<PAGE>
                                                                    EXHIBIT 4.13

                              FORM OF SERIES B NOTE
                                 (Face of Note)

================================================================================

                                                         CUSIP/CINS_____________

            12% Senior Notes due 2010

No. ___                                                              $__________

                        COVAD COMMUNICATIONS GROUP, INC.

promises to pay to _____________________________________________________________

or registered assigns,

      the principal sum of _____________________________________________________

Dollars on February 15, 2010.

Interest Payment Dates: February 15 and August 15

Record Dates: February 1 and August 1





                                      B1-1
<PAGE>

            IN WITNESS WHEREOF, the Company has caused this Note to be signed
manually or by facsimile by its duly authorized officers.

                                       COVAD COMMUNICATIONS GROUP, INC.

                                       BY:
                                           -------------------------------------
                                           Name:
                                           Title:


                                       BY:
                                           -------------------------------------
                                           Name:
                                           Title:

Dated: ___________, 2000

This is one of the Global
Notes referred to in the
within-mentioned Indenture:

United States Trust Company of New York,
as Trustee
By:
    -------------------------------
    Authorized Signatory


================================================================================





                                      B1-2
<PAGE>

                                 (Back of Note)

                            12% Senior Notes due 2010

THIS GLOBAL NOTE IS HELD BY THE DEPOSITARY (AS DEFINED IN THE INDENTURE
GOVERNING THIS NOTE) OR ITS NOMINEE IN CUSTODY FOR THE BENEFIT OF THE BENEFICIAL
OWNERS HEREOF, AND IS NOT TRANSFERABLE TO ANY PERSON UNDER ANY CIRCUMSTANCES
EXCEPT THAT (I) THE TRUSTEE MAY MAKE SUCH NOTATIONS HEREON AS MAY BE REQUIRED
PURSUANT TO SECTION 2.07 OF THE INDENTURE, (II) THIS GLOBAL NOTE MAY BE
EXCHANGED IN WHOLE BUT NOT IN PART PURSUANT TO SECTION 2.06(a) OF THE INDENTURE,
(III) THIS GLOBAL NOTE MAY BE DELIVERED TO THE TRUSTEE FOR CANCELLATION PURSUANT
TO SECTION 2.11 OF THE INDENTURE AND (IV) THIS GLOBAL NOTE MAY BE TRANSFERRED TO
A SUCCESSOR DEPOSITARY WITH THE PRIOR WRITTEN CONSENT OF THE COMPANY.

UNLESS AND UNTIL IT IS EXCHANGED IN WHOLE OR IN PART FOR NOTES IN DEFINITIVE
FORM, THIS NOTE MAY NOT BE TRANSFERRED EXCEPT AS A WHOLE BY THE DEPOSITARY TO A
NOMINEE OF THE DEPOSITARY OR BY A NOMINEE OF THE DEPOSITARY TO THE DEPOSITARY OR
ANOTHER NOMINEE OF THE DEPOSITARY OR BY THE DEPOSITARY OR ANY SUCH NOMINEE TO A
SUCCESSOR DEPOSITARY OR A NOMINEE OF SUCH SUCCESSOR DEPOSITARY. UNLESS THIS
CERTIFICATE IS PRESENTED BY AN AUTHORIZED REPRESENTATIVE OF THE DEPOSITORY TRUST
COMPANY (55 WATER STREET, NEW YORK, NEW YORK) ("DTC"), TO THE COMPANY OR ITS
AGENT FOR REGISTRATION OF TRANSFER, EXCHANGE OR PAYMENT, AND ANY CERTIFICATE
ISSUED IS REGISTERED IN THE NAME OF CEDE & CO. OR SUCH OTHER NAME AS MAY BE
REQUESTED BY AN AUTHORIZED REPRESENTATIVE OF DTC (AND ANY PAYMENT IS MADE TO
CEDE & CO. OR SUCH OTHER ENTITY AS MAY BE REQUESTED BY AN AUTHORIZED
REPRESENTATIVE OF DTC), ANY TRANSFER, PLEDGE OR OTHER USE HEREOF FOR VALUE OR
OTHERWISE BY OR TO ANY PERSON IS WRONGFUL INASMUCH AS THE REGISTERED OWNER
HEREOF, CEDE & CO., HAS AN INTEREST HEREIN.


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<PAGE>

            Capitalized terms used herein shall have the meanings assigned to
them in the Indenture referred to below unless otherwise indicated.

            1. INTEREST. Covad Communications Group, Inc., a Delaware
corporation (the "Company"), promises to pay interest on the principal amount of
this Note at 12% per annum. The Company shall pay interest semi-annually on
February 15 and August 15, commencing on August 15, 2000, or if any such day is
not a Business Day, on the next succeeding Business Day (each an "Interest
Payment Date"). Interest on the Notes will accrue from the most recent date to
which interest has been paid or, if no interest has been paid, from the Closing
Date; PROVIDED that if there is no existing Default in the payment of interest,
and if this Note is authenticated between a record date referred to on the face
hereof and the next succeeding Interest Payment Date, interest shall accrue from
such next succeeding Interest Payment Date; PROVIDED, FURTHER, that the first
Interest Payment Date shall be August 15, 2000. The Company shall pay interest
(including post-petition interest in any proceeding under any Bankruptcy Law) on
overdue principal and premium, if any, from time to time on demand at a rate
that is 1% per annum in excess of the rate then in effect; it shall pay interest
(including post-petition interest in any proceeding under any Bankruptcy Law) on
overdue installments of interest (without regard to any applicable grace
periods) from time to time on demand at the same rate to the extent lawful.
Interest will be computed on the basis of a 360-day year of twelve 30-day
months.

            2. METHOD OF PAYMENT. The Company will pay interest on the Notes
(except defaulted interest) to the Persons who are registered Holders of Notes
at the close of business on February 1 or August 1 preceding the Interest
Payment Date, even if such Notes are cancelled after such record date and on or
before such Interest Payment Date, except as provided in Section 2.12 of the
Indenture with respect to defaulted interest. The Notes will be payable as to
principal, premium and interest at the office or agency of the Company
maintained for such purpose within or without the City and State of New York,
or, at the option of the Company, payment of interest may be made by check
mailed to the Holders at their addresses set forth in the register of Holders,
and provided that payment by wire transfer of immediately available funds will
be required with respect to principal of and interest, premium on, all Global
Notes and all other Notes the Holders of which shall have provided wire transfer
instructions to the Company or the Paying Agent. Such payment shall be in such
coin or currency of the United States of America as at the time of payment is
legal tender for payment of public and private debts.

            3. PAYING AGENT AND REGISTRAR. Initially, United States Trust
Company of New York, the Trustee under the Indenture, will act as Paying Agent
and Registrar. The Company may change any Paying Agent or Registrar without
notice to any Holder. The Company or any of its Subsidiaries may act in any such
capacity.

            4. INDENTURE. The Company issued the Notes under an Indenture dated
as of January 28, 2000 (the "Indenture") between the Company and the Trustee.
The terms of the Notes include those stated in the Indenture and those made part
of the Indenture by reference to the Trust Indenture Act of 1939, as amended (15
U.S. Code Sections 77aaa-77bbbb). The Notes are subject to all such terms, and
Holders are


                                      B1-4
<PAGE>

referred to the Indenture and such Act for a statement of such terms. To the
extent any provision of this Note conflicts with the express provisions of the
Indenture, the provisions of the Indenture shall govern and be controlling. The
Notes are obligations of the Company limited to $475,000,000 in aggregate
principal amount.

            5. OPTIONAL REDEMPTION.

            (a) Except as set forth in subparagraph (b) of this Paragraph 5, the
Company shall not have the option to redeem the Notes prior to February 15,
2005. Thereafter, the Company shall have the option to redeem the Notes, in
whole or in part, at the redemption prices (expressed as percentages of
principal amount) set forth below plus accrued and unpaid interest thereon, if
any, to the applicable redemption date, if redeemed during the twelve-month
period beginning on February 15 of the years indicated below:

         YEAR                                                        PERCENTAGE
         ----                                                        ----------

         2005.......................................................   106.00%
         2006.......................................................   104.00%
         2007.......................................................   102.00%
         2008 and thereafter........................................   100.00%



            (b) Notwithstanding the provisions of subparagraph (a) of this
Paragraph 5, at any time prior to February 15, 2003, the Company, at its option,
may use the net cash proceeds (but only to the extent such proceeds consist of
cash or Cash Equivalents) of one or more Public Equity Offerings to redeem up to
an aggregate of 35% of the Notes issued on the Issue Date under the Indenture at
a redemption price of 112.00% of the aggregate principal amount of the Notes,
plus accrued and unpaid interest, if any, to the date of redemption; PROVIDED
that at least $276.25 million of the aggregate principal amount of the Notes
remains outstanding immediately after the occurrence of such redemption. In
order to effect the foregoing redemption, the Company must mail a notice of
redemption no later than 30 days after the related Public Equity Offering and
must consummate such redemption within 60 days of the closing of such Public
Equity Offering.

            6. MANDATORY REDEMPTION.

            Except as set forth in paragraph 7 below, the Company shall not be
required to make mandatory redemption payments with respect to the Notes.

            7. REPURCHASE AT OPTION OF HOLDER.

            (a) If there is a Change of Control, the Company shall be required
to make an offer (a "Change of Control Offer") to repurchase all or any part
(equal to $1,000 or an integral multiple thereof) of each Holder's Notes at a
purchase price equal to 101% of the aggregate principal amount thereof plus
accrued and unpaid interest to the date of purchase (the "Change of Control
Payment"). Within 10 days following any Change of Control, the Company shall
mail a notice to each Holder setting forth the procedures governing the Change
of Control Offer as required by the Indenture.

            (b) If the Company or a Restricted Subsidiary consummates any Asset
Sales, within five days of each date on which the aggregate amount of Excess
Proceeds exceeds $10.0 million, the Company shall commence an offer to all
Holders of Notes (an "Asset Sale Offer") pursuant to Section 3.09 of the
Indenture to purchase the maximum principal amount of Notes (including any
Additional Notes) that may


                                      B1-5
<PAGE>

be purchased out of the Excess Proceeds at an offer price in cash in an amount
equal to 100% of the principal amount thereof plus accrued and unpaid interest
and Additional Interest thereon, if any, to the date fixed for the closing of
such offer, in accordance with the procedures set forth in the Indenture. To the
extent that the aggregate amount of Notes (including any Additional Notes)
tendered pursuant to an Asset Sale Offer is less than the Excess Proceeds, the
Company (or such Restricted Subsidiary) may use such deficiency for general
corporate purposes. If the aggregate principal amount of Notes surrendered by
Holders thereof exceeds the amount of Excess Proceeds, the Trustee shall select
the Notes to be purchased on a PRO RATA basis. Holders of Notes that are the
subject of an offer to purchase will receive an Asset Sale Offer from the
Company prior to any related purchase date and may elect to have such Notes
purchased by completing the form entitled "Option of Holder to Elect Purchase"
on the reverse of the Notes.

            8. NOTICE OF REDEMPTION. Notice of redemption will be mailed at
least 30 days but not more than 60 days before the redemption date to each
Holder whose Notes are to be redeemed at its registered address. Notes in
denominations larger than $1,000 may be redeemed in part but only in whole
multiples of $1,000, unless all of the Notes held by a Holder are to be
redeemed. On and after the redemption date interest ceases to accrue on Notes or
portions thereof called for redemption.

            9. DENOMINATIONS, TRANSFER, EXCHANGE. The Notes are in registered
form without coupons in denominations of $1,000 and integral multiples of
$1,000. The transfer of Notes may be registered and Notes may be exchanged as
provided in the Indenture. The Registrar and the Trustee may require a Holder,
among other things, to furnish appropriate endorsements and transfer documents
and the Company may require a Holder to pay any taxes and fees required by law
or permitted by the Indenture. The Company need not exchange or register the
transfer of any Note or portion of a Note selected for redemption, except for
the unredeemed portion of any Note being redeemed in part. Also, the Company
need not exchange or register the transfer of any Notes for a period of 15 days
before a selection of Notes to be redeemed or during the period between a record
date and the corresponding Interest Payment Date.

            10. PERSONS DEEMED OWNERS. The registered Holder of a Note will be
treated as its owner for all purposes.

            11. AMENDMENT, SUPPLEMENT AND WAIVER. Subject to certain exceptions,
the Indenture or the Notes may be amended or supplemented with the consent of
the Holders of at least a majority in principal amount of the then outstanding
Notes (and Additional Notes, if any) voting as a single class, and any existing
default or compliance with any provision of the Indenture or the Notes may be
waived with the consent of the Holders of a majority in principal amount of the
then outstanding Notes (and Additional Notes, if any) voting as a single class.
Without the consent of any Holder of a Note, the Indenture or the Notes may be
amended or supplemented to cure any ambiguity, defect or inconsistency, to
provide for uncertificated Notes in addition to or in place of certificated
Notes, to provide for the assumption of the Company's obligations to Holders of
the Notes in case of a merger or consolidation or sale of all or substantially
all of the Company's assets, to make any change that would provide any
additional rights or benefits to the Holders of the Notes or that does not
adversely affect the legal rights under the Indenture of any such Holder, to
comply with the requirements of the Commission in order to effect or maintain
the qualification of the Indenture under the Trust Indenture Act or to provide
for the Issuance of Additional Notes in accordance with the limitations set
forth in the Indenture.

            12. DEFAULTS AND REMEDIES. Events of Default include: (i) default
for 30 days in the payment when due of interest on the Notes (including any
Additional Interest); (ii) default in payment when due of principal of or
premium, if any, on the Notes when the same becomes due and payable at maturity,
upon redemption (including in connection with an offer to purchase) or
otherwise; (iii) failure by the Company or any of its Restricted Subsidiaries to
comply with Section 4.07, 4.09, 4.10, 4.15 or 5.01 of the


                                      B1-6
<PAGE>

Indenture; (iv) failure by the Company or any of its Restricted Subsidiaries for
30 days after notice to the Company by the Trustee or the Holders of at least
25% in principal amount of the Notes (including Additional Notes, if any) then
outstanding voting as a single class to comply with certain other agreements in
the Indenture or the Notes; (v) default under certain other agreements relating
to Debt of the Company which default is caused by a failure to pay principal of
or premium, if any, or interest on such Debt prior to the grace period provided
in such Debt on the date of such default (a "Payment Default") or results in the
acceleration of such Debt prior to its express maturity and, in each case, the
principal amount of any such Debt under which there has been a Payment Default
or the maturity of which has been so accelerated, aggregates $5.0 million or
more; (vi) certain final judgments for the payment of money that remain
undischarged for a period of 60 days; or (vii) certain events of bankruptcy or
insolvency with respect to the Company or any of its Restricted Subsidiaries. If
any Event of Default occurs and is continuing, the Trustee or the Holders of at
least 25% in principal amount of the then outstanding Notes may declare all the
Notes to be due and payable immediately. Notwithstanding the foregoing, in the
case of an Event of Default arising from certain events of bankruptcy or
insolvency, all outstanding Notes will become due and payable without further
action or notice. Holders may not enforce the Indenture or the Notes except as
provided in the Indenture. Subject to certain limitations, Holders of a majority
in principal amount of the then outstanding Notes may direct the Trustee in its
exercise of any trust or power. The Trustee may withhold from Holders of the
Notes notice of any continuing Default or Event of Default (except a Default or
Event of Default relating to the payment of principal or interest) if it
determines that withholding notice is in their interest. The Holders of a
majority in aggregate principal amount of the Notes then outstanding by notice
to the Trustee may on behalf of the Holders of all of the Notes waive any
existing Default or Event of Default and its consequences under the Indenture
except a continuing Default or Event of Default in the payment of interest on,
or the principal of, the Notes. The Company is required to deliver to the
Trustee annually a statement regarding compliance with the Indenture, and the
Company is required upon becoming aware of any Default or Event of Default, to
deliver to the Trustee a statement specifying such Default or Event of Default.

            13. TRUSTEE DEALINGS WITH COMPANY. The Trustee, in its individual or
any other capacity, may make loans to, accept deposits from, and perform
services for the Company or its Affiliates, and may otherwise deal with the
Company or its Affiliates, as if it were not the Trustee.

            14. NO RECOURSE AGAINST OTHERS. A director, officer, employee,
incorporator or stockholder, of the Company, as such, shall not have any
liability for any obligations of the Company under the Notes or the Indenture or
for any claim based on, in respect of, or by reason of, such obligations or
their creation. Each Holder by accepting a Note waives and releases all such
liability. The waiver and release are part of the consideration for the issuance
of the Notes.

            15. AUTHENTICATION. This Note shall not be valid until authenticated
by the manual signature of the Trustee or an authenticating agent.

            16. ABBREVIATIONS. Customary abbreviations may be used in the name
of a Holder or an assignee, such as: TEN COM (= tenants in common), TEN ENT (=
tenants by the entireties), JT TEN (= joint tenants with right of survivorship
and not as tenants in common), CUST (= Custodian), and U/G/M/A (= Uniform Gifts
to Minors Act).


                                      B1-7
<PAGE>

            17. CUSIP NUMBERS. Pursuant to a recommendation promulgated by the
Committee on Uniform Security Identification Procedures, the Company has caused
CUSIP numbers to be printed on the Notes and the Trustee may use CUSIP numbers
in notices of redemption as a convenience to Holders. No representation is made
as to the accuracy of such numbers either as printed on the Notes or as
contained in any notice of redemption and reliance may be placed only on the
other identification numbers placed thereon.

            18. GOVERNING LAW. This Note shall be governed by, and construed in
accordance with, the law of the State of New York.

            The Company will furnish to any Holder upon written request and
without charge a copy of the Indenture and/or the Registration Rights Agreement.
Requests may be made to:

            Covad Communications Group, Inc.
            2330 Central Expressway
            Santa Clara, California 95050
            Attention:  Chief Financial Officer


                                      B1-8

<PAGE>


                                 ASSIGNMENT FORM

To assign this Note, fill in the form below: (I) or (we) assign and transfer
this Note to

--------------------------------------------------------------------------------
                  (Insert assignee's soc. sec. or tax I.D. no.)

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

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

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

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

(Print or type assignee's name, address and zip code)

and irrevocably appoint
                        --------------------------------------------------------
to transfer this Note on the books of the Company.  The agent may substitute
another to act for him.

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

Date:
      ---------------------------
                                    Your Signature:
                                                   -----------------------------
                                    (Sign exactly as your name appears on
                                    the face of this Note)

SIGNATURE GUARANTEE.

Signatures must be guaranteed by an "eligible guarantor institution" meeting the
requirements of the Registrar, which requirements include membership or
participation in the Security Transfer Agent Medallion Program ("STAMP") or such
other "signature guarantee program" as may be determined by the Registrar in
addition to, or in substitution for, STAMP, all in accordance with the
Securities Exchange Act of 1934, as amended.


                                      B1-9
<PAGE>


                       OPTION OF HOLDER TO ELECT PURCHASE

            If you want to elect to have this Note purchased by the Company
pursuant to Section 4.10 or 4.15 of the Indenture, check the box below:

            [ ]  Section 4.10       [ ]  Section 4.15

            If you want to elect to have only part of the Note purchased by the
Company pursuant to Section 4.10 or Section 4.15 of the Indenture, state the
amount you elect to have purchased: $_________

Date:
      ---------------------------
                                    Your Signature:
                                                   -----------------------------
                                    (Sign exactly as your name appears on
                                    the face of this Note)

                                    Tax Identification No:
                                                          ----------------------

Signature Guarantee.

Signatures must be guaranteed by an "eligible guarantor institution" meeting the
requirements of the Registrar, which requirements include membership or
participation in the Security Transfer Agent Medallion Program ("STAMP") or such
other "signature guarantee program" as may be determined by the Registrar in
addition to, or in substitution for, STAMP, all in accordance with the
Securities Exchange Act of 1934, as amended.


                                     B1-10

<PAGE>

              SCHEDULE OF EXCHANGES OF INTERESTS IN THE GLOBAL NOTE


            The following exchanges of a part of this Global Note for an
interest in another Global Note or for a Definitive Note, or exchanges of a part
of another Global Note or Definitive Note for an interest in this Global Note,
have been made:


<TABLE>
<CAPTION>

                           Amount of                                   Principal Amount        Signature of
                          decrease in         Amount of increase        of this Global          authorized
                        Principal Amount         in Principal           Note following          officer of
                            of this             Amount of this           such decrease        Trustee or Note
Date of Exchange          Global Note             Global Note            (or increase)           Custodian
----------------        ----------------      ------------------       ----------------       ---------------
<S>                     <C>                   <C>                      <C>                    <C>

</TABLE>







                                     B1-11