Exhibit 99.1


      CERTIFICATION OF CHIEF EXECUTIVE OFFICER AND CHIEF FINANCIAL OFFICER
                                   PURSUANT TO
                             18 U.S.C. SECTION 1350,
                             AS ADOPTED PURSUANT TO
                  SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

I, Gregory L. Reyes, certify, pursuant to 18 U.S.C. Section 1350, as adopted
pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, that the Quarterly
Report of Brocade Communications Systems, Inc. on Form 10-Q for the quarterly
period ended July 27, 2002 fully complies with the requirements of Section 13(a)
or 15(d) of the Securities Exchange Act of 1934 and that information contained
in such Quarterly Report fairly presents in all material respects the financial
condition and results of operations of Brocade Communications Systems, Inc.

                                            By: /s/ GREGORY L. REYES
                                                -------------------------------
                                                   Gregory L. Reyes
                                                   Chairman of the Board and
                                                   Chief Executive Officer

I, Antonio Canova, certify, pursuant to 18 U.S.C. Section 1350, as adopted
pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, that the Quarterly
Report of Brocade Communications Systems, Inc. on Form 10-Q for the quarterly
period ended July 27, 2002 fully complies with the requirements of Section 13(a)
or 15(d) of the Securities Exchange Act of 1934 and that information contained
in such Quarterly Report fairly presents in all material respects the financial
condition and results of operations of Brocade Communications Systems, Inc.

                                            By: /s/ ANTONIO CANOVA
                                                -------------------------------
                                                   Antonio Canova
                                                   Vice President, Finance and
                                                   Chief Financial Officer