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[GRAY CARY WARE & FREIDENRICH LLP]

                                                                     EXHIBIT 5.1




January 21, 1998


Securities and Exchange Commission
450 Fifth Street, N.W.
Washington, D.C.  20549

RE:     BAY NETWORKS, INC.
        REGISTRATION STATEMENT ON FORM S-3

Ladies and Gentlemen:

As legal counsel for Bay Networks, Inc., a Delaware corporation (the "Company"),
we are rendering this opinion in connection with the preparation and filing of a
registration statement on Form S-3 (the "Registration Statement") relating to
the registration under the Securities Act of 1933, as amended, of 5,093,551
shares of Common Stock, par value $0.01 per share (the "Common Stock"), issued
by the Company pursuant to an Agreement of Merger, dated as of January 13, 1998,
among the Company, TwigCo, Inc., a Delaware corporation and a wholly-owned
subsidiary of the Company, and New Oak Communications, Inc., a Delaware
corporation.

We have examined such instruments, documents and records as we deemed relevant
and necessary for the basis of our opinion hereinafter expressed. In such
examination, we have assumed the genuineness of all signatures and the
authenticity of all documents submitted to us as originals and the conformity to
the originals of all documents submitted to us as copies.

Based on such examination, we are of the opinion that the 5,093,551 shares of
Common Stock of the Company being registered pursuant to the Registration
Statement and to be sold by the selling stockholders are duly authorized shares
of Common Stock and are validly issued, fully paid and nonassessable.

We hereby consent to the filing of this opinion as an exhibit to the
Registration Statement referred to above and the use of our name wherever it
appears in said Registration Statement.

This opinion is to be used only in connection with the issuance of the Common
Stock while the Registration Statement is in effect.

Very truly yours,


/s/ GRAY CARY WARE & FREIDENRICH

GRAY CARY WARE & FREIDENRICH LLP