Exhibit 32.1

      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, Michael Klayko, certify, pursuant to 18 U.S.C. Section 1350, as adopted
pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, that the Annual
Report of Brocade Communications Systems, Inc. on Form 10-K for the fiscal year
ended October 30, 2004 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 Annual Report on Form 10-K fairly presents in all material respects the
financial condition and results of operations of Brocade Communications Systems,
Inc.


                                    By:   /s/ Michael Klayko
                                          ------------------------------
                                          Michael Klayko
                                          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 Annual
Report of Brocade Communications Systems, Inc. on Form 10-K for the fiscal
quarter ended October 30, 2004 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 Annual Report on Form 10-K 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, Administration and
                                          Chief Financial Officer