EXHIBIT 32.1

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

      I, Daniel J. Warmenhoven, 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 Network Appliance, Inc., on Form 10-Q for the quarterly
period ended October 29, 2004 fully complies with the requirements of Section
13(a) or 15(d) of the Securities Exchange Act of 1934, as amended, and that
information contained in such Quarterly Report on Form 10-Q fairly presents, in
all material respects, the financial condition and results of operations of
Network Appliance, Inc.

                                              /s/ DANIEL J. WARMENHOVEN
                                              -------------------------
                                              Daniel J. Warmenhoven
                                              Chief Executive Officer

Date: December 8, 2004