<PAGE>   1
                                                                 EXHIBIT 10.26

                   INTELLECTUAL PROPERTY SECURITY AGREEMENT


      This Intellectual Property Security Agreement (this "IP Agreement") is
made as of the 28th day of February, 2001 by and between (i) VISUAL NETWORKS,
INC., a Delaware corporation with its principal place of business at 2092
Gaither Road, Rockville, Maryland 20850 ("Grantor"), (ii) VISUAL NETWORKS
OPERATIONS, INC., a Delaware corporation ("VNO"), (iii) VISUAL NETWORKS
INVESTMENTS, INC., a California corporation ("VNI"), (iv) VISUAL NETWORKS
TECHNOLOGIES, INC., a California corporation ("VNT"), (v) VISUAL NETWORKS OF
TEXAS, L.P., a Texas limited partnership ("Visual Texas"), (vi) VISUAL
NETWORKS INSURANCE, INC., a Vermont corporation ("Visual Insurance"), (vii)
INVERSE NETWORK TECHNOLOGY, a California corporation ("INT"), and (viii)
AVESTA TECHNOLOGIES, INC., a Delaware corporation ("Avesta") (hereinafter,
Visual, VNO, VNI, VNT, Visual Texas, Visual Insurance, INT, and Avesta are
referred to jointly, severally and collectively as the "Grantor"), and SILICON
VALLEY BANK, a California banking corporation ("Lender").

                                   RECITALS

      A.       Lender has agreed to make advances of money and to extend
certain financial accommodations to Grantor (the "Loan"), pursuant to a
certain Loan and Security Agreement of even date between Grantor and Lender,
as amended from time to time and a certain Accounts Receivable Financing
Agreement dated as of February 28th 2001 (collectively, as amended, the "Loan
Agreement"). The Loan is secured pursuant to the terms of the Loan Agreement.
Lender is willing to enter into certain financial accommodations with Grantor,
but only upon the condition, among others, that Grantor shall grant to Lender
a security interest in certain Copyrights, Trademarks, Patents, and Mask Works
to secure the obligations of Grantor under the Loan Agreement. Defined terms
used but not defined herein shall have the same meanings as in the Loan
Agreement.

      B.       Pursuant to the terms of the Loan Agreement, Grantor has
granted to Lender a security interest in all of Grantor's right title and
interest, whether presently existing or hereafter acquired in, to and under
all of the Collateral (as defined therein).

      NOW, THEREFORE, for good and valuable consideration, receipt of which is
hereby acknowledged and intending to be legally bound, as collateral security
for the prompt and complete payment when due of Grantor's Indebtedness (as
defined below), Grantor hereby represents, warrants, covenants and agrees as
follows:

      1.       Grant of Security Interest. As collateral security for the
prompt and complete payment and performance of all of Grantor's present or
future indebtedness, obligations and liabilities to Lender (hereinafter, the
"Indebtedness"), including, without limitation, under the Loan Agreement,
Grantor hereby grants a security interest in all of Grantor's right, title and
interest in, to and under its intellectual property collateral (all of which
shall collectively be called the "Intellectual Property Collateral"),
including, without limitation, the following:

               (a)    Any and all copyright rights, copyright applications,
      copyright registrations and like protections in each work or authorship
      and derivative work thereof, whether published or unpublished and
      whether or not the same also constitutes a trade secret, now or
      hereafter existing, created, acquired or held, including without
      limitation those set forth on EXHIBIT A attached hereto (collectively,
      the "Copyrights");

               (b)    Any and all trade secrets, and any and all intellectual
      property rights in computer software and computer software products now
      or hereafter existing, created, acquired or held;


<PAGE>   2


               (c)    Any and all design rights which may be available to
      Grantor now or hereafter existing, created, acquired or held;

               (d)    All patents, patent applications and like protections
      including, without limitation, improvements, divisions, continuations,
      renewals, reissues, extensions and continuations-in-part of the same,
      including without limitation the patents and patent applications set
      forth on EXHIBIT B attached hereto (collectively, the "Patents");

               (e)    Any trademark and servicemark rights, whether registered
      or not, applications to register and registrations of the same and like
      protections, and the entire goodwill of the business of Grantor
      connected with and symbolized by such trademarks, including without
      limitation those set forth on EXHIBIT C attached hereto (collectively,
      the "Trademarks");

               (f)    All mask works or similar rights available for the
      protection of semiconductor chips, now owned or hereafter acquired,
      including, without limitation those set forth on EXHIBIT D attached
      hereto (collectively, the "Mask Works");

               (g)    Any and all claims for damages by way of past, present
      and future infringements of any of the rights included above, with the
      right, but not the obligation, to sue for and collect such damages for
      said use or infringement of the intellectual property rights identified
      above;

               (h)    All licenses or other rights to use any of the
      Copyrights, Patents, Trademarks, or Mask Works and all license fees and
      royalties arising from such use to the extent permitted by such license
      or rights;

               (i)    All amendments, extensions, renewals and extensions of
      any of the Copyrights, Trademarks, Patents, or Mask Works; and

               (j)    All proceeds and products of the foregoing, including
      without limitation all payments under insurance or any indemnity or
      warranty payable in respect of any of the foregoing.

      2.       Authorization and Request.  Grantor authorizes and requests
that the Register of Copyrights and the Commissioner of Patents and Trademarks
record this IP Agreement.

      3.       Covenants and Warranties.  Grantor represents, warrants,
covenants and agrees as follows:

               (a)    Grantor is now the sole owner of the Intellectual
      Property Collateral, except for non-exclusive licenses granted by
      Grantor to its customers in the ordinary course of business.

               (b)    Performance of this IP Agreement does not conflict with
      or result in a breach of any IP Agreement to which Grantor is bound,
      except to the extent that certain intellectual property agreements
      prohibit the assignment of the rights thereunder to a third party
      without the licensor's or other party's consent and this IP Agreement
      constitutes a security interest.

               (c)    During the term of this IP Agreement, Grantor will not
      transfer or otherwise encumber any interest in the Intellectual Property
      Collateral, except for non-exclusive licenses granted by Grantor in the
      ordinary course of business or as set forth in this IP Agreement;




<PAGE>   3



               (d)    To its knowledge, each of the Patents is valid and
      enforceable, and no part of the Intellectual Property Collateral has
      been judged invalid or unenforceable, in whole or in part, and no claim
      has been made that any part of the Intellectual Property Collateral
      violates the rights of any third party, except as set forth on the
      schedule attached hereto;

               (e)    Grantor shall promptly advise Lender of any material
      adverse change in the composition of the Collateral, including but not
      limited to any subsequent ownership right of the Grantor in or to any
      Trademark, Patent, Copyright, or Mask Work specified in this IP
      Agreement;

               (f)    Grantor shall (i) protect, defend and maintain the
      validity and enforceability of the Trademarks, Patents, Copyrights, and
      Mask Works, (ii) use its best efforts to detect infringements of the
      Trademarks, Patents, Copyrights, and Mask Works and promptly advise
      Lender in writing of material infringements detected and (iii) not allow
      any Trademarks, Patents, Copyrights, or Mask Works to be abandoned,
      forfeited or dedicated to the public without the written consent of
      Lender, which shall not be unreasonably withheld, unless Grantor
      determines that reasonable business practices suggest that abandonment
      is appropriate.

               (g)    Grantor shall, to the extent determined to be
      appropriate by Grantor's management in its reasonable business judgment,
      register the most recent version of any of Grantor's Copyrights, if not
      so already registered, and shall, from time to time, execute and file
      such other instruments, and take such further actions as Lender may
      reasonably request from time to time to perfect or continue the
      perfection of Lender's interest in the Intellectual Property Collateral;

               (h)    This IP Agreement creates, and in the case of after
      acquired Intellectual Property Collateral, this IP Agreement will create
      at the time Grantor first has rights in such after acquired Intellectual
      Property Collateral, in favor of Lender a valid and perfected first
      priority security interest in the Intellectual Property Collateral in
      the United States securing the payment and performance of the
      obligations evidenced by the Loan Agreement upon making the filings
      referred to in clause (i) below;

               (i)    To its knowledge, except for, and upon, the filing with
      the United States Patent and Trademark office with respect to the
      Patents and Trademarks and the Register of Copyrights with respect to
      the Copyrights and Mask Works necessary to perfect the security
      interests created hereunder and except as has been already made or
      obtained, no authorization, approval or other action by, and no notice
      to or filing with, any U.S. governmental authority or U.S. regulatory
      body is required either (i) for the grant by Grantor of the security
      interest granted hereby or for the execution, delivery or performance of
      this IP Agreement by Grantor in the U.S. or (ii) for the perfection in
      the United States or the exercise by Lender of its rights and remedies
      thereunder;

               (j)    All information heretofore, herein or hereafter supplied
      to Lender by or on behalf of Grantor with respect to the Intellectual
      Property Collateral is accurate and complete in all material respects.

               (k)    Grantor shall not enter into any agreement that would
      materially impair or conflict with Grantor's obligations hereunder
      without Lender's prior written consent, which consent shall not be
      unreasonably withheld. Grantor shall not permit the inclusion in any
      material contract to which it becomes a party of any provisions that
      could or might in any way prevent the creation of a security interest in
      Grantor's rights and interest in any property included within the
      definition of the Intellectual Property Collateral acquired under such
      contracts, except that certain contracts may contain anti-assignment
      provisions that could in effect prohibit the creation of a security
      interest in such contracts.


                                     -3-


<PAGE>   4






               (l)    Upon any executive officer of Grantor obtaining actual
      knowledge thereof, Grantor will promptly notify Lender in writing of any
      event that materially adversely affects the value of any material
      Intellectual Property Collateral, the ability of Grantor to dispose of
      any material Intellectual Property Collateral of the rights and remedies
      of Lender in relation thereto, including the levy of any legal process
      against any of the Intellectual Property Collateral.

      4.       Lender's Rights. Lender shall have the right, but not the
obligation, to take, at Grantor's sole expense, any actions that Grantor is
required under this IP Agreement to take but which Grantor fails to take,
after fifteen (15) days' notice to Grantor. Grantor shall reimburse and
indemnify Lender for all reasonable costs and reasonable expenses incurred in
the reasonable exercise of its rights under this section 4.

      5.       Inspection Rights. Grantor hereby grants to Lender and its
employees, representatives and agents the right to visit, during reasonable
hours upon prior reasonable written notice to Grantor, any of Grantor's plants
and facilities that manufacture, install or store products (or that have done
so during the prior six-month period) that are sold utilizing any of the
Intellectual Property Collateral, and to inspect the products and quality
control records relating thereto upon reasonable written notice to Grantor and
as often as may be reasonably requested, but not more than once in every six
(6) months; provided, however, nothing herein shall entitle Lender access to
Grantor's trade secrets and other proprietary information.

      6.       Further Assurances; Attorney in Fact.

               (a)    On a continuing basis, Grantor will, subject to any
prior licenses, encumbrances and restrictions and prospective licenses, make,
execute, acknowledge and deliver, and file and record in the proper filing and
recording places in the United States, all such instruments, including
appropriate financing and continuation statements and collateral agreements
and filings with the United States Patent and Trademarks Office and the
Register of Copyrights, and take all such action as may reasonably be deemed
necessary or advisable, or as reasonably requested by Lender, to perfect
Lender's security interest in all Copyrights, Patents, Trademarks, and Mask
Works and otherwise to carry out the intent and purposes of this IP Agreement,
or for assuring and confirming to Lender the grant or perfection of a security
interest in all Intellectual Property Collateral.

               (b)    Grantor hereby irrevocably appoints Lender as Grantor's
attorney-in-fact, with full authority in the place and stead of Grantor and in
the name of Grantor, Lender or otherwise, from time to time in Lender's
discretion, upon Grantor's failure or inability to do so, to take any action
and to execute any instrument which Lender may deem necessary or advisable to
accomplish the purposes of this IP Agreement, including:

                      (i)    To modify, in its sole discretion, this IP
      Agreement without first obtaining Grantor's approval of or signature to
      such modification by amending Exhibit A, Exhibit B, Exhibit C, and
      Exhibit D hereof, as appropriate, to include reference to any right,
      title or interest in any Copyrights, Patents, Trademarks or Mask Works
      acquired by Grantor after the execution hereof or to delete any
      reference to any right, title or interest in any Copyrights, Patents,
      Trademarks, or Mask Works in which Grantor no longer has or claims any
      right, title or interest; and

                      (ii)   To file, in its sole discretion, one or more
      financing or continuation statements and amendments thereto, relative to
      any of the Intellectual Property Collateral without the signature of
      Grantor where permitted by law.

      7.       Events of Default.  The occurrence of any of the following
shall constitute an Event of Default under this IP Agreement:


                                     -4-
<PAGE>   5




               (a)    An Event of Default occurs under the Loan Agreement; or
      any document from Grantor to Lender; or

               (b)    Grantor breaches any warranty or agreement made by
      Grantor in this IP Agreement.

      8.       Remedies. Upon the occurrence and continuance of an Event of
Default, Lender shall have the right to exercise all the remedies of a secured
party under the Massachusetts Uniform Commercial Code, including without
limitation the right to require Grantor to assemble the Intellectual Property
Collateral and any tangible property in which Lender has a security interest
and to make it available to Lender at a place designated by Lender. Lender
shall have a nonexclusive, royalty free license to use the Copyrights,
Patents, Trademarks, and Mask Works to the extent reasonably necessary to
permit Lender to exercise its rights and remedies upon the occurrence of an
Event of Default. Grantor will pay any expenses (including reasonable
attorney's fees) incurred by Lender in connection with the exercise of any of
Lender's rights hereunder, including without limitation any expense incurred
in disposing of the Intellectual Property Collateral. All of Lender's rights
and remedies with respect to the Intellectual Property Collateral shall be
cumulative.

      9.       Indemnity. Grantor agrees to defend, indemnify and hold
harmless Lender and its officers, employees, and agents against: (a) all
obligations, demands, claims, and liabilities claimed or asserted by any other
party in connection with the transactions contemplated by this IP Agreement,
and (b) all losses or expenses in any way suffered, incurred, or paid by
Lender as a result of or in any way arising out of, following or consequential
to transactions between Lender and Grantor, whether under this IP Agreement or
otherwise (including without limitation, reasonable attorneys fees and
reasonable expenses), except for losses arising from or out of Lender's gross
negligence or willful misconduct.

      10.      Reassignment. At such time as Grantor shall completely satisfy
all of the obligations secured hereunder, Lender shall execute and deliver to
Grantor all deeds, assignments, and other instruments as may be necessary or
proper to reinvest in Grantor full title to the property assigned hereunder,
subject to any disposition thereof which may have been made by Lender pursuant
hereto.

      11.      Course of Dealing.  No course of dealing, nor any failure to
exercise, nor any delay in exercising any right, power or privilege hereunder
shall operate as a waiver thereof.

      12.      Attorneys' Fees.  If any action relating to this IP Agreement
is brought by either party hereto against the other party, the prevailing
party shall be entitled to recover reasonable attorneys fees, costs and
disbursements.

      13.      Amendments.  This IP Agreement may be amended only by a written
instrument signed by both parties hereto.

      14.      Counterparts.  This IP Agreement may be executed in two or more
counterparts, each of which shall be deemed an original but all of which
together shall constitute the same instrument.

      15.      Law and Jurisdiction. This IP Agreement shall be governed by
and construed in accordance with the laws of the United States and the
Commonwealth of Massachusetts. GRANTOR ACCEPTS FOR ITSELF AND IN CONNECTION
WITH ITS PROPERTIES, UNCONDITIONALLY, THE NON-EXCLUSIVE JURISDICTION OF ANY
STATE OR FEDERAL COURT OF COMPETENT JURISDICTION IN THE COMMONWEALTH OF
MASSACHUSETTS IN ANY ACTION, SUIT, OR PROCEEDING OF ANY KIND, AGAINST IT WHICH
ARISES OUT OF OR BY REASON OF THIS AGREEMENT; PROVIDED, HOWEVER, THAT IF FOR
ANY REASON LENDER CANNOT AVAIL ITSELF OF THE COURTS OF THE COMMONWEALTH OF
MASSACHUSETTS, GRANTOR ACCEPTS JURISDICTION OF THE COURTS AND VENUE IN SANTA
CLARA COUNTY, CALIFORNIA.


                                     -5-
<PAGE>   6


      GRANTOR AND LENDER EACH HEREBY WAIVE THEIR RESPECTIVE RIGHTS TO A JURY
TRIAL OF ANY CLAIM OR CAUSE OF ACTION BASED UPON OR ARISING OUT OF ANY OF THE
LOAN DOCUMENTS OR ANY OF THE TRANSACTIONS CONTEMPLATED THEREIN, INCLUDING
CONTRACT CLAIMS, TORT CLAIMS, BREACH OF DUTY CLAIMS, AND ALL OTHER COMMON LAW
OR STATUTORY CLAIMS. EACH PARTY RECOGNIZES AND AGREES THAT THE FOREGOING
WAIVER CONSTITUTES A MATERIAL INDUCEMENT FOR IT TO ENTER INTO THIS AGREEMENT.
EACH PARTY REPRESENTS AND WARRANTS THAT IT HAS REVIEWED THIS WAIVER WITH ITS
LEGAL COUNSEL AND THAT IT KNOWINGLY AND VOLUNTARILY WAIVES ITS JURY TRIAL
RIGHTS FOLLOWING CONSULTATION WITH LEGAL COUNSEL.

      16.      Confidentiality. In handling any confidential information,
Lender shall exercise the same degree of care that it exercises for its own
proprietary information, but disclosure of information may be made: (i) to
Lender's subsidiaries or affiliates in connection with their present or
prospective business relations with Grantor; (ii) to prospective transferees
or purchasers of any interest in the Loans; (iii) as required by law,
regulation, subpoena, or other order, (iv) as required in connection with
Lender's examination or audit; and (v) as Lender considers appropriate in
exercising remedies under this Agreement. Confidential information does not
include information that either: (a) is in the public domain or in Lender's
possession when disclosed to Lender, or becomes part of the public domain
after disclosure to Lender; or (b) is disclosed to Lender by a third party, if
Lender does not know that the third party is prohibited from disclosing the
information.

                                     -6-

<PAGE>   7


      EXECUTED as a sealed instrument under the laws of the Commonwealth of
Massachusetts on the day and year first written above.

ADDRESS OF GRANTOR:                        GRANTOR:

2092 Gaither Road                          VISUAL NETWORKS, INC.
Rockville, Maryland 20850

                                           By:        /s/ Peter J. Minihane
                                                      ----------------------
                                                      Peter J. Minihane

                                           Title:     Chief Financial Officer
                                                      -------------------------


                                           VISUAL NETWORKS OPERATIONS, INC.

                                           By:        /s/ Peter J. Minihane
                                                      ----------------------
                                                      Peter J. Minihane

                                           Title:     Treasurer
                                                      ----------

                                           VISUAL NETWORKS INVESTMENTS, INC.

                                           By:        /s/ Peter J. Minihane
                                                      ----------------------
                                                      Peter J. Minihane

                                           Title:     Treasurer
                                                      ----------


                                           VISUAL NETWORKS TECHNOLOGIES, INC.

                                           By:        /s/ Peter J. Minihane
                                                      ----------------------
                                                      Peter J. Minihane

                                           Title:     Treasurer
                                                      ----------


                                           VISUAL NETWORKS OF TEXAS, L.P.,
                                           by Visual Networks Texas Operations,
                                           Inc., its General Partner

                                           By:        /s/ Peter J. Minihane
                                                      ----------------------
                                                      Peter J. Minihane

                                           Title:     Treasurer
                                                      ----------

                                           VISUAL NETWORKS INSURANCE, INC.

                                           By:        /s/ Peter J. Minihane
                                                      ----------------------
                                                      Peter J. Minihane

                                           Title:     Treasurer
                                                      ----------
                                     -7-



<PAGE>   8


                                           INVERSE NETWORK TECHNOLOGY

                                           By:        /s/ Peter J. Minihane
                                                      ----------------------
                                                      Peter J. Minihane

                                           Title:     President
                                                      ----------

                                           AVESTA TECHNOLOGIES, INC.

                                           By:        /s/ Peter J. Minihane
                                                      ----------------------
                                                      Peter J. Minihane

                                           Title:     President
                                                      ----------


                                     -8-


<PAGE>   9


                                  EXHIBIT A

                                  COPYRIGHTS



                                    None.





                                     -9-

<PAGE>   10


                                  EXHIBIT B

                                   PATENTS


                                 U.S. Patents

<TABLE>
<CAPTION>

--------------------------------------------------------------------------------------------------------
Patent No.                                                 Title
--------------------------------------------------------------------------------------------------------
<S>             <C>
5,521,907          Method and Apparatus for Non-Intrusive Measurement of Round Trip Delay in
                   Communications Networks
--------------------------------------------------------------------------------------------------------

5,867,483          Method and Apparatus for Measurement of Peak Throughput in Packetized Data
                   Networks
--------------------------------------------------------------------------------------------------------

6,058,102          Method and Apparatus for Performing Service-Level Analysis of Communications
                   Network Performance Metrics
--------------------------------------------------------------------------------------------------------

6,147,998          Method and Apparatus for Performing In-Service Quality of Service Testing
--------------------------------------------------------------------------------------------------------
</TABLE>


                       Pending U.S. Patent Applications

<TABLE>
<CAPTION>
---------------------------------------------------------------------------------------------------------------------------------
Serial No.                                         Title                                     Filed                 Status
---------------------------------------------------------------------------------------------------------------------------------
<S>                <C>                                                                <C>               <C>
09/048,025            Dynamic Modeling of Complex Networks and Prediction of Impacts   03/26/1998         Pending
                      of Faults Therein
---------------------------------------------------------------------------------------------------------------------------------


09/256,647            Network Monitoring System                                        02/23/1999         Awaiting Action
---------------------------------------------------------------------------------------------------------------------------------

09/605,680            Method of Identifying Information Within a                       06/28/2000         Awaiting Action
                      Character String
---------------------------------------------------------------------------------------------------------------------------------
</TABLE>


                     Pending Foreign Patent Applications

<TABLE>
<CAPTION>

--------------------------------------------------------------------------------------------------------------------------------
Country            Serial No.                               Title                      Filing Date                Status
--------------------------------------------------------------------------------------------------------------------------------
<S>               <C>                  <C>                                            <C>              <C>
Canada             2,218,886            Method and Apparatus for Non-Intrusive         04/17/1996        Awaiting Action
                                        Measurement of Round Trip Delay in
                                        Communications Networks
--------------------------------------------------------------------------------------------------------------------------------
</TABLE>





<PAGE>   11



<TABLE>
<CAPTION>
--------------------------------------------------------------------------------------------------------------------------
Country            Serial No.                               Title                      Filing Date       Status
--------------------------------------------------------------------------------------------------------------------------
<S>               <C>                 <C>                                             <C>              <C>
Canada             2,270,890            Method and Apparatus for Measurement of Peak   11/12/1997        Awaiting Action
                                        Throughput in Packetized Data Networks
--------------------------------------------------------------------------------------------------------------------------

Australia          33657/99             Dynamic Modeling of Complex Networks and       9/26/2000         Awaiting Action
                                        Prediction of Impacts of Faults Therein
--------------------------------------------------------------------------------------------------------------------------

Canada             2,301,896            Method and Apparatus for Performing            08/24/1998        Awaiting Action
                                        In-Service Quality of Service Testing
--------------------------------------------------------------------------------------------------------------------------

Canada             2,307,766            Method and Apparatus for Performing            11/06/1998        Awaiting Action
                                        Service-Level Analysis of Communications
                                        Network Performance Metrics
--------------------------------------------------------------------------------------------------------------------------

Europe             99915051.9           Dynamic Modeling of Complex Networks and       9/26/2000         Awaiting Action
                                        Prediction of Impacts of Faults Therein
--------------------------------------------------------------------------------------------------------------------------

Europe             97950579.9           Method and Apparatus for Measurement of Peak   05/1999           Awaiting Action
                                        Throughput in Packetized Data Networks
--------------------------------------------------------------------------------------------------------------------------

Europe             98959404.9           Method and Apparatus for Performing            05/2000           Awaiting Action
                                        Service-Level Analysis of Communications
                                        Network Performance Metrics
--------------------------------------------------------------------------------------------------------------------------

Japan              2000-538359          Dynamic Modeling of Complex Networks and       09/26/2000        Awaiting Action
                                        Prediction of Impacts of Faults Therein
--------------------------------------------------------------------------------------------------------------------------

Germany            19882639.7           Method and Apparatus for Performing            02/25/2000        Awaiting Action
                                        In-Service Quality of Service Testing
--------------------------------------------------------------------------------------------------------------------------

Singapore          20005379-3           Dynamic Modeling of Complex Networks and       9/26/2000         Awaiting Action
                                        Prediction of Impacts of Faults Therein
--------------------------------------------------------------------------------------------------------------------------
</TABLE>



                                     -2-


<PAGE>   12



<TABLE>
<CAPTION>

--------------------------------------------------------------------------------------------------------------------------
Country            Serial No.                               Title                      Filing Date       Status
--------------------------------------------------------------------------------------------------------------------------
<S>              <C>                  <C>                                            <C>                <C>
South Africa                            Dynamic Modeling of Complex Networks and       9/26/2000         Awaiting Action
                                        Prediction of Impacts of Faults Therein
--------------------------------------------------------------------------------------------------------------------------

UK                 00040009.7           Method and Apparatus for Performing            08/24/1998        Awaiting Action
                                        In-Service Quality of Service Testing
--------------------------------------------------------------------------------------------------------------------------
</TABLE>



      Presently, Visual Networks Technologies, Inc. has no International
Patent Cooperation Treaty (PCT) applications pending.  Visual Networks
Technologies, Inc. does not yet own any foreign patents.


                                     -3-

<PAGE>   13


                                  EXHIBIT C

                                  TRADEMARKS


      17.      PENDING U.S. TRADEMARK APPLICATIONS

<TABLE>
<CAPTION>

-------------------------------------------------------------------------------------------------------
SERIAL NO.            MARK                                  STATUS
-------------------------------------------------------------------------------------------------------
<S>                <C>                                   <C>
75/788,699            EWATCHER                              Response to Non-Final Action Filed 9/6/00
-------------------------------------------------------------------------------------------------------

75/612,153            TRINITY                               Non-Final Action mailed 10/17/00
-------------------------------------------------------------------------------------------------------

75/624,707            MAKE IT VISUAL                        Allowed; 1st Extension of Time file on
                                                            7/25/00
-------------------------------------------------------------------------------------------------------

75/745,829            TUNNELVISION                          Allowed; 1st Extension of Time filed on
                                                            10/11/00
-------------------------------------------------------------------------------------------------------

75/745,828            TUNNELVISION                          Accepted; Published on 11/21/00
-------------------------------------------------------------------------------------------------------

76/109,122            VISUAL TRINITY                        Filed 8/14/00
-------------------------------------------------------------------------------------------------------

76/109,116            VISUAL NETWORKS and Design            Filed 8/14/00
-------------------------------------------------------------------------------------------------------

TM00-134              VISUAL EWATCHER                       Filed 8/14/00
-------------------------------------------------------------------------------------------------------

76/127,701            VISUAL TDSLINK                        Filed 9/12/2000
-------------------------------------------------------------------------------------------------------

76/127,702            TDSLINK                               Filed 9/12/2000
-------------------------------------------------------------------------------------------------------

76/139,117            VISUAL SERVICE ADVISOR                Filed 10/2/2000
-------------------------------------------------------------------------------------------------------

76/139,114            VISUAL LINKSAFE                       Filed 10/2/2000
-------------------------------------------------------------------------------------------------------

76/139,116            VISUAL IP INSIGHT                     Filed 10/2/2000
-------------------------------------------------------------------------------------------------------

76/139,115            VISUAL INTERNET BENCHMARK             Filed 10/2/2000
-------------------------------------------------------------------------------------------------------
</TABLE>


<PAGE>   14


                          Registered U.S. Trademarks

<TABLE>
<CAPTION>

--------------------------------------------------------------------------------------------------------------------
REG. NO.                 MARK                                                                 REG. DATE
--------------------------------------------------------------------------------------------------------------------
<S>                    <C>                                                                  <C>
1,970,625                ACCESSRAMP DOCUMENTING THE INFORMATION SUPER HIGHWAY (stylized)      4/23/96
--------------------------------------------------------------------------------------------------------------------

2,007,923                CARAVELLE WATCHER                                                    10/15/96
--------------------------------------------------------------------------------------------------------------------

2,009,418                VISUAL UPTIME                                                        10/22/96
--------------------------------------------------------------------------------------------------------------------

2,032,357                GLOBALWATCHER                                                        1/21/97
--------------------------------------------------------------------------------------------------------------------

2,067,027                MEDIAWATCHER                                                         6/3/97
--------------------------------------------------------------------------------------------------------------------
                                                                                              11/25/97; Cancellation
2,115,387                IWATCHER                                                             filed 8/13/99
--------------------------------------------------------------------------------------------------------------------

2,117,886                TRANSCEIVE                                                           12/2/97; Being Sold
--------------------------------------------------------------------------------------------------------------------

2,122,626                VISUAL NETWORKS                                                      12/23/97
--------------------------------------------------------------------------------------------------------------------

2,155,605                INVERSE NETWORK TECHNOLOGY                                           5/5/98
--------------------------------------------------------------------------------------------------------------------

2,180,579                I (stylized)                                                         8/11/98
--------------------------------------------------------------------------------------------------------------------

2,181,207                INVERSE NETWORK TECHNOLOGY                                           8/11/98
------------------------------ -------------------------------------------------------------------- ---------------------

2,193,550                INVERSE                                                              10/6/98
--------------------------------------------------------------------------------------------------------------------

2,203,246                AVESTA TECNOLOGIES                                                   10/10/98
--------------------------------------------------------------------------------------------------------------------

2,224,976                BURST ADVISOR                                                        2/23/99
--------------------------------------------------------------------------------------------------------------------

2,248,906                MEASUREMENTS THAT MATTER                                             6/1/99
--------------------------------------------------------------------------------------------------------------------

2,278,155                INTERNET MEASUREMENT SERVICE                                         9/14/99
--------------------------------------------------------------------------------------------------------------------

2,282,318                US BENCHMARK REPORT                                                  9/28/99
--------------------------------------------------------------------------------------------------------------------

2,282,319                UK BENCHMARK REPORT                                                  9/28/99
--------------------------------------------------------------------------------------------------------------------

2,288,967                MEASURING QUALITY OF THE INTERNET                                    10/26/99
--------------------------------------------------------------------------------------------------------------------

2,304,103                INVERSE IP INSIGHT                                                   12/28/99
--------------------------------------------------------------------------------------------------------------------

2,389,211                INVERSE IP INSIGHT                                                   9/26/00
--------------------------------------------------------------------------------------------------------------------
</TABLE>

                                     -2-

<PAGE>   15


                    Foreign Pending Trademark Applications

<TABLE>
<CAPTION>

-----------------------------------------------------------------------------------------------------------------------
COUNTRY                            SERIAL NO.            MARK                                            FILING DATE
-----------------------------------------------------------------------------------------------------------------------
<S>                              <C>                  <C>                                            <C>
Canada                             827491                VISUAL NETWORKS                                 10/31/96
-----------------------------------------------------------------------------------------------------------------------

ECT                                393561                BURST ADVISOR                                   10/28/96
-----------------------------------------------------------------------------------------------------------------------

ECT                                001282102             MAKE IT VISUAL                                  8/13/99
-----------------------------------------------------------------------------------------------------------------------

Canada                             1030375               MAKE IT VISUAL                                  9/28/99
-----------------------------------------------------------------------------------------------------------------------
</TABLE>

                        Foreign Registered Trademarks

<TABLE>
<CAPTION>

----------------------------------------------------------------------------------------------------------------------
COUNTRY                            REGISTRATION NO.          MARK                                   REGISTRATION DATE
----------------------------------------------------------------------------------------------------------------------
<S>                              <C>                      <C>                                    <C>
Canada                             490358                    VISUAL UPTIME                          2/20/98
----------------------------------------------------------------------------------------------------------------------

Canada                             523933                    BURST ADVISOR                          2/28/00
----------------------------------------------------------------------------------------------------------------------

ECT                                393546                    VPOP                                   10/28/96
----------------------------------------------------------------------------------------------------------------------

ECT                                393512                    VISUAL NETWORKS                        10/28/96
----------------------------------------------------------------------------------------------------------------------

ECT                                393504                    VISUAL UPTIME                          10/28/96
----------------------------------------------------------------------------------------------------------------------
</TABLE>


                                     -3-



<PAGE>   16


                                  EXHIBIT D

                                  MASK WORKS



                                    None.




                                   SCHEDULE 3(d)

               CLAIMS AGAINST INTELLECTUAL PROPERTY COLLATERAL



1.    SMARTS Claim. On October 31, 1997, a lawsuit was filed against Avesta
Technologies, Inc. ("Avesta") and David Zager (a founder and, at the time, an
employee of Avesta) by Systems Management ARTS Incorporated ("SMARTS") in the
United States District Court for the Southern District of New York, alleging
unfair competition, unjust enrichment and that Avesta and Mr. Zager infringed
two patents held by SMARTS. The complaint also alleges interference with
contractual relations against Avesta, as well as a claim of breach of contract
against Mr. Zager. Avesta answered the complaint, denying all allegations, and
also asserted counterclaims against SMARTS for patent misuse, unfair
competition, interference with business and patent invalidity.

2.    eWatcher Challenge.  AverStar, Inc. ("AverStar") sent a letter dated
August 24, 1999 advising Avesta of AverStar's belief that it has superior
rights to the eWatcher mark.  AverStar has filed a competing trademark
application for the mark in the U.S. Patent and Trademark Office.