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                                                                 EXHIBIT - 10.64

                                 FIFTH AMENDMENT

         THIS FIFTH AMENDMENT (the "Amendment") is made and entered into as of
the 18th day of November, 2003, by and between CA-THE CONCOURSE LIMITED
PARTNERSHIP, A DELAWARE LIMITED PARTNERSHIP ("Landlord"), and BROCADE
COMMUNICATIONS SYSTEMS, INC., A DELAWARE CORPORATION ("Tenant").

                                    RECITALS

A.       Landlord (as successor by conversion to EOP-The Concourse, L.L.C., a
         Delaware limited liability company, the successor in interest to
         Spieker Properties, L.P., a California limited partnership) and Tenant
         are parties to that certain lease dated December 17, 1999, which lease
         has been previously amended by instruments dated February 16, 2000 (the
         "First Amendment"), August 11, 2000 (the "Second Amendment"), November
         30, 2000 (the "Third Amendment") and November ___, 2003 (the "Fourth
         Amendment") (collectively, the "Lease"). Pursuant to the Lease,
         Landlord has leased to Tenant space currently containing approximately
         271,387 rentable square feet (the "Premises") comprised of (i) all of
         the rentable area, approximately 210,667 rentable square feet
         ("Original Premises"), in the building commonly known as The Concourse
         VI located at 1745 Technology Drive, San Jose, California ("Building
         VI"), (ii) 39,043 rentable square feet (the "Expansion Premises")
         described as Suite Nos. 250, 260, 500 on the 2nd, and 5th floors of the
         building commonly known as The Concourse V located at 1741 Technology
         Drive, San Jose, California ("Building V"), and (iii) 21,667 rentable
         square feet (the "Second Expansion Premises") described as Suite No.
         300 on the 3rd floor of Building V, in the project commonly known as
         The Concourse.

B.       Tenant and Landlord mutually desire that the Lease be amended on and
         subject to the following terms and conditions.

         NOW, THEREFORE, in consideration of the mutual covenants and agreements
herein contained and other good and valuable consideration, the receipt and
sufficiency of which are hereby acknowledged, Landlord and Tenant agree as
follows:

I.       AMENDMENT. Retroactively effective as of the date of the Second
         Amendment, Landlord and Tenant agree that the Lease shall be amended in
         accordance with the following terms and conditions:

         A.       Scheduled Term Expiration Date. The parties agree that the
                  "Scheduled Term Expiration Date", unless sooner terminated in
                  accordance with the Lease, shall mean August 31, 2010.

         B.       Section 1, "Rent", of the Second Amendment, shall be deleted
                  in its entirety and replaced with the following:

                  "A.      RENT. Subject to the provisions of Paragraphs 2.B,
                           Base Rent, net of Operating Expenses per Paragraph 7
                           of this Lease and net of any "additional rent"
                           otherwise due under this Lease, for the Premises
                           shall be as follows:

                           1.       ORIGINAL PREMISES FROM TERM COMMENCEMENT
                                    DATE THROUGH

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                                    SCHEDULED TERM EXPIRATION DATE. As of the
                                    Term Commencement Date, the schedule of Base
                                    Rent payable with respect to the Original
                                    Premises during the Term is the following:

                                                                    MONTHLY
                                             PERIOD                BASE RENT
                                    (09/01/00) - (08/31/01)       $516,159.00
                                    (09/01/01) - (08/31/02)       $531,643.00
                                    (09/01/02) - (08/31/03)       $547,593.00
                                    (09/01/03) - (08/31/04)       $564,020.00
                                    (09/01/04) - (08/31/05)       $580,941.00
                                    (09/01/05) - (08/31/06)       $598,369.00
                                    (09/01/06) - (08/31/07)       $616,320.00
                                    (09/01/07) - (08/31/08)       $634,810.00
                                    (09/01/08) - (08/31/09)       $653,854.00
                                    (09/01/09) - (08/31/10)       $673,470.00

                                    All such Base Rent shall be payable by
                                    Tenant in accordance with the terms of the
                                    Lease.

                           2        EXPANSION PREMISES FROM EXPANSION PREMISES
                                    TERM COMMENCEMENT DATE THROUGH SCHEDULED
                                    TERM EXPIRATION DATE. As of the Expansion
                                    Premises Term Commencement Date, the
                                    schedule of Base Rent payable with respect
                                    to the Expansion Premises during the balance
                                    of the Term is the following:

                                                                    MONTHLY
                                             PERIOD                BASE RENT
                                    (09/01/00) - (08/31/01)       $111,273.00
                                    (09/01/01) - (08/31/02)       $114,611.00
                                    (09/01/02) - (08/31/03)       $118,049.00
                                    (09/01/03) - (08/31/04)       $121,591.00
                                    (09/01/04) - (08/31/05)       $125,238.00
                                    (09/01/05) - (08/31/06)       $128,995.00
                                    (09/01/06) - (08/31/07)       $132,865.00
                                    (09/01/07) - (08/31/08)       $136,851.00
                                    (09/01/08) - (08/31/09)       $140,957.00
                                    (09/01/09) - (08/31/10)       $145,185.00

                                    All such Base Rent shall be payable by
                                    Tenant in accordance with the terms of the
                                    Lease.

                           3        SECOND EXPANSION PREMISES FROM SECOND
                                    EXPANSION PREMISES TERM COMMENCEMENT DATE
                                    THROUGH SCHEDULED TERM EXPIRATION DATE. As
                                    of the Second Expansion Premises Term
                                    Commencement Date, the schedule of Base Rent
                                    payable with respect to the Second Expansion
                                    Premises during the balance of the Term is
                                    the following:

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                                                                   MONTHLY
                                             PERIOD               BASE RENT
                                    (01/01/01) - (12/31/01)      $104,002.00
                                    (01/01/02) - (12/31/02)      $107,122.00
                                    (01/01/03) - (12/31/03)      $110,335.00
                                    (01/01/04) - (12/31/04)      $113,645.00
                                    (01/01/05) - (12/31/05)      $117,055.00
                                    (01/01/06) - (12/31/06)      $120,566.00
                                    (01/01/07) - (12/31/07)      $124,183.00
                                    (01/01/08) - (12/31/08)      $127,909.00
                                    (01/01/09) - (12/31/09)      $131,746.00
                                    (01/01/10) - (08/31/10)      $135,698.00

                                    All such Base Rent shall be payable by
                                    Tenant in accordance with the terms of the
                                    Lease.

                           4        TENANT'S PROPORTIONATE SHARE OF OPERATING
                                    EXPENSES. For the period commencing on the
                                    Second Expansion Premises Term Commencement
                                    Date and ending on the Scheduled Term
                                    Expiration Date, Tenant shall pay for
                                    Tenant's Proportionate Share of Operating
                                    Expenses in accordance with the terms of the
                                    Lease."

         C.       Deleted Provisions. Section 3, "Rent", of First Amendment of
                  the Lease and Section 1, "Rent", of Second Amendment to Lease
                  are hereby deleted in their entirety and are of no further
                  force and effect.

II.      MISCELLANEOUS.

         A.       This Amendment sets forth the entire agreement between the
                  parties with respect to the matters set forth herein. Landlord
                  and Tenant acknowledge and agree that this Amendment is
                  intended as a clarification of the Base Rent payable under the
                  Lease only and does not in any way modify Tenant's rent
                  obligations under the Lease. There have been no additional
                  oral or written representations or agreements. Under no
                  circumstances shall Tenant be entitled to any Rent abatement,
                  improvement allowance, leasehold improvements, or other work
                  to the Premises, or any similar economic incentives that may
                  have been provided Tenant in connection with entering into the
                  Lease, unless specifically set forth in this Amendment or the
                  Lease.

         B.       Except as herein modified or amended, the provisions,
                  conditions and terms of the Lease shall remain unchanged and
                  in full force and effect.

         C.       In the case of any inconsistency between the provisions of the
                  Lease and this Amendment, the provisions of this Amendment
                  shall govern and control.

         D.       Submission of this Amendment by Landlord is not an offer to
                  enter into this Amendment but rather is a solicitation for
                  such an offer by Tenant. Landlord shall not be bound by this
                  Amendment until Landlord has executed and delivered the same
                  to Tenant.

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         E.       The capitalized terms used in this Amendment shall have the
                  same definitions as set forth in the Lease to the extent that
                  such capitalized terms are defined therein and not redefined
                  in this Amendment.

         F.       Tenant hereby represents to Landlord that Tenant has dealt
                  with no broker in connection with this Amendment. Tenant
                  agrees to indemnify and hold Landlord, its members,
                  principals, beneficiaries, partners, officers, directors,
                  employees, mortgagee(s) and agents, and the respective
                  principals and members of any such agents (collectively, the
                  "Landlord Related Parties") harmless from all claims of any
                  brokers claiming to have represented Tenant in connection with
                  this Amendment. Landlord hereby represents to Tenant that
                  Landlord has dealt with no broker in connection with this
                  Amendment. Landlord agrees to indemnify and hold Tenant, its
                  members, principals, beneficiaries, partners, officers,
                  directors, employees, and agents, and the respective
                  principals and members of any such agents (collectively, the
                  "Tenant Related Parties") harmless from all claims of any
                  brokers claiming to have represented Landlord in connection
                  with this Amendment.

         G.       Each signatory of this Amendment represents hereby that he or
                  she has the authority to execute and deliver the same on
                  behalf of the party hereto for which such signatory is acting.

                       [SIGNATURES ARE ON FOLLOWING PAGE]

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                  IN WITNESS WHEREOF, Landlord and Tenant have duly executed
         this Amendment as of the day and year first above written.

                           LANDLORD:

                           CA-THE CONCOURSE LIMITED PARTNERSHIP, A
                           DELAWARE LIMITED PARTNERSHIP

                           By: EOM GP, L.L.C., a Delaware limited liability
                               company, its general partner

                               By: Equity Office Management, L.L.C., a
                                   Delaware limited liability company,
                                   its non-member manager

                                   By:    /s/ John W. Petersen
                                          --------------------------------------
                                   Name:  John W. Petersen
                                   Title: Regional Senior Vice President

                           TENANT:

                           BROCADE COMMUNICATIONS SYSTEMS, INC., A
                           DELAWARE CORPORATION

                           By:    /s/ Antonio Canova
                                  ----------------------------------------------
                           Name:  Antonio Canova
                           Title: CFO

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