EXHIBIT 5.1
 
                                      September 19, 1996
 
Sync Research, Inc.
7 Studebaker
Irvine, CA 92718
 
    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 September 19, 1996 (the
"Registration Statement") in connection with the registration under the
Securities Act of 1933, as amended, of a total of 330,500 shares of your Common
Stock reserved for issuance under the Sync Research, Inc. 1996 Non-Executive
Stock Option Plan (the "1996 Plan") and 446,760 shares of your Common Stock
reserved for issuance under the Assumed TyLink Corporation 1994 Equity Incentive
Plan (the "Assumed Plan") (all of which constitute the "Shares"). The 1996 Plan
and the Assumed Plan are referred to as the "Plans." As your legal counsel, we
have examined the proceedings taken and are familiar with the proceedings
proposed to be taken by you in connection with the sale and issuance of the
Shares under the Plans.
 
    It is our opinion that, when issued and sold in the manner referred to in
the Plans and pursuant to the respective agreement which accompanies each grant
under the plan, the Shares will be legally and 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 it appears in the
Registration Statement and any amendments to it.
 
                                        Sincerely,
 
                                        VENTURE LAW GROUP
                                        A Professional Corporation