INTEREST RATE PROVISIONS.  BORROWER AGREES TO
THE TERMS OF THE NOTE AND ACKNOWLEDGES RECEIPT OF A COMPLETED COPY OF THE NOTE.

BORROWER:

F5 LABS, INC.


BY: /s/ Brian Dixon
   ----------------------------
   NAME: Brian Dixon             TITLE: V.P. Finance
         ----------------------        -----------------------
<PAGE>

                                PROMISSORY NOTE

BORROWER: F5 LABS, INC.
          200 1ST AVENUE, WEST, SUITE 500
          SEATTLE, WA 98119

LENDER:   SILICON VALLEY BANK, A CALIFORNIA CHARTERED-BANK
          WASHINGTON LOAN PRODUCTION OFFICE
          915 118th AVENUE, S.E., SUITE 250
          BELLEVUE, WA 98005
-------------------------------------------------------------------------------
-------------------------------------------------------------------------------

PRINCIPAL AMOUNT: $100,000.00    INITIAL RATE: 10.000%    DATE OF NOTE: FEBRUARY
5, 1998

PROMISE TO PAY. F5 LABS, INC. ("BORROWER") PROMISES TO PAY TO SILICON VALLEY
BANK ("LENDER"), OR ORDER, IN LAWFUL MONEY OF THE UNITED STATES OF AMERICA, THE
PRINCIPAL AMOUNT OF ONE HUNDRED THOUSAND & 00/100 DOLLARS ($100,000.00),
TOGETHER WITH INTEREST ON THE UNPAID PRINCIPAL BALANCE FROM FEBRUARY 5, 1998,
UNTIL PAID IN FULL.

PAYMENT. SUBJECT TO ANY PAYMENT CHANGES RESULTING FROM CHANGES IN THE INDEX,
BORROWER WILL PAY THIS LOAN IN ACCORDANCE WITH THE FOLLOWING PAYMENT SCHEDULE:

     THE DRAW PERIOD SHALL BEGIN AS OF THE DATE HEREOF AND SHALL END ON 
     AUGUST 4,1998 (THE "DRAW PERIOD"). BORROWER SHALL PAY REGULAR MONTHLY 
     PAYMENTS OF ALL ACCRUED UNPAID INTEREST BEGINNING ON MARCH 4,1998 AND 
     ALL SUBSEQUENT INTEREST PAYMENTS ARE DUE ON THE SAME DAY OF EACH MONTH 
     THEREAFTER. THE OUTSTANDING PRINCIPAL BALANCE AT THE END OF THE DRAW 
     PERIOD WILL BE PAYABLE IN 30 EQUAL PAYMENTS OF PRINCIPAL PLUS INTEREST 
     BEGINNING SEPTEMBER 4, 1998 AND ALL SUBSEQUENT PAYMENTS OF PRINCIPAL 
     PLUS INTEREST WILL BE DUE ON THE SAME DAY OF EACH MONTH THEREAFTER. THE 
     FINAL PAYMENT DUE, ON FEBRUARY 4, 2001, WILL BE FOR ALL OUTSTANDING 
     PRINCIPAL PLUS ALL ACCRUED INTEREST NO YET PAID.

The annual interest rate for this Note is computed on a 365/360 basis; that is,
by applying the ratio of the annual interest rate over a year of 360 days,
multiplied by the outstanding principal balance, multiplied by the actual number
of days the principal balance is outstanding. Borrower will pay Lender at
Lender's address shown above or at such other place as Lender may designate in
writing. Unless otherwise agreed or required by applicable law, payments will be
applied first to accrued unpaid interest, then to principal, and any remaining
amount to any unpaid collection costs and late charges. VARIABLE

INTEREST RATE. The interest rate on this Note is subject to change from time to
time based on changes in an index which is Lender's Prime Rate (the "Index").
This is the rate Lender charges, or would charge, on 90-day unsecured loans to
the most creditworthy corporate customers. This rate may or may not be the
lowest rate available from Lender at any given time. Lender will tell Borrower
the current Index rate upon Borrower's request. Borrower understands that Lender
may make loans based on other rates as well. The interest rate change will not
occur more often than each time the prime rate is adjusted by Silicon Valley
Bank. THE INDEX CURRENTLY IS 8.500%. THE INTEREST RATE TO BE APPLIED TO THE
UNPAID PRINCIPAL BALANCE OF THIS NOTE WILL BE AT A RATE OF 1.500 PERCENTAGE
POINTS OVER THE INDEX, RESULTING IN A CURRENT RATE OF 10.000%. NOTICE: Under no
circumstances will the interest rate on this Note be more than the maximum rate
allowed by applicable law. Whenever increases occur in the interest rate,
Lender, at its option, may do one or more of the following: (a) increase
Borrowers payments to ensure Borrower's loan will pay off by its original final
maturity date, (b) increase Borrower's payments to cover accruing interest, (c)
increase the number of Borrower's payments, and (d) continue Borrowers payments
at the same amount and increase Borrower's final payment.

PREPAYMENT. Borrower agrees that all loan fees and other prepaid finance charges
are earned fully as of the date of the loan and will not be subject to refund
upon early payment (whether voluntary or as a result of default), except as
otherwise required by law. Except for the foregoing, Borrower may pay without
penalty all or a portion of the amount owed earlier than it is due. Early
payments will not, unless agreed to by Lender in writing, relieve Borrower of
Borrower's obligation to continue to make payments under the payment schedule.
Rather, they will reduce the principal balance due and may result in Borrower
making fewer payments.

DEFAULT. Borrower will be in default if any of the following happens: (a) 
Borrower fails to make any payment when due. (b) Borrower breaks any promise 
Borrower has made to Lender, or Borrower fails to comply with or to perform 
when due any other term, obligation, covenant, or condition contained in this 
Note or any agreement related to this Note, or in any other agreement or loan 
Borrower has with Lender. (c) Borrower 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 property or Borrower's ability to repay this Note or 
perform Borrower's obligations under this Note or any of the Related 
Documents. (d) Any representation or statement made or furnished to Lender by 
Borrower or on Borrower's behalf is false or misleading in any material 
respect either now or at the time made or furnished.  (e) Borrower becomes 
insolvent, a receiver is appointed for any part of Borrower's property, 
Borrower makes an assignment for the benefit of creditors, or any proceeding 
is commenced either by Borrower or against Borrower under any bankruptcy or 
insolvency laws.  (f) Any creditor tries to take any of Borrowees property on 
or in which Lender has a lien or security interest.  This includes a 
garnishment of any of Borrower's accounts with Lender. (g) Any guarantor dies 
or any of the other events described in this default section occurs with 
respect to any guarantor of this Note. (h) A material adverse change occurs 
in Borrower's financial condition, or Lender believes the prospect of payment 
or performance of the Indebtedness is impaired.

LENDER'S RIGHTS. Upon default, Lender may declare the entire unpaid principal 
balance on this Note and all accrued unpaid interest immediately due, without 
notice, and then Borrower will pay that amount. Upon Borrower's failure to 
pay all amounts declared due pursuant to this section, including failure to 
pay upon final maturity, Lender, at its option, may also, if permitted under 
applicable law, increase the variable interest rate on this Note to 6.500 
percentage points over the Index. Lender may hire or pay someone else to help 
collect this Note if Borrower does not pay. Borrower also will pay Lender 
that amount. This includes, subject to any limits under applicable law, 
Lender's attorneys' fees and Lender's legal expenses whether or not there is 
a lawsuit, including attorneys' fees and legal expenses for bankruptcy 
proceedings (including efforts to modify or vacate any automatic stay or 
injunction), appeals, and any anticipated post-judgment collection services. 
Borrower also will pay any court costs, in addition to all other sums 
provided by law. THIS NOTE HAS BEEN DELIVERED TO LENDER AND ACCEPTED BY 
LENDER IN THE STATE OF CALIFORNIA. IF THERE IS A LAWSUIT, BORROWER AGREES 
UPON LENDER'S REQUEST TO SUBMIT TO THE JURISDICTION OF THE COURTS OF KING 
COUNTY, THE STATE OF WASHINGTON. LENDER AND BORROWER HEREBY WAIVE THE RIGHT 
TO ANY JURY TRIAL IN ANY ACTION, PROCEEDING, OR COUNTERCLAIM BROUGHT BY 
EITHER LENDER OR BORROWER AGAINST THE OTHER. (INITIAL HERE __). THIS NOTE 
SHALL BE GOVERNED BY AND CONSTRUED IN ACCORDANCE WITH THE LAWS OF THE STATE 
OF WASHINGTON.

LINE OF CREDIT. This Note evidences a straight line of credit through the end 
of the Draw Period. Once the total amount of principal has been advanced, 
Borrower is not entitled to further loan advances. Advances under this Note, 
as well as directions for payment from Borrowees accounts, may be requested 
orally or in writing by Borrower or by an authorized person. Lender may, but 
need not, require that all oral requests be confirmed in writing. Borrower 
agrees to be liable for all sums either: (a) advanced in accordance with the 
instructions of an authorized person or (b) credited to any of Borrower's 
accounts with Lender. The unpaid principal balance owing on this Note at any 
time may be evidenced by endorsements on this Note or by Lender's internal 
records, including daily computer print-outs. Lender will have no obligation 
to advance funds under this Note if: (a) Borrower of any guarantor is in 
default under the terms of this Note or any agreement that Borrower or 
guarantor has with Lender, including any agreement made in connection with 
the signing of this Note; (b) Borrower or any guarantor ceases doing business 
or is insolvent; (c) any guarantor seeks, claims or otherwise attempts to 
limit, modify or revoke such guarantor's guarantee of this Note or any other 
loan with Lender, and (d) Borrower has applied funds provided pursuant to 
this Note for purposes other than those authorized by Lender:

<PAGE>


                               PROMISSORY NOTE
                                 (CONTINUED)
                                   PAGE 2

AMENDED AND RESTATED BUSINESS LOAN AGREEMENT. This Note is governed by all the
terms and conditions of the Business Loan Agreement of even date herewith,
between Borrower and Lender, as such agreement may be amended from time to time,
which Amended and Restated Business Loan Agreement is incorporated herein by
this reference.

PAYMENT OF LOAN FEE. Borrower shall pay to Lender a fee in the amount of One
Thousand and 00/100 Dollars ($1,000.00) plus all out-of-pocket expenses.

REQUEST TO DEBIT ACCOUNTS. Borrower will regularly deposit funds received 
from its business activities in accounts maintained with Lender. Borrower 
hereby authorizes Lender to debit any accounts with Lender, including, 
without limitation Account Number 33-00 1083-33 for payments of principal and 
interest due on the loan and any other obligations owing from Borrower to 
Lender. Lender will notify Borrower of all debits which Lender makes against 
Borrower's accounts. Any such debits against Borrower's accounts in no way 
shall be deemed a set-off.

ADVANCE RATE. At any time from the date hereof through the end of the Draw
Period, Borrower may request advances (each an "Advance" and collectively, the
"Advances") from Lender in an aggregate amount not to exceed the principal
amount of the Note. To evidence the Advances, Borrower shall deliver to Lender,
at the time of each Advance request, an invoice for the equipment to be
purchased, the date of which shall not be greater than 90 days from the date of
each Advance. The Advances shall only be used to purchase equipment and shall
not exceed eighty percent (80%) of the invoice amount approved by Lender,
excluding taxes, shipping and installation expense.

GENERAL PROVISIONS. Lender may delay or forgo enforcing any of its rights or 
remedies under this Note without losing them. Borrower and any other person 
who signs, guarantees or endorses this Note, to the extent allowed by law, 
waive any applicable statute of limitations, presentment, demand for payment,
protest and notice of dishonor. Upon any change in the terms of this Note, 
and unless otherwise expressly stated in writing, no party who signs this 
Note, whether as maker, guarantor, accommodation maker or endorser, shall be 
released from liability. All such parties agree that Lender may renew or 
extend (repeatedly and for any length of time) this loan, or release any 
party or guarantor or collateral; or impair, fail to realize upon or perfect 
Lender's security interest in the collateral; and take any other action 
deemed necessary by Lender without the consent of or notice to anyone. All 
such parties also agree that Lender may modify this loan without the consent 
of or notice to anyone other than the party with whom the modification is 
made.

PRIOR TO SIGNING THIS NOTE, BORROWER READ AND UNDERSTOOD ALL THE PROVISIONS OF
THIS NOTE, INCLUDING THE VARIABLE INTEREST RATE PROVISIONS. BORROWER AGREES TO
THE TERMS OF THE NOTE AND ACKNOWLEDGES RECEIPT OF A COMPLETED COPY OF THE NOTE.

BORROWER:

F5 LABS, INC.

By: /s/ Brain R. Dixon
   -------------------------------
Name:  Brian R. Dixon
     -----------------------------
Title: V.P Finance
      ----------------------------


<PAGE>

                            LOAN MODIFICATION AGREEMENT

     This Loan Modification Agreement is entered into as of July 14, 1998 by and
between F5 Labs, Inc.   ("Borrower"), whose address is 200 1st Avenue, West,
Suite 500, Seattle, WA  98119 and Silicon Valley Bank ("Lender"), whose address
is 3003 Tasman Drive, Santa Clara, CA  95054 with a loan production office
located at 915 118th Avenue S.E., Suite 250, Bellevue, WA  98005.

1.   DESCRIPTION OF EXISTING INDEBTEDNESS:  Among other indebtedness which may
be owing by Borrower to Lender, Borrower is indebted to Lender pursuant to,
among other documents, a Promissory Note, dated February 5, 1998 in the original
principal amount of Seven Hundred Fifty Thousand and 00/100 Dollars
($750,000.00), as amended from time to time (the "Revolving Note") and a
Promissory Note, dated February 5, 1998, in the original principal amount of One
Hundred Thousand and 00/100 Dollars ($100,000.00), as amended from time to time
(the "Term Note").   The Revolving Note and the Term Note shall be referred to
collectively herein as the "Notes".  The Notes, together with other promissory
notes from Borrower to Lender, are governed by the terms of an Amended and
Restated  Business Loan Agreement dated February 5, 1998, as such agreement may
be amended from time to time, between Borrower and Lender (the "Loan
Agreement").  Defined terms used but not otherwise defined herein shall have the
same meanings as in the Loan Agreement.

Hereinafter, all indebtedness owing by Borrower to Lender shall be referred to
as the "Indebtedness".

2.   DESCRIPTION OF COLLATERAL AND GUARANTIES.  Repayment of the Indebtedness is
secured by the Collateral described in a Commercial Security Agreement and an
Intellectual Property Security Agreement, each dated October 23, 1997.

Hereinafter, the above-described security documents and guaranties, together
with all other documents securing repayment of the Indebtedness shall be
referred to as the "Security Documents".  Hereinafter, the Security Documents,
together with all other documents evidencing or securing the Indebtedness shall
be referred to as the "Existing Loan Documents".

3.   DESCRIPTION OF CHANGE IN TERMS.

     A.   MODIFICATION(S) TO REVOLVING NOTE.

          1.   Payable in one payment of all outstanding principal plus all
               accrued unpaid interest on July 31, 1999.  In addition, Borrower
               will pay regular monthly payments of all accrued unpaid interest,
               beginning July 31, 1998 and all subsequent interest payments will
               be due on the last day of each month thereafter.

          2.   The interest rate to be applied to the unpaid principal balance
               of the Revolving Note is hereby decreased, effective as of this
               date, to a rate equal to one-half of one percentage point
               (0.500%) over Lender's current Index.

          3.   The principal amount of the Revolving Note is hereby increased to
               Two Million and 00/100 Dollars ($2,000,000.00).

     B.   MODIFICATION(S) TO TERM NOTE.

          1.   Subject to any payment changes resulting from changes in the
               Index, Borrower will pay this loan in accordance with the
               following payment schedule:


<PAGE>

               The Draw Period shall begin as of this date and shall end on
               January 31, 1999 (the "Draw Period").  Borrower shall pay regular
               monthly payments of all accrued unpaid interest, beginning on
               July 31, 1998 and all subsequent interest payments will be due on
               the last day of each month thereafter.  The outstanding principal
               balance at the end of the Draw Period will be payable in
               twenty-four (24) equal payments of principal plus interest,
               beginning February 28, 1999 and all subsequent payments of
               principal plus interest will be due on the last day of each month
               thereafter.  The final payment, due on February 4, 2001, will be
               for all outstanding principal plus all accrued interest not yet
               paid.

          2.   The interest rate to be applied to the unpaid principal balance
               of the Term Note is hereby decreased, effective as of this date,
               to a rate equal to one percentage point (1.000%) over Lender's
               current Index.

     C.   MODIFICATION(S) TO LOAN AGREEMENT.

          1.   The first sentence of the paragraph entitled "Borrowing Base
               Formula" is hereby amended as follows:

               Funds shall be advanced under the Revolving Note according to a
               Borrowing Base Formula, determined by Lender, defined as follows:
               the lesser of (i) $2,000,000.00 or (ii) seventy-five percent
               (75%) of Eligible Accounts Receivable, minus in each case, the
               Trinet Employer Group Reserve.

          2.   The paragraph entitled "Accounts Receivable and Accounts Payable"
               is hereby amended in part to provide that the cost of each annual
               audit will be capped at Six Hundred and 00/100 Dollars ($600.00)
               per audit.

4.   CONSISTENT CHANGES.  The Existing Loan Documents are hereby amended
wherever necessary to reflect the changes described above.

5.   PAYMENT OF LOAN FEE.  Borrower shall pay to Lender a fee in the amount of
Five Thousand and 00/100 Dollars ($5,000.00) (the "Loan Fee") plus all
out-of-pocket expenses.

6.   NO DEFENSES OF BORROWER.  Borrower (and each guarantor and pledgor signing
below) agrees that, as of the date hereof, it has no defenses against the
obligations to pay any amounts under the Indebtedness.

7.   CONTINUING VALIDITY.  Borrower (and each guarantor and pledgor signing
below) understands and agrees that in modifying the existing Indebtedness,
Lender is relying upon Borrower's representations, warranties, and agreements,
as set forth in the Existing Loan Documents.  Except as expressly modified
pursuant to this Loan Modification Agreement, the terms of the Existing Loan
Documents remain unchanged and in full force and effect.  Lender's agreement to
modifications to the existing Indebtedness pursuant to this Loan Modification
Agreement in no way shall obligate Lender to make any future modifications to
the Indebtedness.  Nothing in this Loan Modification Agreement shall constitute
a satisfaction of the Indebtedness.  It is the intention of Lender and Borrower
to retain as liable parties all makers and endorsers of Existing Loan Documents,
unless the party is expressly released by Lender in writing.  No maker,
endorser, or guarantor will be released by virtue of this Loan Modification
Agreement.  The terms of this paragraph apply not only to this Loan Modification
Agreement, but also to all subsequent loan modification agreements.


<PAGE>

8.   CONDITIONS.  The effectiveness of this Loan Modification Agreement is
conditioned upon Borrower's payment of the Loan Fee.




     This Loan Modification Agreement is executed as of the date first written
above.

BORROWER:                               LENDER:

F5 LABS, INC.                           SILICON VALLEY BANK


By: /s/ Brian R. Dixon                  By: /s/ Geir B. Hansen
   ------------------------------          -------------------------------
Name: Brian R. Dixon                    Name: Geir B. Hansen

Title: CFO                              Title: AVP


