EXHIBIT 5.1

                                August 17, 2004

Juniper Networks, Inc.
1194 North Mathilda Avenue
Sunnyvale, CA 94089

      RE: REGISTRATION STATEMENT ON FORM S-8

Ladies and Gentlemen:

      We have examined the Registration Statement on Form S-8 to be filed by you
with the Securities and Exchange Commission on or about August 17, 2004 (the
"Registration Statement"), in connection with the registration under the
Securities Act of 1933, as amended (the "Securities Act"), of up to 20,000,000
shares of common stock, par value $0.0001, of Juniper Networks, Inc. (the
"Shares"), that are to be issued pursuant to the Juniper Networks, Inc. Amended
and Restated 1996 Stock Plan (the "Plan"). As your legal counsel, we have
examined the proceedings taken and are familiar with the actions proposed to be
taken by you in connection with the sale and issuance of the Shares under the
Plan and pursuant to the agreements related thereto.

      It is our opinion that, when issued and sold in compliance with applicable
prospectus delivery requirements and in the manner referred to in the Plans and
pursuant to the agreements that accompany the Plans, the Shares will be duly
authorized, validly issued, fully paid and nonassessable.

      We consent to the use of this opinion as an exhibit to the Registration
Statement and further consent to the use of our name wherever appearing in the
Registration Statement, including any prospectus constituting a part thereof,
and any amendments thereto. In giving such consent, we do not consider that we
are "experts" within the meaning of such term as used in the Securities Act, or
the rules and regulations of the Securities and Exchange Commission issued
thereunder, with respect to any part of the Registration Statement, including
this opinion as an exhibit or otherwise.

                                      Very truly yours,

                                      WILSON SONSINI GOODRICH & ROSATI
                                      Professional Corporation