<PAGE>   1
            As filed with the Securities and Exchange Commission on May 21, 1999
                                                     Registration No. 333-______
================================================================================

                                  UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549
                               -------------------

                                    FORM S-8
                             REGISTRATION STATEMENT
                                      UNDER
                           THE SECURITIES ACT OF 1933

                               -------------------

                                REDBACK NETWORKS
             (Exact name of registrant as specified in its charter)

<TABLE>
<S>                                     <C>                               <C>
               DELAWARE                             3576                      77-0438443
     (State or other jurisdiction       (Primary Standard Industrial         (IRS Employer
   of incorporation or organization)     Classification Code Number)      Identification No.)
</TABLE>

                             1389 MOFFETT PARK DRIVE
                               SUNNYVALE, CA 94089
               (Address of principal executive offices) (Zip Code)
                               -------------------

                                REDBACK NETWORKS
                            1999 STOCK INCENTIVE PLAN
                                 1997 STOCK PLAN
                        1999 EMPLOYEE STOCK PURCHASE PLAN
                           1999 DIRECTORS' OPTION PLAN
           SHARES ACQUIRED UNDER WRITTEN COMPENSATION AGREEMENTS WITH
 DAVID COLEMAN, STEVE DE GOLIA, JOYCE GANDOLFI, KAREN HAMERQUIST, JEFF JOHNSON,
       WING KO, DAVE LAWRENCE, ERIC OLSEN, WILLIAM PALTER, KEITH QUIGLEY,
                 GUNA RAMIREDDY, DAVID SHAPIRO, LYNETTE SOUZA,
                           NICK THILLE AND JAY WILLEY
                            (Full title of the Plans)

                               -------------------

                                DENNIS L. BARSEMA
                      PRESIDENT AND CHIEF EXECUTIVE OFFICER
                                REDBACK NETWORKS
                             1389 MOFFETT PARK DRIVE
                               SUNNYVALE, CA 94089
                     (Name and address of agent for service)
                              --------------------

                                  408-548-3500
          (Telephone number, including area code, of agent for service)
                               -------------------

<TABLE>
<CAPTION>
                                       CALCULATION OF REGISTRATION FEE
=============================================================================================================
                Title of                                  Proposed Maximum  Proposed Maximum
               Securities                     Amount          Offering          Aggregate         Amount of
                 to be                        to be             Price           Offering         Registration
               Registered                 Registered (1)    per Share (2)       Price (2)            Fee
               ----------                 --------------  ----------------  ----------------     ------------
<S>                                      <C>              <C>               <C>                  <C>
1999 Stock Incentive Plan and 1997
  Stock Plan 
  Options to Purchase Common Stock           6,295,636          N/A                     N/A                N/A
    Common Stock (par value $0.0001)     6,295,636 Shares      $23.00          $144,799,628         $40,254.00
                                                             

1999 Directors' Option Plan
    Options to Purchase Common Stock         200,000             N/A                    N/A                N/A
    Common Stock (par value $0.0001)      200,000 shares       $23.00            $4,600,000          $1,278.80
--------------------------------------------------------------------------------------------------------------
</TABLE>

<PAGE>   2
<TABLE>
<S>                                      <C>                   <C>              <C>                  <C>
1999 Employee Stock Purchase Plan
  Rights to Purchase Common Stock                               N/A                    N/A                N/A
  Common Stock (par value $0.0001)      1,000,000 shares      $23.00           $23,000,000          $6,394.00

Shares Acquired Under Written 
Compensation Agreements With 
David Coleman, Steve De Golia, 
Joyce Gandolfi, Karen Hamerquist, 
Jeff Johnson, Wing Ko, 
Dave Lawrence, Eric Olsen, 
William Palter, Keith Quigley, 
Guna Ramireddy, David Shapiro, 
Lynette Souza, Nick Thille and 
Jay Willey 
  Common Stock (par value $0.0001)     140,838 shares         $23.00           $3,239,274            $900.52
</TABLE>

(1)     This Registration Statement shall also cover any additional shares of
        Common Stock which become issuable under the 1999 Stock Incentive Plan,
        the 1997 Stock Plan, the 1999 Directors' Option Plan, the 1999 Employee
        Stock Purchase Plan and the Written Compensation Agreements with David
        Coleman, Steve De Golia, Joyce Gandolfi, Karen Hamerquist, Jeff Johnson,
        Wing Ko, Dave Lawrence, Eric Olsen, William Palter, Keith Quigley, Guna
        Ramireddy, David Shapiro, Lynette Souza, Nick Thille and Jay Willey,
        because of any stock dividend, stock split, recapitalization or other
        similar transaction effected without the receipt of consideration which
        results in an increase in the number of the outstanding shares of Common
        Stock of Redback Networks.

(2)     Calculated only for purposes of this offering under Rule 457(h) of the
        Securities Act of 1933, as amended, on the basis of the fair market
        value per share of Common Stock of Redback Networks on May 17, 1999.


<PAGE>   3
                                EXPLANATORY NOTE


               Under General Instruction C of Form S-8, this Registration
Statement contains a prospectus meeting the requirements of Part I of Form S-3
relating to the reoffer by a certain individual of shares of Common Stock, par
value $0.0001 per share, of Redback Networks acquired pursuant to a Written
Agreement.



<PAGE>   4
                                REDBACK NETWORKS

         FORM S-8 CROSS REFERENCE SHEET SHOWING LOCATION OF INFORMATION
                         REQUIRED BY PART I OF FORM S-3



<TABLE>
<CAPTION>
Form S-3 Item Number                             Location/Heading in Prospectus
--------------------                             ------------------------------
<S>                                              <C>
1.  Forepart of Registration Statement and       Cover page
    Outside Front Cover page of Prospectus

2.  Inside Front and Outside Back Cover          Available Information; Incorporation of
    Page of Prospectus                           Certain Information by Reference

3.  Summary Information, Risk Factors and        Risk Factors
    Ratio of Earnings to Fixed Charges

4.  Use of Proceeds                              Not applicable

5.  Determination of Offering Price              Not applicable

6.  Dilution                                     Not applicable

7.  Selling Security Holder                      Selling Security Holder

8.  Plan of Distribution                         Plan of Distribution

9.  Description of Securities to be              Not Applicable
    Registered

10. Interests of Named Experts and Counsel       Not Applicable

11. Material Changes                             Not Applicable

12. Incorporation of Certain Information         Documents Incorporated by Reference

13. Disclosure of Commission Position on         Indemnification
    Indemnification for Securities Act
    Liabilities
</TABLE>

<PAGE>   5
                                     PART II

               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT



Item 3. Incorporation of Documents by Reference

        Redback Networks ("Redback") hereby incorporates by reference into this
Registration Statement the following documents previously filed with the
Securities and Exchange Commission (the "SEC"):

(a) Redback's prospectus filed with the SEC under Rule 424(b) under the
Securities Act of 1933, as amended (the "1933 Act"), in connection with
Registration Statement No. 333-744479 on Form S-1 filed with the SEC on March
16, 1999, the amendment filed on April 22, 1999, the amendment filed on May 4,
1999, the amendment filed on May 12, 1999 and the amendment filed on May 14,
1999, which contains the audited financial statements for the period August 30,
1996 (inception) through December 31, 1996 and for Redback's fiscal years ended
December 31, 1997 and 1998.

(b) The description of Redback's outstanding Common Stock contained in Redback's
Registration Statement No. 0-25853 on Form 8-A filed with the SEC on April 22,
1999, under Section 12 of the 1934 Act, including any amendment or report filed
to update the description.

        All reports and definitive proxy or information statements filed under
Section 13(a), 13(c), 14 or 15(d) of the 1934 Act after the date of this
Registration Statement and prior to the filing of a post-effective amendment
which indicates that all securities offered hereby have been sold or which
deregisters all securities then remaining unsold shall also be incorporated by
reference into this Registration Statement and to be a part hereof from the date
of filing of such documents.

Item 4. Description of Securities

        Not Applicable.

Item 5. Interests of Named Experts and Counsel

        Not Applicable.

Item 6. Indemnification of Directors and Officers

        Section 145 of the Delaware General Corporation Law authorizes a court
to award or a corporation's Board of Directors to grant indemnification to
directors and officers in terms sufficiently broad to permit such
indemnification under certain circumstances for liabilities (including
reimbursement for expenses incurred) arising under the 1933 Act. Redback's
Bylaws provide for mandatory indemnification of its directors and officers and
permissible indemnification of employees and other agents to the maximum extent
permitted by the Delaware General Corporation Law. Redback's Certificate of
Incorporation provides that, under Delaware law, its directors shall not be
liable for monetary damages for breach of their fiduciary duty as directors to
Redback and its stockholders. This provision in the Certificate of Incorporation
does not eliminate the fiduciary duty of the directors, and, in appropriate
circumstances, equitable remedies such as injunctive or other forms of
non-monetary relief will remain available under Delaware law. In addition, each
director will continue to be subject to liability for breach of the director's
duty of loyalty to Redback for acts or omissions not in good faith or involving
intentional misconduct, for knowing violations of law, for actions leading to
improper personal benefit to the director and for payment of dividends or
approval of stock repurchases or redemptions that are unlawful under Delaware
law. The provision also does not affect a director's responsibilities under any
other law, such as the federal securities laws or state or federal environmental
laws. Redback has entered into Indemnification Agreements with its officers and
directors. The Indemnification Agreements provide Redback's officers and
directors with further indemnification to the maximum extent permitted by the
Delaware General Corporation Law.



                                      II-2
<PAGE>   6

Item 7. Exemption from Registration Claimed

        Not Applicable.

Item 8. Exhibits

<TABLE>
<CAPTION>
Exhibit Number    Exhibit
--------------    -------
<S>               <C>
      4           Instrument Defining Rights of Stockholders. Reference is made
                  to Redback's Registration Statement No. 0-25853 on Form 8-A,
                  which is incorporated herein by reference under Item 3(b) of
                  this Registration Statement.

      5           Opinion and consent of Gunderson Dettmer Stough Villeneuve
                  Franklin & Hachigian LLP.

      23.1        Consent of PricewaterhouseCoopers, Independent Accountants.

      23.2        Consent of Gunderson Dettmer Stough Villeneuve Franklin &
                  Hachigian LLP is contained in Exhibit 5.

      24          Power of Attorney. Reference is made to page II-4 of this
                  Registration Statement.

      99.1        Form of Written Compensation Agreement with David Coleman,
                  Steve De Golia, Joyce Gandolfi, Jeff Johnson, Eric Olsen,
                  William Palter, Keith Quigley, David Shapiro, Lynette Souza,
                  Nick Thille and Jay Willey.
</TABLE>

Item 9. Undertakings

        A.      Redback hereby undertakes:

                (1) to file, during any period in which offers or sales are
                being made, a post-effective amendment to this Registration
                Statement

                        (i)     to include any prospectus required by Section
                                10(a)(3) of the 1933 Act,

                        (ii)    to reflect in the prospectus any facts or events
                                arising after the effective date of this
                                Registration Statement (or the most recent
                                post-effective amendment thereof) which,
                                individually or in the aggregate, represent a
                                fundamental change in the information set forth
                                in this Registration Statement and

                        (iii)   to include any material information with respect
                                to the plan of distribution not previously
                                disclosed in this Registration Statement or any
                                material change to such information in this
                                Registration Statement; provided, however, that
                                clauses (1)(i) and (1)(ii) shall not apply if
                                the information required to be included in a
                                post-effective amendment by those paragraphs is
                                contained in periodic reports filed with or
                                furnished to the SEC by Redback under Section 13
                                or Section 15(d) of the 1934 Act that are
                                incorporated by reference in this Registration
                                Statement;

                (2) that for the purpose of determining any liability under the
                1933 Act each such post-effective amendment shall be deemed to
                be a new registration statement relating to the securities
                offered therein and the offering of such securities at that time
                shall be deemed to be the initial bona fide offering thereof and

                (3) to remove from registration by means of a post-effective
                amendment any of the securities being registered which remain
                unsold at the termination of Redback's 1999 Stock Incentive
                Plan, 1997 Stock Plan, 1999 Directors' Option Plan, 1999
                Employee Stock Purchase Plan and Written Compensation Agreements
                with David Coleman, Steve De Golia, Joyce Gandolfi, Karen
                Hamerquist, Jeff Johnson, Wing Ko, Dave Lawrence, Eric Olsen,
                William Palter, Keith Quigley, Guna Ramireddy, David Shapiro,
                Lynette Souza, Nick Thille and Jay Willey.

        B. Redback hereby undertakes that, for purposes of determining any
liability under the 1933 Act, each filing of Redback's annual report under
Section 13(a) or Section 15(d) of the 1934 Act that is incorporated by reference
in this Registration Statement shall be deemed to be a new registration
statement relating to the securities 



                                      II-3
<PAGE>   7

offered therein, and the offering of such securities at that time shall be
deemed to be the initial bona fide offering thereof.

C. Insofar as indemnification for liabilities arising under the 1933 Act may be
permitted to directors, officers or controlling persons of Redback under the
indemnification provisions summarized in Item 6 or otherwise, Redback has been
advised that, in the opinion of the SEC, such indemnification is against public
policy as expressed in the 1933 Act, and is, therefore, unenforceable. In the
event that a claim for indemnification against such liabilities (other than the
payment by Redback of expenses incurred or paid by a director, officer or
controlling person of Redback in the successful defense of any action, suit or
proceeding) is asserted by such director, officer or controlling person in
connection with the securities being registered, Redback will, unless in the
opinion of its counsel the matter has been settled by controlling precedent,
submit to a court of appropriate jurisdiction the question whether such
indemnification by it is against public policy as expressed in the 1933 Act and
will be governed by the final adjudication of such issue.


                                      II-4
<PAGE>   8
REOFFER PROSPECTUS

                                   SIGNATURES


               The Securities Act of 1933, as amended, requires that Redback
certifies that it has reasonable grounds to believe that it meets all of the
requirements for filing on Form S-8 and has had this Registration Statement
signed on its behalf by the undersigned, who is duly authorized, in the City of
San Francisco, State of California on this 21st day of May, 1999.


                                       REDBACK NETWORKS


                                       By: /s/Dennis L. Barsema
                                           -------------------------------------
                                           Dennis L. Barsema
                                           President and Chief Executive Officer



                                POWER OF ATTORNEY



KNOW ALL PERSONS BY THESE PRESENTS:

               That the undersigned officers and directors of Redback Networks,
a Delaware corporation, do hereby constitute and appoint Dennis L. Barsema and
Geoffrey C. Darby, and either of them, the lawful attorneys-in-fact and agents
with full power and authority to do any and all acts and things and to execute
any and all instruments which said attorneys and agents, and either one of them,
determine may be necessary or advisable or required to enable said corporation
to comply with the Securities Act of 1933, as amended, and any rules or
regulations or requirements of the Securities and Exchange Commission in
connection with this Registration Statement. Without limiting the generality of
the foregoing power and authority, the powers granted include the power and
authority to sign the names of the undersigned officers and directors in the
capacities indicated below to this Registration Statement, to any and all
amendments, both pre-effective and post-effective, and supplements to this
Registration Statement, and to any and all instruments or documents filed as
part of or in conjunction with this Registration Statement or amendments or
supplements thereof, and each of the undersigned hereby ratifies and confirms
all that said attorneys and agents, or either one of them, shall do or cause to
be done by virtue hereof. This Power of Attorney may be signed in several
counterparts.

               IN WITNESS WHEREOF, each of the undersigned has executed this
Power of Attorney on the date indicated.

               Under the requirements of the Securities Act of 1933, as amended,
this Registration Statement has been signed below by the following persons in
the capacities and on the dates indicated.

<TABLE>
<CAPTION>
Signature                    Title                                     Date
---------                    -----                                     ----
<S>                          <C>                                       <C> 
/s/Dennis L. Barsema         President, Chief Executive Officer        May 21, 1999
------------------------     and Director                 
Dennis L. Barsema            (Principal Executive Officer)
                             

/s/Geoffrey C. Darby         Chief Financial Officer, Treasurer        May 21, 1999
------------------------     and Secretary (Principal Financial 
Geoffrey C. Darby            and Accounting Officer)            
</TABLE>



<PAGE>   9
REOFFER PROSPECTUS
                             



<TABLE>
<S>                          <C>                                       <C> 
/s/James R. Flach            Director                                  May 21, 1999
------------------------
James R. Flach

/s/Pierre R. Lamond          Director                                  May 21, 1999
------------------------
Pierre R. Lamond

/s/Daniel J. Warmenhoven     Director                                  May 21, 1999
------------------------
Daniel J. Warmenhoven
</TABLE>



<PAGE>   10
REOFFER PROSPECTUS



                             Shares of Common Stock
                                Redback Networks


               This Reoffer Prospectus relates to 140,838 shares of the Common
Stock, par value $0.0001 (the "Common Stock"), of Redback Networks (the
"Company"), which may be offered from time to time by certain key employees
named herein (the "Registered Stockholders"). It is anticipated that the
Registered Stockholders will offer shares for sale at prevailing prices on the
Nasdaq National Market System on the date of sale. The Company will receive no
part of the proceeds of sale made hereunder. All expenses of registration
incurred in connection with this offering are being borne by the Company, but
all selling and other expenses incurred by each of the Registered Stockholders
will be borne by each such Registered Stockholder.

               Following the initial public offering of the Common Stock, the
Common Stock will be traded on the Nasdaq National Market System. The price per
share of the Company's Common Stock as offered in its initial public offering of
such Common Stock is expected to be $23.00.

               The Registered Stockholders and any broker executing selling
orders on behalf of the Registered Stockholders may be deemed to be
"underwriters" within the meaning of the Securities Act of 1933, as amended (the
"Securities Act"), in which event commissions received by such broker may be
deemed to be underwriting commissions under the Securities Act.

          THESE SECURITIES INVOLVE A HIGH DEGREE OF RISK AND SHOULD BE
           CONSIDERED ONLY BY PERSONS WHO CAN AFFORD THE LOSS OF THEIR
                               ENTIRE INVESTMENT.
                     SEE "RISK FACTORS" BEGINNING ON PAGE 3.
    THESE SECURITIES HAVE NOT BEEN APPROVED OR DISAPPROVED BY THE SECURITIES
         AND EXCHANGE COMMISSION NOR HAS THE COMMISSION PASSED UPON THE
           ACCURACY OR ADEQUACY OF THIS PROSPECTUS. ANY REPRESENTATION
                     TO THE CONTRARY IS A CRIMINAL OFFENSE.

               No person is authorized to give any information or to make any
representations, other than those contained in this Prospectus, in connection
with the offering described herein, and, if given or made, such information or
representations must not be relied upon as having been authorized by the Company
or any Registered Stockholder. This Prospectus does not constitute an offer to
sell, or a solicitation of an offer to buy, nor shall there be any sale of these
securities by any person in any jurisdiction in which it is unlawful for such
person to make such offer, solicitation or sale. Neither the delivery of this
Prospectus nor any sale made hereunder shall under any circumstances create an
implication that the information contained herein is correct as of any time
subsequent to the date hereof.

               The date of this Prospectus is May 17, 1999.



<PAGE>   11
                              AVAILABLE INFORMATION

               The Company will be subject to the informational reporting
requirements of the Securities Exchange Act of 1934, as amended (the "Exchange
Act") upon the first date on which its Common Stock is registered under Section
12(g) of the Exchange Act and in accordance therewith will file reports, proxy
statements and other information with the Securities and Exchange Commission
(the "Commission"). Such reports, proxy statements and other information can be
inspected and copied at the Public Reference Room of the Commission, 450 Fifth
Street, N.W., Washington, D.C. 20549 and at the Commission's regional offices at
219 South Dearborn Street, Chicago, IL 60604; 26 Federal Plaza, New York, NY
10007; and 5757 Wilshire Boulevard, Los Angeles, CA 90036, at prescribed rates.
The Common Stock following the Company's initial public offering will be quoted
on the Nasdaq National Market System. Reports, proxy statements, informational
statements and other information concerning the Company can be inspected at the
offices of the National Association of Securities Dealers, Inc.
at 1735 K Street, N.W., Washington, D.C.  20006.

               The Company intends to furnish its stockholders with annual
reports containing additional financial statements and a report thereon by
independent certified public accountants.

               A copy of any document incorporated by reference in the
Registration Statement (not including exhibits to the information that is
incorporated by reference unless such exhibits are specifically incorporated by
reference into the information that the Registration Statement incorporates) of
which this Reoffer Prospectus forms a part but which is not delivered with this
Reoffer Prospectus will be provided by the Company without charge to any person
(including any beneficial owner) to whom this Reoffer Prospectus has been
delivered upon the oral or written request of such person. Such requests should
be directed to Carrie Perzow, Redback Networks, 1389 Moffett Park Drive,
Sunnyvale, CA 94089. The Company's telephone number at that location is (408)
548 3500.


                                TABLE OF CONTENTS
<TABLE>
<CAPTION>
                                                                       Page
<S>                                                                    <C>
THE COMPANY...........................................................   3

RISK FACTORS..........................................................   

REGISTERED STOCKHOLDERS...............................................   

PLAN OF DISTRIBUTION..................................................

DOCUMENTS INCORPORATED BY REFERENCE...................................   

INDEMNIFICATION.......................................................   
</TABLE>



                                        2
<PAGE>   12
                                   THE COMPANY

     Redback Networks (the "Company") is a leading provider of advanced
networking systems that enable carriers, cable operators and service providers
to rapidly deploy high-speed access to the Internet and corporate networks. Our
products, consisting of the Subscriber Management System, or SMS 500 and SMS
1000, combine networking hardware with sophisticated software. Our products
connect and manage large numbers of subscribers using any of the major
high-speed access technologies, including digital subscriber line, which is a
technology that brings high-speed access over standard copper telephone lines,
cable and wireless. We sell our products through our direct sales force,
resellers and distribution partners.
 
     Bridging the gap between high-speed access concentrators and routers
connecting to the Internet backbone, our flagship product, the SMS 1000, is
currently being used by many of the largest carriers and service providers.
UUNET, a subsidiary of MCI Worldcom, SBC, Southwestern Bell Information Systems
and Pacific Bell Internet, subsidiaries of SBC and GTE have been, since
inception, our largest customers in terms of revenues. Other representative
customers include Ameritech, Bell Canada, Bell South, Concentric, Earthlink,
Flashcom, Korea Telecom, Verio and @Work, a division of @Home. They are
representative in terms of, among other things, the type of provider, the
mixture of broadband services offered and the mixture of regional versus
national deployment.
 
     In recent years, there has been a significant increase in demand by
businesses and consumers for broadband, or high-speed, access to the Internet
and to corporate networks. While carriers, cable operators and service providers
are attempting to provide inexpensive and comprehensive broadband access, there
are several major challenges associated with scaling and configuring existing
network architectures to accommodate large numbers of new high-speed
subscribers. We believe widespread deployment of broadband services requires a
new model for subscriber management that efficiently terminates subscriber
connections, manages broadband subscribers, provides flexibility for
connections, and supports multiple broadband access technologies simultaneously.
 
     Our products meet the above requirements. Whether deployed at subscriber
aggregation points by carriers, by cable operators or by service providers, our
products accept a large concentration of high-speed data traffic from such
devices as digital subscriber line concentrators, cable modem termination
systems and wireless termination systems. Our products reduce the processing
requirements placed on routers connecting to the Internet backbone in broadband
networks. Our SMS 1000 today supports up to 4,000 simultaneous subscribers. The
key benefits of our solution include:
 
     - Enhances Broadband Operations. Our products bridge the operational gap
       between "last mile" access networks that serve businesses and homes and
       the routers connecting to the Internet backbone and corporate networks.
 
     - Supports All Major Access Technologies. Our products support all major
       access technologies, including digital subscriber line, cable, wireless
       and dial.
 
     - Facilitates Rapid and Scalable Deployment. Our products allow service
       providers to use existing access, accounting and management control
       systems, enabling them to quickly deploy high-speed access and achieve
       rapid time-to-market for significant revenue-generating services.
 
     - Provides Platform for the Delivery of Value-Added Services. Our products
       enable carriers, cable operators and service providers to create and
       market new service offerings that extend broadband connectivity and
       capabilities.
 
     - Simplifies End-User Administration and Support. Our products allow easy
       configuration and administration of end-user broadband modems, further
       reducing the cost of providing service.
 
     We are focused on delivering subscriber management solutions to carriers
and service providers and intend to use our position in the digital subscriber
line market to penetrate the cable and wireless broadband markets. We believe
our software differentiates our solution and provides a competitive advantage by
delivering advanced subscriber management services and functionality. We will
continue to develop features and functionalities and expand our product family
to further enhance the ability of carriers, cable operators and service
providers to deliver profitable services.




                                      3
<PAGE>   13
               The Company's executive offices are located at 1389 Moffett Park
Drive, Sunnyvale, CA 94089. The Company's telephone number is (408) 548 3500.


                                  RISK FACTORS

     This offering and an investment in our common stock involve a high degree
of risk. You should carefully consider the following risk factors and the other
information in this prospectus before investing in our common stock. Our
business, results of operations and financial condition could be seriously
harmed by any of the following risks. The trading price of our common stock
could decline due to any of these risks, and you may lose all or part of any
investment you make in our common stock.
 
RISKS RELATED TO OUR BUSINESS
 
     OUR BUSINESS IS DIFFICULT TO EVALUATE BECAUSE WE HAVE A LIMITED OPERATING
     HISTORY
 
     We were founded in August 1996 and only began shipping products in material
quantities in the second quarter of 1998. You should consider the risks and
difficulties frequently encountered by companies like ourselves in a new and
rapidly evolving market. From February 28, 1998 to March 31, 1999, we have
experienced significant growth -- from 39 employees to 127 employees. Our
ability to sell products and services, and the level of success, if any, we
achieve, depends, among other things, on the level of demand for broadband
access services, which is a new and rapidly evolving market. See "Risk
Factors -- We are dependent on the widespread adoption of broadband access
services." Our business strategy may be unsuccessful and we may not successfully
address the risks we face.
 
     WE HAVE A HISTORY OF LOSSES AND WE EXPECT TO INCUR FUTURE LOSSES
 
     We incurred net losses of $142,000 from our inception in August 1996
through December 31, 1996, $4.4 million for the year ended December 31, 1997,
$9.9 million for the year ended December 31, 1998 and $3.8 million for the three
months ended March 31, 1999. As of March 31, 1999, we had an accumulated deficit
of approximately $18.2 million. We have not achieved profitability and we expect
to continue to incur net losses in the future.
 
     To date, we have funded our operations from the sale of equity securities,
from bank borrowings and by means of equipment lease financing. We expect to
continue to incur significant product development, sales and marketing, and
general and administrative expense. As a result, we must generate significant
revenues to achieve profitability. We may not sustain recent growth rates in our
revenues, and we may never achieve sufficient revenue levels to achieve
profitability. If we do achieve profitability in some future period, we cannot
be certain that we would sustain profitability on a quarterly or annual basis in
the future.
 
     OUR OPERATING RESULTS ARE LIKELY TO FLUCTUATE SIGNIFICANTLY
 
     Factors likely to cause quarterly fluctuations in revenues and operating
results include:
 
     - Fluctuations in demand for broadband access services;
 
     - The timing and size of sales of our products and services;
 
     - The lack of any significant backlog;
 
     - Announcements of new products and product enhancements by competitors;
 
     - The entry of new competitors into our market, including by acquisition;
 
     - Unexpected delays in introducing new or enhanced products, including
       manufacturing delays;
 
     - Our ability to control expenses;
 
     - Our ability to ship products on a timely basis and at a reasonable cost;
       and
 
     - The mix of our products sold and the mix of distribution channels through
       which our products are sold.



                                        4

<PAGE>   14
 
     A high percentage of our expenses, including those related to engineering,
sales and marketing, research and development, and general administrative
functions, are essentially fixed in the short term. As a result, if we
experience delays in generating or recognizing revenue, our quarterly operating
results are likely to be materially adversely affected. In addition, we plan to
increase our operating expenses to expand our engineering and sales and
marketing operations, broaden our customer support capabilities, develop new
distribution channels, fund increased levels of research and development and
build our operational infrastructure. If growth in our revenues does not outpace
the increase in these expenses, our business, results of operations and
financial condition could be materially adversely affected.
 
     We rely on a single third-party manufacturer to build our products. Any
interruption in the operations of this manufacturer would adversely affect our
ability to meet our scheduled product deliveries to our customers. This would
cause significant variations in our quarterly operating results and our
business, results of operations and financial condition would be materially
adversely affected.
 
     Due to these and other factors, we believe that quarter-to-quarter
comparisons of our operating results may not be meaningful. You should not rely
on our results for one quarter as any indication of our future performance. It
is likely that in some future quarter our operating results may be below the
expectations of public market analysts or investors. If this occurs, the price
of our common stock would likely decrease.
 
     OUR LENGTHY AND VARIABLE SALES CYCLE MAKES IT DIFFICULT FOR US TO PREDICT
     IF OR WHEN A SALE WILL BE MADE
 
     The timing of our sales revenue is difficult to predict because of the
length and variability of the sales cycle for our products. Customers often view
the purchase of our products as a significant and strategic decision. As a
result, customers typically undertake significant procedures relating to the
evaluation, testing, implementation and acceptance of our products. This
evaluation process frequently results in a lengthy sales cycle, typically
ranging from three months to over one year. While our customers are evaluating
our products and before they place an order with us, we may incur substantial
sales and marketing expenses and expend significant management efforts. In
addition, product purchases are frequently subject to unplanned administrative,
processing and other delays. This is particularly true for larger customers for
whom our products represent a very small percentage of their overall purchase
activities. These customers are often engaged in multiple simultaneous
purchasing decisions, some of which may pertain to more immediate needs and
absorb the immediate attention of the customer. If sales forecasted from a
specific customer for a particular quarter are not realized in that quarter or
at all, our business, results of operations and financial condition could be
materially adversely affected.
 
     IN ANY QUARTER, A SMALL NUMBER OF CUSTOMERS ARE LIKELY TO ACCOUNT FOR A
     SUBSTANTIAL MAJORITY OF OUR REVENUE
 
     In each of the last five quarters in the period ended March 31, 1999, we
had at least one customer that accounted for 15% or more of our total revenue in
the quarter. In the fourth quarter of 1998, UUNET, Nortel Networks and GTE and
its affiliated entities accounted for 28%, 13% and 12%, respectively, of our
total revenue. In the first quarter of 1999, UUNET, Southwestern Bell
Information Systems and GTE and its affiliated entities accounted for 43%, 10%
and 7%, respectively, of our total revenue. We anticipate that a small number of
customers with large orders will continue to account for a majority of our
quarterly revenue. However, we do not have any contracts or other agreements
that guarantee continued sales to these or any other customers. If our customers
alter their purchasing habits, or reevaluate their need for our products, or if
we fail to receive a large order in any future period, our business, results of
operations and financial condition would be materially adversely affected.
 


                                        5
<PAGE>   15
 
     WE ARE ENTIRELY DEPENDENT ON OUR SMS PRODUCT FAMILY.
 
     The SMS 1000 and SMS 500 are the only products that we currently sell. We
intend to introduce new products and enhancements to existing products in the
future. Our inability to timely and successfully introduce new products and
product enhancements, or the failure of these new products or enhancements to
achieve market acceptance, could materially adversely affect our business,
results of operations and financial condition.
 
     THERE IS A LIMITED NUMBER OF POTENTIAL CUSTOMERS FOR OUR SMS 1000
 
     To date, substantially all of our revenues have been derived from sales and
service related to the SMS 1000 product. The SMS 1000 and any other new high-end
product that we may develop and introduce in the future are marketed primarily
to large customers. There are only a limited number of large existing and
potential customers and this number is not expected to increase significantly in
the future.
 
     WE FACE NEW RISKS WITH THE INTRODUCTION OF OUR SMS 500 PRODUCT
 
     We recently introduced the SMS 500, which is designed for use by customers
that intend to provide services to a smaller number of subscribers than those
using the SMS 1000. Given this targeted market, sales of the SMS 500 may involve
sales to smaller customers. Sales to smaller customers entail some additional
risks, including increased credit risks, the need for additional sales and
support personnel to support an increased volume of customers and the need to
develop a leasing program to facilitate market acceptance. Our business, results
of operations and financial condition could be materially adversely affected if
any of these risks materialize. To date, we have sold a limited number of our
SMS 500, and revenues from these sales were immaterial. The SMS 500 may not
achieve a significant degree of market acceptance. If the SMS 500 is not
successful, our ability to generate revenues will be limited to sales of the SMS
1000 to our customers with a large number of subscribers, which will have a
material adverse effect on our business, results of operations and financial
condition.
 
     OUR PRODUCTS MUST ANTICIPATE AND MEET SPECIFIC CUSTOMER REQUIREMENTS AND
DEMANDS
 
     Many of our customers require product features and capabilities that our
SMS products may not have. The requirement that we add features to our products
in order to achieve a sale may result in a longer sales cycle, increased
research and development expenses and reduced margins on our products. To
achieve market acceptance for our products, we must effectively and timely
anticipate and adapt to customer requirements and offer products and services
that meet customer demands. Our failure to develop products or offer services
that satisfy customer requirements would materially adversely affect our
business, results of operations and financial condition.
 
     We intend to continue to invest in product and technology development. The
development of new or enhanced products is a complex and uncertain process that
requires the accurate anticipation of technological and market trends. We may
experience design, manufacturing, marketing and other difficulties that could
delay or prevent the development, introduction or marketing of new products and
enhancements. The introduction of new or enhanced products also requires that we
manage the transition from older products in order to minimize disruption in
customer ordering patterns and ensure that adequate supplies of new products can
be delivered to meet anticipated customer demand. Our inability to effectively
manage this transition would materially adversely affect our business, results
of operations and financial condition.
 
     WE NEED TO GAIN ACCEPTANCE IN OTHER BROADBAND ACCESS MARKETS
 
     To date, we have derived substantially all of our revenues from sales of
the SMS 1000 for use in the digital subscriber line market for broadband access.
We intend to expend a substantial amount of time and resources to achieve market
acceptance of our products in other markets, including the cable and wireless
markets. We may be unable to simultaneously or effectively address evolving
demands in these markets, and customers in these markets may choose to implement
competing technologies or products. In addition, if we are not first in these
markets, competitors may gain market acceptance first, thereby
 



                                        6
<PAGE>   16
making it difficult, if not impossible, for us to gain subsequent market
acceptance. If we are unable to achieve acceptance of our products in these
markets, our ability to generate revenues will be limited, and our business,
results of operations and financial condition would be materially adversely
affected.
 
     WE EXPECT INCREASED COMPETITION
 
     We may be unable to compete successfully with current or future
competitors. If we do not compete successfully against current or future
competitors, our business, results of operations and financial condition will be
materially adversely affected. Currently, competition in our market is intense.
The broadband access markets we are targeting, including digital subscriber
line, cable and wireless, are new and rapidly evolving and we expect these
markets to become highly competitive in the future. In addition, we expect new
competitors to emerge in the broadband access market as that market evolves due
to technological innovation and regulatory changes. We face actual and potential
competition from public and private companies providing routers connecting to
the Internet backbone, access concentrators and subscriber aggregation systems.
 
     Cisco, the leading provider of routers connecting to the Internet backbone,
offers products that compete directly with our products, and also provides a
comprehensive range of broadband access systems. We expect companies that offer
access concentrators and routers to incorporate some subscriber management
functionality into their products. These companies include Nortel Networks which
recently agreed to acquire Shasta, a private company providing subscriber
management services, and Ascend, which has announced its pending acquisition by
Lucent. In addition, there are several other private companies that provide
subscriber management features in access concentrators or routing platforms.
 
     Many of our principal competitors, including Cisco, Alcatel, Nortel
Networks/Shasta, Lucent/Ascend, and some companies that may compete with us in
the future, are large public companies that have longer operating histories and
significantly greater financial, technical, marketing and other resources than
we have. As a result, these competitors are able to devote greater resources to
the development, promotion, sale and support of their products. In addition, our
competitors that have large market capitalizations or cash reserves are much
better positioned than we are to acquire other companies, including our
competitors, and thereby acquire new technologies or products that may displace
our product lines. Any of these acquisitions could give our competitors a
strategic advantage that would materially adversely affect our business, results
of operations and financial condition.
 
     Many of our competitors have significantly more established customer
support and professional services organizations than we do. In addition, many of
our competitors have much greater name recognition and have a more extensive
customer base, broader customer relationships and broader product offerings than
our company. These companies can leverage their customer bases and broader
product offerings and adopt aggressive pricing policies to gain market share. We
have encountered, and expect to continue to encounter, potential customers that,
due to existing relationships with our competitors, are committed to the product
offerings of these competitors. As a result, these potential customers may not
consider purchasing our products. We expect to face competition in the following
areas:
 
     - Product pricing;
 
     - Breadth of product lines;
 
     - Sales and distribution capability;
 
     - Product features and enhancements, including product performance,
       reliability, size, compatibility and scalability;
 
     - Product ease of deployment;
 
     - Conformance to industry standards; and
 
     - Technical support and service.
 



                                        7
<PAGE>   17
 
     We expect that competitive pressures may result in price reductions,
reduced margins and loss of market share, which would materially adversely
affect our business, results of operations and financial condition.
 
     WE ARE DEPENDENT ON A SINGLE CONTRACT MANUFACTURER
 
     We rely on a single third-party manufacturer, Electromax, to build our
products. We may not be able to effectively manage our relationship with
Electromax and Electromax may not meet our future requirements for timely
delivery. We have no written agreement with Electromax. We have relationships
with two other third-party manufacturers, one of which currently builds our
prototypes. Although both of these other third-party manufacturers are capable
of building our products, any interruption in the operations of Electromax would
adversely affect our ability to meet our scheduled product deliveries to our
customers, which could cause the loss of existing or potential customers and
could materially adversely affect our business, results of operations and
financial condition.
 
     In addition, the products that Electromax or any other manufacturer builds
for us may be insufficient in quality or in quantity to meet our needs.
Electromax or any other manufacturer may not meet the technological or delivery
requirements of our current products or any future products that we may develop
and introduce. The inability of Electromax or any other of our contract
manufacturers in the future to provide us with adequate supplies of high-quality
products, or the loss of Electromax or any other of our contract manufacturers
in the future, would cause a delay in our ability to fulfill customer orders
while another of our third-party manufacturers begins production and would have
a material adverse effect on our business, results of operations and financial
condition.
 
     SOME OF THE KEY COMPONENTS IN OUR PRODUCTS COME FROM SINGLE OR LIMITED
SOURCES OF SUPPLY
 
     We currently purchase several key components used in the manufacture of our
SMS 500 and our SMS 1000 products from single or limited sources of supply.
These manufacturers include Altera, Brooktree, Connector Technologies,
Foresight, Intel, Level One, Powerspec, Siemens and Ziatech. We have no
guaranteed supply arrangement with these suppliers, and we or our manufacturers
may fail to obtain these supplies in a timely manner in the future. Financial or
other difficulties faced by these suppliers or significant changes in demand for
these components could limit the availability to us of these components. Any
interruption or delay in the supply of any of these components, or the inability
to obtain these components from alternate sources at acceptable prices and
within a reasonable amount of time, would adversely affect our ability to meet
scheduled product deliveries to our customers and would materially adversely
affect our business, results of operations and financial condition. In addition,
qualifying additional suppliers is time-consuming and expensive.
 
     WE MAY BE UNABLE TO MATCH PRODUCTION WITH PRODUCT DEMAND
 
     We currently use a rolling six-month forecast based on anticipated product
orders, product order history and backlog to determine our materials
requirements. Lead times for the materials and components that we order vary
significantly and depend on numerous factors, including the specific supplier,
contract terms and demand for a component at a given time. If actual orders do
not match our forecasts, we may have excess or inadequate inventory of materials
and components, which could materially adversely affect our business, results of
operations and financial condition.
 
     WE MAY BE UNABLE TO PROPERLY MANAGE GROWTH
 
     We have expanded our operations rapidly since our inception. The number of
our employees increased from 39 in February 1998 to 127 in March 1999. We intend
to continue to expand in order to pursue existing and potential market
opportunities and are in the process of hiring additional engineering and sales
personnel. We intend to hire a significant number of engineers in 1999. Our
ability to continue to attract and retain highly skilled personnel is a critical
factor in determining whether we will be successful in the future. Competition
for highly skilled personnel is intense, especially in the San Francisco Bay
Area. We may fail to attract, assimilate or retain qualified personnel to
fulfill our current
 



                                        8
<PAGE>   18
 
or future needs. If we so fail, our business, results of operations and
financial condition could be materially adversely affected. Our planned rapid
growth places a significant demand on management and financial and operational
resources. In order to grow and achieve future success, we must:
 
     - Retain existing personnel;
 
     - Hire, train, manage and retain additional qualified personnel; and
 
     - Effectively manage multiple relationships with our customers, suppliers
       and other third parties.
 
     We are currently seeking to lease additional office space to accommodate
our growing operations. We may be unable to locate necessary office space on
commercially reasonable terms or in a timely manner. Failure to do so would have
a material adverse effect on our business, results of operations and financial
condition. Our current office lease expires in September 1999. Any required
relocation may be disruptive to our business.
 
     OUR PLANNED EXPANSION TO INTERNATIONAL MARKETS WILL INVOLVE NEW RISKS
 
     In 1998, we derived approximately 15% of our revenues from sales to
customers outside of the United States. Our ability to achieve future success
will depend in part on the expansion of our international sales and operations.
International operations are generally subject to a number of risks, including:
 
     - Expenses associated with customizing products for foreign countries;
 
     - Protectionist laws and business practices that favor local competition;
 
     - Dependence on local vendors;
 
     - Multiple, conflicting and changing governmental laws and regulations;
 
     - Longer sales cycles;
 
     - Longer accounts receivable cycles;
 
     - Increased difficulties in collecting accounts receivable;
 
     - Difficulties in managing operations across disparate geographic areas;
 
     - Difficulties associated with enforcing agreements through foreign legal
       systems;
 
     - Reduced or limited protection of our intellectual property rights in some
       countries;
 
     - Foreign currency exchange rate fluctuations; and
 
     - Political and economic instability.
 
     In addition, if we grow internationally, we will need to expand our
worldwide operations and enhance our communications infrastructure. If we fail
to implement and improve these systems, our ability to accurately forecast sales
demand, manage our supply chain and record and report financial and management
information would be adversely affected. This could materially adversely affect
our business, results of operations and financial condition.
 
     UNDETECTED SOFTWARE OR HARDWARE ERRORS COULD HAVE A MATERIAL ADVERSE EFFECT
ON US
 
     Networking products frequently contain undetected software or hardware
errors when first introduced or as new versions are released. We have
experienced minor errors in the past in connection with new products. We expect
that errors will be found from time to time in new or enhanced products after we
begin commercial shipments. These problems may cause us to incur significant
warranty and repair costs, divert the attention of our engineering personnel
from our product development efforts and cause significant customer relations
problems. The occurrence of these problems could result in the delay or loss of
market acceptance of our products and would likely have a material adverse
effect on our business, results of operations and financial condition.
 



                                       9
<PAGE>   19
 
     Our customers use our products to provide broadband access to their
customers. Defects, integration issues or other performance problems in our
products could result in financial or other damages to our customers or could
damage market acceptance for our products. Our customers could also seek damages
for losses from us, which, if they were successful, could have a material
adverse effect on our business, results of operations and financial condition. A
product liability claim brought against us, even if unsuccessful, would likely
be time consuming and costly.
 
     OUR FAILURE AND THE FAILURE OF OUR KEY SUPPLIERS AND CUSTOMERS TO BE YEAR
     2000 COMPLIANT COULD NEGATIVELY IMPACT OUR BUSINESS
 
     The Year 2000 computer issue creates a variety of risks for us. If systems
do not correctly recognize date information when the year changes to 2000, our
business, results of operations and financial condition could be materially
adversely affected. The risks involve:
 
     - Potential warranty or other claims by our customers;
 
     - Errors in systems we use to run our business;
 
     - Errors in systems used by our suppliers;
 
     - Errors in systems used by our customers; and
 
     - Potential reduced spending by other companies on broadband Internet
       access products as a result of significant information systems spending
       on Year 2000 remediation.
 
     Our internal systems include both our information technology, and
non-information technology systems. We have conducted an initial audit of our
material internal information technology systems, including both our own
software products and third-party software and hardware technology. We have not
yet initiated an assessment of our non-information technology systems. To the
extent that we are unable to test the technology provided by third-party
vendors, we are seeking assurances from these vendors that their systems are
Year 2000 compliant. We may experience material unanticipated problems and costs
caused by undetected errors or defects in the technology used in our internal
information technology and non-information technology systems. These
unanticipated problems and costs could have a material adverse effect on our
business, results of operations and financial condition.
 
     We intend to contact our critical suppliers to determine if the suppliers'
operations and the products and services provided to us are Year 2000 compliant.
Where practicable, we will attempt to mitigate our risks with respect to the
failure of our suppliers to be Year 2000 compliant by locating Year 2000
compliant replacement suppliers. However, our failure to mitigate our Year 2000
risks remains a possibility and could have a material adverse impact on our
business, results of operations and financial condition.
 
     We have been informed by Electromax, our contract manufacturer, that its
manufacturing systems are Year 2000 compliant. However, Electromax may
experience material unanticipated problems and costs caused by undetected errors
or defects in the technology used in their internal information technology and
non-information technology systems. These unanticipated problems and costs could
cause manufacturing delays or difficulties for our products and harm
Electromax's operations. Additionally, Electromax has not yet ascertained
whether any of its suppliers is Year 2000 compliant. The failure of a supplier
of Electromax to be Year 2000 compliant could also adversely affect Electromax's
operations. Any of these events could materially adversely affect our business,
results of operations and financial condition.
 
     We believe that the SMS 1000 is Year 2000 compliant. However, despite
testing by us and by current and potential customers, and despite assurances
from developers of products incorporated into the SMS 1000, the SMS 1000 may
contain undetected errors or defects associated with Year 2000 date functions.
We believe that, based solely on internal testing, the recently introduced SMS
500 is
 



                                       10
<PAGE>   20
 
Year 2000 compliant. We have made assurances to our customers that the SMS 1000
and the SMS 500 are Year 2000 compliant. The failure of our products to be Year
2000 compliant would result in numerous customer claims, which could have a
material adverse impact on our business, results of operations and financial
condition.
 
     We do not currently have any information concerning the Year 2000
compliance status of our customers. Our current or potential customers may incur
significant expenses to achieve Year 2000 compliance. If our customers are not
Year 2000 compliant, they may experience material costs to remedy problems, or
they may face litigation costs. In either case, spending on Year 2000 issues
could reduce or eliminate the budgets that our current or potential customers
could have for purchases of our products. As a result, our business, results of
operations and financial condition could be materially adversely affected.
 
     To date, our Year 2000 related costs have not been material. We have funded
these costs from available cash without separately accounting for these costs.
Although our future Year 2000 compliance costs are not expected to be
significant, we may experience unanticipated material problems and costs
associated with Year 2000 compliance that could adversely affect our business,
results of operations and financial condition. We have not yet developed any
contingency plan to address situations that may result if we are unable to
achieve Year 2000 readiness of our critical operations. The cost of developing
and implementing a Year 2000 contingency plan may be material.
 
     If our internal systems, our products or the internal systems at our
manufacturers are not Year 2000 compliant, our business, results of operation
and financial condition would be materially adversely affected.
 
     WE MAY BE UNABLE TO PROTECT OUR PROPRIETARY TECHNOLOGY
 
     We rely on a combination of patent, copyright, trademark and trade secret
laws and restrictions on disclosure to protect our intellectual property rights.
We have filed one U.S. patent application. There can be no assurance that this
application will be approved, that any issued patents will protect our
intellectual property or that any issued patents will not be challenged by third
parties. Furthermore, other parties may independently develop similar or
competing technology or design around any patents that may be issued to us.
Although we attempt to protect our intellectual property rights, we may be
unable to prevent the misappropriation of our intellectual property,
particularly in foreign countries where the laws may not protect our proprietary
rights as fully as in the United States.
 
     Others may allege that our products infringe upon their proprietary rights.
Any parties asserting that our products infringe upon their proprietary rights
would force us to defend ourselves or our customers, manufacturers or suppliers
against alleged infringement of intellectual property rights. We could incur
substantial costs to prosecute or defend this litigation. In addition,
intellectual property litigation could force us to do one or more of the
following:
 
     - Cease selling, incorporating or using products or services that
       incorporate the challenged intellectual property;
 
     - Obtain from the holder of the infringed intellectual property right a
       license to sell or use the relevant technology, which license may not be
       available on acceptable terms, if at all; or
 
     - Redesign those products or services that incorporate the disputed
       technology.
 
     In the event of a successful claim of infringement against us and our
failure or inability to develop non-infringing technology or license the
infringed technology on acceptable terms and on a timely basis, our business,
results of operations and financial condition would be materially adversely
affected. We may be subject to these claims in the future.
 
     We may in the future initiate claims or litigation against third parties
for infringement of our proprietary rights in order to determine the scope and
validity of our proprietary rights or the proprietary
 



                                       11
<PAGE>   21
 
rights of competitors. These claims could result in costly litigation and the
diversion of our technical and management personnel. As a result, our business,
results of operations and financial condition could be materially adversely
affected.
 
     WE MAY NEED ADDITIONAL CAPITAL, WHICH MAY NOT BE AVAILABLE
 
     At March 31, 1999, we had approximately $5.3 million in cash, cash
equivalents and short-term investments. In April 1999, we used approximately
$2.5 million of these amounts to repay outstanding debt obligations. In April
1999, we also secured a commitment for a $2.0 million asset-based borrowing
facility. We believe that these amounts, combined with proceeds from this
offering and cash anticipated to be available from future operations, will
enable us to meet our working capital requirements for at least the next 12
months. However, if cash from available sources is insufficient, or if cash is
used for acquisitions or other unanticipated uses, we may need additional
capital.
 
     The development and marketing of new products and the expansion of reseller
channels and associated support personnel will require a significant commitment
of resources. In addition, if the market for broadband access develops at a
slower pace than anticipated or if we fail to establish significant market share
and achieve a meaningful level of revenue, we may continue to incur significant
operating losses and utilize significant amounts of capital. As a result, we
could be required to raise substantial additional capital. Additional capital
may not be available to us at all, or if available, may be available only on
unfavorable terms. Any inability to raise additional capital when we require it
would materially adversely affect our business, results of operations and
financial condition. Any additional issuance of equity or equity-related
securities will be dilutive to our stockholders.
 
RISKS RELATED TO THE BROADBAND ACCESS INDUSTRY
 
     WE ARE DEPENDENT ON THE WIDESPREAD ADOPTION OF BROADBAND ACCESS SERVICES
 
     Sales of our products depend on the increased use and widespread adoption
of broadband access services, and the ability of our customers to market and
sell broadband access services. Our business, results of operations and
financial condition would be materially adversely affected if the use of
broadband access services does not increase as anticipated or if our customers'
broadband access services are not received well by the marketplace. Critical
issues concerning use of broadband access services are unresolved and will
likely affect use of broadband access services. These issues include:
 
     - Security;
 
     - Reliability;
 
     - Bandwidth;
 
     - Congestion;
 
     - Cost;
 
     - Ease of access; and
 
     - Quality of service.
 
     Even if these issues are resolved, if the market for products that provide
broadband access to the Internet and to corporate networks fails to develop, or
develops at a slower pace than anticipated, our business, results of operations
and financial condition would be materially adversely affected.
 
     THE BROADBAND ACCESS SERVICES MARKET IS SUBJECT TO RAPID CHANGE
 
     The broadband access services market is new and is characterized by rapid
technological change, frequent enhancements to existing products and new product
introductions, changes in customer requirements and evolving industry standards.
We may be unable to respond quickly or effectively to these developments. The
introduction of new products by competitors, market acceptance of products based
on
 



                                       12
<PAGE>   22
 
new or alternative technologies, or the emergence of new industry standards,
could render our existing or future products obsolete, which would materially
adversely affect our business, results of operations and financial condition.
 
     The emergence of new industry standards might require us to redesign our
products. If our products fail to comply with widely adopted industry standards,
our customers and potential customers may not purchase our products. This would
have a material adverse effect on our business, results of operations and
financial condition.
 
     OUR BUSINESS MAY BE ADVERSELY AFFECTED BY GOVERNMENT REGULATION OF THE
     COMMUNICATIONS INDUSTRY
 
     The jurisdiction of the Federal Communications Commission, or FCC, extends
to the communications industry, to our customers and to the products and
services that our customers sell. Future FCC regulations, or regulations set
forth by other regulatory bodies, may adversely affect the broadband access
services industry. Regulation of our customers may have a material adverse
affect on our business, results of operations and financial condition. For
example, FCC regulatory policies that affect the availability of data and
Internet services may impede our customers' penetration into broadband access
markets. In addition, international regulatory bodies are beginning to adopt
standards for the communications industry. The delays that these governmental
processes entail may cause order cancellations or postponements of product
purchases by our customers, which would materially adversely affect our
business, results of operations and financial condition.
 
RISKS RELATED TO THE SECURITIES MARKETS
 
     OUR STOCK PRICE MAY BE VOLATILE
 
     Prior to this offering, you could not buy or sell our common stock
publicly. An active public market for our common stock may not develop or be
sustained after this offering. The market for technology stocks has been
extremely volatile. The following factors could cause the market price of our
common stock to fluctuate significantly from the price paid by investors in this
offering:
 
     - Our loss of a major customer;
 
     - Our addition or the departure of key Redback Networks personnel;
 
     - Variations in our quarterly operating results;
 
     - Announcements by us or our competitors of significant contracts, new
       products or product enhancements, acquisitions, distribution
       partnerships, joint ventures or capital commitments;
 
     - Changes in financial estimates by securities analysts;
 
     - Our sales of common stock or other securities in the future;
 
     - Changes in market valuations of broadband access technology companies;
 
     - Changes in market valuations of networking and telecommunications
       companies; and
 
     - Fluctuations in stock market prices and volumes.
 
     OUR BUSINESS MAY BE ADVERSELY AFFECTED BY CLASS ACTION LITIGATION DUE TO
     STOCK PRICE VOLATILITY
 
     Securities class action litigation has often been brought against a company
following periods of volatility in the market price of its securities. If our
stock price is volatile, we may be the target of similar litigation. Our
management's attention and resources may be diverted by any securities
litigation, and we may incur substantial related costs, possibly resulting in a
material adverse effect to our business, results of operations and financial
condition.
 
                                       13
<PAGE>   23
 
     CONTROL BY EXISTING STOCKHOLDERS MAY LIMIT YOUR ABILITY TO INFLUENCE THE
     OUTCOME OF DIRECTOR ELECTIONS AND CERTAIN TRANSACTIONS
 
     Upon completion of this offering, our executive officers, directors and
principal stockholders and their affiliates will beneficially own approximately
49.0% of our outstanding common stock (48.1% if the underwriters' over-allotment
option is exercised in full). These stockholders, if acting together, would be
able to significantly influence all matters requiring approval by our
stockholders, including the election of directors and the approval of mergers or
other business combination transactions.
 
     OUR MANAGEMENT HAS BROAD DISCRETION IN USE OF PROCEEDS
 
     The net proceeds from this offering will be added to our general working
capital upon completion of this offering. We cannot specify with certainty how
we will use the net proceeds. Accordingly, our management will have considerable
discretion in the application of the net proceeds. See "Use of Proceeds."
 
     SUBSTANTIAL SALES OF OUR COMMON STOCK COULD ADVERSELY AFFECT OUR STOCK
     PRICE
 
     Sales of a substantial number of shares of our common stock after this
offering could adversely affect the market price of our common stock by
potentially introducing a large number of sellers of our common stock into a
market in which our common stock price is already volatile, thus driving our
common stock price down. In addition, the sale of these shares could impair our
ability to raise capital through the sale of additional equity securities. Based
on shares outstanding as of March 31, 1999, upon completion of this offering, we
will have 21,034,119 shares of common stock outstanding, or 21,409,119 shares if
the underwriters' over-allotment option is exercised in full. Our directors,
executive officers and current stockholders have executed lock-up agreements
that limit their ability to sell shares of our common stock. These stockholders
have agreed, subject to limited exceptions, not to sell or otherwise dispose of
any shares of our common stock for a period of at least 180 days after the date
of this prospectus without the prior written approval of Morgan Stanley & Co.
Incorporated. When these lock-up agreements expire, these shares and the shares
of common stock underlying any options held by these individuals will become
eligible for sale, in some cases pursuant only to the volume, manner of sale and
notice requirements of Rule 144.
 
     INVESTORS WILL EXPERIENCE IMMEDIATE DILUTION
 
     The initial public offering price of our common stock is expected to be
substantially higher than the book value per share of our outstanding common
stock immediately after the offering. Accordingly, if you purchase our common
stock in this offering, you will incur immediate dilution of approximately
$20.29 in the book value per share of our common stock from the price you pay
for our common stock. This calculation assumes that you purchased our common
stock for $23.00 per share.
 
     ANTI-TAKEOVER PROVISIONS IN OUR CHARTER DOCUMENTS AND DELAWARE LAW COULD
     PREVENT OR DELAY A CHANGE IN CONTROL OF OUR COMPANY
 
     Provisions in our bylaws and in our certificate of incorporation, both as
amended and restated upon the closing of this offering, may have the effect of
delaying or preventing a change of control or changes in management of our
company. These provisions include:
 
     - The stipulation that a special meeting of stockholders may only be called
       by stockholders owning at least 50% of our outstanding shares;
 
     - The ability of our board of directors to issue preferred stock without
       stockholder approval; and
 


                                       14
<PAGE>   24
 
     - The right of our board of directors to elect a director to fill a vacancy
       created by the expansion of the board of directors.
 
Furthermore, we are subject to the provisions of section 203 of the Delaware
General Corporation Law. These provisions prohibit a stockholder owning 15% or
more of our outstanding voting stock from consummating a merger or combination
with us unless this stockholder receives board approval for the transaction or
unless 66 2/3% of the outstanding shares of our voting stock not owned by this
stockholder approve the merger or combination.
 

                             REGISTERED STOCKHOLDERS

               The Reoffer Prospectus relates to shares of Common Stock which
have been acquired by certain key employees (the "Registered Stockholders") of
the Company. Registered Stockholders acquired shares of Common Stock to be
offered hereunder pursuant to the exercise of options granted under the 1997
Stock Plan.

               The following table sets forth certain information with respect
to the Registered Stockholders as of March 31, 1999:


<TABLE>
<CAPTION>
                                              Number of                      Number of      Percentage
                                               Shares                         Shares           of
                                             Beneficially    Number of      Beneficially      Shares
                                              Owned as       Shares to         Owned       Beneficially
                                                 of              be            After          Owned
   Registered          Position with           March 31,      Offered         Offering        After
  Stockholder           the Company            1999(1)         Hereby           (1)          Offering(2)
  -----------          -------------         ------------    ---------      -----------    -------------
<S>                   <C>                    <C>             <C>            <C>            <C>
David Coleman         Customer Support          40,500          2,250          38,250            *
                      Engineer                                                               

Steve De Golia        Regional Sales            57,500         57,500               0            *
                      Director                                                               
                                                                                             
Joyce Gandolfi        Contract Recruiter        64,750          2,200          62,500            *
                                                                                             
Karen Hamerquist      Account Manager           17,500          4,375          13,125            *
                                                                                             
Jeff Johnson          Software Engineer        117,500          5,000         112,500            *
                                                                                             
Wing Ko               Software Engineer         30,000          7,500          22,500            *
                                                                                             
Dave Lawrence         Hardware Engineer        121,150          5,000         116,250            *
                                                                                             
Eric Olsen            Hardware Engineering      25,000          1,000          24,000            *
                      Manager                                                                
                                                                                             
William Palter        Software Engineer         27,000          4,013          22,987            *
                                                                                             
Keith Quigley         Account Manager           25,000         10,000          15,000            *
                                                                                             
Guna Ramireddy        Software Engineer         25,000         15,000          10,000            *
                                                                                             
David Shapiro         Sales Engineer            17,000         17,000               0            *
                                                                                             
Lynette Souza         Marketing                 26,750          2,000          24,750            *
                      Communications                                                         
                      Specialist                                                             
                                                                                             
Nick Thille           Software Engineer        110,000          5,000         105,000            *
                                                                                             
Jay Wiley             Software Engineer         12,000          3,000           9,000            *
                                                                                       
--------------------------------------------------------------------------------------------------
</TABLE>

-       Represents beneficial ownership of less than 1% of the outstanding
        shares of our Common Stock.


(1) Percentage of beneficial ownership includes Common Stock of which such
individual has the right to acquire beneficial ownership within 60 days of March
31, 1999, including but not limited to, upon the exercise of an option.



                                       15
<PAGE>   25

(2) Percentage of beneficial ownership is calculated assuming 18,534,119 shares
of Common Stock were outstanding on March 31, 1999. The number of shares
outstanding after the offering under this Reoffer Prospectus includes the
2,500,000 shares of Common Stock offered for sale by the Company in its initial
public offering.


                              PLAN OF DISTRIBUTION

               The shares of Common Stock covered by this Reoffer Prospectus are
being registered by the Company for the account of the Registered Stockholders.
The Company understands that none of such shares will be offered through
underwriters.

               Shares of Common Stock covered by this Reoffer Prospectus may be
offered and sold from time to time by the Registered Stockholders through
brokers through the Nasdaq National Market System or otherwise, at the prices
prevailing at the time of such sales. To the Company's knowledge, no specific
brokers or dealers have been designated by the Registered Stockholders nor has
any agreement been entered into in respect of brokerage commissions or for the
exclusive or coordinated sale of any securities which may be offered pursuant to
this Reoffer Prospectus. The Company will pay all expenses of preparing and
reproducing this Reoffer Prospectus, but will not receive the proceeds from
sales by the Registered Stockholders. The price per share of the Common Stock as
offered in the initial public offering of such Common Stock is expected to be
$23.00.

               The Company will not receive any of the proceeds from the
offering hereunder. All expenses of registration incurred in connection with
this offering are being borne by the Company, but all selling and other expenses
incurred by the individual Registered Stockholders will be borne by such
Registered Stockholders.

               The price per share of Common Stock, as offered in the initial
public offering is expected to be $23.00.



                                       16
<PAGE>   26
                       DOCUMENTS INCORPORATED BY REFERENCE

        Redback hereby incorporates by reference into this Registration
Statement the following documents previously filed with the Commission:

        (a)    Redback's prospectus filed with the SEC under Rule 424(b) under
               the Securities Act of 1933, as amended (the "1933 Act"), in
               connection with Registration Statement No. 333-744479 on Form S-1
               filed with the SEC on March 16, 1999, the amendment filed on
               April 22, 1999, the amendment filed on May 4, 1999 and the
               amendment filed on May 12, 1999 and the amendment filed on May
               14, 1999, which contains the audited financial statements for the
               period August 30, 1996 (inception) through December 31, 1996 and
               for Redback's fiscal years ended December 31, 1997 and 1998.

        (b)    Redback's Registration Statement No. 0-25853 on Form 8-A filed
               with the Commission on April 28, 1999 together with amendments
               thereto, pursuant to Section 12 of the Exchange Act, in which
               there is described the terms, rights and provisions applicable to
               the Company's outstanding Common Stock.

               All of such documents are on file with the Commission. All
documents subsequently filed by the Company pursuant to Section 13(a), 13(c), 14
or 15(d) of the Exchange Act prior to the filing of a post-effective amendment
which indicates that all securities to be offered pursuant hereto have been sold
or which deregisters all such securities then remaining unsold shall be deemed
to be incorporated by reference in this Prospectus and to be a part hereof from
the date of the filing of such documents.


                                 INDEMNIFICATION


        Section 145 of the Delaware General Corporation Law authorizes a court
to award or a corporation's Board of Directors to grant indemnification to
directors and officers in terms sufficiently broad to permit such
indemnification under certain circumstances for liabilities (including
reimbursement for expenses incurred) arising under the 1933 Act. Redback's
Bylaws provide for mandatory indemnification of its directors and officers and
permissible indemnification of employees and other agents to the maximum extent
permitted by the Delaware General Corporation Law. Redback's Certificate of
Incorporation provides that, under Delaware law, its directors shall not be
liable for monetary damages for breach of their fiduciary duty as directors to
Redback and its stockholders. This provision in the Certificate of Incorporation
does not eliminate the fiduciary duty of the directors, and, in appropriate
circumstances, equitable remedies such as injunctive or other forms of
non-monetary relief will remain available under Delaware law. In addition, each
director will continue to be subject to liability for breach of the director's
duty of loyalty to Redback for acts or omissions not in good faith or involving
intentional misconduct, for knowing violations of law, for actions leading to
improper personal benefit to the director and for payment of dividends or
approval of stock repurchases or redemptions that are unlawful under Delaware
law. The provision also does not affect a director's responsibilities under any
other law, such as the federal securities laws or state or federal environmental
laws. Redback has entered into Indemnification Agreements with its officers and
directors. The Indemnification Agreements provide Redback's officers and
directors with further indemnification to the maximum extent permitted by the
Delaware General Corporation Law.



                                       17
<PAGE>   27
                                  EXHIBIT INDEX

<TABLE>
<CAPTION>
                                                                                   Sequentially
Exhibit Number    Exhibit                                                          Numbered Page
--------------    -------                                                          -------------
<S>               <C>                                                              <C>           
      4           Instrument Defining Rights of Stockholders. Reference is made
                  to Redback's Registration Statement No. 0-25853 on Form 8-A,
                  which is incorporated herein by reference under Item 3(b) of
                  this Registration Statement.

      5           Opinion and consent of Gunderson Dettmer Stough Villeneuve
                  Franklin & Hachigian LLP.

      23.1        Consent of PricewaterhouseCoopers LLP, Independent
                  Accountants.

      23.2        Consent of Gunderson Dettmer Stough Villeneuve Franklin &
                  Hachigian LLP is contained in Exhibit 5.

      24          Power of Attorney. Reference is made to page II-4 of this
                  Registration Statement.

      99.1        Form of Written Compensation Agreement with David Coleman,
                  Steve De Golia, Joyce Gandolfi, Jeff Johnson, Eric Olsen,
                  William Palter, Keith Quigley, David Shapiro, Lynette Souza,
                  Nick Thille and Jay Willey.
</TABLE>
[{"type": "S-8", "sequence": "1", "description": "FORM S-8", "secsgml_size_bytes": 88993}]
{"company-data": {"conformed-name": "REDBACK NETWORKS INC", "cik": "0001081290", "assigned-sic": "7389", "irs-number": "770438443"}, "filing-values": {"form-type": "S-8", "act": "33", "file-number": "333-79043", "film-number": "99632077"}, "business-address": {"street1": "1389 MOFFETT PARK DR", "city": "SUNNYVALE", "state": "CA", "zip": "94089", "phone": "4085483500"}, "mail-address": {"street1": "1389 MOFFETT PARK DR", "city": "SUNNYVALE", "state": "CA", "zip": "94089"}}
1
            As filed with the Securities and Exchange Commission on May 21, 1999
                                                     Registration No. 333-______
================================================================================

                                  UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549
                               -------------------

                                    FORM S-8
                             REGISTRATION STATEMENT
                                      UNDER
                           THE SECURITIES ACT OF 1933

                               -------------------

                                REDBACK NETWORKS
             (Exact name of registrant as specified in its charter)
DELAWARE                             3576                      77-0438443
     (State or other jurisdiction       (Primary Standard Industrial         (IRS Employer
   of incorporation or organization)     Classification Code Number)      Identification No.)
1389 MOFFETT PARK DRIVE
                               SUNNYVALE, CA 94089
               (Address of principal executive offices) (Zip Code)
                               -------------------

                                REDBACK NETWORKS
                            1999 STOCK INCENTIVE PLAN
                                 1997 STOCK PLAN
                        1999 EMPLOYEE STOCK PURCHASE PLAN
                           1999 DIRECTORS' OPTION PLAN
           SHARES ACQUIRED UNDER WRITTEN COMPENSATION AGREEMENTS WITH
 DAVID COLEMAN, STEVE DE GOLIA, JOYCE GANDOLFI, KAREN HAMERQUIST, JEFF JOHNSON,
       WING KO, DAVE LAWRENCE, ERIC OLSEN, WILLIAM PALTER, KEITH QUIGLEY,
                 GUNA RAMIREDDY, DAVID SHAPIRO, LYNETTE SOUZA,
                           NICK THILLE AND JAY WILLEY
                            (Full title of the Plans)

                               -------------------

                                DENNIS L. BARSEMA
                      PRESIDENT AND CHIEF EXECUTIVE OFFICER
                                REDBACK NETWORKS
                             1389 MOFFETT PARK DRIVE
                               SUNNYVALE, CA 94089
                     (Name and address of agent for service)
                              --------------------

                                  408-548-3500
          (Telephone number, including area code, of agent for service)
                               -------------------
CALCULATION OF REGISTRATION FEE
=============================================================================================================
                Title of                                  Proposed Maximum  Proposed Maximum
               Securities                     Amount          Offering          Aggregate         Amount of
                 to be                        to be             Price           Offering         Registration
               Registered                 Registered (1)    per Share (2)       Price (2)            Fee
               ----------                 --------------  ----------------  ----------------     ------------
1999 Stock Incentive Plan and 1997
  Stock Plan 
  Options to Purchase Common Stock           6,295,636          N/A                     N/A                N/A
    Common Stock (par value $0.0001)     6,295,636 Shares      $23.00          $144,799,628         $40,254.00
                                                             

1999 Directors' Option Plan
    Options to Purchase Common Stock         200,000             N/A                    N/A                N/A
    Common Stock (par value $0.0001)      200,000 shares       $23.00            $4,600,000          $1,278.80
--------------------------------------------------------------------------------------------------------------
2
1999 Employee Stock Purchase Plan
  Rights to Purchase Common Stock                               N/A                    N/A                N/A
  Common Stock (par value $0.0001)      1,000,000 shares      $23.00           $23,000,000          $6,394.00

Shares Acquired Under Written 
Compensation Agreements With 
David Coleman, Steve De Golia, 
Joyce Gandolfi, Karen Hamerquist, 
Jeff Johnson, Wing Ko, 
Dave Lawrence, Eric Olsen, 
William Palter, Keith Quigley, 
Guna Ramireddy, David Shapiro, 
Lynette Souza, Nick Thille and 
Jay Willey 
  Common Stock (par value $0.0001)     140,838 shares         $23.00           $3,239,274            $900.52
(1)     This Registration Statement shall also cover any additional shares of
        Common Stock which become issuable under the 1999 Stock Incentive Plan,
        the 1997 Stock Plan, the 1999 Directors' Option Plan, the 1999 Employee
        Stock Purchase Plan and the Written Compensation Agreements with David
        Coleman, Steve De Golia, Joyce Gandolfi, Karen Hamerquist, Jeff Johnson,
        Wing Ko, Dave Lawrence, Eric Olsen, William Palter, Keith Quigley, Guna
        Ramireddy, David Shapiro, Lynette Souza, Nick Thille and Jay Willey,
        because of any stock dividend, stock split, recapitalization or other
        similar transaction effected without the receipt of consideration which
        results in an increase in the number of the outstanding shares of Common
        Stock of Redback Networks.

(2)     Calculated only for purposes of this offering under Rule 457(h) of the
        Securities Act of 1933, as amended, on the basis of the fair market
        value per share of Common Stock of Redback Networks on May 17, 1999.
3
                                EXPLANATORY NOTE

               Under General Instruction C of Form S-8, this Registration
Statement contains a prospectus meeting the requirements of Part I of Form S-3
relating to the reoffer by a certain individual of shares of Common Stock, par
value $0.0001 per share, of Redback Networks acquired pursuant to a Written
Agreement.
4
                                REDBACK NETWORKS

         FORM S-8 CROSS REFERENCE SHEET SHOWING LOCATION OF INFORMATION
                         REQUIRED BY PART I OF FORM S-3
Form S-3 Item Number                             Location/Heading in Prospectus
--------------------                             ------------------------------
1.  Forepart of Registration Statement and       Cover page
    Outside Front Cover page of Prospectus

2.  Inside Front and Outside Back Cover          Available Information; Incorporation of
    Page of Prospectus                           Certain Information by Reference

3.  Summary Information, Risk Factors and        Risk Factors
    Ratio of Earnings to Fixed Charges

4.  Use of Proceeds                              Not applicable

5.  Determination of Offering Price              Not applicable

6.  Dilution                                     Not applicable

7.  Selling Security Holder                      Selling Security Holder

8.  Plan of Distribution                         Plan of Distribution

9.  Description of Securities to be              Not Applicable
    Registered

10. Interests of Named Experts and Counsel       Not Applicable

11. Material Changes                             Not Applicable

12. Incorporation of Certain Information         Documents Incorporated by Reference

13. Disclosure of Commission Position on         Indemnification
    Indemnification for Securities Act
    Liabilities
5
                                     PART II

               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

Item 3. Incorporation of Documents by Reference

        Redback Networks ("Redback") hereby incorporates by reference into this
Registration Statement the following documents previously filed with the
Securities and Exchange Commission (the "SEC"):

(a) Redback's prospectus filed with the SEC under Rule 424(b) under the
Securities Act of 1933, as amended (the "1933 Act"), in connection with
Registration Statement No. 333-744479 on Form S-1 filed with the SEC on March
16, 1999, the amendment filed on April 22, 1999, the amendment filed on May 4,
1999, the amendment filed on May 12, 1999 and the amendment filed on May 14,
1999, which contains the audited financial statements for the period August 30,
1996 (inception) through December 31, 1996 and for Redback's fiscal years ended
December 31, 1997 and 1998.

(b) The description of Redback's outstanding Common Stock contained in Redback's
Registration Statement No. 0-25853 on Form 8-A filed with the SEC on April 22,
1999, under Section 12 of the 1934 Act, including any amendment or report filed
to update the description.

        All reports and definitive proxy or information statements filed under
Section 13(a), 13(c), 14 or 15(d) of the 1934 Act after the date of this
Registration Statement and prior to the filing of a post-effective amendment
which indicates that all securities offered hereby have been sold or which
deregisters all securities then remaining unsold shall also be incorporated by
reference into this Registration Statement and to be a part hereof from the date
of filing of such documents.

Item 4. Description of Securities

        Not Applicable.

Item 5. Interests of Named Experts and Counsel

        Not Applicable.

Item 6. Indemnification of Directors and Officers

        Section 145 of the Delaware General Corporation Law authorizes a court
to award or a corporation's Board of Directors to grant indemnification to
directors and officers in terms sufficiently broad to permit such
indemnification under certain circumstances for liabilities (including
reimbursement for expenses incurred) arising under the 1933 Act. Redback's
Bylaws provide for mandatory indemnification of its directors and officers and
permissible indemnification of employees and other agents to the maximum extent
permitted by the Delaware General Corporation Law. Redback's Certificate of
Incorporation provides that, under Delaware law, its directors shall not be
liable for monetary damages for breach of their fiduciary duty as directors to
Redback and its stockholders. This provision in the Certificate of Incorporation
does not eliminate the fiduciary duty of the directors, and, in appropriate
circumstances, equitable remedies such as injunctive or other forms of
non-monetary relief will remain available under Delaware law. In addition, each
director will continue to be subject to liability for breach of the director's
duty of loyalty to Redback for acts or omissions not in good faith or involving
intentional misconduct, for knowing violations of law, for actions leading to
improper personal benefit to the director and for payment of dividends or
approval of stock repurchases or redemptions that are unlawful under Delaware
law. The provision also does not affect a director's responsibilities under any
other law, such as the federal securities laws or state or federal environmental
laws. Redback has entered into Indemnification Agreements with its officers and
directors. The Indemnification Agreements provide Redback's officers and
directors with further indemnification to the maximum extent permitted by the
Delaware General Corporation Law.

                                      II-2
6

Item 7. Exemption from Registration Claimed

        Not Applicable.

Item 8. Exhibits
Exhibit Number    Exhibit
--------------    -------
4           Instrument Defining Rights of Stockholders. Reference is made
                  to Redback's Registration Statement No. 0-25853 on Form 8-A,
                  which is incorporated herein by reference under Item 3(b) of
                  this Registration Statement.

      5           Opinion and consent of Gunderson Dettmer Stough Villeneuve
                  Franklin & Hachigian LLP.

      23.1        Consent of PricewaterhouseCoopers, Independent Accountants.

      23.2        Consent of Gunderson Dettmer Stough Villeneuve Franklin &
                  Hachigian LLP is contained in Exhibit 5.

      24          Power of Attorney. Reference is made to page II-4 of this
                  Registration Statement.

      99.1        Form of Written Compensation Agreement with David Coleman,
                  Steve De Golia, Joyce Gandolfi, Jeff Johnson, Eric Olsen,
                  William Palter, Keith Quigley, David Shapiro, Lynette Souza,
                  Nick Thille and Jay Willey.
Item 9. Undertakings

        A.      Redback hereby undertakes:

                (1) to file, during any period in which offers or sales are
                being made, a post-effective amendment to this Registration
                Statement

                        (i)     to include any prospectus required by Section
                                10(a)(3) of the 1933 Act,

                        (ii)    to reflect in the prospectus any facts or events
                                arising after the effective date of this
                                Registration Statement (or the most recent
                                post-effective amendment thereof) which,
                                individually or in the aggregate, represent a
                                fundamental change in the information set forth
                                in this Registration Statement and

                        (iii)   to include any material information with respect
                                to the plan of distribution not previously
                                disclosed in this Registration Statement or any
                                material change to such information in this
                                Registration Statement; provided, however, that
                                clauses (1)(i) and (1)(ii) shall not apply if
                                the information required to be included in a
                                post-effective amendment by those paragraphs is
                                contained in periodic reports filed with or
                                furnished to the SEC by Redback under Section 13
                                or Section 15(d) of the 1934 Act that are
                                incorporated by reference in this Registration
                                Statement;

                (2) that for the purpose of determining any liability under the
                1933 Act each such post-effective amendment shall be deemed to
                be a new registration statement relating to the securities
                offered therein and the offering of such securities at that time
                shall be deemed to be the initial bona fide offering thereof and

                (3) to remove from registration by means of a post-effective
                amendment any of the securities being registered which remain
                unsold at the termination of Redback's 1999 Stock Incentive
                Plan, 1997 Stock Plan, 1999 Directors' Option Plan, 1999
                Employee Stock Purchase Plan and Written Compensation Agreements
                with David Coleman, Steve De Golia, Joyce Gandolfi, Karen
                Hamerquist, Jeff Johnson, Wing Ko, Dave Lawrence, Eric Olsen,
                William Palter, Keith Quigley, Guna Ramireddy, David Shapiro,
                Lynette Souza, Nick Thille and Jay Willey.

        B. Redback hereby undertakes that, for purposes of determining any
liability under the 1933 Act, each filing of Redback's annual report under
Section 13(a) or Section 15(d) of the 1934 Act that is incorporated by reference
in this Registration Statement shall be deemed to be a new registration
statement relating to the securities 

                                      II-3
7

offered therein, and the offering of such securities at that time shall be
deemed to be the initial bona fide offering thereof.

C. Insofar as indemnification for liabilities arising under the 1933 Act may be
permitted to directors, officers or controlling persons of Redback under the
indemnification provisions summarized in Item 6 or otherwise, Redback has been
advised that, in the opinion of the SEC, such indemnification is against public
policy as expressed in the 1933 Act, and is, therefore, unenforceable. In the
event that a claim for indemnification against such liabilities (other than the
payment by Redback of expenses incurred or paid by a director, officer or
controlling person of Redback in the successful defense of any action, suit or
proceeding) is asserted by such director, officer or controlling person in
connection with the securities being registered, Redback will, unless in the
opinion of its counsel the matter has been settled by controlling precedent,
submit to a court of appropriate jurisdiction the question whether such
indemnification by it is against public policy as expressed in the 1933 Act and
will be governed by the final adjudication of such issue.

                                      II-4
8
REOFFER PROSPECTUS

                                   SIGNATURES

               The Securities Act of 1933, as amended, requires that Redback
certifies that it has reasonable grounds to believe that it meets all of the
requirements for filing on Form S-8 and has had this Registration Statement
signed on its behalf by the undersigned, who is duly authorized, in the City of
San Francisco, State of California on this 21st day of May, 1999.

                                       REDBACK NETWORKS

                                       By: /s/Dennis L. Barsema
                                           -------------------------------------
                                           Dennis L. Barsema
                                           President and Chief Executive Officer

                                POWER OF ATTORNEY

KNOW ALL PERSONS BY THESE PRESENTS:

               That the undersigned officers and directors of Redback Networks,
a Delaware corporation, do hereby constitute and appoint Dennis L. Barsema and
Geoffrey C. Darby, and either of them, the lawful attorneys-in-fact and agents
with full power and authority to do any and all acts and things and to execute
any and all instruments which said attorneys and agents, and either one of them,
determine may be necessary or advisable or required to enable said corporation
to comply with the Securities Act of 1933, as amended, and any rules or
regulations or requirements of the Securities and Exchange Commission in
connection with this Registration Statement. Without limiting the generality of
the foregoing power and authority, the powers granted include the power and
authority to sign the names of the undersigned officers and directors in the
capacities indicated below to this Registration Statement, to any and all
amendments, both pre-effective and post-effective, and supplements to this
Registration Statement, and to any and all instruments or documents filed as
part of or in conjunction with this Registration Statement or amendments or
supplements thereof, and each of the undersigned hereby ratifies and confirms
all that said attorneys and agents, or either one of them, shall do or cause to
be done by virtue hereof. This Power of Attorney may be signed in several
counterparts.

               IN WITNESS WHEREOF, each of the undersigned has executed this
Power of Attorney on the date indicated.

               Under the requirements of the Securities Act of 1933, as amended,
this Registration Statement has been signed below by the following persons in
the capacities and on the dates indicated.
Signature                    Title                                     Date
---------                    -----                                     ----
/s/Dennis L. Barsema         President, Chief Executive Officer        May 21, 1999
------------------------     and Director                 
Dennis L. Barsema            (Principal Executive Officer)
                             

/s/Geoffrey C. Darby         Chief Financial Officer, Treasurer        May 21, 1999
------------------------     and Secretary (Principal Financial 
Geoffrey C. Darby            and Accounting Officer)
9
REOFFER PROSPECTUS
/s/James R. Flach            Director                                  May 21, 1999
------------------------
James R. Flach

/s/Pierre R. Lamond          Director                                  May 21, 1999
------------------------
Pierre R. Lamond

/s/Daniel J. Warmenhoven     Director                                  May 21, 1999
------------------------
Daniel J. Warmenhoven
10
REOFFER PROSPECTUS

                             Shares of Common Stock
                                Redback Networks

               This Reoffer Prospectus relates to 140,838 shares of the Common
Stock, par value $0.0001 (the "Common Stock"), of Redback Networks (the
"Company"), which may be offered from time to time by certain key employees
named herein (the "Registered Stockholders"). It is anticipated that the
Registered Stockholders will offer shares for sale at prevailing prices on the
Nasdaq National Market System on the date of sale. The Company will receive no
part of the proceeds of sale made hereunder. All expenses of registration
incurred in connection with this offering are being borne by the Company, but
all selling and other expenses incurred by each of the Registered Stockholders
will be borne by each such Registered Stockholder.

               Following the initial public offering of the Common Stock, the
Common Stock will be traded on the Nasdaq National Market System. The price per
share of the Company's Common Stock as offered in its initial public offering of
such Common Stock is expected to be $23.00.

               The Registered Stockholders and any broker executing selling
orders on behalf of the Registered Stockholders may be deemed to be
"underwriters" within the meaning of the Securities Act of 1933, as amended (the
"Securities Act"), in which event commissions received by such broker may be
deemed to be underwriting commissions under the Securities Act.

          THESE SECURITIES INVOLVE A HIGH DEGREE OF RISK AND SHOULD BE
           CONSIDERED ONLY BY PERSONS WHO CAN AFFORD THE LOSS OF THEIR
                               ENTIRE INVESTMENT.
                     SEE "RISK FACTORS" BEGINNING ON PAGE 3.
    THESE SECURITIES HAVE NOT BEEN APPROVED OR DISAPPROVED BY THE SECURITIES
         AND EXCHANGE COMMISSION NOR HAS THE COMMISSION PASSED UPON THE
           ACCURACY OR ADEQUACY OF THIS PROSPECTUS. ANY REPRESENTATION
                     TO THE CONTRARY IS A CRIMINAL OFFENSE.

               No person is authorized to give any information or to make any
representations, other than those contained in this Prospectus, in connection
with the offering described herein, and, if given or made, such information or
representations must not be relied upon as having been authorized by the Company
or any Registered Stockholder. This Prospectus does not constitute an offer to
sell, or a solicitation of an offer to buy, nor shall there be any sale of these
securities by any person in any jurisdiction in which it is unlawful for such
person to make such offer, solicitation or sale. Neither the delivery of this
Prospectus nor any sale made hereunder shall under any circumstances create an
implication that the information contained herein is correct as of any time
subsequent to the date hereof.

               The date of this Prospectus is May 17, 1999.
11
                              AVAILABLE INFORMATION

               The Company will be subject to the informational reporting
requirements of the Securities Exchange Act of 1934, as amended (the "Exchange
Act") upon the first date on which its Common Stock is registered under Section
12(g) of the Exchange Act and in accordance therewith will file reports, proxy
statements and other information with the Securities and Exchange Commission
(the "Commission"). Such reports, proxy statements and other information can be
inspected and copied at the Public Reference Room of the Commission, 450 Fifth
Street, N.W., Washington, D.C. 20549 and at the Commission's regional offices at
219 South Dearborn Street, Chicago, IL 60604; 26 Federal Plaza, New York, NY
10007; and 5757 Wilshire Boulevard, Los Angeles, CA 90036, at prescribed rates.
The Common Stock following the Company's initial public offering will be quoted
on the Nasdaq National Market System. Reports, proxy statements, informational
statements and other information concerning the Company can be inspected at the
offices of the National Association of Securities Dealers, Inc.
at 1735 K Street, N.W., Washington, D.C.  20006.

               The Company intends to furnish its stockholders with annual
reports containing additional financial statements and a report thereon by
independent certified public accountants.

               A copy of any document incorporated by reference in the
Registration Statement (not including exhibits to the information that is
incorporated by reference unless such exhibits are specifically incorporated by
reference into the information that the Registration Statement incorporates) of
which this Reoffer Prospectus forms a part but which is not delivered with this
Reoffer Prospectus will be provided by the Company without charge to any person
(including any beneficial owner) to whom this Reoffer Prospectus has been
delivered upon the oral or written request of such person. Such requests should
be directed to Carrie Perzow, Redback Networks, 1389 Moffett Park Drive,
Sunnyvale, CA 94089. The Company's telephone number at that location is (408)
548 3500.

                                TABLE OF CONTENTS
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THE COMPANY...........................................................   3

RISK FACTORS..........................................................   

REGISTERED STOCKHOLDERS...............................................   

PLAN OF DISTRIBUTION..................................................

DOCUMENTS INCORPORATED BY REFERENCE...................................   

INDEMNIFICATION.......................................................
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                                   THE COMPANY

     Redback Networks (the "Company") is a leading provider of advanced
networking systems that enable carriers, cable operators and service providers
to rapidly deploy high-speed access to the Internet and corporate networks. Our
products, consisting of the Subscriber Management System, or SMS 500 and SMS
1000, combine networking hardware with sophisticated software. Our products
connect and manage large numbers of subscribers using any of the major
high-speed access technologies, including digital subscriber line, which is a
technology that brings high-speed access over standard copper telephone lines,
cable and wireless. We sell our products through our direct sales force,
resellers and distribution partners.
 
     Bridging the gap between high-speed access concentrators and routers
connecting to the Internet backbone, our flagship product, the SMS 1000, is
currently being used by many of the largest carriers and service providers.
UUNET, a subsidiary of MCI Worldcom, SBC, Southwestern Bell Information Systems
and Pacific Bell Internet, subsidiaries of SBC and GTE have been, since
inception, our largest customers in terms of revenues. Other representative
customers include Ameritech, Bell Canada, Bell South, Concentric, Earthlink,
Flashcom, Korea Telecom, Verio and @Work, a division of @Home. They are
representative in terms of, among other things, the type of provider, the
mixture of broadband services offered and the mixture of regional versus
national deployment.
 
     In recent years, there has been a significant increase in demand by
businesses and consumers for broadband, or high-speed, access to the Internet
and to corporate networks. While carriers, cable operators and service providers
are attempting to provide inexpensive and comprehensive broadband access, there
are several major challenges associated with scaling and configuring existing
network architectures to accommodate large numbers of new high-speed
subscribers. We believe widespread deployment of broadband services requires a
new model for subscriber management that efficiently terminates subscriber
connections, manages broadband subscribers, provides flexibility for
connections, and supports multiple broadband access technologies simultaneously.
 
     Our products meet the above requirements. Whether deployed at subscriber
aggregation points by carriers, by cable operators or by service providers, our
products accept a large concentration of high-speed data traffic from such
devices as digital subscriber line concentrators, cable modem termination
systems and wireless termination systems. Our products reduce the processing
requirements placed on routers connecting to the Internet backbone in broadband
networks. Our SMS 1000 today supports up to 4,000 simultaneous subscribers. The
key benefits of our solution include:
 
     - Enhances Broadband Operations. Our products bridge the operational gap
       between "last mile" access networks that serve businesses and homes and
       the routers connecting to the Internet backbone and corporate networks.
 
     - Supports All Major Access Technologies. Our products support all major
       access technologies, including digital subscriber line, cable, wireless
       and dial.
 
     - Facilitates Rapid and Scalable Deployment. Our products allow service
       providers to use existing access, accounting and management control
       systems, enabling them to quickly deploy high-speed access and achieve
       rapid time-to-market for significant revenue-generating services.
 
     - Provides Platform for the Delivery of Value-Added Services. Our products
       enable carriers, cable operators and service providers to create and
       market new service offerings that extend broadband connectivity and
       capabilities.
 
     - Simplifies End-User Administration and Support. Our products allow easy
       configuration and administration of end-user broadband modems, further
       reducing the cost of providing service.
 
     We are focused on delivering subscriber management solutions to carriers
and service providers and intend to use our position in the digital subscriber
line market to penetrate the cable and wireless broadband markets. We believe
our software differentiates our solution and provides a competitive advantage by
delivering advanced subscriber management services and functionality. We will
continue to develop features and functionalities and expand our product family
to further enhance the ability of carriers, cable operators and service
providers to deliver profitable services.

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               The Company's executive offices are located at 1389 Moffett Park
Drive, Sunnyvale, CA 94089. The Company's telephone number is (408) 548 3500.

                                  RISK FACTORS

     This offering and an investment in our common stock involve a high degree
of risk. You should carefully consider the following risk factors and the other
information in this prospectus before investing in our common stock. Our
business, results of operations and financial condition could be seriously
harmed by any of the following risks. The trading price of our common stock
could decline due to any of these risks, and you may lose all or part of any
investment you make in our common stock.
 
RISKS RELATED TO OUR BUSINESS
 
     OUR BUSINESS IS DIFFICULT TO EVALUATE BECAUSE WE HAVE A LIMITED OPERATING
     HISTORY
 
     We were founded in August 1996 and only began shipping products in material
quantities in the second quarter of 1998. You should consider the risks and
difficulties frequently encountered by companies like ourselves in a new and
rapidly evolving market. From February 28, 1998 to March 31, 1999, we have
experienced significant growth -- from 39 employees to 127 employees. Our
ability to sell products and services, and the level of success, if any, we
achieve, depends, among other things, on the level of demand for broadband
access services, which is a new and rapidly evolving market. See "Risk
Factors -- We are dependent on the widespread adoption of broadband access
services." Our business strategy may be unsuccessful and we may not successfully
address the risks we face.
 
     WE HAVE A HISTORY OF LOSSES AND WE EXPECT TO INCUR FUTURE LOSSES
 
     We incurred net losses of $142,000 from our inception in August 1996
through December 31, 1996, $4.4 million for the year ended December 31, 1997,
$9.9 million for the year ended December 31, 1998 and $3.8 million for the three
months ended March 31, 1999. As of March 31, 1999, we had an accumulated deficit
of approximately $18.2 million. We have not achieved profitability and we expect
to continue to incur net losses in the future.
 
     To date, we have funded our operations from the sale of equity securities,
from bank borrowings and by means of equipment lease financing. We expect to
continue to incur significant product development, sales and marketing, and
general and administrative expense. As a result, we must generate significant
revenues to achieve profitability. We may not sustain recent growth rates in our
revenues, and we may never achieve sufficient revenue levels to achieve
profitability. If we do achieve profitability in some future period, we cannot
be certain that we would sustain profitability on a quarterly or annual basis in
the future.
 
     OUR OPERATING RESULTS ARE LIKELY TO FLUCTUATE SIGNIFICANTLY
 
     Factors likely to cause quarterly fluctuations in revenues and operating
results include:
 
     - Fluctuations in demand for broadband access services;
 
     - The timing and size of sales of our products and services;
 
     - The lack of any significant backlog;
 
     - Announcements of new products and product enhancements by competitors;
 
     - The entry of new competitors into our market, including by acquisition;
 
     - Unexpected delays in introducing new or enhanced products, including
       manufacturing delays;
 
     - Our ability to control expenses;
 
     - Our ability to ship products on a timely basis and at a reasonable cost;
       and
 
     - The mix of our products sold and the mix of distribution channels through
       which our products are sold.

                                        4
14
 
     A high percentage of our expenses, including those related to engineering,
sales and marketing, research and development, and general administrative
functions, are essentially fixed in the short term. As a result, if we
experience delays in generating or recognizing revenue, our quarterly operating
results are likely to be materially adversely affected. In addition, we plan to
increase our operating expenses to expand our engineering and sales and
marketing operations, broaden our customer support capabilities, develop new
distribution channels, fund increased levels of research and development and
build our operational infrastructure. If growth in our revenues does not outpace
the increase in these expenses, our business, results of operations and
financial condition could be materially adversely affected.
 
     We rely on a single third-party manufacturer to build our products. Any
interruption in the operations of this manufacturer would adversely affect our
ability to meet our scheduled product deliveries to our customers. This would
cause significant variations in our quarterly operating results and our
business, results of operations and financial condition would be materially
adversely affected.
 
     Due to these and other factors, we believe that quarter-to-quarter
comparisons of our operating results may not be meaningful. You should not rely
on our results for one quarter as any indication of our future performance. It
is likely that in some future quarter our operating results may be below the
expectations of public market analysts or investors. If this occurs, the price
of our common stock would likely decrease.
 
     OUR LENGTHY AND VARIABLE SALES CYCLE MAKES IT DIFFICULT FOR US TO PREDICT
     IF OR WHEN A SALE WILL BE MADE
 
     The timing of our sales revenue is difficult to predict because of the
length and variability of the sales cycle for our products. Customers often view
the purchase of our products as a significant and strategic decision. As a
result, customers typically undertake significant procedures relating to the
evaluation, testing, implementation and acceptance of our products. This
evaluation process frequently results in a lengthy sales cycle, typically
ranging from three months to over one year. While our customers are evaluating
our products and before they place an order with us, we may incur substantial
sales and marketing expenses and expend significant management efforts. In
addition, product purchases are frequently subject to unplanned administrative,
processing and other delays. This is particularly true for larger customers for
whom our products represent a very small percentage of their overall purchase
activities. These customers are often engaged in multiple simultaneous
purchasing decisions, some of which may pertain to more immediate needs and
absorb the immediate attention of the customer. If sales forecasted from a
specific customer for a particular quarter are not realized in that quarter or
at all, our business, results of operations and financial condition could be
materially adversely affected.
 
     IN ANY QUARTER, A SMALL NUMBER OF CUSTOMERS ARE LIKELY TO ACCOUNT FOR A
     SUBSTANTIAL MAJORITY OF OUR REVENUE
 
     In each of the last five quarters in the period ended March 31, 1999, we
had at least one customer that accounted for 15% or more of our total revenue in
the quarter. In the fourth quarter of 1998, UUNET, Nortel Networks and GTE and
its affiliated entities accounted for 28%, 13% and 12%, respectively, of our
total revenue. In the first quarter of 1999, UUNET, Southwestern Bell
Information Systems and GTE and its affiliated entities accounted for 43%, 10%
and 7%, respectively, of our total revenue. We anticipate that a small number of
customers with large orders will continue to account for a majority of our
quarterly revenue. However, we do not have any contracts or other agreements
that guarantee continued sales to these or any other customers. If our customers
alter their purchasing habits, or reevaluate their need for our products, or if
we fail to receive a large order in any future period, our business, results of
operations and financial condition would be materially adversely affected.
 

                                        5
15
 
     WE ARE ENTIRELY DEPENDENT ON OUR SMS PRODUCT FAMILY.
 
     The SMS 1000 and SMS 500 are the only products that we currently sell. We
intend to introduce new products and enhancements to existing products in the
future. Our inability to timely and successfully introduce new products and
product enhancements, or the failure of these new products or enhancements to
achieve market acceptance, could materially adversely affect our business,
results of operations and financial condition.
 
     THERE IS A LIMITED NUMBER OF POTENTIAL CUSTOMERS FOR OUR SMS 1000
 
     To date, substantially all of our revenues have been derived from sales and
service related to the SMS 1000 product. The SMS 1000 and any other new high-end
product that we may develop and introduce in the future are marketed primarily
to large customers. There are only a limited number of large existing and
potential customers and this number is not expected to increase significantly in
the future.
 
     WE FACE NEW RISKS WITH THE INTRODUCTION OF OUR SMS 500 PRODUCT
 
     We recently introduced the SMS 500, which is designed for use by customers
that intend to provide services to a smaller number of subscribers than those
using the SMS 1000. Given this targeted market, sales of the SMS 500 may involve
sales to smaller customers. Sales to smaller customers entail some additional
risks, including increased credit risks, the need for additional sales and
support personnel to support an increased volume of customers and the need to
develop a leasing program to facilitate market acceptance. Our business, results
of operations and financial condition could be materially adversely affected if
any of these risks materialize. To date, we have sold a limited number of our
SMS 500, and revenues from these sales were immaterial. The SMS 500 may not
achieve a significant degree of market acceptance. If the SMS 500 is not
successful, our ability to generate revenues will be limited to sales of the SMS
1000 to our customers with a large number of subscribers, which will have a
material adverse effect on our business, results of operations and financial
condition.
 
     OUR PRODUCTS MUST ANTICIPATE AND MEET SPECIFIC CUSTOMER REQUIREMENTS AND
DEMANDS
 
     Many of our customers require product features and capabilities that our
SMS products may not have. The requirement that we add features to our products
in order to achieve a sale may result in a longer sales cycle, increased
research and development expenses and reduced margins on our products. To
achieve market acceptance for our products, we must effectively and timely
anticipate and adapt to customer requirements and offer products and services
that meet customer demands. Our failure to develop products or offer services
that satisfy customer requirements would materially adversely affect our
business, results of operations and financial condition.
 
     We intend to continue to invest in product and technology development. The
development of new or enhanced products is a complex and uncertain process that
requires the accurate anticipation of technological and market trends. We may
experience design, manufacturing, marketing and other difficulties that could
delay or prevent the development, introduction or marketing of new products and
enhancements. The introduction of new or enhanced products also requires that we
manage the transition from older products in order to minimize disruption in
customer ordering patterns and ensure that adequate supplies of new products can
be delivered to meet anticipated customer demand. Our inability to effectively
manage this transition would materially adversely affect our business, results
of operations and financial condition.
 
     WE NEED TO GAIN ACCEPTANCE IN OTHER BROADBAND ACCESS MARKETS
 
     To date, we have derived substantially all of our revenues from sales of
the SMS 1000 for use in the digital subscriber line market for broadband access.
We intend to expend a substantial amount of time and resources to achieve market
acceptance of our products in other markets, including the cable and wireless
markets. We may be unable to simultaneously or effectively address evolving
demands in these markets, and customers in these markets may choose to implement
competing technologies or products. In addition, if we are not first in these
markets, competitors may gain market acceptance first, thereby
 

                                        6
16
making it difficult, if not impossible, for us to gain subsequent market
acceptance. If we are unable to achieve acceptance of our products in these
markets, our ability to generate revenues will be limited, and our business,
results of operations and financial condition would be materially adversely
affected.
 
     WE EXPECT INCREASED COMPETITION
 
     We may be unable to compete successfully with current or future
competitors. If we do not compete successfully against current or future
competitors, our business, results of operations and financial condition will be
materially adversely affected. Currently, competition in our market is intense.
The broadband access markets we are targeting, including digital subscriber
line, cable and wireless, are new and rapidly evolving and we expect these
markets to become highly competitive in the future. In addition, we expect new
competitors to emerge in the broadband access market as that market evolves due
to technological innovation and regulatory changes. We face actual and potential
competition from public and private companies providing routers connecting to
the Internet backbone, access concentrators and subscriber aggregation systems.
 
     Cisco, the leading provider of routers connecting to the Internet backbone,
offers products that compete directly with our products, and also provides a
comprehensive range of broadband access systems. We expect companies that offer
access concentrators and routers to incorporate some subscriber management
functionality into their products. These companies include Nortel Networks which
recently agreed to acquire Shasta, a private company providing subscriber
management services, and Ascend, which has announced its pending acquisition by
Lucent. In addition, there are several other private companies that provide
subscriber management features in access concentrators or routing platforms.
 
     Many of our principal competitors, including Cisco, Alcatel, Nortel
Networks/Shasta, Lucent/Ascend, and some companies that may compete with us in
the future, are large public companies that have longer operating histories and
significantly greater financial, technical, marketing and other resources than
we have. As a result, these competitors are able to devote greater resources to
the development, promotion, sale and support of their products. In addition, our
competitors that have large market capitalizations or cash reserves are much
better positioned than we are to acquire other companies, including our
competitors, and thereby acquire new technologies or products that may displace
our product lines. Any of these acquisitions could give our competitors a
strategic advantage that would materially adversely affect our business, results
of operations and financial condition.
 
     Many of our competitors have significantly more established customer
support and professional services organizations than we do. In addition, many of
our competitors have much greater name recognition and have a more extensive
customer base, broader customer relationships and broader product offerings than
our company. These companies can leverage their customer bases and broader
product offerings and adopt aggressive pricing policies to gain market share. We
have encountered, and expect to continue to encounter, potential customers that,
due to existing relationships with our competitors, are committed to the product
offerings of these competitors. As a result, these potential customers may not
consider purchasing our products. We expect to face competition in the following
areas:
 
     - Product pricing;
 
     - Breadth of product lines;
 
     - Sales and distribution capability;
 
     - Product features and enhancements, including product performance,
       reliability, size, compatibility and scalability;
 
     - Product ease of deployment;
 
     - Conformance to industry standards; and
 
     - Technical support and service.
 

                                        7
17
 
     We expect that competitive pressures may result in price reductions,
reduced margins and loss of market share, which would materially adversely
affect our business, results of operations and financial condition.
 
     WE ARE DEPENDENT ON A SINGLE CONTRACT MANUFACTURER
 
     We rely on a single third-party manufacturer, Electromax, to build our
products. We may not be able to effectively manage our relationship with
Electromax and Electromax may not meet our future requirements for timely
delivery. We have no written agreement with Electromax. We have relationships
with two other third-party manufacturers, one of which currently builds our
prototypes. Although both of these other third-party manufacturers are capable
of building our products, any interruption in the operations of Electromax would
adversely affect our ability to meet our scheduled product deliveries to our
customers, which could cause the loss of existing or potential customers and
could materially adversely affect our business, results of operations and
financial condition.
 
     In addition, the products that Electromax or any other manufacturer builds
for us may be insufficient in quality or in quantity to meet our needs.
Electromax or any other manufacturer may not meet the technological or delivery
requirements of our current products or any future products that we may develop
and introduce. The inability of Electromax or any other of our contract
manufacturers in the future to provide us with adequate supplies of high-quality
products, or the loss of Electromax or any other of our contract manufacturers
in the future, would cause a delay in our ability to fulfill customer orders
while another of our third-party manufacturers begins production and would have
a material adverse effect on our business, results of operations and financial
condition.
 
     SOME OF THE KEY COMPONENTS IN OUR PRODUCTS COME FROM SINGLE OR LIMITED
SOURCES OF SUPPLY
 
     We currently purchase several key components used in the manufacture of our
SMS 500 and our SMS 1000 products from single or limited sources of supply.
These manufacturers include Altera, Brooktree, Connector Technologies,
Foresight, Intel, Level One, Powerspec, Siemens and Ziatech. We have no
guaranteed supply arrangement with these suppliers, and we or our manufacturers
may fail to obtain these supplies in a timely manner in the future. Financial or
other difficulties faced by these suppliers or significant changes in demand for
these components could limit the availability to us of these components. Any
interruption or delay in the supply of any of these components, or the inability
to obtain these components from alternate sources at acceptable prices and
within a reasonable amount of time, would adversely affect our ability to meet
scheduled product deliveries to our customers and would materially adversely
affect our business, results of operations and financial condition. In addition,
qualifying additional suppliers is time-consuming and expensive.
 
     WE MAY BE UNABLE TO MATCH PRODUCTION WITH PRODUCT DEMAND
 
     We currently use a rolling six-month forecast based on anticipated product
orders, product order history and backlog to determine our materials
requirements. Lead times for the materials and components that we order vary
significantly and depend on numerous factors, including the specific supplier,
contract terms and demand for a component at a given time. If actual orders do
not match our forecasts, we may have excess or inadequate inventory of materials
and components, which could materially adversely affect our business, results of
operations and financial condition.
 
     WE MAY BE UNABLE TO PROPERLY MANAGE GROWTH
 
     We have expanded our operations rapidly since our inception. The number of
our employees increased from 39 in February 1998 to 127 in March 1999. We intend
to continue to expand in order to pursue existing and potential market
opportunities and are in the process of hiring additional engineering and sales
personnel. We intend to hire a significant number of engineers in 1999. Our
ability to continue to attract and retain highly skilled personnel is a critical
factor in determining whether we will be successful in the future. Competition
for highly skilled personnel is intense, especially in the San Francisco Bay
Area. We may fail to attract, assimilate or retain qualified personnel to
fulfill our current
 

                                        8
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or future needs. If we so fail, our business, results of operations and
financial condition could be materially adversely affected. Our planned rapid
growth places a significant demand on management and financial and operational
resources. In order to grow and achieve future success, we must:
 
     - Retain existing personnel;
 
     - Hire, train, manage and retain additional qualified personnel; and
 
     - Effectively manage multiple relationships with our customers, suppliers
       and other third parties.
 
     We are currently seeking to lease additional office space to accommodate
our growing operations. We may be unable to locate necessary office space on
commercially reasonable terms or in a timely manner. Failure to do so would have
a material adverse effect on our business, results of operations and financial
condition. Our current office lease expires in September 1999. Any required
relocation may be disruptive to our business.
 
     OUR PLANNED EXPANSION TO INTERNATIONAL MARKETS WILL INVOLVE NEW RISKS
 
     In 1998, we derived approximately 15% of our revenues from sales to
customers outside of the United States. Our ability to achieve future success
will depend in part on the expansion of our international sales and operations.
International operations are generally subject to a number of risks, including:
 
     - Expenses associated with customizing products for foreign countries;
 
     - Protectionist laws and business practices that favor local competition;
 
     - Dependence on local vendors;
 
     - Multiple, conflicting and changing governmental laws and regulations;
 
     - Longer sales cycles;
 
     - Longer accounts receivable cycles;
 
     - Increased difficulties in collecting accounts receivable;
 
     - Difficulties in managing operations across disparate geographic areas;
 
     - Difficulties associated with enforcing agreements through foreign legal
       systems;
 
     - Reduced or limited protection of our intellectual property rights in some
       countries;
 
     - Foreign currency exchange rate fluctuations; and
 
     - Political and economic instability.
 
     In addition, if we grow internationally, we will need to expand our
worldwide operations and enhance our communications infrastructure. If we fail
to implement and improve these systems, our ability to accurately forecast sales
demand, manage our supply chain and record and report financial and management
information would be adversely affected. This could materially adversely affect
our business, results of operations and financial condition.
 
     UNDETECTED SOFTWARE OR HARDWARE ERRORS COULD HAVE A MATERIAL ADVERSE EFFECT
ON US
 
     Networking products frequently contain undetected software or hardware
errors when first introduced or as new versions are released. We have
experienced minor errors in the past in connection with new products. We expect
that errors will be found from time to time in new or enhanced products after we
begin commercial shipments. These problems may cause us to incur significant
warranty and repair costs, divert the attention of our engineering personnel
from our product development efforts and cause significant customer relations
problems. The occurrence of these problems could result in the delay or loss of
market acceptance of our products and would likely have a material adverse
effect on our business, results of operations and financial condition.
 

                                       9
19
 
     Our customers use our products to provide broadband access to their
customers. Defects, integration issues or other performance problems in our
products could result in financial or other damages to our customers or could
damage market acceptance for our products. Our customers could also seek damages
for losses from us, which, if they were successful, could have a material
adverse effect on our business, results of operations and financial condition. A
product liability claim brought against us, even if unsuccessful, would likely
be time consuming and costly.
 
     OUR FAILURE AND THE FAILURE OF OUR KEY SUPPLIERS AND CUSTOMERS TO BE YEAR
     2000 COMPLIANT COULD NEGATIVELY IMPACT OUR BUSINESS
 
     The Year 2000 computer issue creates a variety of risks for us. If systems
do not correctly recognize date information when the year changes to 2000, our
business, results of operations and financial condition could be materially
adversely affected. The risks involve:
 
     - Potential warranty or other claims by our customers;
 
     - Errors in systems we use to run our business;
 
     - Errors in systems used by our suppliers;
 
     - Errors in systems used by our customers; and
 
     - Potential reduced spending by other companies on broadband Internet
       access products as a result of significant information systems spending
       on Year 2000 remediation.
 
     Our internal systems include both our information technology, and
non-information technology systems. We have conducted an initial audit of our
material internal information technology systems, including both our own
software products and third-party software and hardware technology. We have not
yet initiated an assessment of our non-information technology systems. To the
extent that we are unable to test the technology provided by third-party
vendors, we are seeking assurances from these vendors that their systems are
Year 2000 compliant. We may experience material unanticipated problems and costs
caused by undetected errors or defects in the technology used in our internal
information technology and non-information technology systems. These
unanticipated problems and costs could have a material adverse effect on our
business, results of operations and financial condition.
 
     We intend to contact our critical suppliers to determine if the suppliers'
operations and the products and services provided to us are Year 2000 compliant.
Where practicable, we will attempt to mitigate our risks with respect to the
failure of our suppliers to be Year 2000 compliant by locating Year 2000
compliant replacement suppliers. However, our failure to mitigate our Year 2000
risks remains a possibility and could have a material adverse impact on our
business, results of operations and financial condition.
 
     We have been informed by Electromax, our contract manufacturer, that its
manufacturing systems are Year 2000 compliant. However, Electromax may
experience material unanticipated problems and costs caused by undetected errors
or defects in the technology used in their internal information technology and
non-information technology systems. These unanticipated problems and costs could
cause manufacturing delays or difficulties for our products and harm
Electromax's operations. Additionally, Electromax has not yet ascertained
whether any of its suppliers is Year 2000 compliant. The failure of a supplier
of Electromax to be Year 2000 compliant could also adversely affect Electromax's
operations. Any of these events could materially adversely affect our business,
results of operations and financial condition.
 
     We believe that the SMS 1000 is Year 2000 compliant. However, despite
testing by us and by current and potential customers, and despite assurances
from developers of products incorporated into the SMS 1000, the SMS 1000 may
contain undetected errors or defects associated with Year 2000 date functions.
We believe that, based solely on internal testing, the recently introduced SMS
500 is
 

                                       10
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Year 2000 compliant. We have made assurances to our customers that the SMS 1000
and the SMS 500 are Year 2000 compliant. The failure of our products to be Year
2000 compliant would result in numerous customer claims, which could have a
material adverse impact on our business, results of operations and financial
condition.
 
     We do not currently have any information concerning the Year 2000
compliance status of our customers. Our current or potential customers may incur
significant expenses to achieve Year 2000 compliance. If our customers are not
Year 2000 compliant, they may experience material costs to remedy problems, or
they may face litigation costs. In either case, spending on Year 2000 issues
could reduce or eliminate the budgets that our current or potential customers
could have for purchases of our products. As a result, our business, results of
operations and financial condition could be materially adversely affected.
 
     To date, our Year 2000 related costs have not been material. We have funded
these costs from available cash without separately accounting for these costs.
Although our future Year 2000 compliance costs are not expected to be
significant, we may experience unanticipated material problems and costs
associated with Year 2000 compliance that could adversely affect our business,
results of operations and financial condition. We have not yet developed any
contingency plan to address situations that may result if we are unable to
achieve Year 2000 readiness of our critical operations. The cost of developing
and implementing a Year 2000 contingency plan may be material.
 
     If our internal systems, our products or the internal systems at our
manufacturers are not Year 2000 compliant, our business, results of operation
and financial condition would be materially adversely affected.
 
     WE MAY BE UNABLE TO PROTECT OUR PROPRIETARY TECHNOLOGY
 
     We rely on a combination of patent, copyright, trademark and trade secret
laws and restrictions on disclosure to protect our intellectual property rights.
We have filed one U.S. patent application. There can be no assurance that this
application will be approved, that any issued patents will protect our
intellectual property or that any issued patents will not be challenged by third
parties. Furthermore, other parties may independently develop similar or
competing technology or design around any patents that may be issued to us.
Although we attempt to protect our intellectual property rights, we may be
unable to prevent the misappropriation of our intellectual property,
particularly in foreign countries where the laws may not protect our proprietary
rights as fully as in the United States.
 
     Others may allege that our products infringe upon their proprietary rights.
Any parties asserting that our products infringe upon their proprietary rights
would force us to defend ourselves or our customers, manufacturers or suppliers
against alleged infringement of intellectual property rights. We could incur
substantial costs to prosecute or defend this litigation. In addition,
intellectual property litigation could force us to do one or more of the
following:
 
     - Cease selling, incorporating or using products or services that
       incorporate the challenged intellectual property;
 
     - Obtain from the holder of the infringed intellectual property right a
       license to sell or use the relevant technology, which license may not be
       available on acceptable terms, if at all; or
 
     - Redesign those products or services that incorporate the disputed
       technology.
 
     In the event of a successful claim of infringement against us and our
failure or inability to develop non-infringing technology or license the
infringed technology on acceptable terms and on a timely basis, our business,
results of operations and financial condition would be materially adversely
affected. We may be subject to these claims in the future.
 
     We may in the future initiate claims or litigation against third parties
for infringement of our proprietary rights in order to determine the scope and
validity of our proprietary rights or the proprietary
 

                                       11
21
 
rights of competitors. These claims could result in costly litigation and the
diversion of our technical and management personnel. As a result, our business,
results of operations and financial condition could be materially adversely
affected.
 
     WE MAY NEED ADDITIONAL CAPITAL, WHICH MAY NOT BE AVAILABLE
 
     At March 31, 1999, we had approximately $5.3 million in cash, cash
equivalents and short-term investments. In April 1999, we used approximately
$2.5 million of these amounts to repay outstanding debt obligations. In April
1999, we also secured a commitment for a $2.0 million asset-based borrowing
facility. We believe that these amounts, combined with proceeds from this
offering and cash anticipated to be available from future operations, will
enable us to meet our working capital requirements for at least the next 12
months. However, if cash from available sources is insufficient, or if cash is
used for acquisitions or other unanticipated uses, we may need additional
capital.
 
     The development and marketing of new products and the expansion of reseller
channels and associated support personnel will require a significant commitment
of resources. In addition, if the market for broadband access develops at a
slower pace than anticipated or if we fail to establish significant market share
and achieve a meaningful level of revenue, we may continue to incur significant
operating losses and utilize significant amounts of capital. As a result, we
could be required to raise substantial additional capital. Additional capital
may not be available to us at all, or if available, may be available only on
unfavorable terms. Any inability to raise additional capital when we require it
would materially adversely affect our business, results of operations and
financial condition. Any additional issuance of equity or equity-related
securities will be dilutive to our stockholders.
 
RISKS RELATED TO THE BROADBAND ACCESS INDUSTRY
 
     WE ARE DEPENDENT ON THE WIDESPREAD ADOPTION OF BROADBAND ACCESS SERVICES
 
     Sales of our products depend on the increased use and widespread adoption
of broadband access services, and the ability of our customers to market and
sell broadband access services. Our business, results of operations and
financial condition would be materially adversely affected if the use of
broadband access services does not increase as anticipated or if our customers'
broadband access services are not received well by the marketplace. Critical
issues concerning use of broadband access services are unresolved and will
likely affect use of broadband access services. These issues include:
 
     - Security;
 
     - Reliability;
 
     - Bandwidth;
 
     - Congestion;
 
     - Cost;
 
     - Ease of access; and
 
     - Quality of service.
 
     Even if these issues are resolved, if the market for products that provide
broadband access to the Internet and to corporate networks fails to develop, or
develops at a slower pace than anticipated, our business, results of operations
and financial condition would be materially adversely affected.
 
     THE BROADBAND ACCESS SERVICES MARKET IS SUBJECT TO RAPID CHANGE
 
     The broadband access services market is new and is characterized by rapid
technological change, frequent enhancements to existing products and new product
introductions, changes in customer requirements and evolving industry standards.
We may be unable to respond quickly or effectively to these developments. The
introduction of new products by competitors, market acceptance of products based
on
 

                                       12
22
 
new or alternative technologies, or the emergence of new industry standards,
could render our existing or future products obsolete, which would materially
adversely affect our business, results of operations and financial condition.
 
     The emergence of new industry standards might require us to redesign our
products. If our products fail to comply with widely adopted industry standards,
our customers and potential customers may not purchase our products. This would
have a material adverse effect on our business, results of operations and
financial condition.
 
     OUR BUSINESS MAY BE ADVERSELY AFFECTED BY GOVERNMENT REGULATION OF THE
     COMMUNICATIONS INDUSTRY
 
     The jurisdiction of the Federal Communications Commission, or FCC, extends
to the communications industry, to our customers and to the products and
services that our customers sell. Future FCC regulations, or regulations set
forth by other regulatory bodies, may adversely affect the broadband access
services industry. Regulation of our customers may have a material adverse
affect on our business, results of operations and financial condition. For
example, FCC regulatory policies that affect the availability of data and
Internet services may impede our customers' penetration into broadband access
markets. In addition, international regulatory bodies are beginning to adopt
standards for the communications industry. The delays that these governmental
processes entail may cause order cancellations or postponements of product
purchases by our customers, which would materially adversely affect our
business, results of operations and financial condition.
 
RISKS RELATED TO THE SECURITIES MARKETS
 
     OUR STOCK PRICE MAY BE VOLATILE
 
     Prior to this offering, you could not buy or sell our common stock
publicly. An active public market for our common stock may not develop or be
sustained after this offering. The market for technology stocks has been
extremely volatile. The following factors could cause the market price of our
common stock to fluctuate significantly from the price paid by investors in this
offering:
 
     - Our loss of a major customer;
 
     - Our addition or the departure of key Redback Networks personnel;
 
     - Variations in our quarterly operating results;
 
     - Announcements by us or our competitors of significant contracts, new
       products or product enhancements, acquisitions, distribution
       partnerships, joint ventures or capital commitments;
 
     - Changes in financial estimates by securities analysts;
 
     - Our sales of common stock or other securities in the future;
 
     - Changes in market valuations of broadband access technology companies;
 
     - Changes in market valuations of networking and telecommunications
       companies; and
 
     - Fluctuations in stock market prices and volumes.
 
     OUR BUSINESS MAY BE ADVERSELY AFFECTED BY CLASS ACTION LITIGATION DUE TO
     STOCK PRICE VOLATILITY
 
     Securities class action litigation has often been brought against a company
following periods of volatility in the market price of its securities. If our
stock price is volatile, we may be the target of similar litigation. Our
management's attention and resources may be diverted by any securities
litigation, and we may incur substantial related costs, possibly resulting in a
material adverse effect to our business, results of operations and financial
condition.
 
                                       13
23
 
     CONTROL BY EXISTING STOCKHOLDERS MAY LIMIT YOUR ABILITY TO INFLUENCE THE
     OUTCOME OF DIRECTOR ELECTIONS AND CERTAIN TRANSACTIONS
 
     Upon completion of this offering, our executive officers, directors and
principal stockholders and their affiliates will beneficially own approximately
49.0% of our outstanding common stock (48.1% if the underwriters' over-allotment
option is exercised in full). These stockholders, if acting together, would be
able to significantly influence all matters requiring approval by our
stockholders, including the election of directors and the approval of mergers or
other business combination transactions.
 
     OUR MANAGEMENT HAS BROAD DISCRETION IN USE OF PROCEEDS
 
     The net proceeds from this offering will be added to our general working
capital upon completion of this offering. We cannot specify with certainty how
we will use the net proceeds. Accordingly, our management will have considerable
discretion in the application of the net proceeds. See "Use of Proceeds."
 
     SUBSTANTIAL SALES OF OUR COMMON STOCK COULD ADVERSELY AFFECT OUR STOCK
     PRICE
 
     Sales of a substantial number of shares of our common stock after this
offering could adversely affect the market price of our common stock by
potentially introducing a large number of sellers of our common stock into a
market in which our common stock price is already volatile, thus driving our
common stock price down. In addition, the sale of these shares could impair our
ability to raise capital through the sale of additional equity securities. Based
on shares outstanding as of March 31, 1999, upon completion of this offering, we
will have 21,034,119 shares of common stock outstanding, or 21,409,119 shares if
the underwriters' over-allotment option is exercised in full. Our directors,
executive officers and current stockholders have executed lock-up agreements
that limit their ability to sell shares of our common stock. These stockholders
have agreed, subject to limited exceptions, not to sell or otherwise dispose of
any shares of our common stock for a period of at least 180 days after the date
of this prospectus without the prior written approval of Morgan Stanley & Co.
Incorporated. When these lock-up agreements expire, these shares and the shares
of common stock underlying any options held by these individuals will become
eligible for sale, in some cases pursuant only to the volume, manner of sale and
notice requirements of Rule 144.
 
     INVESTORS WILL EXPERIENCE IMMEDIATE DILUTION
 
     The initial public offering price of our common stock is expected to be
substantially higher than the book value per share of our outstanding common
stock immediately after the offering. Accordingly, if you purchase our common
stock in this offering, you will incur immediate dilution of approximately
$20.29 in the book value per share of our common stock from the price you pay
for our common stock. This calculation assumes that you purchased our common
stock for $23.00 per share.
 
     ANTI-TAKEOVER PROVISIONS IN OUR CHARTER DOCUMENTS AND DELAWARE LAW COULD
     PREVENT OR DELAY A CHANGE IN CONTROL OF OUR COMPANY
 
     Provisions in our bylaws and in our certificate of incorporation, both as
amended and restated upon the closing of this offering, may have the effect of
delaying or preventing a change of control or changes in management of our
company. These provisions include:
 
     - The stipulation that a special meeting of stockholders may only be called
       by stockholders owning at least 50% of our outstanding shares;
 
     - The ability of our board of directors to issue preferred stock without
       stockholder approval; and
 

                                       14
24
 
     - The right of our board of directors to elect a director to fill a vacancy
       created by the expansion of the board of directors.
 
Furthermore, we are subject to the provisions of section 203 of the Delaware
General Corporation Law. These provisions prohibit a stockholder owning 15% or
more of our outstanding voting stock from consummating a merger or combination
with us unless this stockholder receives board approval for the transaction or
unless 66 2/3% of the outstanding shares of our voting stock not owned by this
stockholder approve the merger or combination.
 

                             REGISTERED STOCKHOLDERS

               The Reoffer Prospectus relates to shares of Common Stock which
have been acquired by certain key employees (the "Registered Stockholders") of
the Company. Registered Stockholders acquired shares of Common Stock to be
offered hereunder pursuant to the exercise of options granted under the 1997
Stock Plan.

               The following table sets forth certain information with respect
to the Registered Stockholders as of March 31, 1999:
Number of                      Number of      Percentage
                                               Shares                         Shares           of
                                             Beneficially    Number of      Beneficially      Shares
                                              Owned as       Shares to         Owned       Beneficially
                                                 of              be            After          Owned
   Registered          Position with           March 31,      Offered         Offering        After
  Stockholder           the Company            1999(1)         Hereby           (1)          Offering(2)
  -----------          -------------         ------------    ---------      -----------    -------------
David Coleman         Customer Support          40,500          2,250          38,250            *
                      Engineer                                                               

Steve De Golia        Regional Sales            57,500         57,500               0            *
                      Director                                                               
                                                                                             
Joyce Gandolfi        Contract Recruiter        64,750          2,200          62,500            *
                                                                                             
Karen Hamerquist      Account Manager           17,500          4,375          13,125            *
                                                                                             
Jeff Johnson          Software Engineer        117,500          5,000         112,500            *
                                                                                             
Wing Ko               Software Engineer         30,000          7,500          22,500            *
                                                                                             
Dave Lawrence         Hardware Engineer        121,150          5,000         116,250            *
                                                                                             
Eric Olsen            Hardware Engineering      25,000          1,000          24,000            *
                      Manager                                                                
                                                                                             
William Palter        Software Engineer         27,000          4,013          22,987            *
                                                                                             
Keith Quigley         Account Manager           25,000         10,000          15,000            *
                                                                                             
Guna Ramireddy        Software Engineer         25,000         15,000          10,000            *
                                                                                             
David Shapiro         Sales Engineer            17,000         17,000               0            *
                                                                                             
Lynette Souza         Marketing                 26,750          2,000          24,750            *
                      Communications                                                         
                      Specialist                                                             
                                                                                             
Nick Thille           Software Engineer        110,000          5,000         105,000            *
                                                                                             
Jay Wiley             Software Engineer         12,000          3,000           9,000            *
                                                                                       
--------------------------------------------------------------------------------------------------
-       Represents beneficial ownership of less than 1% of the outstanding
        shares of our Common Stock.

(1) Percentage of beneficial ownership includes Common Stock of which such
individual has the right to acquire beneficial ownership within 60 days of March
31, 1999, including but not limited to, upon the exercise of an option.

                                       15
25

(2) Percentage of beneficial ownership is calculated assuming 18,534,119 shares
of Common Stock were outstanding on March 31, 1999. The number of shares
outstanding after the offering under this Reoffer Prospectus includes the
2,500,000 shares of Common Stock offered for sale by the Company in its initial
public offering.

                              PLAN OF DISTRIBUTION

               The shares of Common Stock covered by this Reoffer Prospectus are
being registered by the Company for the account of the Registered Stockholders.
The Company understands that none of such shares will be offered through
underwriters.

               Shares of Common Stock covered by this Reoffer Prospectus may be
offered and sold from time to time by the Registered Stockholders through
brokers through the Nasdaq National Market System or otherwise, at the prices
prevailing at the time of such sales. To the Company's knowledge, no specific
brokers or dealers have been designated by the Registered Stockholders nor has
any agreement been entered into in respect of brokerage commissions or for the
exclusive or coordinated sale of any securities which may be offered pursuant to
this Reoffer Prospectus. The Company will pay all expenses of preparing and
reproducing this Reoffer Prospectus, but will not receive the proceeds from
sales by the Registered Stockholders. The price per share of the Common Stock as
offered in the initial public offering of such Common Stock is expected to be
$23.00.

               The Company will not receive any of the proceeds from the
offering hereunder. All expenses of registration incurred in connection with
this offering are being borne by the Company, but all selling and other expenses
incurred by the individual Registered Stockholders will be borne by such
Registered Stockholders.

               The price per share of Common Stock, as offered in the initial
public offering is expected to be $23.00.

                                       16
26
                       DOCUMENTS INCORPORATED BY REFERENCE

        Redback hereby incorporates by reference into this Registration
Statement the following documents previously filed with the Commission:

        (a)    Redback's prospectus filed with the SEC under Rule 424(b) under
               the Securities Act of 1933, as amended (the "1933 Act"), in
               connection with Registration Statement No. 333-744479 on Form S-1
               filed with the SEC on March 16, 1999, the amendment filed on
               April 22, 1999, the amendment filed on May 4, 1999 and the
               amendment filed on May 12, 1999 and the amendment filed on May
               14, 1999, which contains the audited financial statements for the
               period August 30, 1996 (inception) through December 31, 1996 and
               for Redback's fiscal years ended December 31, 1997 and 1998.

        (b)    Redback's Registration Statement No. 0-25853 on Form 8-A filed
               with the Commission on April 28, 1999 together with amendments
               thereto, pursuant to Section 12 of the Exchange Act, in which
               there is described the terms, rights and provisions applicable to
               the Company's outstanding Common Stock.

               All of such documents are on file with the Commission. All
documents subsequently filed by the Company pursuant to Section 13(a), 13(c), 14
or 15(d) of the Exchange Act prior to the filing of a post-effective amendment
which indicates that all securities to be offered pursuant hereto have been sold
or which deregisters all such securities then remaining unsold shall be deemed
to be incorporated by reference in this Prospectus and to be a part hereof from
the date of the filing of such documents.

                                 INDEMNIFICATION

        Section 145 of the Delaware General Corporation Law authorizes a court
to award or a corporation's Board of Directors to grant indemnification to
directors and officers in terms sufficiently broad to permit such
indemnification under certain circumstances for liabilities (including
reimbursement for expenses incurred) arising under the 1933 Act. Redback's
Bylaws provide for mandatory indemnification of its directors and officers and
permissible indemnification of employees and other agents to the maximum extent
permitted by the Delaware General Corporation Law. Redback's Certificate of
Incorporation provides that, under Delaware law, its directors shall not be
liable for monetary damages for breach of their fiduciary duty as directors to
Redback and its stockholders. This provision in the Certificate of Incorporation
does not eliminate the fiduciary duty of the directors, and, in appropriate
circumstances, equitable remedies such as injunctive or other forms of
non-monetary relief will remain available under Delaware law. In addition, each
director will continue to be subject to liability for breach of the director's
duty of loyalty to Redback for acts or omissions not in good faith or involving
intentional misconduct, for knowing violations of law, for actions leading to
improper personal benefit to the director and for payment of dividends or
approval of stock repurchases or redemptions that are unlawful under Delaware
law. The provision also does not affect a director's responsibilities under any
other law, such as the federal securities laws or state or federal environmental
laws. Redback has entered into Indemnification Agreements with its officers and
directors. The Indemnification Agreements provide Redback's officers and
directors with further indemnification to the maximum extent permitted by the
Delaware General Corporation Law.

                                       17
27
                                  EXHIBIT INDEX
Sequentially
Exhibit Number    Exhibit                                                          Numbered Page
--------------    -------                                                          -------------
4           Instrument Defining Rights of Stockholders. Reference is made
                  to Redback's Registration Statement No. 0-25853 on Form 8-A,
                  which is incorporated herein by reference under Item 3(b) of
                  this Registration Statement.

      5           Opinion and consent of Gunderson Dettmer Stough Villeneuve
                  Franklin & Hachigian LLP.

      23.1        Consent of PricewaterhouseCoopers LLP, Independent
                  Accountants.

      23.2        Consent of Gunderson Dettmer Stough Villeneuve Franklin &
                  Hachigian LLP is contained in Exhibit 5.

      24          Power of Attorney. Reference is made to page II-4 of this
                  Registration Statement.

      99.1        Form of Written Compensation Agreement with David Coleman,
                  Steve De Golia, Joyce Gandolfi, Jeff Johnson, Eric Olsen,
                  William Palter, Keith Quigley, David Shapiro, Lynette Souza,
                  Nick Thille and Jay Willey.