Document:

<PAGE>

                                 EXHIBIT 4.19

Amendment and Waiver No. 2 to the Loan Documents, dated as of December 29, 1999,
among ICG Equipment, Inc., ICG NetAhead, Inc., ICG Services, Inc., as Parent,
 certain Initial Lender Parties party thereto, Morgan Stanley Senior Funding,
Inc., as Sole Book-Runner and Lead Arranger, Royal Bank of Canada, as Collateral
  Agent and as Administrative Agent for such Lender Parties, Bank of America,
N.A., as Documentation Agent and Barclays Bank Plc, as Co-Documentation Agent.

<PAGE>

                                                                  EXECUTION COPY

                       AMENDMENT AND WAIVER NO. 2 TO THE
                                LOAN DOCUMENTS

                                               Dated as of December 29, 1999

          AMENDMENT AND WAIVER NO. 2 TO THE CREDIT AGREEMENT dated as of August
12, 1999, and Amendment No. 1 thereto dated as of September 30, 1999 (such
Credit Agreement as so amended, the "Credit Agreement") among ICG Equipment,
Inc., a Colorado corporation ("ICG Equipment"), ICG NetAhead, Inc., a Delaware
corporation ("ICG NetAhead" and, together with ICG Equipment, the "Borrowers"),
ICG Services, Inc., as Parent, certain Initial Lender Parties party thereto,
Morgan Stanley Senior Funding, Inc., as Sole Book-Runner and Lead Arranger,
Royal Bank of Canada, as Collateral Agent and as Administrative Agent for such
Lender Parties, Bank of America, N.A., as Documentation Agent and Barclays Bank
Plc, as Co-Documentation Agent. Capitalized terms not otherwise defined in this
Amendment and Waiver have the same meanings as specified therefor in the Credit
Agreement.

          PRELIMINARY STATEMENTS:

          (1)  The Borrowers and the Parent have requested that the Lender
Parties agree to amend the Credit Agreement to (a) enable the Borrowers and the
Parent to make additional capital expenditures in the fourth fiscal quarter of
the year 1999, (b) enable the Borrowers to make intercompany advances to the
Parent pursuant to the terms of certain intercompany promissory notes, and (c)
enable the Parent to make intercompany advances to the Borrowers pursuant to the
terms of certain intercompany promissory notes.

          (2)  The Borrowers and the Parent have disclosed to the Lender Parties
the existence of certain intercompany debt owed (i) by the Borrowers to the
Parent and (ii) by the Parent to the Borrowers.

          (3)  The Borrowers and the Parent have also requested that the Lender
Parties amend the Security Agreement to permit termination of Assigned
Agreements under certain circumstances and to waive and amend certain other
requirements of the Loan Documents.

          (4)  The Borrowers and the Parent have requested that the Lender
Parties waive the requirements of Section 5.02(e) of the Credit Agreement to
permit the transfer of certain property and assets from ICG Equipment to Qwest
Communications Corporation (the "Transferred Property") pursuant to the
Indefeasible Right of Use Agreement between ICG Equipment and Qwest
Communications Corporation, a Delaware corporation ("Qwest"), dated as of June
25, 1999 ("IRU Agreement"), Amendment No. 1 to the IRU Agreement as in effect on
December 31, 1999 and in the form approved by the Lead Arranger ("IRU Amendment
No. 1")
<PAGE>

                                       2

and the IRU Agreement between ICG Equipment and Qwest as in effect on December
31, 1999 and in the form approved by the Lead Arranger ("IRU Agreement No. 2").

          (5)  The Lender Parties have agreed to such amendments and waivers on
the terms and conditions set forth herein.

          SECTION 1. Amendments to Credit Agreement. The Credit Agreement is,
                     ------------------------------
effective as of the date hereof and subject to the satisfaction of the
conditions precedent set forth in Section 5, hereby amended as follows:

          (a)  Section 1.01 is amended to add the following new definitions:

               "Amendment and Waiver No. 2" means the Amendment and Waiver No. 2
          to this Agreement dated as of December 29, 1999.

               "Equity Exchange" means (i) any exchange or conversion by the
          Parent of Parent Debt held by the Parent for, or into, Equity
          Interests in ICG Equipment pursuant to the terms of the Parent Notes
          or Section 5.01(q)(iii), (ii) the exchange or conversion of Parent
          Debt held by the Parent in an aggregate principal amount at least
          equal to $100,000,000 for, or into, Equity Interests in ICG Equipment
          on or before December 31, 1999 pursuant to the terms of Amendment and
          Waiver No. 2, and (iii) the contribution of cash required to be made
          by the Parent in return for Equity Interests in ICG Equipment pursuant
          to Section 5.01(q)(i).

               "Indentures" mean the Indenture dated as of February 12, 1998, in
          respect of the 10% Senior Discount Notes due 2008, together with the
          Indenture dated as of April 27, 1998, in respect of the 9 7/8% Senior
          Discount Notes due 2008, in each case, between the Parent and Norwest
          Bank Colorado, National Association, as trustee, and, in each case, as
          in effect on the date of Amendment and Waiver No. 2.

               "Parent Debt" means the Debt owed to the Parent by the Borrowers
          and evidenced by the Parent Notes.

               "Parent Investment" means the Investment by the Parent in the
          Parent Debt.

               "Parent Notes" means the intercompany notes from each of the
          Borrowers dated as of December 29, 1999 evidencing the aggregate Debt
          owed by each Borrower to the Parent in the form delivered pursuant to
          Amendment and Waiver No. 2.
<PAGE>

                                       3

               "Services Debt" means the Debt owed by the Parent to each of the
          Borrowers and evidenced by the Services Notes.

               "Services Investments" means the Investment by the Borrowers in
          the Services Debt.

               "Services Notes" means the intercompany promissory notes from the
          Parent to each of the Borrowers dated as of December 29, 1999
          evidencing the aggregate Debt owed by the Parent to each Borrower in
          the form delivered pursuant to Amendment and Waiver No. 2."

          (b)  Section 1.01 is hereby further amended by amending and restating
the following definitions in their entirety to read as follows:

               "Existing Debt" means Debt of each Loan Party and its
          Subsidiaries (other than Services Debt and Parent Debt) outstanding
          immediately before giving effect to the consummation of the
          Transaction.

               "Related Documents" means the Parent Notes, the Services Notes,
          and the Tax Sharing Agreement."

          (c)  Section 5.01(i) is amended by adding to the end thereto the
following words:

               "; provided, however, that the Parent and its Subsidiaries may
          consummate the transactions contemplated by the Equity Exchange."

          (d)  A new Section 5.01(q) is added after the existing Section 5.01(p)
to read as follows:

               "(q) Conditions Subsequent to Initial Extension of Credit.
                    ----------------------------------------------------
          Deliver to the Lead Arranger and the Administrative Agent:

               (i) as soon as possible and in any event on or before January 31,
          2000, evidence satisfactory to the Lead Arranger and the
          Administrative Agent, that all amounts standing to the credit of the
          Parent in any deposit account, other bank account or investment
          account held or maintained by the Parent, have been transferred to
          accounts held and maintained by, and in the name of, ICG Equipment
          and, in each case, shall constitute a contribution of such amounts in
          return for Equity Interests in ICG Equipment issued to the Parent by
          ICG Equipment,
<PAGE>

                                       4

               (ii)   as soon as possible and in any event on or before February
          29, 2000, the Pledged Account Letters referred to in the Security
          Agreement, duly executed by each Person required by the Lead Arranger
          to execute such Pledged Account Letters,

               (iii)  on or before December 31 of each year, commencing with
          December 31, 2000, evidence satisfactory to the Lead Arranger and the
          Administrative Agent, that Parent Debt in an aggregate principal
          amount of at least $100,000,000 has, during such year, been exchanged
          by the Parent for Equity Interests in ICG Equipment, in each case on
          terms and conditions satisfactory to the Lead Arranger and the
          Administrative Agent, and

               (iv)   evidence that all other action has been taken as the Lead
          Arranger may deem necessary or desirable in order to effect the
          transactions contemplated by Amendment and Waiver No. 2.

          (e)  Section 5.02(b)(i) is hereby amended by adding an additional sub-
     clause (C) thereto as follows:

               "(C) The Parent Debt, payable on the terms, and subject to the
          provisions, of the Parent Note."

         (f) Section 5.02 (b)(iii) is hereby amended by: (i) deleting the word
     "and" at the end of subclauses (D) and (E) thereof, (ii) adding a new sub-
     clause (F) to read as follows:

               "(F) in the case of the Parent, the Services Debt provided that,
     in each case, such Services Debt (x) shall constitute Pledged Debt, (y)
     shall be on terms acceptable to the Required Lenders and (z) shall be
     evidenced by promissory notes in form and substance satisfactory to the
     Required Lenders and such promissory notes shall be pledged as security for
     the Obligations of the holder thereof under the Loan Documents to which
     such holder is a party and delivered to the Collateral Agent pursuant to
     the terms of the Security Agreement; and"

          , and (iii) making the existing sub-clause (F) a new sub-clause (G)
     and amending such sub-clause in its entirety to read as follows: "(G) other
     unsecured Debt which is owed to any Person, other than to the Parent by a
     Borrower, in an aggregate principal amount not to exceed $350,000,000 at
     any one time outstanding.

          (g) Section 5.02(f)(i) is amended in its entirety to read as follows:
<PAGE>

                                       5

               "(i) Investments by the Parent and its Subsidiaries in their
               respective Subsidiaries outstanding on the date hereof and
               additional Investments in the Borrowers and wholly owned
               Subsidiaries of a Borrower now existing or organized hereafter,
               provided that any such Subsidiary has become a Subsidiary
               Guarantor to the extent required by Section 5.01(j)."

          (h)  Section 5.02(f) is hereby amended by adding an additional sub-
     clause (viii) thereto as follows:

               "(viii) the Parent Investment and the Services Investment."

          (i)  (a) Section 5.02(g)(i) is amended in its entirety to read as
     follows:

               "(i) each Borrower may (A) declare and pay dividends and
               distributions payable only in stock of each Borrower, and (B)
               issue Equity Interests in such Borrower to the Parent".

               , and (b) the reference to Section 5.02(b) (iii)(F) in the final
               line of Section 5.02(g)(ii) is amended by changing such
               reference to "Section 5.02 (b) (iii)(G)"

          (j)  Section 5.02(h) is amended by adding to the end thereof the
     following words:

               "or any other such amendment made solely in connection with the
               Equity Exchange and consented to in writing by the Lead Arranger
               and the Administrative Agent."

          (k)  The second and third lines of the table in Section 6.01(q) of the
     Credit Agreement are hereby amended in their entirety to read as follows:

               "December 31, 1999                      436,000,000

               March 31, 2000                                0

          (l)  Section 6.01 is hereby further amended by adding an additional
     subclause (r) thereto as follows:

               "(r) Any Borrower shall make, or the Parent shall accept or
               receive, in each case whether by payment in cash or in-kind, or
               by way of set-off, netting or otherwise, (a) any payment of
               principal on or in respect of the Parent Debt other than in
               accordance with the terms of the Parent Note or
<PAGE>

                                       6

               pursuant to the Equity Exchange, or (b) any payment of interest
               or any other amount (other than principal) on or in respect of
               the Parent Debt other than (i) pursuant to the Equity Exchange,
               or (ii) such payments as are applied by the Parent to meet (A)
               interest obligations which are due and payable pursuant to the
               Indentures or (B) any reasonable costs and expenses incurred by
               the Parent in the ordinary course of its business in an aggregate
               amount not to exceed $5,000,000 in any Fiscal Year."

          (m)  Schedule 4.01(s) is amended by deleting the information contained
     therein in its entirety and substituting therefor the information contained
     on Schedule I hereto.

          (n)  Schedule 4.01(w) is amended by deleting the word "None" contained
     therein in its entirety and substituting therefor the information contained
     on Schedule II hereto.

          (o)  Schedule 4.01(y) is amended by deleting the information contained
     therein in its entirety and substituting therefor the information contained
     on Schedule III hereto.

          SECTION 2.  Waiver to the Credit Agreement.  Effective as of the date
                      ------------------------------
hereof and subject to the satisfaction of the conditions precedent set forth in
Section 5, the Lender Parties hereby agree to waive:

          (a)  any and all of the Defaults and Events of Default under Section
               6.01(b) and (c) that have occurred and are continuing as a result
               of the failure of each of the Borrowers and the Parent to comply
               with the requirements of Section 4.01(s), (w) and (y) and Section
               5.02(b)(i)(B) of the Credit Agreement prior to this Amendment and
               Waiver, in each case, solely in connection with their non-
               disclosure of the Parent Debt, the Services Debt, the Parent
               Investment and the Services Investment.

          (b)  the requirements of Section 5.02(e), solely to the extent
               necessary to permit the Borrowers to consummate the transactions
               contemplated by IRU Amendment No. 1 and IRU Agreement No. 2.

          (c)  the requirement in Section 26(a)(ii) of the Security Agreement
               that a written request to release the Collateral be delivered to
               the Collateral Agent at least ten Business Days prior to such
               release, provided, that such request is delivered at least one
                        --------
               Business Day prior to the date hereof and all other requirements
               of Section 26 are complied with in accordance with their terms.
<PAGE>

                                       7

          SECTION 3.  Amendment to the Security Agreement.  The Security
                      -----------------------------------
Agreement is, effective as of the date hereof and subject to the satisfaction of
the conditions precedent set forth in Section 5, hereby amended as follows by
amending Section 14(b)(ii) in its entirety to read as follows:

               "(ii) amend or otherwise modify any Assigned Agreement or give
               any consent, waiver or approval thereunder, except in the
               ordinary course of business and in a manner that would not
               reasonably be expected to have a Material Adverse Effect;"

          SECTION 4.  Release.  Each of the Lender Parties hereby agree that,
                      -------
solely to the extent, if any, necessary to permit the transactions contemplated
by the IRU Agreement, IRU Amendment No. 1, and IRU Agreement No. 2, all of the
Liens in favor of the Lender Parties solely in respect of the Transferred
Property, shall be deemed to be released, terminated and no longer in effect. In
furtherance of this Section 4 each of the Lender Parties authorizes the
Administrative Agent to execute any documents and to take any and all other
action reasonably required by the Borrowers, at the Borrowers' expense, to
effectuate the release pursuant to Section 26 of the Security Agreement.

          SECTION 5.  Conditions of Effectiveness.  This Amendment and Waiver
                      ---------------------------
shall become effective as of the date first above written when and only when:

          (a)   the Lead Arranger shall have received the following:

          (i)   counterparts of this Amendment and Waiver executed by the
     Borrowers, the Parent, and the Required Lenders or, as to any of the Lender
     Parties, advice satisfactory to the Lead Arranger that such Lender Party
     has executed this Amendment and Waiver,

          (ii)  certified copies of the Parent Notes and the Services Notes,
     duly executed by the Parent and each of the Borrowers,

          (iii) certified copies of the IRU Agreement, IRU Amendment No. 1 and
     IRU Agreement No. 2 and all other documents, instruments and agreements
     entered into in respect thereof or related thereto,

          (iv)  any filings, or recordings, or consents of any Persons requested
     by the Lead Arranger in order to create or perfect a security interest in
     favor of the Secured Parties in any Collateral of the Borrowers, and

          (v)   any other items reasonably requested by any Lender Party;
<PAGE>

                                       8

          (b)  the Lead Arranger is satisfied with all bank accounts and all
other investment accounts of the Borrowers and the Parent and with the system of
cash management operated by the Parent and the Borrowers;

          (c)  the Parent has exchanged indebtedness owed to it by ICG
Equipment, in an aggregate principal amount of not less than $100,000,000 for an
Equity Interest in ICG Equipment, in each case on terms and conditions,
satisfactory to each of the Lead Arranger; and

          (d)  all of the accrued fees and expenses of the Agents and the Lender
Parties (including the accrued fees and expenses of counsel to the Lead
Arranger, the fees and expenses referred in Sections 9 and 10 of this Amendment
and Waiver and all other fees payable in connection with this Amendment and
Waiver) shall have been paid in full.

          SECTION 6. Representations and Warranties of the Borrower. The
                     ----------------------------------------------
Parent and each Borrower represent and warrant as follows:

          (a)  Each Loan Party and each of its Subsidiaries (i) is a corporation
     duly organized, validly existing and in good standing under the laws of the
     jurisdiction of its incorporation, (ii) is duly qualified and in good
     standing as a foreign corporation in each other jurisdiction in which it
     owns or leases property or in which the conduct of its business requires it
     to so qualify or be licensed except where the failure to so qualify or be
     licensed could not be reasonably likely to have a Material Adverse Effect
     and (iii) has all requisite corporate power and authority (including,
     without limitation, all governmental licenses, permits and other approvals)
     to own or lease and operate its properties and to carry on its business as
     now conducted and as proposed to be conducted.

          (b)  The execution, delivery and performance by each Loan Party of
     this Amendment and Waiver, the Parent Notes, the Services Notes and the
     Transaction Documents as amended hereby, to which it is or is to be a
     party, are within such Loan Party's corporate powers, have been duly
     authorized by all necessary corporate action, and do not (i) contravene
     such Loan Party's charter or bylaws, (ii) violate any law, rule, regulation
     (including, without limitation, Regulation X of the Board of Governors of
     the Federal Reserve System), order, writ, judgment, injunction, decree,
     determination or award, (iii) conflict with or result in the breach of, or
     constitute a default or require any payment to be made under, any contract,
     loan agreement, indenture, mortgage, deed of trust, lease or other
     instrument binding on or affecting any Loan Party, any of its Subsidiaries
     or any of their properties in such a manner as would be reasonably likely
     to have a Material Adverse Effect or (iv) except for the Liens created
     under the Transaction Documents, result in or require the creation or
     imposition of any Lien upon or with respect to any of the properties of any
     Loan Party or any of its Subsidiaries. No Loan Party or any of its
     Subsidiaries is in violation of any such law, rule, regulation, order,
<PAGE>

                                       9

     writ, judgment, injunction, decree, determination or award or in breach of
     any such contract, loan agreement, indenture, mortgage, deed of trust,
     lease or other instrument, the violation or breach of which could be
     reasonably likely to have a Material Adverse Effect.

          (c)  No authorization or approval or other action by, and no notice to
     or filing with, any governmental authority or regulatory body or any other
     third party is required for the due execution, delivery or performance by
     any Loan Party party of this Amendment and Waiver, the Parent Notes, the
     Services Notes or any of the Transaction Documents, as amended hereby, to
     which it is or is to be a party.

          (d)  This Amendment and Waiver and each of the Parent Notes and the
     Services Notes have been duly executed and delivered by the Parent and the
     Borrowers. This Amendment and Waiver and each of the Parent Notes and the
     Services Notes and each of the other Transaction Documents, as amended
     hereby, to which any Loan Party is a party are legal, valid and binding
     obligations of each Loan Party thereto, enforceable against such Loan Party
     in accordance with their respective terms.

          (e)  There is no action, suit, investigation, litigation or proceeding
     affecting any Loan Party or any of its Subsidiaries, including any
     Environmental Action, pending or threatened before any court, governmental
     agency or arbitrator that (i) could be reasonably likely to have a Material
     Adverse Effect or (ii) purports to affect the legality, validity or
     enforceability of this Amendment and Waiver or any of the other Transaction
     Documents as amended hereby.

          (f)  All filings and other actions necessary or desirable to perfect
     and protect the security interest in the Collateral created under the
     Collateral Documents have been duly made or taken and are in full force and
     effect, and the Collateral Documents create in favor of the Collateral
     Agent for the benefit of the Secured Parties a valid and, together with
     such filings and other actions, perfected first priority security interest
     in the Collateral, securing the payment of the Secured Obligations, and all
     filings and other actions necessary or desirable to perfect and protect
     such security interest have been duly taken. The Loan Parties are the legal
     and beneficial owners of the Collateral free and clear of any Lien, except
     for the liens and security interests created or permitted under the Loan
     Documents.

          (g)  The representations and warranties set forth in each of the
     Transaction Documents are correct on and as of this date, before and after
     giving effect to this Amendment and Waiver, as though made on and as of
     such date.

          (h)  No event has occurred and is continuing that constitutes a
Default. No event has occurred and is continuing that constitutes, or would,
with the lapse of time or the
<PAGE>

                                       10

giving of notice constitute, a default under any material agreement to
which any Loan Party is a party.

          SECTION 7.  Reference to and Effect on the Credit Agreement,
                      ------------------------------------------------
the Security Agreement, the Notes and the Transaction Documents.  (a) On and
---------------------------------------------------------------
after the effectiveness of this Amendment and Waiver, each reference in the
Credit Agreement to "this Agreement", "hereunder", "hereof" or words of like
import referring to the Credit Agreement, and each reference in the, Notes and
each of the other Transaction Documents to "the Credit Agreement", "thereunder",
"thereof" or words of like import referring to the Credit Agreement, shall mean
and be a reference to the Credit Agreement, as amended by this Amendment and
Waiver.

          (b)  On and after the effectiveness of this Amendment and Waiver, each
reference in the Security Agreement to "this Agreement", "hereunder", "hereof"
or words of like import referring to the Security Agreement, and each reference
in the Credit Agreement, Notes and each of the other Transaction Documents to
"the Security Agreement", "thereunder", "thereof" or words of like import
referring to the Security Agreement, shall mean and be a reference to the
Security Agreement, as amended by this Amendment and Waiver.

          (c)  The Credit Agreement, the Security Agreement, the Notes and each
of the other Transaction Documents, as specifically amended by this Amendment
and Waiver, are and shall continue to be in full force and effect and are hereby
in all respects ratified and confirmed. Without limiting the generality of the
foregoing, the Collateral Documents and all of the Collateral described therein
do and shall continue to secure the payment of all Obligations of the Loan
Parties under the Transaction Documents, in each case as amended by this
Amendment and Waiver.

          (d)  The execution, delivery and effectiveness of this Amendment and
Waiver shall not, except as expressly provided herein, operate as a waiver of
any right, power or remedy of any Lender or the Agents under any of the
Transaction Documents, nor constitute a waiver of any provision of any of the
Transaction Documents.

          SECTION 8.  Consent of the Parent.  The Parent, as guarantor under the
                      ---------------------
Parent Guaranty, hereby consents to this Amendment and Waiver and hereby
confirms and agrees that notwithstanding the effectiveness of this Amendment and
Waiver, the Parent Guaranty is, and shall continue to be, in full force and
effect and is hereby ratified and confirmed in all respects, except that, on and
after the effectiveness of this Amendment and Waiver, (i) each reference in the
Parent Guaranty to the "Credit Agreement", "thereunder", "thereof" or words of
like import shall mean and be a reference to the Credit Agreement, as amended by
this Amendment and Waiver, and (ii) each reference in the Parent Guaranty to the
"Security Agreement", ""thereunder", thereof or words of like import shall mean
and be a reference to the Security Agreement as amended by this Amendment and
Waiver.
<PAGE>

                                      11

          SECTION 9.  Costs and Expenses. The Borrowers agree jointly and
                      ------------------
severally to pay on demand all reasonable costs and expenses of the Lead
Arranger in connection with the preparation, execution, delivery and
administration, modification and amendment of this Amendment and Waiver and the
other instruments and documents to be delivered hereunder (including, without
limitation, the reasonable fees and expenses of counsel for the Lead Arranger)
in accordance with the terms of Section 9.04 of the Credit Agreement.

          SECTION 10. Amendment Fee. The Borrowers agree to pay an amount equal
                      -------------
to 0.10% of the sum of (i) the aggregate Tranche A Term Commitments held by
those Lenders that have, on or prior to December 31, 1999, executed this
Amendment and Waiver, (ii) the aggregate Tranche B Term Commitments held by
those Lenders that have, on or prior to December 31, 1999, executed this
Amendment and Waiver and (iii) the aggregate Working Capital Commitments held by
those Lenders that have, on or prior to December 31, 1999, executed this
Amendment and Waiver, payable to the Administrative Agent for the account of
such Lenders, ratably in accordance with their respective interests in such
Tranche A Term Commitments, Tranche B Term Commitments and Working Capital
Commitments.

          SECTION 11. Execution in Counterparts. This Amendment and Waiver may
                      -------------------------
be executed in any number of counterparts and by different parties hereto in
separate counterparts, each of which when so executed shall be deemed to be an
original and all of which taken together shall constitute but one and the same
agreement. Delivery of an executed counterpart of a signature page to this
Amendment and Waiver by telecopier shall be effective as delivery of a manually
executed counterpart of this Amendment and Waiver.

          SECTION 12. Governing Law.  This Amendment and Waiver shall be
                      -------------
governed by, and construed in accordance with, the laws of the State of New
York.
<PAGE>

          IN WITNESS WHEREOF, the parties hereto have caused this Amendment and
Waiver to be executed by their respective officers thereunto duly authorized, as
of the date first above written.

                                      ICG EQUIPMENT, INC., as Borrower

                                      By   /s/ Don Teague
                                          ---------------------------------
                                          Title:

                                      ICG NETAHEAD, INC., as Borrower

                                      By   /s/ Don Teague
                                          ---------------------------------
                                          Title:

                                      ICG SERVICES, INC., as Parent Guarantor

                                      By   /s/ Don Teague
                                          ---------------------------------
                                          Title:
<PAGE>

                                      MORGAN STANLEY SENIOR FUNDING,
                                      INC.,
                                         as Sole Book-Runner, Lead Arranger and
                                         Lender Party

                                      By  /s/ T. Morgan Edwards II
                                          ---------------------------------
                                          Title:  Vice President
<PAGE>

                                      ROYAL BANK OF CANADA,
                                       as Administrative Agent, Collateral Agent
                                       and Lender Party

                                      By  /s/ Kevin K. Cornwell
                                          ---------------------------------
                                          Title:  Managing Director
<PAGE>

                                      BANK OF AMERICA, N.A.,
                                         as Documentation Agent and Lender Party

                                      By  /s/ Julie Schell
                                          ---------------------------------
                                          Title:  Vice President
<PAGE>

                                      BARCLAYS BANK PLC
                                         as Co-Documentation Agent and Lender
                                         Party

                                      By  /s/ Craig J. Lewis
                                          ---------------------------------
                                          Title:  Director
<PAGE>

                                      FINOVA CAPITAL CORPORATION

                                      By  /s/ Jeffrey S. Kilrey
                                          ---------------------------------
                                          Title:  Senior Vice President
<PAGE>

                                      FIRST UNION NATIONAL BANK

                                      By  /s/ Mark L. Cook
                                          ---------------------------------
                                          Title: Senior Vice President
<PAGE>

                                      GENERAL ELECTRIC CAPITAL
                                      CORPORATION

                                      By  /s/ Ken Gacevich
                                          ---------------------------------
                                          Title:  Vice President
<PAGE>

                                      STEIN ROE FLOATING RATE LIMITED
                                      LIABILITY COMPANY

                                      By  /s/ Jim R. Fellows
                                          ---------------------------------
                                          Title:
<PAGE>

                                      STEIN ROE AND FARNHAM
                                      INCORPORATED
                                      AS AGENT FOR KEYPORT LIFE
                                      INSURANCE COMPANY

                                      By  /s/  Jim R. Fellows
                                          ---------------------------------
                                          Title: Vice President and Portfolio
                                                 Manager
<PAGE>

                                      STEIN ROE FARNHAM CLO 1 LTD.,
                                      by Stein Roe & Farnham Incorporated,
                                      As Portfolio Manager

                                      By  /s/  Jim R. Fellows
                                          ---------------------------------
                                          Title:  Vice President and Portfolio
                                                  Manager
<PAGE>

                                      FRANKLIN FLOATING RATE TRUST

                                      By  /s/ Chauncey Lufkin
                                          ---------------------------------
                                          Title: Vice President
<PAGE>

                                      ELT LTD.

                                      By  /s/ Kelly C. Walker
                                          ---------------------------------
                                          Title:  Autorized Agent
<PAGE>

ELF Funding Trust 1
By: Highland Capital Management, L.P.
As Collateral Manager

By  /s/ Mark K. Okada
    ----------------------------
Name:  Mark K. Okada
Title: Executive Vice President
       Highland Capital Management, L.P.

Pamco Cayman Ltd.
By: Highland Capital Management, L.P.
As Collateral Manager

By  /s/ Mark K. Okada
    ----------------------------
Name:  Mark K. Okada
Title: Executive Vice President
       Highland Capital Management, L.P.
<PAGE>

                   Schedule I To Amendment And Waiver No. 2

                              ICG Equipment, Inc.

                     Schedule 4.01(s) to Credit Agreement

                                 Existing Debt

                         Capitalized Lease Obligations

<TABLE>
<CAPTION>
          Parties                     Type of Agreement                 Value
---------------------------------------------------------------------------------------------
 <S>                                  <C>                    <C>
 1.   MSF Network Technologies        Fiber Use Agreement    Present Value     $2,430,228.46
          and ICG Equipment, Inc.                            Payment              $81,024.60
                                                             Interest Rate             12.50%
                                                             Number of Payments          100

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

 2.   Platte River Power Authority    Fiber Use Agreement    Present Value     $3,760,252.32
          and ICG Equipment, Inc.                            Payment             $461,577.60
                                                             Interest Rate             12.50%
                                                             Number of Payments           20
</TABLE>

Inter-company payables owing to ICG Services Inc. (Parent Debt) in the amount of
$718,492,882.45 as of September 30, 1999.
<PAGE>

                   SCHEDULE I TO AMENDMENT AND WAIVER NO. 2

                              ICG NETAHEAD, Inc.

                     SCHEDULE 4.01(s) TO CREDIT AGREEMENT

                                 Existing Debt

                           Capital Lease Obligations

<TABLE>
<CAPTION>
                                                      Principal             Tax                 FMV of MLP
                                                      ---------             ---                 ----------
<S>                           <C>                     <C>                   <C>                 <C>
Short-term portion            Ameritech               254,785.48          18,744.24              273,529.72
                              Comdisco #1             861,190.67          75,767.10              936,957.77
                              Comdisco #2             662,353.06          59,204.76              721,557.82
                              Comdisco #3              55,853.30           5,156.48               61,009.78
                              Comdisco #4              36,335.26           3,464.76               39,800.02
                              Comdisco #5             519,795.49          51,193.60              570,989.09
                              Cisco #1                 17,034.33           1,687.56               18,721.89
                              Cisco #2                129,777.20          12,856.90              142,634.10
                              Cisco #3                 30,980.53           3,096.80               34,077.33
                              Cisco #4                 30,796.05           3,023.72               33,819.77
                              Cisco #5                110,767.22          11,072.46              121,839.68

Total short-term portion                            2,709,668.59         245,268.38            2,954,936.97
                                                    ------------         ----------            ------------

Long-term portion             Ameritech                        -                  -                       -
                              Comdisco #1                      -                  -                       -
                              Comdisco #2                      -                  -                       -
                              Comdisco #3              15,128.71           1,289.12               16,417.83
                              Comdisco #4              20,007.26           1,732.38               21,739.64
                              Comdisco #5             436,412.09          38,395.20              474,807.29
                              Cisco #1                 17,849.75           1,567.02               19,416.77
                              Cisco #2                135,989.48          11,938.55              147,928.03
                              Cisco #3                 35,120.80           3,096.80               38,217.60
                              Cisco #4                 29,652.25           2,591.76               32,244.01
                              Cisco #5                125,570.49          11,072.46              136,642.95

Total long-term portion                               815,730.83          71,683.29              887,414.12
                                                      ----------          ---------              ----------

Total obligation per amortization schedule          3,525,399.42         316,951.67            3,842,351.09
                                                    ============         ==========            ============
</TABLE>
<PAGE>

                   SCHEDULE I TO AMENDMENT AND WAIVER NO. 2

                              ICG SERVICES, INC.

                     SCHEDULE 4.01(s) TO CREDIT AGREEMENT

                      Existing Debt as of August 11, 1999

1.       ICG Services, Inc. Indentures:

        Notes                Principal     Accrued Interest to   Principal plus
                                             August 11, 1999    Accrued Interest
--------------------------------------------------------------------------------

       10% Notes            $331,646,700       $16,217,911       $347,864,611
(Issued February 12, 1998)

      9-7/8% Notes          $275,598,368        $7,596,477       $283,194,845
(Issued April 27, 1998)     ------------        ----------       ------------

2.       Guarantor  of  a  Promissory  Note in the amount  of $33,076,754,  made
         by ICG 161,  L.P., owner of property located  at  161  Inverness  Drive
         West, Englewood, Colorado 80112.

3.       Inter-company  payables  (Services  Debt) owing to ICG NetAhead Inc. in
         the amount of $206,418,344.07 as of September 30, 1999.

4.       Inter-company payables owing to ICG 161 in the amount of  $2,500,000.00
         as of September 30, 1999.
<PAGE>

                   SCHEDULE II TO AMENDMENT AND WAIVER NO. 2

                              ICG EQUIPMENT, INC.

                     SCHEDULE 4.01(w) TO CREDIT AGREEMENT

                                  Investments

Intercompany receivables from ICG 161 in the amount of $33,202.28 as of
September 30, 1999.
<PAGE>

                   SCHEDULE II TO AMENDMENT AND WAIVER NO. 2

                              ICG NETAHEAD, INC.

                     SCHEDULE 4.01(w) TO CREDIT AGREEMENT

                                  Investments

Inter-company receivables from ICG Services, Inc. (Services Investment) in the
amount of $206,418,344.07 as of September 30, 1999.
<PAGE>

                   SCHEDULE II TO AMENDMENT AND WAIVER NO. 2

                              ICG SERVICES, INC.

                     SCHEDULE 4.01(w) TO CREDIT AGREEMENT

                                  Investments

ICG Services, Inc. has made the following investments as of August 11, 1999:

1.   An investment of $10,000,000 in NorthPoint Communications, Inc. for 555,555
     shares of Class B Common Stock (convertible)

2.   An investment of $1,000,000 in International ThinkLink Corporation for
     1,250,000 shares of Series C Preferred Stock (convertible)

3.   An investment of $34,933,606.11 in ICG ChoiceCom, L.P., a Delaware Limited
     Partnership, in exchange for a 49% interest in the Partnership

4.   An investment of $12,489,803.33 in ICG Ohio LINX, Inc., an Ohio corporation
     for 20 shares of Common Stock.

                                Other Investments

1.   Inter-company receivables (Parent Investment) from ICG Equipment, Inc. in
     the amount of $718,492,882.45 as of September 30, 1999.

<PAGE>

                  SCHEDULE III TO AMENDMENT AND WAIVER NO. 2

                              ICG EQUIPMENT, INC.

                     SCHEDULE 4.01(y) TO CREDIT AGREEMENT

                              Material Contracts

<TABLE>
<CAPTION>
             Parties                          Type of Agreement       Effective Date or Term         Comments
-----------------------------------------------------------------------------------------------------------------
<S>                                          <C>                      <C>                        <C>
1.  Aspect Telecommunications and ICG        Equipment Purchase and       March 27, 1998
         Equipment                                Installation

2.  Cisco Systems, Inc. and ICG              Hardware Purchase and        October 8, 1998        Confidentiality
         Equipment, Inc.                        Software License                                 release pending

3.  Lucent Technologies and ICG                 Software Support          April 16, 1998
         Equipment, Inc.                           Agreement

4.  Lucent Technologies, ICG Telecom          General Agreement          September 9, 1996;      Confidentiality
         Group, Inc. (Assignor) and ICG                                  September 8, 1999       release pending
         Equipment (Assignee)                                             (See Assignment
                                                                             Agreement?)

5.  McLeod USA and ICG Equipment, Inc.        Joint construction         April 19, 1999         Confidentiality
                                                                                                 release pending
                                             of fiber optic cables

6.  MSLI, LLC and ICG Equipment, Inc.           Software License              Undated            Confidentiality
                                                                                                 release pending
7.  Northern Telecom, Inc., ICG Telecom      Equipment Purchase and      April 9, 1998 to
         Group, Inc., ICG Equipment, Inc.        Software License          April 8, 2001
         and ICG Services, Inc.

8.  CarrAmerica Development, Inc.              Office Space Lease       December 11, 1998 to
         (Landlord) and ICG Equipment,        [Panorama Corporate        January 31, 2003
         Inc.                                 Center V (Suite 300)]

9.  CarrAmerica Development, Inc.              Office Space Lease       December 1, 1998 to
         (Landlord) and ICG Equipment,        [Panorama Corporate       December 1, 2003
         Inc.                                 Center V (Suite 400)]

10. Platte River Power Authority and ICG      Fiber Use Agreement         January 8, 1999
         Equipment, Inc.                       (for 24 fibers in
                                               Platte River's              20 years with a
                                                   facilities)             20-year option

11. Qwest Communications Corporation and        Equipment Purchase             Undated            Confidentiality
          ICG Equipment, Inc.                                                                    release pending

12. Qwest Communications Corporation and      Fiber Optic Right-to-Use     June 26, 1997         Confidentiality
          ICG Telecom Group, Inc.                                                                release pending

13. Qwest Communications Corporation and       Addendum to above           June 27, 1998         Confidentiality
          ICG Equipment, Inc.                  Agreement, changing                               release pending
                                              party from ICG Telecom
                                                Group, Inc. to ICG
                                                 Equipment, Inc.

14. All Assigned Agreements listed on Schedule II to the Security Agreement

15. ICG Services, Inc.                        Inter-company payables       February 12, 1998
</TABLE>
<PAGE>

                    SCHEDULE III TO AMENDMENT AND WAIVER NO.2

                               ICG NETAHEAD, INC.

                      SCHEDULE 4.01(y) TO CREDIT AGREEMENT

                               Material Contracts

<TABLE>
<CAPTION>
            Parties                            Type of Agreement      Effective Date or Term       Comments
-------------------------------------------------------------------------------------------------------------
<S>                                          <C>                      <C>                          <C>
1.  Cisco and ICG NetAhead, Inc.                   Integrated          September 24, 1998 to
                                             Communications Service     September 24, 2000
                                              Provider Purchase and
                                               License Agreement

2.  ICG Telecom Group, Inc. and ICG                Dedicated              August 24, 1998
         NetAhead, Inc.                        Telecommunications
                                                    Services

3.  Lucent Technologies and ICG NetAhead        Software Support          April 1, 1998 to
                                                   Agreement             December 31, 1998

4.  Mindspring Enterprises, Inc. and ICG        Network Services         February 17, 1999
         NetAhead, Inc.                            Agreement

5.  ICG Services, Inc.                          Inter-company            February 17, 1999
                                                 receivables
</TABLE><PAGE>

                                 EXHIBIT 4.20

Amendment No. 3 to the Loan Documents, dated as of February 11, 2000, among ICG
  Equipment, Inc. ICG NetAhead, Inc., ICG Services, Inc., as Parent, certain
Initial Lender Parties party thereto, Morgan Stanley Senior Funding, Inc., as
Sole Book-Runner and Lead Arranger, Royal Bank of Canada, as Collateral Agent
and as Administrative Agent for such Lender Parties, Bank of America, N.A., as
     Documentation Agent and Barclays Bank Plc, as Co-Documentation Agent.

<PAGE>

                            AMENDMENT NO. 3 TO THE
                                LOAN DOCUMENTS

                                           Dated as of February 11, 2000

         AMENDMENT NO. 3 TO THE CREDIT AGREEMENT dated as of August 12, 1999, as
amended by Amendment No. 1 thereto dated as of September 30, 1999 and Amendment
and Waiver No. 2 thereto dated as of December 29, 1999 (such Credit Agreement as
so amended, the "Credit Agreement") among ICG Equipment, Inc., a Colorado
corporation ("ICG Equipment"), ICG NetAhead, Inc., a Delaware corporation ("ICG
NetAhead" and, together with ICG Equipment, the "Borrowers"), ICG Services,
Inc., as Parent, certain Initial Lender Parties party thereto, Morgan Stanley
Senior Funding, Inc., as Sole Book-Runner and Lead Arranger, Royal Bank of
Canada, as Collateral Agent and as Administrative Agent for such Lender Parties,
Bank of America, N.A., as Documentation Agent and Barclays Bank Plc, as Co-
Documentation Agent. Capitalized terms not otherwise defined in this Amendment
have the same meanings as specified therefor in the Credit Agreement.

         PRELIMINARY STATEMENTS:

         (1) The Borrowers and the Parent have requested that the Lender Parties
agree to amend the Credit Agreement to enable the Borrowers and the Parent to
make additional capital expenditures in the fiscal year 2000 and to obtain the
capital required to finance these additional capital expenditures.

         (2) The Lender Parties have agreed to such amendments on the terms and
conditions set forth herein.

         SECTION 1. Amendments to Credit Agreement. The Credit Agreement is,
                    ------------------------------
effective as of the date hereof and subject to the satisfaction of the
conditions precedent set forth in Section 3, hereby amended as follows:

         (a) Section 1.01 is amended by amending and restating the following
    definition in its entirety to read as follows:

         " "Applicable Margin" means, at any time, (a) in respect of the Tranche
     A Term Facility and the Working Capital Facility, (i) for the first six
     calendar months following the Effective Date, 3.125% in the case of
     Eurodollar Rate Advances, and 2.125% in the case of Base Rate Advances, and
     (ii) thereafter, a percentage per annum determined by reference to the ICG
     Total Leverage Ratio as set forth below and (b) in respect of the Tranche B
     Term Facility, 3.750% in the case of Eurodollar Rate Advances, and 2.750%
     in the case of Base Rate Advances.
<PAGE>

                                       2

<TABLE>
<CAPTION>
ICG Total Leverage Ratio             Base Rate Advances      Eurodollar Rate Advances
<S>                                  <C>                     <C>
       ** 10:1                              2.375%                     3.375%

        * 10:1,  and ** 7.5:1               2.000%                     3.000%

        * 7.5:1, and  * 5.0:1               1.750%                     2.750%

        * 5.0:1                             1.500%                     2.500%
</TABLE>

The Applicable Margin for each Base Rate Advance shall be determined by
reference to the ICG Total Leverage Ratio in effect from time to time and the
Applicable Margin for each Eurodollar Rate Advance shall be determined by
reference to the ratio in effect on the first day of each Interest Period for
such Advance; provided, however, that no change in the Applicable Margin shall
be effective until three Business Days after the date on which the
Administrative Agent receives the financial statements required to be delivered
pursuant to Section 5.03(b) or (c), as the case may be, and a certificate of the
Chief Financial Officer of each Borrower demonstrating the ICG Total Leverage
Ratio."

         (b)   Section 2.06(b)(ii)(A)  shall be amended by  adding at the end of
    the parenthetical therein the following:

         "and other than Net Cash Proceeds required to prepay or repay Debt
    permitted pursuant to Section 5.02(b)(iii)(B) and (C) so long as the asset
    that is the subject of such sale, lease, transfer or other disposition
    secures such Debt".

         (c)   Section 5.02(b)(iii)(B) is  hereby  amended  to  read  in full as
    follows:

         "(B)(x) Debt secured by Liens permitted by Section 5.02(a)(iv) in an
    aggregate amount (together with the aggregate amount outstanding under
    subsection (C) below) not to exceed $475,000,000 which Debt shall be
    incurred in calendar year 2000 and (y) other Debt secured by Liens permitted
    by Section 5.02(a)(iv) not to exceed $25,000,000 during any consecutive
    12-month period,"

         (d) Section 5.02 (b)(iii)(C) is hereby amended by (i) deleting the
    figure "$385,000,000" in the second line thereof and replacing such figure
    with the phrase "(together with the aggregate amount outstanding under
    subsection (B) above) $475,000,000 " and (ii) deleting the parenthetical
    therein.

         (e) The second column for each fiscal quarter of the year 2000 of the
    tables in the following Sections are hereby amended in their entirety to
    read:

*  less than or equals to

** is greater than

<PAGE>

                                        3

                     (i)      for Section 5.04(a) as follows:

                     "                               2000

                           1/st/ Quarter             2.5:1
                           2/nd/ Quarter             1.25:1
                           3/rd/ Quarter             1.20:1
                           4/th/ Quarter             1.25:1    "

                     and

                     (ii)     for Section 5.04(b) as follows:

                      "                               2000
                          1/st/ Quarter          $25,000,000
                          2/nd/ Quarter          $32,000,000
                          3/rd/ Quarter          $41,000,000
                          4/th/ Quarter          $69,000,000 "

         (f) The third, fourth, fifth and sixth lines of the tables in the
    following Sections are hereby amended in their entirety to read:

                     (i)      for Section 5.04(c) as follows:

                     "March 31, 2000                  3.00:1
                      June 30, 2000                   4.00:1
                      September 30, 2000              4.00:1
                      December 31, 2000               3.00:1"

                     and

                     (ii)     for Section 5.04(d) as follows:

                     "March 31, 2000                  9.00:1
                      June 30, 2000                   10.00:1
                      September 30, 2000              10.00:1
                      December 31, 2000               7.00:1"

         (g) Section 5.04(e) is hereby amended by deleting the ratio "3.75:1" in
    the fourth line thereof and substituting therefor the following:
<PAGE>

                                        4

         "(A) For each fiscal quarter set forth below, the ratio set forth below
    for such fiscal quarter:

                     "Fiscal Quarter Ending In            Ratio
                      -------------------------           ------
                      March 31, 2000                      3.75:1
                      June 30, 2000                       3.00:1
                      September 30, 2000                  2.50:1
                      December 31, 2000                   2.75:1

         and (B) for each fiscal quarter thereafter, 3.75:1."

         (h) The third, fourth, fifth and sixth lines of the tables in the
    following Sections are hereby amended in their entirety to read:

                     (i)      for Section 6.01(p)(i) as follows:

                       "March 31, 2000               $134,000,000
                        June 30, 2000                $145,000,000
                        September 30, 2000           $190,000,000
                        December 31, 2000            $253,000,000"

                     (ii)     for Section 6.01(p)(ii) as follows:

                       "March 31, 2000               $62,400,000
                        June 30, 2000                $57,100,000
                        September 30, 2000           $77,500,000
                        December 31, 2000            $128,000,000"

                     and

                     (iii)    for Section 6.01(p)(v) as follows:

                       "March 31, 2000                 1.75:1
                        June 30, 2000                  1.75:1
                        September 30, 2000             1.25:1
                        December 31, 2000              1.50:1"
<PAGE>

                                        5

         (i) Section 6.01(p)(ii) is also amended by deleting the phrase "the
    fiscal quarter ended June 30, 2000 " in clause (B) therein and replacing
    such phrase with the phrase "the fiscal quarters ended June 30, 2000,
    September 30, 2000 and December 31, 2000 ".

         (j) The third, fourth, fifth and sixth lines of the table in Section
    6.01(q) are hereby amended in their entirety to read as follows:

                     "March 31, 2000              232,000,000
                      June 30, 2000               407,000,000
                      September 30, 2000          402,000,000
                      December 31, 2000           183,000,000"

         (k) The proviso in Section 6.01(q) is amended by (i) adding immediately
    after the word "period " in the first line thereof the phrase "commencing
    with the period ending March 31, 2000 " and (ii) adding at the end thereof
    the following:

         "; provided further that ICG and its Subsidiaries shall be entitled to
            ----------------
    make additional Capital Expenditures, in any such period commencing with the
    period March 31, 2000 and ending with the period September 30, 2000, in an
    amount equal to 10% of the amount permitted in the immediately succeeding
    period in accordance with the chart above and the amount permitted in such
    succeeding period shall be reduced by the amount of such additional Capital
    Expenditures."

         SECTION 2. Acknowledgment. Each of the Lender Parties hereby
                    --------------
acknowledges that it has received the forecast for the Fiscal Year 2000 in
satisfaction of the obligations of each applicable Loan Party pursuant to
Section 5.03(d) of the Credit Agreement.

         SECTION 3.  Conditions of Effectiveness.  This Amendment shall become
                     ---------------------------
effective as of the date first above written when and only when:

                 (a)   the Lead Arranger shall have received the following:

         (i) counterparts of this Amendment executed by the Borrowers, the
    Parent, and the Required Lenders or, as to any of the Lender Parties, advice
    satisfactory to the Lead Arranger that such Lender Party has executed this
    Amendment,

         (ii) any filings, or recordings, or consents of any Persons requested
    by the Lead Arranger in order to create or perfect a security interest in
    favor of the Secured Parties in any Collateral of the Borrowers, and
<PAGE>

                                        6

         (iii) any other items reasonably requested by  any Lender Party;

         (b) all of the accrued fees and expenses of the Agents and the Lender
    Parties (including the accrued fees and expenses of counsel to the Lead
    Arranger, the fees and expenses referred in Sections 7 and 8 of this
    Amendment and all other fees payable in connection with this Amendment)
    shall have been paid in full.

         SECTION 4. Representations and Warranties of the Borrower. The Parent
and each Borrower represent and warrant as follows:

         (a) Each Loan Party and each of its Subsidiaries (i) is a corporation
    duly organized, validly existing and in good standing under the laws of the
    jurisdiction of its incorporation, (ii) is duly qualified and in good
    standing as a foreign corporation in each other jurisdiction in which it
    owns or leases property or in which the conduct of its business requires it
    to so qualify or be licensed except where the failure to so qualify or be
    licensed could not be reasonably likely to have a Material Adverse Effect
    and (iii) has all requisite corporate power and authority (including,
    without limitation, all governmental licenses, permits and other approvals)
    to own or lease and operate its properties and to carry on its business as
    now conducted and as proposed to be conducted.

          (b) The execution, delivery and performance by each Loan Party of this
    Amendment and the Transaction Documents as amended hereby, to which it is or
    is to be a party, are within such Loan Party's corporate powers, have been
    duly authorized by all necessary corporate action, and do not (i) contravene
    such Loan Party's charter or bylaws, (ii) violate any law, rule, regulation
    (including, without limitation, Regulation X of the Board of Governors of
    the Federal Reserve System), order, writ, judgment, injunction, decree,
    determination or award, (iii) conflict with or result in the breach of, or
    constitute a default or require any payment to be made under, any contract,
    loan agreement, indenture, mortgage, deed of trust, lease or other
    instrument binding on or affecting any Loan Party, any of its Subsidiaries
    or any of their properties in such a manner as would be reasonably likely to
    have a Material Adverse Effect or (iv) except for the Liens created under
    the Transaction Documents, result in or require the creation or imposition
    of any Lien upon or with respect to any of the properties of any Loan Party
    or any of its Subsidiaries. No Loan Party or any of its Subsidiaries is in
    violation of any such law, rule, regulation, order, writ, judgment,
    injunction, decree, determination or award or in breach of any such
    contract, loan agreement, indenture, mortgage, deed of trust, lease or other
    instrument, the violation or breach of which could be reasonably likely to
    have a Material Adverse Effect.

         (c) No authorization or approval or other action by, and no notice to
    or filing with, any governmental authority or regulatory body or any other
    third party is required for the due execution, delivery or performance by
    any Loan Party of this Amendment or any of the Transaction Documents, as
    amended hereby, to which it is or is to be a party.
<PAGE>

                                        7

         (d) This Amendment has been duly executed and delivered by the Parent
    and the Borrowers. This Amendment and each of the other Transaction
    Documents, as amended hereby, to which any Loan Party is a party are legal,
    valid and binding obligations of each Loan Party thereto, enforceable
    against such Loan Party in accordance with their respective terms.

         (e) There is no action, suit, investigation, litigation or proceeding
    affecting any Loan Party or any of its Subsidiaries, including any
    Environmental Action, pending or threatened before any court, governmental
    agency or arbitrator that (i) could be reasonably likely to have a Material
    Adverse Effect or (ii) purports to affect the legality, validity or
    enforceability of this Amendment or any of the other Transaction Documents
    as amended hereby.

         (f) All filings and other actions necessary or desirable to perfect and
    protect the security interest in the Collateral created under the Collateral
    Documents have been duly made or taken and are in full force and effect, and
    the Collateral Documents create in favor of the Collateral Agent for the
    benefit of the Secured Parties a valid and, together with such filings and
    other actions, perfected first priority security interest in the Collateral,
    securing the payment of the Secured Obligations, and all filings and other
    actions necessary or desirable to perfect and protect such security interest
    have been duly taken. The Loan Parties are the legal and beneficial owners
    of the Collateral free and clear of any Lien, except for the liens and
    security interests created or permitted under the Loan Documents.

         (g) The representations and warranties set forth in each of the
    Transaction Documents are correct on and as of this date, before and after
    giving effect to this Amendment, as though made on and as of such date.

         (h) No event has occurred and is continuing that constitutes a Default.
    No event has occurred and is continuing that constitutes, or would, with the
    lapse of time or the giving of notice constitute, a default under any
    material agreement to which any Loan Party is a party.

         SECTION 5. Reference to and Effect on the Credit Agreement, the
                    ----------------------------------------------------
Security Agreement, the Notes and the Transaction Documents. (a) On and after
-----------------------------------------------------------
the effectiveness of this Amendment, each reference in the Credit Agreement to
"this Agreement", "hereunder", "hereof" or words of like import referring to the
Credit Agreement, and each reference in the, Notes and each of the other
Transaction Documents to "the Credit Agreement", "thereunder", "thereof" or
words of like import referring to the Credit Agreement, shall mean and be a
reference to the Credit Agreement, as amended by this Amendment.
<PAGE>

                                        8

         (b) On and after the effectiveness of this Amendment, each reference in
    the Security Agreement to "this Agreement", "hereunder", "hereof" or words
    of like import referring to the Security Agreement, and each reference in
    the Credit Agreement, Notes and each of the other Transaction Documents to
    "the Security Agreement", "thereunder", "thereof" or words of like import
    referring to the Security Agreement, shall mean and be a reference to the
    Security Agreement, as amended by this Amendment.

         (c) The Credit Agreement, the Security Agreement, the Notes and each of
    the other Transaction Documents, as specifically amended by this Amendment,
    are and shall continue to be in full force and effect and are hereby in all
    respects ratified and confirmed. Without limiting the generality of the
    foregoing, the Collateral Documents and all of the Collateral described
    therein do and shall continue to secure the payment of all Obligations of
    the Loan Parties under the Transaction Documents, in each case as amended by
    this Amendment.

         (d) The execution, delivery and effectiveness of this Amendment shall
    not, except as expressly provided herein, operate as a waiver of any right,
    power or remedy of any Lender or the Agents under any of the Transaction
    Documents, nor constitute a waiver of any provision of any of the
    Transaction Documents.

         SECTION 6. Consent of the Parent. The Parent, as guarantor under the
                    ---------------------
Parent Guaranty, hereby consents to this Amendment and hereby confirms and
agrees that notwithstanding the effectiveness of this Amendment, the Parent
Guaranty is, and shall continue to be, in full force and effect and is hereby
ratified and confirmed in all respects, except that, on and after the
effectiveness of this Amendment, (i) each reference in the Parent Guaranty to
the "Credit Agreement", "thereunder", "thereof" or words of like import shall
mean and be a reference to the Credit Agreement, as amended by this Amendment,
and (ii) each reference in the Parent Guaranty to the "Security Agreement",
""thereunder", thereof or words of like import shall mean and be a reference to
the Security Agreement as amended by this Amendment.

         SECTION 7. Costs and Expenses. The Borrowers agree jointly and
                    ------------------
severally to pay on demand all reasonable costs and expenses of the Lead
Arranger in connection with the preparation, execution, delivery and
administration, modification and amendment of this Amendment and the other
instruments and documents to be delivered hereunder (including, without
limitation, the reasonable fees and expenses of counsel for the Lead Arranger)
in accordance with the terms of Section 9.04 of the Credit Agreement.

         SECTION 8. Amendment Fee. The Borrowers agree to pay an amount equal to
                    -------------
0.25% of the sum of (i) the aggregate Tranche A Term Commitments held by those
Lenders that have, on or prior to February 11, 2000, executed this Amendment,
(ii) the aggregate Tranche B Term Commitments held by those Lenders that have,
on or prior to February 11, 2000, executed this Amendment and (iii) the
aggregate Working Capital Commitments held by those Lenders
<PAGE>

                                       9

that have, on or prior to February 11, 2000, executed this Amendment, payable to
the Administrative Agent for the account of such Lenders, ratably in accordance
with their respective interests in such Tranche A Term Commitments, Tranche B
Term Commitments and Working Capital Commitments.

         SECTION 9. Execution in Counterparts. This Amendment may be executed in
                    -------------------------
any number of counterparts and by different parties hereto in separate
counterparts, each of which when so executed shall be deemed to be an original
and all of which taken together shall constitute but one and the same agreement.
Delivery of an executed counterpart of a signature page to this Amendment by
telecopier shall be effective as delivery of a manually executed counterpart of
this Amendment.

         SECTION 10. Governing Law.  This  Amendment shall be  governed  by, and
                     -------------
construed in accordance with, the laws of the State of New York.
<PAGE>

         IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be
executed by their respective officers thereunto duly authorized, as of the date
first above written.

                                            ICG EQUIPMENT, INC., as Borrower

                                            By /s/ Don Teague
                                              ------------------------------
                                              Title:  Executive Vice President,
                                                      General Counsel and
                                                      Secretary

                                            ICG NETAHEAD, INC., as Borrower

                                            By /s/ Don Teague
                                              ------------------------------
                                              Title:  Executive Vice President,
                                                      General Counsel and
                                                      Secretary

                                            ICG SERVICES, INC., as Parent
                                            Guarantor

                                            By /s/ Don Teague
                                              ------------------------------
                                              Title:  Executive Vice President,
                                                      General Counsel and
                                                      Secretary
<PAGE>

                                            MORGAN STANLEY SENIOR FUNDING, INC.,
                                              as Sole Book-Runner, Lead Arranger
                                              and Lender Party

                                            By /s/ T. Morgan Edwards II
                                              ------------------------------
                                              Title: T. MORGAN EDWARDS II
                                                     VICE PRESIDENT
<PAGE>

                                            ROYAL BANK OF CANADA,
                                             as Administrative Agent, Collateral
                                             Agent and Lender Party

                                            By /s/ Kevin K. Cornwell
                                              ------------------------------
                                              Title: Managing Director
<PAGE>

                                            BANK OF AMERICA, N.A.,
                                              as Documentation Agent and  Lender
                                              Party

                                            By /s/ Julie A. Schell
                                              ------------------------------
                                              Title: JULIE A. SCHELL
                                                     VICE PRESIDENT
<PAGE>

                                            BARCLAYS BANK PLC
                                              as Co-Documentation Agent and
                                              Lender Party

                                            By /s/ Daniele Iacovone
                                              ------------------------------
                                              Title: Daniele Iacovone
                                                     Associate Director
<PAGE>

                          Initial Lenders

                          PARIBAS, LOS ANGELES AGENCY

                          By  /s/ Darlynn Ernst Kitcher/  /s/ Thomas G. Brandt
                            ----------------------------------------------------
                          Title:  Darlynn Ernst Kitcher       Thomas G. Brandt
                                  Vice President              Managing Director

<PAGE>

                                            FINOVA CAPITAL CORPORATION

                                            By /s/ Andrew J. Pluta
                                              ------------------------------
                                              Title: Vice President
<PAGE>

                                            FIRST UNION NATIONAL BANK

                                            By /s/ Mark L. Cook
                                              ------------------------------
                                              Title: Senior Vice President
<PAGE>

                                            GENERAL ELECTRIC CAPITAL
                                            CORPORATION

                                            By /s/ Thomas P. Waters
                                              ------------------------------
                                              Title: Senior Vice President
<PAGE>

                                            IBM CREDIT
                                            as a Lender

                                            By /s/ Thomas S. Curcio
                                              ------------------------------
                                              Name:  Thomas S. Curcio
                                              Title: Manager of Credit

                                     S-31
<PAGE>

                                            STEIN ROE FLOATING RATE LIMITED
                                            LIABILITY COMPANY

                                            By /s/ Brian W. Good
                                              ------------------------------
                                              Title: Brian W. Good
                                                     Vice President,
                                                     Stein Roe & Farnham
                                                     Incorporated, as Advisor
                                                     to the Stien Roe Floating
                                                     Rate Limited Liability
                                                     Company

<PAGE>

                                            STEIN ROE AND FARNHAM
                                            INCORPORATED
                                            AS AGENT FOR KEYPORT LIFE
                                            INSURANCE COMPANY

                                            By /s/ Brian W. Good
                                              ------------------------------
                                              Title:  Brian W. Good
                                                      Vice President and
                                                      Portfolio Manager

<PAGE>

                                          STEIN ROE FARNHAM CLO 1 LTD.
                                          By: Stein Roe & Farnham Incorporated,
                                              as Portfolio Manager

                                          By /s/ Brian W. Good
                                            ------------------------------
                                              Title: Brian W. Good
                                                     Vice President and
                                                     Portfolio Manager

<PAGE>

                                            PILGRIM PRIME RATE TRUST
                                            By: Pilgrim Investment, Inc., as its
                                                Investment Manager

                                            By /s/ Robert L. Wilson
                                              ------------------------------
                                              Title: Robert L. Wilson
                                                     Vice President

<PAGE>

                                            KZH HIGHLAND-2 LLC

                                            By /s/ Peter Chin
                                              ------------------------------
                                              Title:Peter Chin
                                                    Authorized Agent

<PAGE>

                                            PILGRIM CLO 1999 - 1 LTD.
                                              By:  Pilgrim Investments, Inc., as
                                                   its investment manager

                                            By /s/ Robert L. Wilson
                                              ------------------------------
                                              Title:  Robert L. Wilson
                                                      Vice President
<PAGE>

                                            FRANKLIN FLOATING RATE TRUST

                                            By /s/ Chauncey Lufkin
                                              ------------------------------
                                              Title: Chauncey Lufkin
                                                     Vice President
<PAGE>

                                            ELT LTD.

                                            By /s/ Kelly C. Walker
                                              ------------------------------
                                              Title: Kelly C. Walker
                                                     Authorized Agent
<PAGE>

                                   ELF FUNDING TRUST 1
                                   By: Highland Capital Management, L.P.
                                        As Collateral Managers

                                   By /s/ Mark K. Okade
                                      ------------------------------
                                   Name:  Mark K. Okade CFA
                                   Title: Executive Vice President
                                          Highland Capital Management, L.P.

                                   PAMCO CAYMAN LTD.
                                   By: Highland Capital Management, L.P.
                                     As Collateral Manager

                                   By /s/ Mark K. Okade
                                      ------------------------------
                                      Name:  Mark K. Okade CFA
                                      Title: Executive Vice President
                                             Highland Capital Management, L.P.
<PAGE>

                                   GLENEAGLES TRADING LLC

                                   By /s/ Kelly C. Walker
                                     ------------------------------
                                     Name:  Kelly C. Walker
                                     Title:  Vice President

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