<PAGE>

                                                                   Exhibit 10.11

[LOGO OF BANK ONE APPEARS HERE]

                                LOAN AGREEMENT

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     Principal       Loan Date        Maturity        Loan No.     Call
     $5,000,000.00   07-02-1999       07-02-2000                   078105
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     Collateral      Account          Officer         Initials
     328             1518454676       00410
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 References in the shaded area are for Lender's use only and do not limit the
        applicability of this document to any particular loan or item.
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Borrower:  CARRIER ACCESS CORPORATION, A DELAWARE CORPORATION
           5395 PEARL PARKWAY
           BOULDER,CO 80301

Lender:    Bank One, Colorado, NA
           Corporate Lending - Boulder
           1125 17th Street
           Denver, Co 80217

================================================================================

THIS LOAN AGREEMENT between CARRIER ACCESS CORPORATION, A DELAWARE CORPORATION
("Borrower") and Bank One, Colorado, NA ("Lender") is made and executed as of
July 2, 1998. This Agreement governs all loans, credit facilities and/or other
financial accommodations described herein and, unless otherwise agreed to in
writing by Lender and Borrower, all other present and future loans, credit
facilities and other financial accommodations provided by Lender to Borrower.
All such loans, credit facilities and other financial accommodations, together
with all renewals, extensions and modifications thereof, 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; and (b) 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 July 2, 1998, and shall continue
thereafter until all Loans and other obligations owing by Borrower to Lender
hereunder have been paid in full and Lender has no commitments or obligations to
make further Advances under the Loans to Borrower.

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 as adopted in
the State of Colorado. All references to dollar amounts shall mean amounts in
lawful money of the United States of America.

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

     Account. The word "Account" means a trade account receivable of Borrower
     for goods sold or leased or for services rendered by Borrower in the
     ordinary course of its business.

     Account Debtor. The words "Account Debtor" mean the person or entity
     obligated upon an Account.

     Advance. The word "Advance" means any advance or other disbursement of Loan
     proceeds under this Agreement.

     Borrower. The word "Borrower" means CARRIER ACCESS CORPORATION, A DELAWARE
     CORPORATION.

     Borrowing Base. The words "Borrowing Base" mean The Borrowing Base will be,
     as determined by Lender from time to time, the lesser of (a) $5,000,000.00;
     or (b) the sum of (i) 75.00% of the aggregate amount of Eligible Accounts,
     plus (ii) 50.00% of the aggregate amount of Eligible Inventory backed by
     eligible purchase orders not exceeding $500,000.00 or the Accounts
     Receivable Borrowing Base, whichever is less.

     Collateral. The word "Collateral" means and includes without limitation all
     property and assets granted as collateral for any 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.

     Committed Sum. The words "Committed Sum" mean an amount equal to
     $5,000,000.00.

     Eligible Accounts. The words "Eligible Accounts" mean, at any time, all of
     Borrower's Accounts which contain terms and conditions acceptable to Lender
     and in which Lender has a first lien security interest, less the amount of
     all returns, discounts, credits, and offsets of any nature; provided,
     however, unless otherwise agreed to by Lender in writing, Eligible Accounts
     do not include;

           (a) Accounts with respect to which the Account Debtor is an officer,
           an employee or agent of Borrower and to which the Account Debtor is a
           subsidiary of, or affiliated with or related to Borrower or its
           shareholders, officers, or directors.

           (b) All Accounts with respect to which Borrower has furnished a
           payment and/or performance bond and that portion of any Accounts for
           or representing retainage, if any, until all prerequisites to the
           immediate payment of such retainage have been satisfied.

           (c) Accounts with respect to which goods are placed on consignment or
           subject to a guaranteed sale or other terms by reason of which the
           payment by the Account Debtor may be conditional.

           (d) Accounts with respect to which the Account Debtor is not a
           resident of, or whose principal place of business is located outside
           of, the United States or its territories, except to the extent such
           Accounts are supported by insurance, bonds or other assurances
           satisfactory to Lender in its sole and absolute discretion.

           (e) Accounts with respect to which Borrower is or may become liable
           to the Account Debtor for goods sold or services rendered by the
           Account Debtor to Borrower.

           (f) Accounts which are subject to dispute, counterclaim, of setoff.

           (g) Accounts with respect to which all goods have not been shipped or
           delivered, or all services have not been rendered, to the Account
           Debtor.

           (h) Accounts with respect to which Lender, in its sole discretion,
           deems the creditworthiness or financial condition of the Account
           Debtor to be unsatisfactory.

           (i) Accounts of any Account Debtor who has filed or has had filed
           against it a petition in bankruptcy or an application for relief
           under any provision of any state or federal bankruptcy, insolvency,
           or debtor-in-relief acts; or who has had appointed a trustee,
           custodian, or receiver for the assets of such Account Debtor; or who
           has made an assignment for the benefit of creditors or has become
           insolvent or fails generally to pay its debts (including its
           payrolls) as such debts become due.

           (j) Accounts which have not been paid or are not due and payable in
           full within 90 days from the original invoice date.

     Eligible Inventory. The words "Eligible Inventory" mean, at any time, the
     aggregate value of all of Borrower's Inventory as defined below except:

           (a) Inventory which is not owned by Borrower free and clear of all
           security interests, liens, encumbrances, and claims of third parties,
           except Lender's security interest.

           (b) Inventory which Lender, in its sole and absolute discretion,
           deems to be obsolete, unsalable, damaged, defective, or unfit for
           further processing.

           (c) Inventory which has been returned or rejected.

           (d) Inventory which is held by others on consignment, sale on
           approval or otherwise not in Borrower's physical possession, except
           upon the written consent of Lender.

           (e) Inventory located outside the United States.

     For purposes of this Agreement, Eligible Inventory shall be valued at the
     lower of cost or market value.

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

     Grantor. The word "Grantor" means and includes each and all of the persons
     or entities granting a Security Interest in any Collateral for any of the
     Loans.

     Guarantor. The word "Guarantor" means and includes without limitation, each
     and all of the guarantors, sureties, and accommodation parties for any of
     the Loans.

     Indebtedness. The word "Indebtedness" means the indebtedness evidenced by
     the Note, including all principal and accrued interest thereon, together
     with all other liabilities, costs and expenses for which Borrower is
     responsible under this Agreement or under any of the Related Documents. In
     addition, the word "Indebtedness" includes all other obligations, debts and
     liabilities, plus any accrued interest

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07-02-1999                        LOAN AGREEMENT                          Page 2
Loan No.                           (Continued)
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     thereon, owing by Borrower, or any one or more of them, to Lender of any
     kind or character, now existing or hereafter arising, as well as all
     present and future claims by Lender against Borrower, or any one or more of
     them, and all renewals, extensions, modifications, substitutions and
     rearrangements of any of the foregoing; whether such Indebtedness arises by
     note, draft, acceptance, guaranty, endorsement, letter of credit,
     assignment, overdraft, indemnity agreement or otherwise; whether such
     Indebtedness is voluntary or involuntary, due or not due, direct or
     indirect, absolute or contingent, liquidated or unliquidated; whether
     Borrower may be liable individually or jointly with others; whether
     Borrower may be liable primarily or secondarily or as debtor, maker,
     comaker, drawer, endorser, guarantor, surety, accommodation party or
     otherwise.

     Inventory. The word "Inventory" means all raw materials and all tangible
     personal property, goods, merchandise and other personal property now owned
     or hereafter acquired by Borrower which is held for sale or lease in the
     ordinary course of Borrower's business, excluding all work in progress,
     spare parts, packaging materials, supplies and any advertising costs
     capitalized into inventory.

     Lender. The word "Lender" means Bank One, Colorado, NA, its successors and
     assigns.

     Line of Credit. The words "Line of Credit" mean the credit facility
     described in the Section titled "LINE OF CREDIT" below.

     Note. The word "Note" means any and all promissory note or notes which
     evidence Borrower's Loans in favor of Lender, as well as any amendment,
     modification, renewal or replacement thereof.

     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 (i) not yet due, or (ii)
     being contested in good faith by appropriate proceedings and for which
     Borrower has established adequate reserves; (c) 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 any indebtedness
     permitted under this Agreement; and (d) liens and security interests which,
     as of the date of this Agreement, have been disclosed to and approved by
     the Lender in writing.

     Related Documents. The words "Related Documents" mean and include without
     limitation the Note and all 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 Note.

     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 security interest, 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, 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.

Line of Credit. Subject to the other terms and conditions herein, Lender hereby
establishes a Line of Credit for Borrower through which Lender agrees to make
advances to Borrower from time to time from the effective date of this Agreement
until the maturity date of the Note evidencing the Line of Credit, provided the
aggregate amount of such advances outstanding at any time does not exceed the
lesser of the amount equal to the Borrowing Base or an amount equal to the
Committed Sum. Within the foregoing limits, Borrower may borrow, partially or
wholly prepay, and reborrow under this Agreement.

     Borrowing Base Compliance. If at any time the aggregate principal amount
     outstanding under the Line of Credit shall exceed the applicable Borrowing
     Base, Borrower shall pay to Lender an amount equal to the difference
     between the outstanding principal balance under the Line of Credit and the
     Borrowing Base.

     Representations and Warranties Concerning Accounts. With respect to the
     Accounts, Borrower represents and warrants to Lender: (a) Each Account
     represented by Borrower to be an Eligible Account for purposes of this
     Agreement conforms to the requirements of the definition of an Eligible
     Account; and (b) All Account information listed on reports and schedules
     delivered to Lender will be true and correct, subject to immaterial
     variance.

     Representations and Warranties Concerning Inventory. With respect to the
     Inventory, Borrower represents and warrants to Lender: (a) All Inventory
     represented by Borrower to be Eligible Inventory for purposes of this
     Agreement conforms to the requirements of the definition of Eligible
     Inventory; (b) All Inventory values listed on schedules delivered to Lender
     will be true and correct, subject to immaterial variance; (c) The value of
     the Inventory will be determined on a consistent accounting basis; (d)
     Except as reflected in the Inventory schedules delivered to Lender, all
     Eligible Inventory is now and at all times hereafter will be of good and
     merchantable quality, free from defects; and (e) Lender, its assigns, or
     agents shall have the right at any time and at Borrower's expense to
     inspect and examine the Inventory and to check and test the same as to
     quality, quantity, value, and condition.

Representations and Warranties. Borrower represents and warrants to Lender, as
of the date of this Agreement, as of the date of each request for an Advance, as
of the date of any renewal, extension or modification of any Loan, and at all
times any Loans or Lender's commitment to make Loans hereunder is outstanding:

     Organization. Borrower is a corporation which is duly organized, validly
     existing, and in good standing under the laws of the State of Delaware and
     is duly qualified and in good standing in all other 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.

     Authorization. The execution, delivery, and performance of this Agreement
     and all Related Documents to which Borrower is a party 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 certificate of incorporation, or bylaws, or
     any agreement or other instrument binding upon Borrower or (b) any law,
     governmental regulation, court decree, or order applicable to Borrower.
     Borrower has all requisite power and authority to execute and deliver this
     Agreement and all other Related Documents to which Borrower is a party.

     Financial Information. Each financial statement of Borrower supplied to
     Lender truly and completely discloses 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 and all other Related Documents to which
     Borrower is a party constitute legal, valid and binding obligations of
     Borrower enforceable against Borrower in accordance with their respective
     terms, except as limited by bankruptcy, insolvency or similar laws of
     general application relating to the enforcement of creditors' rights and
     except to the extent specific remedies may generally be limited by
     equitable principles.

     Properties. Except for Permitted Liens, Borrower is the sole owner of, 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
     six (6) years.

     Compliance. Except as disclosed in writing to Lender (a) Borrower is
     conducting Borrower's businesses in material compliance with all applicable
     federal, state and local laws, statutes, ordinances, rules, regulations,
     orders, determinations and court decisions, including without limitation,
     those pertaining to health or environmental matters, and (b) Borrower
     otherwise does not have any known material contingent liability in
     connection with the release into the environment, disposal or the improper
     storage of any toxic or hazardous substance or solid waste.

     Litigation and Claims. No litigation, claim, investigation, administrative
     proceeding or similar action (including those for unpaid taxes) against
     Borrower is pending or threatened, and no other event has occurred which
     may in any one case or in the aggregate 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. 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 that have been
     disclosed in writing to Lender which are 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 and approved by
     Lender in writing, Borrower has not entered into any Security Agreements,
     granted a Security Interest or permitted the filing or attachment of any
     Security Interests on or affecting any of the Collateral, except in favor
     of Lender.

     Licenses, Trademarks and Patents. Borrower possesses and will continue to
     possess all permits, licenses, trademarks, patents and rights thereto which
     are needed to conduct Borrower's business and Borrower's business does not
     conflict with or violate any valid rights of others with respect to the
     foregoing.

     Commercial Purposes.  Borrower intends to use the Loan proceeds soley for
     business or commercial related purposes approved by Lender.
<PAGE>

07-02-1999                      LOAN AGREEMENT                            Page 3
Loan No                           (Continued)

================================================================================

and such proceeds will not be used for the purchasing or carrying of "margin
stock" as defined in Regulation U issued by the Board of Governors of the
Federal Reserve System.

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.

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 5395 PEARL PARKWAY, BOULDER, CO 80301. 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.

Survival of Representations and Warranties. Borrower understands and agrees that
Lender, without independent investigation, is relying upon the above
representations and warranties in extending the Loans to Borrower. Borrower
further agrees that the foregoing representations and warranties shall be
continuing in nature and shall remain in full force and effect during the term
of this Agreement.

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

Depository Relationship. Establish and maintain its primary operating accounts
with Lender.

Litigation. Promptly inform Lender in writing of (a) all material adverse
changes in Borrower's financial condition, (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, and
(c) the creation, occurrence or assumption by Borrower of any actual or
contingent liabilities not permitted under this Agreement.

Financial Records. Maintain its books and records in accordance with generally
accepted accounting principles, applied on a consistent basis, and permit Lender
to examine, audit and make and take away copies or reproductions of Borrower's
books and records at all reasonable times. 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.

Financial Statements. Furnish Lender with, as soon as available, but in no event
later than one hundred twenty (120) days after the end of each fiscal year,
Borrower's balance sheet, income statement, and statement of changes in
financial position 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 five (35) days after the end of each fiscal quarter, Borrower's balance
sheet, income statement, and statement of changes in financial position for the
period ended, prepared and certified, subject to year-end review adjustments, 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 at all times with the following covenants
and ratios:

     Debt to Tangible Net Worth Ratio. Maintain, at all times, a ratio of total
     liabilities to Tangible Net Worth of less than 1.25 TO 1.00.

     Current Ratio. Maintain, at all times, a ratio of Liquid Assets plus
     inventory, to current liabilities in excess of 1.50 TO 1.00.

For purposes of this Agreement and to the extent the following terms are
utilized in this Agreement, the term "Tangible Net Worth" shall mean borrower's
total assets excluding all intangible assets (including, without limitation,
goodwill, trademarks, patents, copyrights, organization expenses, and similar
intangible items) less total liabilities excluding Subordinated Debt. The term
"Subordinated Debt" shall mean all indebtedness owing by Borrower which has been
subordinated by written agreement to all indebtedness now or hereafter owing by
Borrower to Lender, such agreement to be in form and substance acceptable to
Lender. The term "Working Capital" shall mean Borrower's Liquid Assets plus
inventory, less current liabilities. The term "Liquid Assets" shall mean
borrower's unencumbered cash, marketable securities and accounts receivable net
of reserves. The term "Cash Flow" shall mean net income after taxes, and
exclusive of extraordinary items, plus depreciation and amortization. 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.

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 thirty (30) days' prior
written notice to Lender. 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.

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 Fees and Charges. In addition to all other agreed upon fees and charges,
pay the following: UNUSED BALANCE FEE OF .25%.

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 principles. 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. 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, all applicable environmental statutes, rules, regulations and
ordinances and with all minimum funding standards and other requirements of
ERISA and other laws applicable to Borrower's employee benefit plans.

Compliance Certificate. Unless waived in writing by Lender, provide Lender 35
days after each calendar quarter with a certificate executed by Borrower's chief
financial officer, or other officer or person acceptable to Lender, (a)
certifying that the representations and warranties set forth in this Agreement
are true and correct as of the date of the certificate and that, as of the date
of the certificate, no Event of Default exists under this Agreement, and (b)
demonstrating compliance with all financial covenants set forth in this
Agreement.

Environmental Compliance and Reports. Borrower shall comply in all respects with
all federal, state and local environment 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
<PAGE>

07-02-1999                      LOAN AGREEMENT                            Page 4
Loan No                          (Continued)
================================================================================
      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; and 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.

      Borrowing Base Certificate. Within 35 days after each month when line is
      in use, Borrower shall deliver to Lender a borrowing base certificate, in
      form and detail satisfactory to Lender, along with such supporting
      documentation as Lender may request, including without limitation, an
      accounts receivable aging report and/or a list or schedule of Borrower's
      accounts receivable, inventory and/or equipment.

      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:

      Maintain Basic Business. Engage in any business activities substantially
      different than those in which Borrower is presently engaged.

      Continuity of Operations. Cease operations, liquidate, dissolve or merge
      or consolidate with or into any other entity.

      Indebtedness. Create, incur or assume additional indebtedness for borrowed
      money, including capital leases, or guarantee any indebtedness owing by
      others, other than (a) current unsecured trade debt incurred in the
      ordinary course of business, (b) indebtedness owing to Lender, (c)
      borrowings outstanding as of the date hereof and disclosed to Lender in
      writing, and (d) any borrowings otherwise approved by Lender in writing.

      Liens. Mortgage, assign, pledge, grant a security interest in or otherwise
      encumber Borrower's assets, except as allowed as a Permitted Lien.

      Transfer of Assets. Transfer, sell or otherwise dispose of any of
      Borrower's assets other than in the ordinary course of business.

      Change in Management. Permit a change in the senior executive or
      management personnel of Borrower.

      Transfer of Ownership. Permit the sale, pledge or other transfer of any
      ownership interest in Borrower.

      Investments. Invest in, or purchase, create, form or acquire any interest
      in, any other enterprise or entity.

      Loans. Make any loans to any person or entity.

      Dividends. Pay any dividends on Borrower's capital stock or purchase,
      redeem, retire or otherwise acquire any of Borrower's capital stock or
      alter or amend Borrower's capital structure.

      Affiliates. Enter into any transaction, including, without limitation, the
      purchase, sale, or exchange of property or the rendering of any service,
      with any Affiliate of Borrower, except in the ordinary course of and
      pursuant to the reasonable requirements of Borrower's business and upon
      fair and reasonable terms no less favorable than would be obtained in a
      comparable arm's length transaction with a person or entity not an
      Affiliate of Borrower. As used herein, the term "Affiliate" means any
      individual or entity directly or indirectly controlling, controlled by or
      under common control with, another entity or individual.

CONDITIONS PRECEDENT TO ADVANCES. Lender's obligation to make any Advances or to
provide any other financial accommodations to or for the benefit of Borrower
hereunder shall be subject to the conditions precedent that as of the date of
such advance or disbursement and after giving effect thereto (a) all
representations and warranties made to Lender in this Agreement and the Related
Documents shall be true and correct as of and as if made on such date, (b) no
material adverse change in the financial condition of Borrower or any Guarantor
since the effective date of the most recent financial statements furnished to
Lender, or in the value of any Collateral, shall have occurred and be
continuing, (c) no event has occurred and is continuing, or would result from
the requested advance or disbursement, which with notice or lapse of time, or
both, would constitute an Event of Default, (d) no Guarantor has sought, claimed
or otherwise attempted to limit, modify or revoke such Guarantor's guaranty of
any Loan, and (e) Lender has received all Related Documents appropriately
executed by Borrower and all other proper parties.

ADDITIONAL AFFIRMATIVE COVENANT - TANGIBLE NET WORTH. Borrower covenants and
agrees with Lender that, while this Agreement is in effect, Borrower will comply
at all times with the following covenant and ratio. Borrower will maintain a
minimum Tangible Net Worth of $16,000,000.00 plus 75% of the net proceeds from
any public and/or private equity offering.

LINE OF CREDIT CLEARANCE. Borrower shall, at least once during "the term of the
Line of Credit" reduce and maintain the outstanding principal balance of the
Line of Credit to ZERO for a period of at least thirty (30) consecutive calendar
days.

ADDITIONAL AFFIRMATIVE COVENANT - ACCOUNTS RECEIVABLE AGINGS. Borrower shall
furnish to Lender a listing and aging of all accounts receivable within thirty-
five (35) days of each quarter end.

ADDITIONAL PROVISION. Notwithstanding anything to the contrary contained in this
Agreement, if Borrower's net shareholder's equity is in excess of
$45,000,000.00, then Borrower may, without the prior written consent of Lender,
invest in, or purchase, create, form or acquire an interest in any other
enterprise or entity.

RIGHT OF SETOFF. Unless a lien would be prohibited by law or would render a
nontaxable account taxable, Borrower grants to Lender a contractual possessory
security interest in, and hereby assigns, conveys, delivers, pledges, and
transfers to Lender all Borrower's right, title and interest in and to,
Borrower's accounts with Lender (whether checking, savings, or any other
account), including without limitation all accounts held jointly with someone
else and all accounts Borrower may open in the future. Borrower authorizes
Lender, to the extent permitted by applicable law, to charge or setoff all sums
owing on the Indebtedness against any and all such accounts.

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 any of the Indebtedness.

      Other Defaults. Failure of Borrower, any Guarantor or any Grantor to
      comply with or to perform when due any other term, obligation, covenant or
      condition contained in this Agreement, the Note or in any of the other
      Related Documents, or failure of Borrower to comply with or to perform any
      other term, obligation, covenant or condition contained in any other
      agreement now existing or hereafter arising between Lender and Borrower.

      False Statements. Any warranty, representation or statement made or
      furnished to Lender under this Agreement or the Related Documents is false
      or misleading in any material respect.

      Default to Third Party. The occurrence of any event which permits the
      acceleration of the maturity of any indebtedness owing by Borrower,
      Grantor or any Guarantor to any third party under any agreement or
      undertaking.

      Bankruptcy or Insolvency. If the Borrower, Grantor or any Guarantor: (i)
      becomes insolvent, or makes a transfer in fraud of creditors, or makes an
      assignment for the benefit of creditors, or admits in writing its
      inability to pay its debts as they become due; (ii) generally is not
      paying its debts as such debts become due; (iii) has a receiver, trustee
      or custodian appointed for, or take possession of, all or substantially
      all of the assets of such party or any of the Collateral, either in a
      proceeding brought by such party or in a proceeding brought against such
      party and such appointment is not discharged or such possession is not
      terminated within sixty (60) days after the effective date thereof or such
      party consents to or acquiesces in such appointment or possession; (iv)
      files a petition for relief under the United States Bankruptcy Code or any
      other present or future federal or state insolvency, bankruptcy or similar
      laws (all of the foregoing hereinafter collectively called "Applicable
      Bankruptcy Law") or an involuntary petition for relief is filed against
      such party under any Applicable Bankruptcy Law and such involuntary
      petition is not dismissed within sixty (60) days after the filing thereof,
      or an order for relief naming such party is entered under any Applicable
      Bankruptcy Law, or any composition, rearrangement, extension,
      reorganization or other relief of debtors now or hereafter existing is
      requested or consented to by such party; (v) fails to have discharged
      within a period of sixty (60) days any attachment, sequestration or
      similar writ levied upon any property of such party; or (vi) fails to pay
      within thirty (30) days any final money judgment against such party.

      Liquidation, Death and Related Events. If Borrower, Grantor or any
      Guarantor is an entity, the liquidation, dissolution, merger or
      consolidation of any such entity or, if any of such parties is an
      individual, the death or legal incapacity of any such individual.

      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.

EFFECT OF AN EVENT OF DEFAULT. If any Event of Default shall occur, Lender may,
at its option, without further notice or demand, (a) terminate all commitments
and obligations of Lender to make Loans to Borrower, if any, (b) declare all
Loans and any other indebtedness

<PAGE>

07-02-1999                       LOAN AGREEMENT                           Page 5
Loan No                            (Continued)
================================================================================
immediately due and payable, (c) refuse to advance any additional amounts under
the Note or to provide any other financial accommodations under this Agreement,
or (d) exercise all the rights and remedies provided in the Note or in any of
the Related Documents or available at law, in equity, or otherwise; provided,
however, if any Event of Default of the type described in the "Bankruptcy or
Insolvency" subsection above shall occur, all Loans and any other Indebtedness
shall automatically become due and payable, without any notice, demand or action
by Lender. 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.

     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 Colorado. Subject to the provisions on arbitration,
     this Agreement shall be governed by and construed in accordance with the
     laws of the State of Colorado without regard to any conflict of laws or
     provisions thereof.

     JURY WAIVER. THE UNDERSIGNED AND LENDER (BY ITS ACCEPTANCE HEREOF) HEREBY
     VOLUNTARILY, KNOWINGLY, IRREVOCABLY AND UNCONDITIONALLY WAIVE ANY RIGHT TO
     HAVE A JURY PARTICIPATE IN RESOLVING ANY DISPUTE (WHETHER BASED UPON
     CONTRACT, TORT OR OTHERWISE) BETWEEN OR AMONG THE UNDERSIGNED AND LENDER
     ARISING OUT OF OR IN ANY WAY RELATED TO THIS DOCUMENT OR ANY OTHER RELATED
     DOCUMENT. THIS PROVISION IS A MATERIAL INDUCEMENT TO LENDER TO PROVIDE THE
     FINANCING DESCRIBED HEREIN OR IN THE OTHER RELATED DOCUMENTS.

     ARBITRATION. Lender and Borrower agree that upon the written demand of
     either party, whether made before or after the institution of any legal
     proceedings, but prior to the rendering of any judgment in that proceeding,
     all disputes, claims and controversies between them, whether individual,
     joint, or class in nature, arising from this Agreement, any Related
     Document or otherwise, including without limitation contract disputes and
     tort claims, shall be arbitrated pursuant to the Commercial Rules of the
     American Arbitration Association. Any arbitration proceeding held pursuant
     to this arbitration provision shall be conducted in the city nearest the
     Borrower's address having an AAA regional office, or at any other place
     selected by mutual agreement of the parties. No act to take or dispose of
     any Collateral shall constitute a waiver of this arbitration agreement or
     be prohibited by this arbitration agreement. This arbitration provision
     shall not limit the right of either party during any dispute, claim or
     controversy to seek, use, and employ ancillary, provisional or preliminary
     rights and/or remedies, judicial or otherwise, for the purposes of
     realizing upon, preserving, protecting, foreclosing upon or proceeding
     under forcible entry and detainer for possession of, any real or personal
     property, and any such action shall not be deemed an election of remedies.
     This includes, without limitation, obtaining injunctive relief or a
     temporary restraining order, invoking a power of sale under any deed of
     trust or mortgage, obtaining a writ of attachment or imposition of a
     receivership, or exercising any rights relating to personal property,
     including taking or disposing of such property with or without judicial
     process pursuant to Article 9 of the Uniform Commercial Code. Any disputes,
     claims, or controversies concerning the lawfulness or reasonableness of any
     act, or exercise of any right or remedy, concerning any Collateral,
     including any claim to rescind, reform, or otherwise modify any agreement
     relating to the Collateral, shall also be arbitrated; provided however that
     no arbitrator shall have the right or the power to enjoin or restrain any
     act of either party. Judgment upon any award rendered by any arbitrator may
     be entered in any court having jurisdiction. Nothing in this arbitration
     provision shall preclude either party from seeking equitable relief from a
     court of competent jurisdiction. The statute of limitations, estoppel,
     waiver, laches and similar doctrines which would otherwise be applicable in
     an action brought by a party shall be applicable in any arbitration
     proceeding, and the commencement of an arbitration proceeding shall be
     deemed the commencement of any action for this purpose. The Federal
     Arbitration Act (Title 9 of the United States Code) shall apply to the
     construction, interpretation, and enforcement of this arbitration
     provision.

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

     Consent to Loan Participation. Borrower agrees and consents to Lender's
     sale or transfer, whether now or later, of one or more participation
     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.

     Costs and Expenses. Borrower agrees to pay upon demand all of Lender's
     expenses, including 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 hire one or more attorneys to help collect the Indebtedness if
     Borrower does not pay, and Borrower will pay Lender's reasonable attorneys'
     fees.

     Notices. All notices required to be given under this Agreement shall be
     given in writing, 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, it 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.

     Counterparts. This Agreement may be executed in one or more counterparts,
     each of which shall be deemed an original and all of which together shall
     constitute the same document. Signature pages may be detached from the
     counterparts to a single copy of this Agreement to physically form one
     document.

     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.

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

     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 or Guarantor, 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 consents may be granted or
withheld in the sole discretion of Lender
<PAGE>

07-02-1999                       LOAN AGREEMENT                           Page 6
Loan No                           (Continued)

================================================================================

BORROWER ACKNOWLEDGES HAVING READ ALL THE PROVISIONS OF THIS LOAN AGREEMENT, AND
BORROWER AGREES TO ITS TERMS. THIS AGREEMENT IS EXECUTED AS OF THE DATE SET
FORTH ABOVE.

BORROWER:

CARRIER ACCESS CORPORATION, A DELAWARE CORPORATION

By: /s/ Nancy Pierce
   -----------------------------------------------
   NANCY PIERCE, CFO TREAS/SECRETARY

LENDER:

Bank One, Colorado, NA

By:
   -----------------------------------------------
   Authorized Officer
<PAGE>

                        CORPORATE RESOLUTION TO BORROW

--------------------------------------------------------------------------------
    Principal      Loan Date      Maturity     Loan No.    Call     Collateral
  $5,000,000.00    07-02-1999    07-02-2000               078105       328

    Account         Officer       Initials
   1518454676        00410
--------------------------------------------------------------------------------
   References in the shaded area are for Lender's use only and do not limit the
   applicability of this document to any particular loan or item.
--------------------------------------------------------------------------------

Borrower:  CARRIER ACCESS CORPORATION,      Lender: Bank One, Colorado, NA
           A DELAWARE CORPORATION                   Corporate Lending - Boulder
           5395 PEARL PARKWAY                       1125 17TH STREET
           BOULDER,CO 80301                         DENVER, CO 80217

================================================================================

1, the undersigned officer of CARRIER ACCESS CORPORATION, A DELAWARE CORPORATION
(the "Corporation"), HEREBY CERTIFY that the Corporation is organized and
existing under and by virtue of the laws of the State of Delaware as a
corporation for profit, with its principal office at 5395 PEARL PARKWAY,
BOULDER, CO 80301, and is duly authorized to transact business in the State of
Colorado.

I FURTHER CERTIFY that at a meeting of the Directors of the Corporation, duly
called and held and at which a quorum was present and voting, or by other duly
authorized corporate action in lieu of a meeting, the following resolutions were
adopted:

BE IT RESOLVED, that any one (1) of the following named officers, employees, or
agents of this Corporation, whose actual signatures are shown below:

        NAMES                   POSITIONS                ACTUAL SIGNATURES
        -----                   ---------                -----------------

        ROGER L. KOENIG         PRESIDENT AND CEO        /s/ Roger L. Koenig

        NANCY PIERCE            CFO TREAS/SECRETARY      /s/ Nancy Pierce

acting for and on behalf of the Corporation and as its act and deed be, and they
hereby are, authorized and empowered:

  Borrow Money. To negotiate and borrow money from Bank One, Colorado, NA
  ("Lender"), including letters of credit, and guarantee borrowings of others,
  on such terms as may be agreed upon between the Corporation's officers,
  employees or agents named above and Lender, and in such amount or amounts as
  in their judgment should be borrowed and/or guaranteed, without limitation.

  Execute Evidences of Debt. To execute and deliver to Lender promissory notes,
  checks, drafts, acceptances, agreements (including without limitation loan
  agreements), and guarantees of the Corporation at such rates of interest and
  on such terms as may be agreed upon between the Corporation's officers,
  employees or agents named above, and Lender, evidencing sums of money borrowed
  or guaranteed, or any indebtedness or obligation of the Corporation to Lender,
  and also to execute and deliver to Lender one or more renewals, extensions,
  modifications, refinancings, consolidations or substitutions for any one or
  more of, or any portion of, the foregoing.

  Grant Security. To mortgage, pledge, transfer, endorse, hypothecate, or
  otherwise encumber and deliver to Lender, as security for the payment of any
  loans so obtained or guaranteed, any promissory notes so executed or any other
  or further indebtedness of the Corporation or of others to Lender at any time
  owing, however the same may be evidenced, any property now or hereafter
  belonging to the Corporation or in which the Corporation now or hereafter may
  have an interest, including without limitation all real property and all
  personal property (tangible or intangible) of the Corporation. Such property
  may be mortgaged, pledged, transferred, endorsed, hypothecated, or encumbered
  at the time such loans are obtained or such indebtedness is incurred, or at
  any other time or times, and may be either in addition to or in lieu of any
  property theretofore mortgaged, pledged, transferred, endorsed, hypothecated,
  or encumbered.

  Execute Security Documents. To execute and deliver to Lender the forms of
  mortgage, deed of trust, pledge agreement, hypothecation agreement, and other
  security agreements and financing statements which may be submitted by Lender,
  and which shall evidence the terms and conditions under and pursuant to which
  such liens and encumbrances, or any of them, are given; and also to execute
  and deliver to Lender any other written instruments, any chattel paper, or any
  other collateral, of any kind or nature, which they may in their discretion
  deem reasonably necessary or proper in connection with or pertaining to the
  giving of the liens and encumbrances.

  Negotiate Items. To draw, endorse, and discount with Lender all drafts, trade
  acceptances, promissory notes, or other evidences of indebtedness payable to
  or belonging to the Corporation in which the Corporation may have an interest,
  and either to receive cash for the same or to cause such proceeds to be
  credited to the account of the Corporation with Lender, or to cause such other
  disposition of the proceeds derived therefrom as they may deem advisable.

  Further Acts. In the case of lines of credit, to designate additional or
  alternate individuals as being authorized to request advances thereunder, and
  in all cases, to do and perform such other acts and things, to pay any and all
  fees and costs, and to execute and deliver such other documents and
  agreements, including agreements waiving the right to a trial by jury, as they
  may in their discretion deem reasonably necessary or proper in order to carry
  into effect the provisions of these Resolutions.

BE IT FURTHER RESOLVED, that any and all acts authorized pursuant to these
Resolutions and performed prior to the passage of these Resolutions are hereby
ratified and approved, that these Resolutions shall remain in full force and
effect and Lender may rely on these Resolutions until written notice of their
revocation shall have been delivered to and received by Lender. Any such notice
shall not affect any of the Corporation's agreements or commitments in effect at
the time notice is delivered and received by Lender.

I FURTHER CERTIFY that the officers, employees, and agents named above are duly
elected, appointed, or employed by or for the Corporation, as the case may be,
and occupy the positions set opposite their respective names; that the foregoing
Resolutions now stand of record on the books of the Corporation; and that the
Resolutions are in full force and effect and have not been modified or revoked
in any manner whatsoever.

IN TESTIMONY WHEREOF, I have hereunto set my hand on July 2, 1998 and attest
that the signatures set opposite the names listed above are their genuine
signatures.

                                   CERTIFIED TO AND ATTESTED BY:

                                   X /s/ Nancy Pierce
                                   ---------------------------------------------
                                   (Signature)

                                         Nancy Pierce
                                   ---------------------------------------------
                                   (Printed Name)

                                         SEC/Treasurer/CFO
                                   ---------------------------------------------
                                   (Title)
<PAGE>

BANK1ONE(R)

                         COMMERCIAL SECURITY AGREEMENT

--------------------------------------------------------------------------------
    Principal      Loan Date      Maturity     Loan No.    Call     Collateral
  $5,000,000.00    07-02-1999    07-02-2000               078105       328

    Account         Officer       Initials
   1518454676        00410
--------------------------------------------------------------------------------

    References in the shaded area are for Lender's use only and do not limit the
applicability of this document to any particular loan or item.

Borrower:  CARRIER ACCESS CORPORATION,      Lender: BANK ONE, COLORADO, NA
           A DELAWARE CORPORATION                   Corporate Lending - Boulder
           5395 PEARL PARKWAY                       1125 17TH STREET
           BOULDER,CO 80301                         DENVER, CO 80217

================================================================================

THIS COMMERCIAL SECURITY AGREEMENT is entered into by CARRIER ACCESS
CORPORATION, A DELAWARE CORPORATION (referred to below as "Grantor") for the
benefit of Bank One, Colorado, NA (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 as adopted in
the State of Colorado ("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:

         All inventory, chattel paper, accounts, equipment, general intangibles,
         excluding patents

     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 proceeds (including, without limitation, insurance proceeds)
         from the sale, lease, destruction, loss, or other disposition of any of
         the property described in this Collateral section.

         (d) 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
         Grantor's 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 any of the
     Events of Default set forth below in the section titled "Events of
     Default."

     Grantor. The word "Grantor" means CARRIER ACCESS CORPORATION, A DELAWARE
     CORPORATION, its successors and assigns (which is a debtor under the Code).

     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 the indebtedness evidenced by
     the Note, including all principal and accrued interest thereon, together
     with all other liabilities, costs and expenses for which Grantor is
     responsible under this Agreement or under any of the Related Documents. In
     addition, the word "Indebtedness" includes all other obligations, debts and
     liabilities, plus any accrued interest thereon, owing by Grantor, or any
     one or more of them, to Lender of any kind or character, now existing or
     hereafter arising, as well as all present and future claims by Lender
     against Grantor, or any one or more of them, and all renewals, extensions,
     modifications, substitutions and rearrangements of any of the foregoing;
     whether such Indebtedness arises by note, draft, acceptance, guaranty,
     endorsement, letter of credit, assignment, overdraft, indemnity agreement
     or otherwise; whether such Indebtedness is voluntary or involuntary, due or
     not due, direct or indirect, absolute or contingent, liquidated or
     unliquidated; whether Grantor may be liable individually or jointly with
     others; whether Grantor may be liable primarily or secondarily or as
     debtor, maker, comaker, drawer, endorser, guarantor, surety, accommodation
     party or otherwise.

     Lender. The word "Lender" means Bank One, Colorado, NA, its successors and
     assigns (which is a secured party under the Code).

     Note. The word "Note" means the promissory note dated July 2, 1998, in the
     principal amount of $5,000,000.00 from CARRIER ACCESS CORPORATION, A
     DELAWARE CORPORATION to Lender, together with all renewals of, extensions
     of, modifications of, refinancings of, consolidations of and substitutions
     for such promissory note.

     Related Documents. The words "Related Documents" mean and include without
     limitation the Note and all 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 Note.

OBLIGATIONS OF GRANTOR. Grantor represents, 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 irrevocably appoints Lender as its
     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 has disclosed to Lender all tradenames and assumed
     names currently used by Grantor, all tradenames and assumed names used by
     Grantor within the previous six (6) years and all of Grantor's current
     business locations. Grantor will notify Lender in writing at least thirty
     (30) days prior to the occurrence of any of the following: (i) any changes
     in Grantor's name, tradename(s) or assumed name(s), or (ii) any change in
     Grantor's business location(s) or the location of any of the Collateral.

     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.

     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 or 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 Colorado, 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
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07-02-1999               COMMERCIAL SECURITY AGREEMENT                    Page 2
Loan No                           (Continued)
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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 is the owner of the
Collateral and 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 governmental charges or levies upon the Collateral and provide Lender
evidence of such payment upon its request. 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 is conducting and will
continue to conduct Grantor's businesses in material compliance with all
federal, state and local laws, statutes, ordinances, rules, regulations, orders,
determinations and court decisions applicable to Grantor's businesses and to the
production, disposition or use of the Collateral, including without limitation,
those pertaining to health and environmental matters such as the Comprehensive
Environmental Response, Compensation, and Liability Act of 1980, as amended by
the Superfund Amendments and Reauthorization Act of 1986 (collectively, together
with any subsequent amendments, hereinafter called "CERCLA"), the Resource
Conservation and Recovery Act of 1976, as amended by the Used Oil Recycling Act
of 1980, the Solid Waste Disposal Act Amendments of 1980, and the Hazardous
Substance Waste Amendments of 1984 (collectively, together with any subsequent
amendments, hereinafter called "RCRA"). Grantor represents and warrants that (i)
none of the operations of Grantor is the subject of a federal, state or local
investigation evaluating whether any material remedial action is needed to
respond to a release or disposal of any toxic or hazardous substance or solid
waste into the environment; (ii) Grantor has not filed any notice under any
federal, state or local law indicating that Grantor is responsible for the
release into the environment, the disposal on any premises in which Grantor is
conducting its businesses or the improper storage, of any material amount of any
toxic or hazardous substance or solid waste or that any such toxic or hazardous
substance or solid waste has been released, disposed of or is improperly stored,
upon any premises on which Grantor is conducting its businesses; and (iii)
Grantor otherwise does not have any known material contingent liability in
connection with the release into the environment, disposal or the improper
storage, of any such toxic or hazardous substance or solid waste. The terms
"hazardous substance" and "release", as used herein, shall have the meanings
specified in CERCLA, and the terms "solid waste" and "disposal", as used herein,
shall have the meanings specified in RCRA; provided, however, that to the extent
that the laws of the State of Colorado establish meanings for such terms which
are broader than that specified in either CERCLA or RCRA, such broader meanings
shall apply. 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 termination of this Agreement.

Maintenance of Casualty Insurance. Grantor shall procure and maintain all risk
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
thirty (30) 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. If
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.

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. Application of insurance proceeds to
the payment of the Indebtedness will not extend, postpone or waive any payments
otherwise due, or change the amount of such payments to be made and proceeds may
be applied in such order and such amounts as Lender may elect.

Solvency of Grantor. As of the date hereof, and after giving effect to this
Agreement and the completion of all other transactions contemplated by Grantor
at the time of the execution of this Agreement, (i) Grantor is and will be
solvent, (ii) the fair salable value of Grantor's assets exceeds and will
continue to exceed Grantor's liabilities (both fixed and contingent), (iii)
Grantor is paying and will continue to be able to pay its debts as they mature,
and (iv) if Grantor is not an individual. Grantor has and will have sufficient
capital to carry on Grantor's businesses and all businesses in which Grantor is
about to engage.

Lien Not Released. The lien, security interest and other security rights of
Lender hereunder shall not be impaired by any indulgence, moratorium or release
granted by Lender, including but not limited to, the following; (a) any renewal,
extension, increase or modification of any of the Indebtedness; (b) any
surrender, compromise, release, renewal, extension, exchange or substitution
granted in respect of any of the Collateral; (c) any release or indulgence
granted to any endorser, guarantor or surety of any of the Indebtedness; (d) any
release of any other collateral for any of the Indebtedness; (e) any acquisition
of any additional collateral for any of the Indebtedness; and (f) any waiver or
failure to exercise any right, power or remedy granted herein, by law or in any
of the Related Documents.

Request for Environment Inspections. Upon Lender's reasonable request from time
to time, Grantor will obtain at Grantor's expense an inspection or audit
report(s) addressed to Lender of Grantor's operations from an engineering or
consulting firm approved by Lender, indicating the presence or absence of toxic
and hazardous substances, underground storage tanks and solid waste on any
premises in which Grantor is conducting a business; provided, however, Grantor
will be obligated to pay for the cost of any such inspection or audit no more
than one time in any twelve (12) month period unless Lender has reason to
believe that toxic or hazardous substance or solid wastes have been dumped or
released on any such premises. If Grantor fails to order or obtain an inspection
or audit within ten (10) days after Lender's request, Lender may at its option
order such inspection or audit, and Grantor grants to Lender and its agents,
employees, contractors and consultants access to the premises in which it is
conducting its business and a license (which is coupled with an interest and is
irrevocable) to obtain inspections and audits. Grantor agrees to promptly
provide Lender with a copy of the results of any such inspection or audit
received by Grantor. The cost of such inspections and audits by Lender shall be
a part of the indebtedness, secured by the Collateral and payable by Grantor on
demand.
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07-02-1999                   COMMERCIAL SECURITY AGREEMENT                Page 3
Loan No                               (Continued)

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     Landlord's Waivers. Grantor agrees that upon the request of Lender, Grantor
     shall cause each landlord of real property leased by Grantor at which any
     of the Collateral is located from time to time to execute and deliver
     agreements satisfactory in form and substance to Lender by which such
     landlord waives or subordinates any rights it may have in 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 be payable on demand by
Lender. 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, the
     Note, any of the other Related Documents or in any other agreement now
     existing or hereafter arising between Lender and Grantor.

     False Statements. Any warranty, representation or statement made or
     furnished to Lender under this Agreement, the Note or any of the other
     Related Documents is false or misleading in any material respect.

     Default to Third Party. The occurrence of any event which permits the
     acceleration of the maturity of any indebtedness owing by Grantor or any
     Guarantor to any third party under any agreement or undertaking.

     Bankruptcy or Insolvency. If the Grantor or any Guarantor: (i) becomes
     insolvent, or makes a transfer in fraud of creditors, or makes an
     assignment for the benefit of creditors, or admits in writing its inability
     to pay its debts as they become due; (ii) generally is not paying its debts
     as such debts become due; (iii) has a receiver, trustee or custodian
     appointed for, or take possession of, all or substantially all of the
     assets of such party or any of the Collateral, either in a proceeding
     brought by such party or in a proceeding brought against such party and
     such appointment is not discharged or such possession is not terminated
     within sixty (60) days after the effective date thereof or such party
     consents to or acquiesces in such appointment or possession; (iv) files a
     petition for relief under the United States Bankruptcy Code or any other
     present or future federal or state insolvency, bankruptcy or similar laws
     (all of the foregoing hereinafter collectively called "Applicable
     Bankruptcy Law") or an involuntary petition for relief is filed against
     such party under any Applicable Bankruptcy Law and such involuntary
     petition is not dismissed within sixty (60) days after the filing thereof,
     or an order for relief naming such party is entered under any Applicable
     Bankruptcy Law, or any composition, rearrangement, extension,
     reorganization or other relief of debtors now or hereafter existing is
     requested or consented to by such party; (v) fails to have discharged
     within a period of sixty (60) days any attachment, sequestration or similar
     writ levied upon any property of such party; or (vi) fails to pay within
     thirty (30) days any final money judgment against such party.

     Liquidation, Death and Related Events. If Grantor or any Guarantor is an
     entity, the liquidation, dissolution, merger or consolidation of any such
     entity or, if any of such parties is an individual, the death or legal
     incapacity of any such individual.

     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.

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 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 dispose of the Collateral or the proceeds thereof in its own
     name or that of Grantor. Lender may sell the Collateral (as a unit or in
     parcels) at public auction or private sale. Lender may buy the Collateral,
     or any portion thereof, (i) at any public sale, and (ii) at any private
     sale if the Collateral is of a type customarily sold in a recognized market
     or is of a type which is the subject of widely distributed standard price
     quotations. Lender shall not be obligated to make any sale of Collateral
     regardless of a notice of sale having been given. Lender may adjourn any
     public or private sale from time to time by announcement at the time and
     place fixed therefor, and such sale may, without further notice, be made at
     the time and place to which it was so adjourned. Unless the Collateral is
     perishable or threatens to decline speedily in value or is of a type
     customarily sold on a recognized market, Lender will give Grantor
     reasonable notice of the time and place of any public sale thereof or 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 prior to the date any
     public sale, or after which a private sale, of any of such Collateral is to
     be held. 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. Any sale
     of Collateral through the public trustee shall be deemed a commercially
     reasonable sale.

     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. The receiver may be appointed by a court of competent jurisdiction
     upon ex parte application and without notice, notice being expressly
     waived.

     Collect Revenues, Apply Accounts. Lender, either itself or through a
     receiver, may collect the payments, rents, income, and revenues from the
     Collateral. Lender may 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. 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 collection, 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 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. Grantor waives any right to require Lender to proceed against
     any third party, exhaust any other security for the indebtedness or
     pursue any other right or remedy available to Lender.

     Cumulative Remedies. All of Lender's rights and remedies, whether evidenced
     by this Agreement or the Related Documents or by any

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07-02-1999              COMMERCIAL SECURITY AGREEMENT                     Page 4
Loan No                           (Continued)

================================================================================

     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.

     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 and supercedes all prior written and
     oral agreements and understandings, if any, regarding same. 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 Colorado. Subject to the provisions on arbitration
     in any Related Document, this Agreement shall be governed by and construed
     in accordance with the laws of the State of Colorado without regard to any
     conflict of laws or provisions thereof.

    JURY WAIVER. THE UNDERSIGNED AND LENDER (BY ITS ACCEPTANCE HEREOF) HEREBY
    VOLUNTARILY, KNOWINGLY, IRREVOCABLY AND UNCONDITIONALLY WAIVE ANY RIGHT TO
    HAVE A JURY PARTICIPATE IN RESOLVING ANY DISPUTE (WHETHER BASED UPON
    CONTRACT, TORT OR OTHERWISE) BETWEEN OR AMONG THE UNDERSIGNED AND LENDER
    ARISING OUT OF OR IN ANY WAY RELATED TO THIS DOCUMENT OR ANY OTHER RELATED
    DOCUMENT. THIS PROVISION IS A MATERIAL INDUCEMENT TO LENDER TO PROVIDE THE
    FINANCING DESCRIBED HEREIN OR IN THE OTHER RELATED DOCUMENTS.

    Attorneys' Fees; Expenses. Grantor will upon demand pay to Lender the amount
    of any and all costs and expenses (including without limitation, reasonable
    attorneys' fees and expenses) which Lender may incur in connection with (i)
    the perfection and preservation of the collateral assignment and security
    interests created under this Agreement, (ii) the custody, preservation, use
    or operation of, or the sale of, collection from, or other realization upon,
    the Collateral, (iii) the exercise or enforcement of any of the rights of
    Lender under this Agreement, or (iv) the failure by Grantor to perform or
    observe any of the provisions hereof.

    Termination. Upon (i) the satisfaction in full of the Indebtedness and all
    obligations hereunder, (ii) the termination or expiration of any commitment
    of Lender to extend credit that would become Indebtedness hereunder, and
    (iii) Lender's receipt of a written request from Grantor for the termination
    hereof, this Agreement and the security interests created hereby shall
    terminate. Upon termination of this Agreement and Grantor's written request,
    Lender will, at Grantor's sole cost and expense, return to Grantor such of
    the Collateral as shall not have been sold or otherwise disposed of or
    applied pursuant to the terms hereof and execute and deliver to Grantor such
    documents as Grantor shall reasonably request to evidence such termination.

    Indemnity. Grantor hereby agrees to indemnify, defend and hold harmless
    Lender, and its officers, directors, shareholders, employees, agents and
    representatives (each an "INDEMNIFIED PERSON") from and against any and all
    liabilities, obligations, claims, losses, damages, penalties, actions,
    judgments, suits, costs, expenses or disbursements of any kind or nature
    (collectively, the "Claims") which may be imposed on, incurred by or
    asserted against, any Indemnified Person (whether or not caused by any
    Indemnified Person's sole, concurrent or contributory negligence) arising in
    connection with the Related Documents, the Indebtedness or the Collateral
    (including, without limitation, the enforcement of the Related Documents and
    the defense of any Indemnified Person's action and/or inactions in
    connection with the Related Documents), except to the limited extent that
    the Claims against the Indemnified Person are approximately caused by such
    Indemnified Person's willful misconduct. The indemnification provided for in
    this Section shall survive the termination of this Agreement and shall
    extend and continue to benefit each individual or entity who is or has at
    any time been an Indemnified Person hereunder.

    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.

    Notices. All notices required to be given under this Agreement shall be
    given in writing, 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 irrevocably appoints Lender as its true
    and lawful attorney-in-fact, such power of attorney being coupled with an
    interest, with full power of substitution to do the following in the place
    and stead of Grantor and in the name of Grantor: (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.

    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; provided, however,
    Grantor's rights and obligations hereunder may not be assigned or otherwise
    transferred without the prior written consent of Lender.

    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 to thereafter 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.

GRANTOR ACKNOWLEDGES HAVING READ ALL THE PROVISIONS OF THIS COMMERCIAL SECURITY
AGREEMENT, AND GRANTOR AGREES TO ITS TERMS. THIS AGREEMENT IS DATED JULY 2,
1998.

GRANTOR:

CARRIER ACCESS CORPORATION, A DELAWARE CORPORATION

By: /s/ Nancy Pierce
   -----------------------------------------------
     NANCY PIERCE, CFO TREAS/SECRETARY
<PAGE>

[LOGO OF BANK ONE APPEARS HERE]

                                PROMISSORY NOTE
-------------------------------------------------------------------------------
      Principal          Loan Date       Maturity       Loan No.         Call
    $5,000,000.00       07-02-1999      07-02-2000                      078105
-------------------------------------------------------------------------------
     Collateral         Account           Officer       Initials
        328            1518454676         00410
-------------------------------------------------------------------------------

   References in the shaded area are for Lender's use only and do not limit the
   applicability of this document to any particular loan or item.
--------------------------------------------------------------------------------

Borrower:  CARRIER ACCESS CORPORATION,   Lender: Bank One, Colorado, NA
           A DELAWARE CORPORATION        Corporate Lending - Boulder
           5395 PEARL PARKWAY            1125 17th Street
           BOULDER,CO 80301              Denver, CO 80217

================================================================================

Principal Amount: $5,000,000.00                      Date of Note: July 2, 1999

PROMISE TO PAY. For value received, CARRIER ACCESS CORPORATION, A DELAWARE
CORPORATION ("Borrower") promises to pay to Bank One, Colorado, NA ("Lender"),
or order, in lawful money of the United States of America, the principal amount
of Five Million & 00/100 Dollars ($5,000,000.00) ("Total Principal Amount") or
so much as may be outstanding, together with interest on the unpaid outstanding
principal balance from the date advanced until paid in full.

PAYMENT. This Note shall be payable as follows: Interest shall be due and
payable monthly as it accrues, commencing on August 2, 1999 and continuing on
the same day of each month thereafter during the term of this Note, and the
outstanding principal balance of this Note, together with all accrued but unpaid
interest, shall be due and payable on July 2, 2000. 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 the address designated by Lender
from time to time in writing. If any payment of principal of or interest on this
Note shall become due on a day which is not a Business Day, such payment shall
be made on the next succeeding Business Day. As used herein, the term "Business
Day" shall mean any day other than a Saturday, Sunday or any other day on which
national banking associations are authorized to be closed. Unless otherwise
agreed to, in writing, or otherwise 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, late charges and other charges, provided,
however, upon delinquency or other default, Lender reserves the right to apply
payments among principal, interest, late charges, collection costs and other
charges at its discretion. The books and records of Lender shall be prima facie
evidence of all outstanding principal of and accrued but unpaid interest on this
Note. This Note may be executed in connection with a loan agreement. Any such
loan agreement may contain additional rights, obligations and terms.

VARIABLE INTEREST RATE. The interest rate on this Note is subject to fluctuation
based upon the Prime Rate of interest in effect from time to time (the "Index")
(which rate may not be the lowest, best or most favorable rate of interest which
Lender may charge on loans to its customers). "Prime Rate" shall mean the rate
announced from time to time by Lender as its prime rate. Each change in the rate
to be charged on this Note will become effective without notice on the same day
as the Index changes. Except as otherwise provided herein, the unpaid principal
balance of this Note will accrue interest at a rate per annum which will from
time to time be equal to the sum of the Index, plus 0.000%. NOTICE: Under no
circumstances will the interest rate on this Note be more than the maximum rate
allowed by applicable law.

PREPAYMENT. Borrower may pay without fee all or a portion of the principal
amount owed hereunder earlier than it is due. All prepayments shall be applied
to the indebtedness owing hereunder in such order and manner as Lender may from
time to time determine in its sole discretion.

LATE CHARGE. If a payment is 10 days or more late, Borrower will be charged
5.000% of the regularly scheduled payment or $25.00, whichever is greater, up to
the maximum amount of $250.00 per late charge.

DEFAULT. Borrower will be in default if any of the following happens: (a)
Borrower fails to make any payment of principal or interest when due under this
Note or any other indebtedness owing now or hereafter by Borrower to Lender; (b)
failure of Borrower or any other party to comply with or perform any term,
obligation, covenant or condition contained in this Note or in any other
promissory note, credit agreement, loan agreement, guaranty, security agreement,
mortgage, deed of trust or any other instrument, agreement or document, whether
now or hereafter existing, executed in connection with this Note (the Note and
all such other instruments, agreements, and documents shall be collectively
known herein as the "RELATED DOCUMENTS"); (c) Any representation or statement
made or furnished to Lender herein, in any of the Related Documents or in
connection with any of the foregoing is false or misleading in any material
respect; (d) Borrower or any other party liable for the payment of this Note,
whether as maker, endorser, guarantor, surety or otherwise, becomes insolvent or
bankrupt, has a receiver or trustee appointed for any part of its property,
makes an assignment for the benefit of its creditors, or any proceeding is
commenced either by any such party or against it under any bankruptcy or
insolvency laws; (e) the occurrence of any event of default specified in any of
the other Related Documents or in any other agreement now or hereafter arising
between Borrower and Lender; (f) the occurrence of any event which permits the
acceleration of the maturity of any indebtedness owing now or hereafter by
Borrower to any third party; or (g) the liquidation, termination, dissolution,
death or legal incapacity of Borrower or any other party liable for the payment
of this Note, whether as maker, endorser, guarantor, surety, or otherwise.

LENDER'S RIGHTS. Upon default, Lender may at its option, without further notice
or demand (i) declare the entire unpaid principal balance on this Note, all
accrued unpaid interest and all other costs and expenses for which Borrower is
responsible for under this Note and any other Related Document immediately due,
(ii) refuse to advance any additional amounts under this Note, (iii) foreclose
all liens securing payment hereof, (iv) pursue any other rights, remedies and
recourses available to the Lender, including without limitation, any such
rights, remedies or recourses under the Related Documents, at law or in equity,
or (v) pursue any combination of the foregoing. Upon default, including failure
to pay upon final maturity, Lender, at its option, may also, if permitted under
applicable law, do one or both of the following: (a) increase the variable
interest rate on this Note to 3.000 percentage points over the Index, and (b)
add any unpaid accrued interest to principal and such sum will bear interest
therefrom until paid at the rate provided in this Note (including any increased
rate). The interest rate will not exceed the maximum rate permitted by
applicable law. Lender may hire an attorney to help collect this Note if
Borrower does not pay and Borrower will pay Lender's reasonable attorneys' fees
and all other costs of collection, unless prohibited by applicable law. This
Note has been delivered to Lender and accepted by Lender in the State of
Colorado. Subject to the provisions on arbitration, this Note shall be governed
by and construed in accordance with the laws of the State of Colorado without
regard to any conflict of laws or provisions thereof.

PURPOSE. Borrower agrees that no advances under this Note shall be used for
personal, family, or household purposes and that all advances hereunder shall be
used solely for business, commercial, agricultural or other similar purposes.

JURY WAIVER. THE BORROWER AND LENDER (BY ITS ACCEPTANCE HEREOF) HEREBY
VOLUNTARILY, KNOWINGLY, IRREVOCABLY AND UNCONDITIONALLY WAIVE ANY RIGHT TO HAVE
A JURY PARTICIPATE IN RESOLVING ANY DISPUTE (WHETHER BASED UPON CONTRACT, TORT
OR OTHERWISE) BETWEEN BORROWER AND LENDER ARISING OUT OF OR IN ANY WAY RELATED
TO THIS NOTE OR THE OTHER RELATED DOCUMENTS. THIS PROVISION IS A MATERIAL
INDUCEMENT TO LENDER TO PROVIDE THE FINANCING EVIDENCED BY THIS NOTE.

DISHONORED ITEM FEE. Borrower will pay a fee to Lender of $20.00 if Borrower
makes a payment on Borrower's loan and the check or preauthorized charge with
which Borrower pays is later dishonored.

RIGHT OF SETOFF. Unless a lien would be prohibited by law or would render a
nontaxable account taxable, Borrower grants to Lender a contractual possessory
security interest in, and hereby assigns, conveys, delivers, pledges, and
transfers to Lender all Borrower's right, title and interest in and to,
Borrower's accounts with Lender (whether checking, savings, or any other
account), including without limitation all accounts held jointly with someone
else and all accounts Borrower may open in the future. Borrower authorizes
Lender, to the extent permitted by applicable law, to charge or setoff all sums
owning on this Note against any and all such accounts.

LINE OF CREDIT. This Note evidences a revolving line of credit. Borrower may
request advances and make payments hereunder from time to time, provided that it
is understood and agreed that the aggregate principal amount outstanding from
time to time hereunder shall not at any time exceed the Total Principal Amount.
The unpaid principal balance of this Note shall increase and decrease with each
new advance or payment hereunder, as the case may be. Subject to the terms
hereof, Borrower may borrow, repay and reborrow hereunder. 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.

ARBITRATION. Lender and Borrower agree that upon the written demand of either
party, whether made before or after the institution of any legal proceedings,
but prior to the rendering of any judgment in that proceeding, all disputes,
claims and controversies between them, whether individual, joint, or class in
nature, arising from this Note, any Related Document or otherwise, including
without limitation contract disputes and tort claims, shall be arbitrated
pursuant to the Commercial Rules of the American Arbitration Association. Any
arbitration proceeding held pursuant to this arbitration provision shall be
conducted in the city nearest the Borrower's address having an AAA regional
office, or at any other place selected by mutual agreement to the parties. No
act to take or dispose of any collateral shall constitute a waiver of this
arbitration agreement or be prohibited by this arbitration agreement. This
arbitration provision shall not limit the right of either party during any
dispute, claim or controversy to seek, use, and employ ancillary, provisional or
preliminary rights and/or remedies, judicial or otherwise, for the purposes
<PAGE>

07-02-1999                     PROMISSORY NOTE                            Page 2
Loan No                          (Continued)
================================================================================
of realizing upon, preserving, protecting, foreclosing upon or proceeding under
forcible entry and detainer for possession of, any real or personal property,
and any such action shall not be deemed an election of remedies. This includes,
without limitation, obtaining injunctive relief or a temporary restraining
order, invoking a power of sale under any deed of trust or mortgage, obtaining a
writ of attachment or imposition of a receivership, or exercising any rights
relating to personal property, including taking or disposing of such property
with or without judicial process pursuant to Article 9 of the Uniform Commercial
Code. Any disputes, claims, or controversies concerning the lawfulness or
reasonableness of any act, or exercise of any right or remedy, concerning any
collateral, including any claim to rescind, reform, or otherwise modify any
agreement relating to the collateral, shall also be arbitrated; provided however
that no arbitrator shall have the right or the power to enjoin or restrain any
act of either party. Judgment upon any award rendered by any arbitrator may be
entered in any court having jurisdiction. Nothing in this arbitration provision
shall preclude either party from seeking equitable relief from a court of
competent jurisdiction. The statute of limitations, estoppel, waiver, laches and
similar doctrines which would otherwise be applicable in an action brought by a
party shall be applicable in any arbitration proceeding, and the commencement of
an arbitration proceeding shall be deemed the commencement of any action for
these purpose. The Federal Arbitration Act (Title 9 of the United States Code)
shall apply to the construction, interpretation, and enforcement of this
arbitration provision.

ADDITIONAL PROVISION - RIGHT TO CURE. Notwithstanding anything to the contrary
contained in this Note or in any Related Document, no condition, event or
failure shall be a default under this Note or an "Event of Default" as defined
in any Related Document, provided that (A) such condition, event or failure is
other than (i) a failure to pay any sum due under the provisions of this Note or
(ii) the commencement of a bankruptcy or insolvency proceeding by or against
Borrower or any Guarantor, or by or against any party that has granted
collateral to secure this Note, and (B) if, after Lender sends Borrower written
notice demanding cure of any such condition, event or failure, Borrower cures or
causes to be cured such event, condition or failure within ten (10) days after
such notice. Any notice delivered hereunder to Borrower shall be effective when
deposited with a nationally recognized overnight courier or when deposited in
the United States mail, first class postage prepaid, addressed to Borrower at
Borrower's last known mailing address.

ADDENDUM. An exhibit, titled "ADDENDUM," is attached to this Note and by this
reference is made a part of this Note just as it all the provisions, terms and
conditions of the Exhibit had been fully set forth in this Note.

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 Note, or
release any party or guarantor or collateral; or unjustifiably 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 Note 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:

CARRIER ACCESS CORPORATION, A DELAWARE CORPORATION

By: /s/ Nancy Pierce
   -----------------------------------------------
   NANCY PIERCE, CFO TREAS/SECRETARY

================================================================================
<PAGE>

                                   ADDENDUM

THIS ADDENDUM is executed with respect to the Promissory Note in the original
principal amount of $5,000,000.00 dated July 2, 1998 [and maturing on July 2,
1999 (the "Note") , made by Carrier Access Corporation, A Colorado Corporation
(referred to in this Addendum as "Borrower") payable to the order of Bank One,
Colorado, N.A. ("Lender"), and is hereby incorporated into and made a part of
the Note. Terms used in this Addendum with their initial letters capitalized are
used as defined in the Note, unless they are otherwise expressly defined herein.

     1. The paragraph in the Note having the caption "VARIABLE INTEREST RATE" is
hereby deleted in its entirety and the following is hereby substituted in lieu
thereof:

     VARIABLE INTEREST RATE. Subject to designation of a different interest rate
     index by Borrower as provided below, the interest rate on this Note is
     subject to fluctuation based upon the Prime Rate of interest in effect from
     time to time (the "Index") (which rate may not be the lowest, best or most
     favorable rate of interest which Lender may charge on loans to its
     customers). "Prime Rate" shall mean the rate announced from time to time
     by Lender as its prime rate. Each change in the variable interest rate to
     be charged on this Note will become effective without notice on the same
     day as the Index changes. Except as otherwise provided herein, the unpaid
     principal balance of this Note will accrue interest at a rate per annum
     which will from time to time be equal to the sum of the Index, plus 0.00%.

     INTEREST RATE OPTIONS. The following interest rate options are available
     under this Note:

     (a) Default Option. The interest rate margin and index described in the
     "VARIABLE INTEREST RATE" paragraph above (the "Default Option").

     (b) ONE MONTH LONDON INTERBANK OFFERED RATE. A margin of 2.50 percentage
     points over the one month LONDON INTERBANK OFFERED RATE ("LIBOR"). For
     purposes of this Note, the one month LIBOR rate shall mean the one month
     offered rate for U.S. Dollar deposits of not less than $1,000,000.00 as of
     11:00 A.M. City of London, England time two London Business Days prior to
     the first date of each one month Interest Period (as defined below) of this
     Note as shown on the display designated as "British Bankers Assoc. Interest
     Settlement Rates" on the Dow Jones Telerate Service ("Telerate"), Page
     3750 (or such other page as may replace that page on that service for the
     purpose of displaying such rate). Provided, however, that if such LIBOR
     rate is not available on Telerate then such offered rate shall be otherwise
     independently determined by Lender from an alternate, substantially similar
     independent source or service available to Lender or shall be calculated by
     Lender by a substantially similar methodology as that theretofore used to
     determine such offered rate in Telerate.

     (c) THREE MONTH LONDON INTERBANK OFFERED RATE. A margin of 2.50 percentage
     points over the three month LONDON INTERBANK OFFERED RATE ("LIBOR"). For
     purposes of this Note, the three month LIBOR rate shall mean the three
     month offered rate for U.S. Dollar deposits of not less than $1,000,000.00
     as of 11:00 A.M. City of London, England time two London Business Days
     prior to the first date of each three month Interest Period (as defined
     below) of this Note as shown on the display designated as "British Bankers
     Assoc. Interest Settlement Rates" on the Dow Jones Telerate Service
     ("Telerate"), Page 3750 (or such other page as may replace that page on
     that service for the purpose of displaying such rate). Provided, however,
     that if such LIBOR rate is not available on Telerate then such offered rate
     shall be otherwise independently determined by Lender from an alternate,
     substantially similar independent source or service available

<PAGE>

     to Lender or shall be calculated by Lender by a substantially similar
     methodology as that theretofore used to determine such offered rate in
     Telerate.

     NOTICE: Under no circumstances will the interest rate on this Note be more
     than the maximum rate allowed by applicable law.

     If used in this Note, "London Business Day" means any day other than a
     Saturday, Sunday or a day on which banking institutions are generally
     authorized or obligated by law or executive order to close in the City of
     London, England.

     When the interest rate is based on a LIBOR rate, a Treasury Securities Rate
     or a Fixed Rate (an "Option Rate"), the rate shall be in effect for a
     period of the number of months as indicated in the rate option description
     (the "Interest Period") , in any case extended to the next succeeding
     business day when necessary, beginning on a borrowing date, conversion date
     or expiration date of the then current Interest Period. Adjustments in the
     interest rate due to changes in the maximum nonusurious interest rate
     allowed (the "Highest Lawful Rate") shall be made on the effective day of
     any change in the Highest Lawful Rate.

     Provided Borrower is not in default under this Note, Borrower may designate
     in advance which of the above interest rate indexes shall be applicable to
     any loan advance under this Note. In the absence of any such designation
     the interest rate option shall be the Default Option. Thereafter unpaid
     principal balances under this Note may be converted (at the end of an
     Interest Period if the index used to determine the interest rate therefore
     is an option Rate) to another of the above interest rate options, or
     continued for an additional interest period, when applicable, as designated
     by Borrower in advance; and in the absence of sufficient advance
     designation as determined by the Lender as to conversion to or continuation
     of an Option Rate index, the rate shall be converted to the Default Option.
     Notwithstanding the foregoing, an Option Rate index may not be elected for
     a loan or advance under this Note, nor any conversion to or continuation of
     an Option Rate index be elected, if the Interest Period thereof would
     extend beyond the maturity of this Note.

     Each loan or advance under this Note at conversion into or continuation of
     an Option Rate shall be in a minimum amount of $500,000.00 with no more
     than two tranches outstanding at any time. Unless otherwise provided
     herein, accrued interest on amounts for which the interest rate is based on
     a LIBOR rate or a Treasury Securities Rate shall be due and payable at the
     end of the respective Interest Period therefor.

     Borrower shall pay to Lender from time to time such amounts as Lender may
     determine to be necessary to compensate Lender for any costs incurred by
     Lender which Lender determines are attributable to its making or
     maintaining any LIBOR rates hereunder or its obligation to make any such
     LIBOR rates hereunder, or any reduction in any amount receivable by Lender
     under this Note in respect of any such rates or such obligation (such
     increases in costs and reductions in amounts receivable being herein called
     "Additional Costs"), resulting from any change after the date of this Note
     in U.S. federal, state, municipal, or foreign laws or regulations
     (including Regulation D), or the adoption or making after such date of any
     interpretations, directives, or requirements applying to a class of banks
     including Lender of or under any U.S. federal, state, municipal, or any
     foreign laws or regulations (whether or not having the force of law) by any
     court or governmental or monetary authority charged with the interpretation
     or administration thereof ("Regulatory Change"), which: (1) changes the
     basis of taxation of any amounts payable to Lender under this Note in
     respect of any such LIBOR rates (other than taxes imposed on the overall
     net income of the Lender); or (2) imposes or modifies any reserve, special
     deposit, compulsory loan, or similar requirements relating to any
     extensions of credit or other assets of, or
<PAGE>

     any deposits with or other liabilities of Lender (including any of such
     LIBOR rates or any deposits referred to in the definition of any LIBOR
     rate); or (3) imposes any other condition affecting this Note (or any of
     such extensions of credit or liabilities) . Lender will notify the Borrower
     of any event occurring after the date of this Note which will entitle
     Lender to compensation pursuant to this paragraph as promptly as
     practicable after it obtains knowledge thereof and determines to request
     such compensation. Determinations by Lender for purposes of this paragraph
     of the effect of any Regulatory change in its costs of making or
     maintaining LIBOR rates or on amounts receivable by it in respect of LIBOR
     rates, and of the additional amounts required to compensate Lender in
     respect of any Additional Costs, shall be presumed prima facie correct.
                                                        ----- -----

     In respect of any LIBOR Loans, in the event that Lender shall have
     determined that dollar deposits of the relevant amount for the relevant
     Interest Period for such LIBOR Loans are not available or that, by reason
     of circumstances affecting such market, adequate and reasonable means do
     not exist for ascertaining the LIBOR rate applicable to such Interest
     Period, as the case may be, Lender shall promptly give notice of such
     determination to the Borrower and (i) any notice of new LIBOR Loans (or
     conversion of existing loans to LIBOR Loans) previously given by the
     Borrower and not yet borrowed (or converted, as the case may be) shall be
     deemed a notice to make loans bearing interest at the Default Option, and
     (ii) the Borrower shall be obligated either to prepay or to convert any
     outstanding LIBOR Loans on the last day of the then current Interest Period
     or Periods with respect thereto, as Borrower shall elect.

     Without prejudice to any other provisions of this Note, the Borrower agrees
     to indemnify Lender against any loss or expense which Lender may sustain or
     incur as a consequence of any default by the Borrower in payment when due
     of any amount due hereunder in respect of any LIBOR Loan, including, but
     not limited to, any loss of profit, premium or penalty incurred by Lender
     in respect of funds borrowed by it for the purpose of making or maintaining
     such LIBOR Loan, as determined by Lender in the exercise of its sole but
     reasonable discretion. A certificate as to any such loss or expense shall
     be promptly submitted by Lender to the Borrower and shall, in the absence
     of manifest error, be conclusive and binding as to the amount thereof.

     If at any time any new law, treaty or regulation enacted after the date
     hereof, or any change after the date hereof in any existing law, treaty or
     regulation, or any interpretation thereof after the date hereof by any
     governmental or other regulatory authority charged with the administration
     thereof, shall make it unlawful for Lender to fund any LIBOR Loans which it
     is committed to make hereunder with moneys obtained in the Eurodollar
     market, the commitment of Lender to fund LIBOR Loans shall, upon the
     happening of such event forthwith be suspended for the duration of such
     illegality, and Lender shall by written notice to the Borrower declare that
     the commitment with respect to such loans has been so suspended and, if and
     when such illegality ceases to exist, such suspension shall cease and
     Lender shall similarly notify the Borrower. If any such change shall make
     it unlawful for Lender to continue in effect the funding in the applicable
     Eurodollar market of any LIBOR Loan previously made by it hereunder, Lender
     shall, upon the happening of such event, notify the Borrower in writing
     stating the reasons therefor, and the Borrower shall, on the earlier of (i)
     the last day of the then current Interest Period or (ii) if required by
     such law, regulation or interpretation, on such date as shall be specified
     in such notice, either convert all LIBOR Loans to loans bearing interest at
     the Default Option or prepay all LIBOR Loans to Lender in full, as Borrower
     shall elect.

     Lender may, but shall not be required to, make LIBOR Loans hereunder with
     funds obtained outside the United States.
<PAGE>

     2.  Except as expressly modified by this Addendum, all of the terms and
conditions of the Note continue unchanged and in full force and effect.

Dated with effect as of the date of the Note.

CARRIER ACCESS CORPORATION,
A DELAWARE CORPORATION

By: /s/ Nancy Pierce
   ----------------------------------------
   Nancy Pierce, CFO Treasurer/Secretary
<PAGE>

                         AGREEMENT TO PROVIDE INSURANCE
<TABLE>
<CAPTION>
--------------------------------------------------------------------------------------------
  Principal    Loan Date    Maturity  Loan No. Call  Collateral   Account   Officer Initials
<S>            <C>         <C>        <C>     <C>    <C>        <C>         <C>     <C>
$5,000,000.00  07-02-1999  07-02-2000         078105    328     1518454676   00410
--------------------------------------------------------------------------------------------
</TABLE>
  References in the shaded area are for Lender's use only and do not limit the
  applicability of this document to any particular loan or item.
--------------------------------------------------------------------------------


Borrower:  CARRIER ACCESS CORPORATION,     Lender: Bank One, Colorado, NA
           A DELAWARE CORPORATION                  Corporate Lending - Boulder
           5395 PEARL PARKWAY                      1125 17th Street
           BOULDER,CO 80301                        Denver, CO 80217

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INSURANCE REQUIREMENTS. CARRIER ACCESS CORPORATION, A DELAWARE CORPORATION
("Grantor") understands that insurance coverage is required in connection with
the extending of a loan or the providing of other financial accommodations to
Grantor by Lender. These requirements are set forth in the security documents.
The following minimum insurance coverages must be provided on the following
described collateral (the "Collateral"):

Collateral:  All inventory, chattel paper, accounts, equipment, general
             intangibles, excluding patents.

             Type. All risks, including fire, theft and liability.

             Amount. Full insurable value.

             Basis. Replacement value.

             Endorsements. Lender's loss payable clause with stipulation that
             coverage will not be cancelled or diminished without a minimum of
             thirty (30) days' prior written notice to Lender.

INSURANCE COMPANY. Grantor may obtain insurance from any insurance company
Grantor may choose that is reasonably acceptable to Lender. Grantor understands
that credit may not be denied solely because insurance was not purchased through
Lender.

INSURANCE MAILING ADDRESS. All documents and other materials relating to
insurance for this loan should be mailed, delivered or directed to the following
address:

             Banc One Comml Loan Servicing
             P O Box 63124  AZ1-2570
             Phoenix, AZ 85082-3124

FAILURE TO PROVIDE INSURANCE. Grantor agrees to deliver to Lender, no later than
on or before closing, evidence of the required insurance as provided above, with
an effective date of July 2, 1998, or earlier. Grantor acknowledges and agrees
that if Grantor fails to provide any required insurance or fails to continue
such insurance in force, Lender may do so at Grantor's expense as provided in
the applicable security document. The cost of any such insurance, at the option
of Lender, shall be payable on demand or shall be added to the indebtedness as
provided in the security document. GRANTOR ACKNOWLEDGES THAT IF LENDER SO
PURCHASES ANY SUCH INSURANCE, THE INSURANCE WILL PROVIDE LIMITED PROTECTION
AGAINST PHYSICAL DAMAGE TO THE COLLATERAL, UP TO THE BALANCE OF THE LOAN;
HOWEVER, GRANTOR'S EQUITY IN THE COLLATERAL MAY NOT BE INSURED. IN ADDITION, THE
INSURANCE MAY NOT PROVIDE ANY PUBLIC LIABILITY OR PROPERTY DAMAGE
INDEMNIFICATION AND MAY NOT MEET THE REQUIREMENTS OF ANY FINANCIAL
RESPONSIBILITY LAWS.

AUTHORIZATION. For purposes of insurance coverage on the Collateral, Grantor
authorizes Lender to provide to any person (including any insurance agent or
company) all information Lender deems appropriate, whether regarding the
Collateral, the loan or other financial accommodations, or both.

GRANTOR ACKNOWLEDGES HAVING READ ALL THE PROVISIONS OF THIS AGREEMENT TO PROVIDE
INSURANCE AND AGREES TO ITS TERMS. THIS AGREEMENT IS DATED JULY 2, 1998.

GRANTOR:

CARRIER ACCESS CORPORATION, A DELAWARE CORPORATION

By: /s/ Nancy Pierce
   -----------------------------------------------
   NANCY PIERCE, CFO TREAS/SECRETARY

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                              FOR LENDER USE ONLY
                            INSURANCE VERIFICATION

DATE:                                                       PHONE:
     ---------------                                              --------------

AGENT'S NAME:
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INSURANCE COMPANY:
                  --------------------------------------------------------------

POLICY NUMBER:
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EFFECTIVE DATES:
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COMMENTS:
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