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                                                                    EXHIBIT 23.1

                        CONSENT OF INDEPENDENT AUDITORS


       We consent to the incorporation by reference in the Registration
Statement (Form S-8 No. 333-56496) pertaining to the 1997 Stock Plan, 2000 Stock
Plan, 2000 Employee Stock Purchase Plan and 2000 Director Option Plan of CoSine
Communications, Inc. of our report dated January 26, 2001, with respect to the
consolidated financial statements and financial statement schedule of CoSine
Communications, Inc. included in the Annual Report (Form 10-K) for the year
ended December 31, 2000.

                                        /s/ Ernst & Young LLP

San Jose, California
March 29, 2001


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