<PAGE>

                                                                    Exhibit 4.30

              [FORM OF 11-7/8% SENIOR NOTE DUE JANUARY 15, 2010]

CUSIP NO. U3143AB4

No. 2                                                                   $130,000

          Focal Communications Corporation, a Delaware corporation (herein
called the "Company", which term includes any successor Person under the
            -------
indenture referred to on the reverse of this Note) for value received, hereby
promises to pay to Cede & Co., or registered assigns, the principal amount of
two hundred seventy-five million dollars ($275,000,000) (which principal amount
may from time to time be increased or decreased to such other principal amounts
(which shall not exceed $275,000,000 at any time) by adjustments made to the
Schedule annexed hereto by the Trustee hereinafter referred to in accordance
with the indenture referred to on the reverse of this Note) on January 15, 2010.

          Interest Payment Dates:    January 15 and July 15, commencing on July
                                     15, 2000.

          Regular Record Dates:      January 1 and July 1.

          UNLESS THIS CERTIFICATE IS PRESENTED BY AN AUTHORIZED REPRESENTATIVE
OF THE DEPOSITORY TRUST COMPANY, A NEW YORK CORPORATION ("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 IN SUCH OTHER NAME
AS IS REQUESTED BY AN AUTHORIZED REPRESENTATIVE OF DTC (AND ANY PAYMENT IS MADE
TO CEDE & CO. OR TO SUCH OTHER ENTITY AS IS 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.

          TRANSFERS OF THIS GLOBAL NOTE SHALL BE LIMITED TO TRANSFERS IN WHOLE,
BUT NOT IN PART, TO NOMINEES OF DTC OR TO A SUCCESSOR THEREOF OR SUCH
SUCCESSOR'S NOMINEE AND TRANSFERS OF PORTIONS OF THIS GLOBAL NOTE SHALL BE
LIMITED TO TRANSFERS MADE IN ACCORDANCE WITH THE RESTRICTIONS SET FORTH IN THE
INDENTURE REFERRED TO ON THE REVERSE HEREOF.

          THIS NOTE HAS NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS
AMENDED (THE "SECURITIES ACT").  THE HOLDER BY PURCHASING THIS NOTE AGREES FOR
THE BENEFIT OF THE COMPANY AND THE INITIAL PURCHASERS OF THIS NOTE THAT THIS
NOTE MAY NOT BE RESOLD, PLEDGED OR OTHERWISE TRANSFERRED (X) PRIOR TO THE SECOND
ANNIVERSARY (OR SUCH EARLIER DATE PROVIDED FOR IN RULE 144(K) UNDER THE
SECURITIES ACT OR ANY SUCCESSOR PROVISION THERETO) OF THE ISSUANCE HEREOF (OR A
PREDECESSOR NOTE HERETO) OR (Y) IF LATER, BY ANY HOLDER THAT WAS AN AFFILIATE OF
THE COMPANY AT ANY TIME DURING THE THREE MONTHS PRECEDING THE DATE OF SUCH
TRANSFER, IN EITHER CASE OTHER THAN (1) TO THE COMPANY, (2) SO LONG AS THIS NOTE
IS ELIGIBLE FOR RESALE PURSUANT TO RULE 144A UNDER THE SECURITIES
<PAGE>

ACT ("RULE 144A"), TO A PERSON WHOM THE SELLER REASONABLY BELIEVES IS A
QUALIFIED INSTITUTIONAL BUYER WITHIN THE MEANING OF RULE 144A PURCHASING FOR ITS
OWN ACCOUNT OR FOR THE ACCOUNT OF A QUALIFIED INSTITUTIONAL BUYER TO WHOM NOTICE
IS GIVEN THAT THE RESALE, PLEDGE OR OTHER TRANSFER IS BEING MADE IN RELIANCE ON
RULE 144A (AS INDICATED BY THE BOX CHECKED BY THE TRANSFEROR ON THE CERTIFICATE
OF TRANSFER ON THE REVERSE OF THIS NOTE), (3) IN AN OFFSHORE TRANSACTION IN
ACCORDANCE WITH REGULATION S UNDER THE SECURITIES ACT (AS INDICATED BY THE BOX
CHECKED BY THE TRANSFEROR ON THE CERTIFICATE OF TRANSFER ON THE REVERSE OF THIS
NOTE), AND, IF SUCH TRANSFER IS BEING EFFECTED BY CERTAIN TRANSFERORS SPECIFIED
IN THE INDENTURE PRIOR TO THE EXPIRATION OF THE "40-DAY RESTRICTED PERIOD"
(WITHIN THE MEANING OF RULE 903(c)(3) OF REGULATION S UNDER THE SECURITIES ACT),
A CERTIFICATE WHICH MAY BE OBTAINED FROM THE COMPANY OR THE TRUSTEE IS DELIVERED
BY THE TRANSFEREE TO THE COMPANY AND THE TRUSTEE, (4) TO AN INSTITUTION THAT IS
AN "ACCREDITED INVESTOR" AS DEFINED IN RULE 501(a)(1), (2), (3) OR (7) UNDER THE
SECURITIES ACT (AS INDICATED BY THE BOX CHECKED BY THE TRANSFEROR ON THE
CERTIFICATE OF TRANSFER ON THE REVERSE OF THIS NOTE) THAT IS ACQUIRING THIS NOTE
FOR INVESTMENT PURPOSES AND NOT FOR DISTRIBUTION IN VIOLATION OF THE SECURITIES
ACT OR ANY OTHER APPLICABLE SECURITIES LAWS, AND A CERTIFICATE IN THE FORM
ATTACHED TO THIS NOTE IS DELIVERED BY THE TRANSFEREE TO THE COMPANY AND THE
TRUSTEE (PROVIDED THAT CERTAIN HOLDERS SPECIFIED IN THE INDENTURE MAY NOT
TRANSFER THIS NOTE PURSUANT TO THIS CLAUSE (4) PRIOR TO THE EXPIRATION OF THE
"40-DAY RESTRICTED PERIOD" (WITHIN THE MEANING OF RULE 903(c)(3) OF REGULATION S
UNDER THE SECURITIES ACT)), (5) PURSUANT TO AN EXEMPTION FROM REGISTRATION UNDER
THE SECURITIES ACT PROVIDED BY RULE 144 (IF APPLICABLE) UNDER THE SECURITIES
ACT, OR (6) PURSUANT TO AN EFFECTIVE REGISTRATION STATEMENT UNDER THE SECURITIES
ACT, IN EACH CASE IN ACCORDANCE WITH ANY APPLICABLE SECURITIES LAWS OF ANY STATE
OF THE UNITED STATES. AN INSTITUTIONAL ACCREDITED INVESTOR HOLDING THIS NOTE
AGREES IT WILL FURNISH TO THE COMPANY AND THE TRUSTEE SUCH CERTIFICATES AND
OTHER INFORMATION AS THE COMPANY MAY REASONABLY REQUIRE TO CONFIRM THAT ANY
TRANSFER BY IT OF THIS NOTE COMPLIES WITH THE FOREGOING RESTRICTIONS. THE HOLDER
HEREOF, BY PURCHASING THIS NOTE, REPRESENTS AND AGREES FOR THE BENEFIT OF THE
COMPANY THAT IT IS (1) A QUALIFIED INSTITUTIONAL BUYER WITHIN THE MEANING OF
RULE 144(A) OR (2) AN INSTITUTION THAT IS AN "ACCREDITED INVESTOR" AS DEFINED IN
RULE 501(a)(1), (2), (3) OR (7) UNDER THE SECURITIES ACT AND THAT IT IS HOLDING
THIS NOTE FOR INVESTMENT PURPOSES AND NOT FOR DISTRIBUTION OR (3) A NON-U.S.
PERSON OUTSIDE THE UNITED STATES WITHIN THE MEANING OF (OR AN ACCOUNT SATISFYING
THE REQUIREMENTS OF PARAGRAPH (k)(2) OF RULE 902 UNDER) REGULATION S UNDER THE
SECURITIES ACT.

          Reference is hereby made to the further provisions of this Note set
forth on the reverse hereof, which further provisions shall for all purposes
have the same effect as if set forth at this place.

                                       2
<PAGE>

          Unless the certificate of authentication hereon has been executed by
the Trustee referred to on the reverse hereof by manual signature, this Note
shall not be entitled to any benefit under the indenture referred to on the
reverse of this Note or be valid or obligatory for any purpose.


          IN WITNESS WHEREOF, the Company has caused this instrument to be duly
executed.

Dated: January 12, 2000

                                                       FOCAL COMMUNICATIONS
                                                       CORPORATION


                                                       by___________________
                                                         Name:
                                                         Title:


Attest:


______________________

                                       3
<PAGE>

                               (REVERSE OF NOTE)

                     11 7/8% Senior Discount Note Due 2010

     1.   Indenture.
          ---------

     This Note is one of a duly authorized issue of Notes of the Company
designated as its 11.875% Senior Notes due January 15, 2010 (the "Notes"),
                                                                  -----
issued under an indenture, dated as of January 12, 2000 (herein, as amended from
time to time, called the "Indenture"), between the Company and Harris Trust and
                          ---------
Savings Bank, as trustee (herein called the "Trustee", which term includes any
                                             -------
successor trustee under the Indenture).  The Notes are limited in aggregate
principal amount to $275,000,000.  Reference is hereby made to the Indenture and
all indentures supplemental thereto for a statement of the respective rights,
limitations of rights, duties and immunities thereunder of the Company, the
Trustee and the Holder of this Note and of the terms upon which this Note is,
and is to be, authenticated and delivered.  All terms used in this Note which
are defined in the Indenture shall have the meanings assigned to them in the
Indenture.

     2.   Principal Amount and Interest.
          -----------------------------

          The Company will pay the principal amount of this Note on January 15,
2010.

          This Note will bear interest on the outstanding aggregate principal
amount thereof at a rate of 11.875 % per annum computed on a semiannual bond
equivalent basis from the Issue Date.

          If (i) the Company has not filed a registration statement (the
"Exchange Offer Registration Statement") under the Securities Act of 1933, as
 -------------------------------------
amended (the "Securities Act"), registering a security substantially identical
              --------------
to this Note (except that such Note will not contain terms with respect to
transfer restrictions) pursuant to an exchange offer (the "Registered Exchange
                                                           -------------------
Offer") on or prior to April 14, 2000 or (ii) the Exchange Offer Registration
-----
Statement relating to the Registered Exchange Offer has not become or been
declared effective prior to August 12, 2000, or (iii) neither the Registered
Exchange Offer has been consummated nor a registration statement registering
this Note for resale (a "Shelf Registration Statement") has been declared
                         ----------------------------
effective prior to September 11, 2000 or (iv) after the Shelf Registration
Statement has been declared effective, such Shelf Registration Statement
thereafter ceases to be effective or usable (subject to certain exceptions set
forth in the Registration Agreement) in connection with resales of this Note or
notes issued in exchange for this Note pursuant to the Registered Exchange Offer
("Exchange Notes") in accordance with and during the periods specified in the
  --------------
Registration Agreement without being succeeded promptly by an additional
registration statement filed and declared effective, in the case of each of the
immediately preceding clauses (i) through (iv) upon the terms and conditions set
forth in the Registration Agreement (each such event referred to in such clauses
(i) through (iv), a "Registration Default"), then interest will accrue on this
                     --------------------
Note and the Exchange Notes (in addition to the stated interest on this Note and
the Exchange Notes) (the "Step-Up") and be payable in cash semiannually in
                          -------
arrears on January 15 and July 15 of each year, beginning on the January 15 or
July 15 immediately following a Registration Default (such interest to be
payable to the Holder of record as of the January 1 and July 1, as the case may
be, immediately preceding January 15 or July 15), at a rate of 0.50% per annum
during the 90-day period immediately following the occurrence of a Registration
Default and shall increase by a rate per annum equal to 0.25% at the end of each
subsequent 90-day period.  In no event shall such rate exceed 1.50% per annum in
the aggregate regardless of the number of Registration Defaults.

                                       4
<PAGE>

          The Company shall pay interest on overdue principal and premium, if
any, and interest on overdue installments of interest, to the extent lawful, at
a rate per annum equal to the interest rate payable on this Note.

          Any such interest not so punctually paid or duly provided for will
forthwith cease to be payable to the Holder on such Regular Record Date and may
either be paid to the Person in whose name this Note (or one or more Predecessor
Notes) is registered at the close of business on a Special Record Date for the
payment of such Defaulted Interest to be fixed by the Trustee, notice of which
shall be given to the Holder of this Note not less than 10 calendar days prior
to such Special Record Date.

     3.   Method of Payment.
          ------------------

          The Company will pay principal, premium, if any, and as provided
above, interest in money of the United States that at the time of payment is
legal tender for payment of public and private debts.  Payments in respect of
Notes represented by Global Notes (including principal, premium, interest and
Defaulted Interest, if any) will be made by wire transfer of immediately
available funds to the accounts specified by the nominee for the Depositary.
With respect to certificated Notes, the Paying Agent will make all payments of
principal, premium, interest and Defaulted Interest, if any, by wire transfer of
immediately available funds to the United States dollar accounts maintained by
the Holders entitled thereto with banks in the United States, or, if no such
account is designated by the relevant Holder to the Trustee or the Paying Agent
at least 30 days prior to the relevant due date for payment (or such other date
as the Trustee may accept in its discretion), by mailing a check to the
registered address of such Holder.  If a payment date is a date other than a
Business Day at a place of payment, payment may be made at that place on the
next succeeding day that is a Business Day and no interest shall accrue for the
intervening period.

     4.   Paying Agent and Note Registrar.
          --------------------------------

          Initially, the Trustee will act as authenticating agent, Paying Agent
and Note Registrar.  The Trustee may be removed by action of the Holders of not
less than a majority in principal amount of the outstanding Notes, or by the
Company or certain bona fide Holders of Notes upon the occurrence of certain
events.  The Company may change any Paying Agent or Note Registrar with notice
in writing to the Trustee.  The Company, any Subsidiary or any Affiliate of
either of them may act as Paying Agent or Note Registrar.

     5.   Optional Redemption.
          --------------------

          This Note is subject to redemption upon not less than 30 nor more than
60 days' prior written notice to each Holder of Notes to be redeemed at such
Holder's address appearing in the Note Register, in principal amounts or at any
time on or after January 15, 2005, at the following Redemption Prices plus
accrued and unpaid interest, if any, thereon to but excluding the  Redemption
Date, if redeemed during the periods indicated below:

<TABLE>
<CAPTION>
     From and Including       To and Including      Redemption Price
     ------------------       ----------------      ----------------
    <S>                       <C>                   <C>
    January 15, 2005          January 14, 2006           105.938%
    January 15, 2006          January 14, 2007           103.958%
    January 15, 2007          January 14, 2008           101.979%
</TABLE>

                                       5
<PAGE>

    January 15, 2008 and thereafter                      100.000%

          This Note will be redeemable at any time and from time to time prior
to January 15, 2003 in the event that the Company receives Net Cash Proceeds
from the sale of its Capital Stock (other than Disqualified Stock) in one or
more Public Equity Offerings, in which case the Company may, at its option, use
all or a portion of any such Net Cash Proceeds to redeem up to 35% of initially
outstanding aggregate principal amount of the Notes; provided, that at least 65%
                                                     --------
of the original aggregate principal amount of the Notes remains outstanding
after each such redemption.  Such redemption must occur on a date of redemption
within 90 days of such sale and upon not less than 30 nor more than 60 days'
prior written notice, in  principal amounts of $1,000 or integral multiples
thereof at a redemption price equal to 111.875% of the principal amount of the
Notes to be redeemed plus Additional Interest, if any, to but excluding the date
of redemption.

          If, after giving effect to the offer by the Company to repurchase all
or any part of each Holder's Notes made upon the occurrence of a Change of
Control as set forth in Section 7 hereto, at least 95% of the original aggregate
principal amount of the Notes has been redeemed or repurchased pursuant to the
Indenture, the Company shall have the right to redeem the balance of the Notes
at a redemption price equal to 101% of the principal amount thereof plus accrued
and unpaid interest, if any, thereon to but excluding the date of redemption.
The Company may exercise this right by giving the Holders notice of such
redemption within 30 days following the payment date with respect to the
Company's earlier repurchase offer.

     6.   No Sinking Fund.
          ----------------

          The Notes do not have the benefit of any sinking fund obligations.

     7.   Repurchase of Notes at the Option of Holders upon a Change of Control.
          ----------------------------------------------------------------------

          Upon the occurrence of a Change of Control, each Holder will have the
right to require the Company to repurchase all or any part (equal to $1,000
principal amount or an integral multiple thereof) of such Holder's Notes at a
purchase price ("Change of Control Purchase Price") equal to 101% of the
                 --------------------------------
principal amount thereof plus accrued and unpaid interest, if any, thereon to
but excluding the payment date for the Change of Control Purchase Price.

          Within 30 days following any Change of Control, the Company or the
Trustee (at the expense of the Company) shall mail a notice to each Holder
regarding the Company's offer to repurchase all or any part of such Holder's
Notes.  The Holder of this Note may elect to have this Note or a portion hereof
in an authorized denomination purchased by completing the form entitled "Option
of Holder to Elect Purchase" appearing below and tendering this Note pursuant to
the offer described in the notice.  Unless the Company defaults in the payment
of the Change of Control Purchase Price with respect thereto, all Notes or
portions thereof accepted for payment pursuant to the offer described in the
notice will cease to accrue interest from and after the payment date for the
Change of Control Purchase Price.

     8.   Repurchase of Notes at the Option of Holders upon an Asset Sale.
          ----------------------------------------------------------------

          If at any time the Company or any Restricted Subsidiary engages in any
Asset Sale, as a result of which the aggregate amount of Excess Proceeds
calculated as of any date exceeds $5,000,000, the Company shall, within 30 days
of such date, make an offer to purchase (an "Asset Sale Offer") on a pro rata
                                             ----------------
basis (a) Notes at a purchase price (the

                                       6
<PAGE>

"Offer Purchase Price") in cash equal to 100% of the principal amount thereof,
 --------------------
plus accrued and unpaid interest thereon, if any, to but excluding the purchase
date and (b) to the extent required by the terms thereof, any other indebtedness
of the Company that is pari passu with the Notes. The pro rata amount of such
Excess Proceeds to be used to purchase Notes shall be in an amount equal to the
aggregate amount of such Excess Proceeds multiplied by the quotient obtained by
dividing the principal amount of the outstanding Notes by the sum of such
principal amount and the principal amount of such other Indebtedness. In the
event the aggregate Offer Purchase Price of the outstanding Notes tendered
pursuant to an Asset Sale Offer is in excess of the Excess Proceeds to be used
to purchase such Notes, such Excess Proceeds shall be applied to purchase such
Notes on a pro rated basis in principal amounts of $1,000 or an integral
multiple thereof.

          Within 30 days of the date the amount of Excess Proceeds exceeds
$5,000,000, the Company or the Trustee (at the expense of the Company) shall
mail to each Holder a written notice regarding the Asset Sale Offer.  The Holder
of this Note may elect to have this Note or a portion hereof in an authorized
denomination purchased by completing the form entitled "Option of Holder to
Elect Purchase" appearing below and tendering this Note pursuant to the Asset
Sale Offer.  Unless the Company defaults in the payment of the Offer Purchase
Price with respect thereto, all Notes or portions thereof selected for payment
pursuant to the Asset Sale Offer will cease to accrue interest from and after
the purchase date.

     9.   Denominations; Transfer; Exchange.
          ----------------------------------

          The Notes are issuable only in registered form without coupons in
denominations of $1,000 principal amount and any integral multiple thereof.  A
Holder may register the transfer or exchange of Notes in accordance with the
Indenture.  No service charge shall be made for any such registration of
transfer or exchange, but the Company may require payment of a sum sufficient to
cover any tax or other governmental charge payable in connection therewith.

     10.  Persons Deemed Owners.
          ----------------------

          Prior to due presentment of this Note for registration of transfer,
the Company, the Trustee, the Paying Agent and the Note Registrar may deem and
treat the Person in whose name this Note is registered as the owner hereof for
all purposes, whether or not this Note be overdue, and none of the Company, the
Trustee, the Paying Agent or the Note Registrar shall be affected by notice to
the contrary.

     11.  Unclaimed Money.
          ----------------

          Subject to certain notice provisions, the Trustee and the Paying Agent
shall pay to the Company upon written request any money held by them for the
payment of principal, premium, if any, or interest that remains unclaimed for
two years.  After payment to the Company, Holders entitled to such money must
look only to the Company for payment as general creditors, and all
responsibility and liability of the Trustee and the Paying Agent with respect to
such money shall cease.

     12.  Discharge Prior to Redemption.
          ------------------------------

          If the Company deposits with the Trustee United States dollars or U.S.
Government Obligations sufficient to pay the principal, premium, if any, and
accrued interest on the Notes to redemption, the Company will, with the
exceptions of certain

                                       7
<PAGE>

sections thereof, be discharged from the Indenture and the Notes, including
certain covenants set forth in the Indenture.

     13.  Amendment; Waiver.
          ------------------

          The Indenture permits, with certain exceptions as therein provided,
the amendment thereof and the modification of the rights and obligations of the
Company and the rights of the Holders of the Notes under the Indenture at any
time by the Company and the Trustee with the consent of the Holders of not less
than a majority in aggregate principal amount of the Notes at the time
outstanding.  The Indenture also contains provisions permitting the Holders of
not less than a majority in aggregate principal amount of the Notes at the time
outstanding, on behalf of the Holders of all the Notes, to waive certain past
defaults under the Indenture and their consequences.

     14.  Restrictive Covenants.
          ----------------------

          The Indenture contains certain covenants which, among other things,
restrict the ability of the Company and Restricted Subsidiaries to incur
additional indebtedness (and, in the case of Restricted Subsidiaries, issue
preferred stock), pay dividends or make distributions in respect of the
Company's or Restricted Subsidiaries' capital stock, make other restricted
payments, enter into sale and leaseback transactions, incur liens, cause
encumbrances or restrictions to exist on the ability of Restricted Subsidiaries
to pay dividends or make distributions in respect of their capital stock, issue
and sell capital stock of Restricted Subsidiaries, enter into transactions with
affiliates, sell assets, or amalgamate, consolidate, merge or sell or otherwise
dispose of all or substantially all of their property and assets.

     15.  Defaults and Remedies.
          ----------------------

          With the exception of certain Events of Defaults specified below, if
an Event of Default occurs and is continuing, the Trustee or the Holders of not
less than 25% of the aggregate principal amount of the outstanding Notes may
declare the principal amount of, and any accrued and unpaid interest on, all
Notes then outstanding to be immediately due and payable.  If a bankruptcy or
insolvency default with respect to the Company or a Restricted Subsidiary occurs
and is continuing, the Notes immediately become due and payable.  Holders may
not enforce the Indenture or the Notes except as provided in the Indenture.  The
Trustee may require indemnity satisfactory to it before it enforces the
Indenture or the Notes.  Subject to certain limitations, Holders of not less
than a majority in principal amount of the outstanding Notes will have the right
to direct the time, method and place of conducting any proceeding for exercising
any remedy available to the Trustee.

     16.  No Recourse Against Others.
          ---------------------------

          No controlling Person, director, officer, employee, incorporator or
stockholder of the Company, as such, shall have any liability for any covenant,
agreement or other 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, solely by reason of its past, present or future status as a
controlling Person, director, officer, employee, incorporator or stockholder of
the Company.  Each Holder by accepting a Note waives and releases all such
liability (but only such liability).  The waiver and release are part of the
consideration for the issuance of the Notes.

                                       8
<PAGE>

     17.  Governing Law.
          --------------

          THIS SECURITY SHALL BE GOVERNED BY, AND CONSTRUED IN ACCORDANCE WITH,
THE LAWS OF THE STATE OF NEW YORK BUT WITHOUT GIVING EFFECT TO APPLICABLE
PRINCIPLES OF CONFLICTS OF LAW TO THE EXTENT THAT THE APPLICATION OF THE LAWS OF
ANOTHER JURISDICTION WOULD BE REQUIRED THEREBY.

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

          Focal Communications Corporation
          200 N. LaSalle
          Chicago, Illinois 60601
          Attention:  Chief Financial Officer

     18.  Ranking.
          --------

          The Notes are senior unsecured obligations of the Company ranking pari
passu in right of payment with all existing and future senior indebtedness of
the Company, and will rank senior in right of payment to all existing and future
subordinated Indebtedness of the Company.  Holders of secured Indebtedness of
the Company, however, will have claims that are prior to the claims of the
Holders with respect to the assets securing such other indebtedness except to
the extent the Notes are equally and ratably secured by such assets.

                                       9
<PAGE>

______________________________________________________________________

                            CERTIFICATE OF TRANSFER

To assign this Note, fill in the form below:

I or we assign and transfer this Note to

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

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


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


______________________________________________________________________

Date: ________________ Your Signature: _____________________


______________________________________________________________________
Sign exactly as your name appears on the other side of this Note.

                                       10
<PAGE>

In connection with any transfer of any of the Notes evidenced by this
certificate occurring prior to the expiration of the period referred to in Rule
144(k) under the Securities Act of 1933 (the "Securities Act") after the later
of the date of original issuance of such Notes and the last date, if any, on
which such Notes were owned by Focal Communications Corporation or any
Affiliate, the undersigned confirms that such Notes are being transferred in
accordance with the terms of such Notes:

CHECK ONE BOX BELOW

     (1)  [_]  to Focal Communications Corporation; or

     (2)  [_]  pursuant to an effective registration statement under the
               Securities Act; or

     (3)  [_]  inside the United States to a "qualified institutional buyer" (as
                                              -----------------------------
               defined in Rule 144A under the Securities Act of 1933) that
               purchases for its own account or for the account of a qualified
               institutional buyer to whom notice is given that such transfer is
               being made in reliance on Rule 144A under the Securities Act, in
               each case pursuant to and in compliance with Rule 144A under the
               Securities Act; or

     (4)  [_]  outside the United States in an offshore transaction within the
               meaning of Regulation S under the Securities Act in compliance
               with Rule 904 under the Securities Act;

     (5)  [_]  pursuant to another available exemption from registration
               provided by Rule 144 under the Securities Act; or

     (6)  [_]  to an institution that is an "accredited investor" as defined in
               Rule 501(a)(1), (2), (3) or (7) under the Securities Act that is
               acquiring this Note for investment purposes and not for
               distribution in violation of the Securities Act or any other
               applicable securities laws.

     Unless one of the boxes is checked, the Trustee will refuse to register any
     of the Notes evidenced by this certificate in the name of any person other
     than the registered holder thereof; provided, however, that if box (3),
                                         --------  -------
     (4), (5) or (6) is checked, the Trustee may require, prior to registering
     any such transfer of the Notes, such legal opinions, certifications and
     other information as the Company has reasonably requested to confirm that
     such transfer is being made pursuant to an exemption from, or in a
     transaction not subject to, the registration requirements of the Securities
     Act, such as the exemption provided by Rule 144 under the Securities Act.

                                       11
<PAGE>

______________________
Signature



Signature Guarantee:

_______________________                      _____________________________
[Signature must be guaranteed                Signature
by an eligible Guarantor
Institution (banks, stock
brokers, savings and loan
associations and credit
unions) with membership in
an approved guarantee
medallion program pursuant
to Securities and Exchange
Commission Rule 17Ad-15]

____________________________________________________________



             TO BE COMPLETED BY PURCHASER IF (3) ABOVE IS CHECKED.

          The undersigned represents and warrants that it is purchasing this
Note for its own account or an account with respect to which it exercises sole
investment discretion and that it and any such account is a "qualified
                                                             ---------
institutional buyer" within the meaning of Rule 144A under the Securities Act,
-------------------
and is aware that the sale to it is being made in reliance on Rule 144A under
the Securities Act and acknowledges that it has received such information
regarding the Company as the undersigned has requested pursuant to Rule 144A
under the Securities Act or has determined not to request such information and
that it is aware that the transferor is relying upon the foregoing
representations of the undersigned in order to claim the exemption from
registration provided by Rule 144A under the Securities Act.


Dated: ________________       ______________________________________________
                              NOTICE: To be executed by an executive officer

                                       12
<PAGE>

               SCHEDULE OF INCREASES OR DECREASES IN GLOBAL NOTE

          The following increases or decreases in this Global Note have been
made:

<TABLE>
<CAPTION>
                                                                Principal Amount of this
             Amount of decrease in    Amount of increase in       Global Note following     Signature of authorized
Date of        Principal Amount         Principal Amount             such decrease or      signatory  of Trustee or
Exchange      of this Global Note      of this Global Note               increase                Notes Custodian
--------    -----------------------  -----------------------  ---------------------------  -------------------------
<S>         <C>                      <C>                      <C>                          <C>
</TABLE>

                                       13
<PAGE>

                      OPTION OF HOLDER TO ELECT PURCHASE

          If you want to elect to have this Note purchased by the Company
pursuant to Section 4.07 or 4.08 of the Indenture, check the box:

                                      [_]

          If you want to elect to have only part of this Note purchased by the
Company pursuant to Section 4.07 or 4.08 of the Indenture, state the amount in
principal amount ($1,000 or an integral multiple thereof): $


Date: _______________    Your Signature:       ____________________
                                              (Sign exactly as your name appears
                                              on the other side of this Note)

Signature Guarantee: _______________________________________
                     Signature must be guaranteed by an eligible Guarantor
                     Institution (banks, stock brokers, savings and loan
                     associations and credit unions) with membership in an
                     approved guarantee medallion program pursuant to Securities
                     and Exchange Commission Rule 17Ad-15.

                                       14
<PAGE>

          Harris Trust and Savings Bank, as Trustee, certifies that this is one
of the Notes referred to in the within-mentioned Indenture.

     Date: January 12, 2000

                                               HARRIS TRUST AND SAVINGS BANK,
                                                   as Trustee



                                               by____________________
                                                   Authorized Signatory

                                       15