Document:

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                                                                 EXHIBIT 10.2(b)
                                AMENDMENT NO. 1

     AMENDMENT NO. 1 dated as of December 17, 1999, between MEDIACOM ILLINOIS
LLC, a limited liability company duly organized and validly existing under the
laws of the State of Delaware ("Mediacom Illinois"); MEDIACOM INDIANA LLC, a
                                -----------------
limited liability company duly organized and validly existing under the laws of
the State of Delaware ("Mediacom Indiana"); MEDIACOM IOWA LLC, a limited
                        ----------------
liability company duly organized and validly existing under the laws of the
State of Delaware ("Mediacom Iowa"); MEDIACOM MINNESOTA LLC, a limited liability
                    -------------
company duly organized and validly existing under the laws of the State of
Delaware ("Mediacom Minnesota"); MEDIACOM WISCONSIN LLC, a limited liability
           ------------------
company duly organized and validly existing under the laws of the State of
Delaware ("Mediacom Wisconsin"); and ZYLSTRA COMMUNICATIONS CORP., a corporation
           ------------------
validly existing under the laws of the State of Minnesota ("Zylstra", and,
                                                            -------
together with Mediacom Illinois, Mediacom Indiana, Mediacom Iowa, Mediacom
Minnesota and Mediacom Wisconsin, the "Borrowers"), the lenders party thereto
                                       ---------
(the "Lenders") and The Chase Manhattan Bank, as Administrative Agent for the
      -------
Lenders.

     The Borrowers, the Lenders and the Administrative Agent are parties to a
Credit Agreement dated as of November 5, 1999 ( the "Credit Agreement"),
                                                     ----------------
providing, subject to the terms and conditions thereof, for extensions of credit
to be made by said Lenders to the Borrowers. The parties wish to amend the
Credit Agreement in certain respects, and accordingly, the parties hereto hereby
agree as follows:

     Section 1. Definitions. Except as otherwise defined in this Amendment No.
                -----------
1, terms defined in the Credit Agreement are used herein as defined therein.

     Section 2. Amendments. Upon the execution and delivery of this Amendment
                ----------
No. 1 by the Borrowers and Majority Lenders, but effective as of the date
hereof, the Credit Agreement shall be amended as follows:

     2.01. References in the Credit Agreement (including references to the
Credit Agreement as amended hereby) to "this Agreement" (and indirect references
such as "hereunder", "hereby", "herein" and "hereof") shall be deemed to be
references to the Credit Agreement as amended hereby.

     2.02. Section 8.13 of the Credit Agreement is hereby amended to read in its
entirety as follows:

     "8.13 Interest Rate Protection Agreements. The Borrowers will, on or prior
           -----------------------------------
   to April 30, 2000, enter into, and thereafter maintain in full force and
   effect, one or more Interest Rate Protection Agreements with one or more of
   the Lenders or their affiliates (and/or with a bank or other financial
   institution having capital, surplus and undivided profits of at least
   $500,000,000), that effectively enables the Borrowers (in a manner
   satisfactory to the Majority Lenders) to protect themselves, in a manner and
   on terms reasonably satisfactory to the Majority Lenders, against adverse
   fluctuations in the three-

                                 Amendment No. 1
                                 ---------------
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                                      -2-

     month London interbank offered rates as to a notional principal amount
     which, together with that portion of the aggregate outstanding principal
     amount of Indebtedness of the Borrowers bearing a fixed rate of interest,
     shall in the aggregate be at least equal to 50% of the aggregate
     outstanding principal amount of the Indebtedness (including Affiliate
     Subordinated Indebtedness) of the Borrowers."

  Section 3.  Miscellaneous.  Except as herein provided, the Credit Agreement
              -------------
shall remain unchanged and in full force and effect.  This Amendment No. 1 may
be executed in any number of counterparts, all of which taken together shall
constitute one and the same amendatory instrument and any of the parties hereto
may execute this Amendment No. 1 by signing any such counterpart.  This
Amendment No. 1 shall be governed by, and construed in accordance with, the law
of the State of New York.

                                 Amendment No. 1
                                 ---------------
<PAGE>

                                      -3-

  IN WITNESS WHEREOF, the parties hereto have caused this Amendment No. 1 to be
duly executed and delivered as of the day and year first above written.

                              MEDIACOM ILLINOIS LLC
                              MEDIACOM INDIANA LLC
                              MEDIACOM IOWA LLC
                              MEDIACOM MINNESOTA LLC
                              MEDIACOM WISCONSIN LLC

                              By  MEDIACOM LLC, a Member

                              By:_________________________
                                 Name:
                                 Title:

                              ZYLSTRA COMMUNICATIONS CORP.

                              By:_________________________
                                 Name:
                                 Title:

                              THE CHASE MANHATTAN BANK,
                              as Administrative Agent

                              By:_________________________
                                 Name:
                                 Title:

                                 Amendment No. 1
                                 ---------------<PAGE>

                                                                 EXHIBIT 10.2(c)
                                AMENDMENT NO. 2

  AMENDMENT NO. 2 dated as of February 4, 2000, between MEDIACOM ILLINOIS LLC, a
limited liability company duly organized and validly existing under the laws of
the State of Delaware ("Mediacom Illinois"); MEDIACOM INDIANA LLC, a limited
                        -----------------
liability company duly organized and validly existing under the laws of the
State of Delaware ("Mediacom Indiana"); MEDIACOM IOWA LLC, a limited liability
                    ----------------
company duly organized and validly existing under the laws of the State of
Delaware ("Mediacom Iowa"); MEDIACOM MINNESOTA LLC, a limited liability company
           -------------
duly organized and validly existing under the laws of the State of Delaware

("Mediacom Minnesota"); MEDIACOM WISCONSIN LLC, a limited liability company duly
--------------------
organized and validly existing under the laws of the State of Delaware

("Mediacom Wisconsin"); and ZYLSTRA COMMUNICATIONS CORP., a corporation validly
--------------------
existing under the laws of the State of Minnesota ("Zylstra", and, together with
                                                    -------
Mediacom Illinois, Mediacom Indiana, Mediacom Iowa, Mediacom Minnesota and
Mediacom Wisconsin, the "Borrowers"), the lenders party thereto (the "Lenders")
                         ---------                                    -------
and The Chase Manhattan Bank, as Administrative Agent for the Lenders.

  The Borrowers, the Lenders and the Administrative Agent are parties to a
Credit Agreement dated as of November 5, 1999 (as amended by Amendment No. 1
thereto dated as of December 17, 1999, the "Credit Agreement"), providing,
                                            ----------------
subject to the terms and conditions thereof, for extensions of credit to be made
by said Lenders to the Borrowers. The parties wish to amend the Credit Agreement
to provide for the replacement of Mediacom Management Corporation by Mediacom
Communications Corporation as Manager of the Borrowers, and accordingly, the
parties hereto hereby agree as follows:

          Section 1.  Definitions.  Except as otherwise defined in this
                      -----------
Amendment No. 2, terms defined in the Credit Agreement are used herein as
defined therein.

          Section 2.  Amendments.  Subject to the satisfaction of the conditions
                      ----------
specified in Section 3 hereof, but effective as of the date hereof, the Credit
Agreement shall be amended as follows:

          2.01. References in the Credit Agreement (including references to the
Credit Agreement as amended hereby) to "this Agreement" (and indirect references
such as "hereunder", "hereby", "herein" and "hereof") shall be deemed to be
references to the Credit Agreement as amended hereby.

          2.02.  Definitions.  Section 1.01 of the Credit Agreement shall be
                 -----------
amended by amending the following definitions to read in their entirety as
follows:

          "Management Agreements" shall mean, collectively, (a) the Management
           ---------------------
     Agreement dated February 4, 2000 between Mediacom Illinois and Mediacom
     Communications Corporation, (b) the Management Agreement dated February 4,
     2000 between Mediacom Indiana and Mediacom Communications Corporation, (c)
     the Management Agreement dated February 4, 2000 between Mediacom Iowa and

                                 Amendment No. 2
                                 ---------------
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                                      -2-

     Mediacom Communications Corporation, (d) the Management Agreement dated
     February 4, 2000 between Mediacom Minnesota and Mediacom Communications
     Corporation, (e) the Management Agreement dated February 4, 2000 between
     Mediacom Wisconsin and Mediacom Communications Corporation, and (f) the
     Management Agreement dated February 4, 2000 between Zylstra and Mediacom
     Communications Corporation in each case as the same shall, subject to
     Section 8.19 hereof, be modified and supplemented and in effect from time
     to time.

          "Manager" shall mean Mediacom Communications Corporation, or any
           -------
     successor in such capacity as manager of the Borrowers.

          "Obligors" shall mean, collectively, the Borrowers, Mediacom, Mediacom
           --------
     Communications Corporation and, effective upon execution and delivery of
     any Subsidiary Guarantee Agreement, each Subsidiary of the Borrowers so
     executing and delivering such Subsidiary Guarantee Agreement.

          2.03.  Events of Default.  Section 9.01(l)(ii) of the Credit Agreement
                 -----------------
shall be amended to read in its entirety as follows:

         "(ii) Mediacom Communications Corporation or Mediacom shall cease to
     act as Manager of the Borrowers;"

          Section 3.  Conditions.
                      ----------

          3.01.  Execution.  This Amendment No. 2 shall have been executed and
                 ---------
delivered by the Borrowers, the Administrative Agent and the Majority Lenders.

          3.02.  Management Fee Subordination Agreement.  The Management Fee
                 --------------------------------------
Subordination Agreement shall have been duly executed and delivered by the
Borrowers, Mediacom Communications Corporation and the Administrative Agent.

          3.03.  Organizational Documents.  The Administrative Agent shall have
                 ------------------------
received a certified copy of the charter and by-laws of Mediacom Communications
Corporation and of corporate authority for Mediacom Communications Corporation
(including, without limitation, board of directors resolutions, and evidence of
incumbency, including specimen signatures of the officers of Mediacom
Communications Corporation) with respect to the execution, delivery and
performance of the Management Fee Subordination Agreement (and the
Administrative Agent and each Lender may conclusively rely on such certificate
until it receives notice in writing from Mediacom Communications Corporation to
the contrary).

          3.04.  Replacement of Existing Management Agreements.  The
                 ---------------------------------------------
Administrative Agent shall have received evidence that each of the management
agreements between the

                                 Amendment No. 2
                                 ---------------
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                                      -3-

Borrowers and Mediacom Management Corporation (the "Existing Management
                                                    -------------------
Agreements") shall be terminated concurrently with the execution and delivery of
----------
this Amendment No. 2 by the Borrowers, the Administrative Agent and the Majority
Lenders and replaced with management agreements between the Borrowers and
Mediacom Communications Corporation, each with terms substantially similar to
the Existing Management Agreements and subject to any variations permitted by
Section 8.19 of the Credit Agreement.

          3.05.  Opinion of Counsel to the Obligors.  An opinion of Cooperman
                 ----------------------------------
Levitt Winikoff Lester & Newman, P.C., counsel to the Obligors, as to the due
execution, delivery, legality and enforceability of the Management Fee
Subordination Agreement referred to in Section 3.02 above, and covering such
other matters as the Administrative Agent or any Lender may reasonably request
(and the Borrowers hereby instruct such counsel to deliver such opinion to the
Lenders and the Administrative Agent).

          Section 4.  Miscellaneous.  Except as herein provided, the Credit
                      -------------
Agreement shall remain unchanged and in full force and effect.  This Amendment
No. 2 may be executed in any number of counterparts, all of which taken together
shall constitute one and the same amendatory instrument and any of the parties
hereto may execute this Amendment No. 2 by signing any such counterpart.  This
Amendment No. 2 shall be governed by, and construed in accordance with, the law
of the State of New York.

                                 Amendment No. 2
                                 ---------------
<PAGE>

                                      -4-

  IN WITNESS WHEREOF, the parties hereto have caused this Amendment No. 2 to be
duly executed and delivered as of the day and year first above written.

                               MEDIACOM ILLINOIS LLC
                               MEDIACOM INDIANA LLC
                               MEDIACOM IOWA LLC
                               MEDIACOM MINNESOTA LLC
                               MEDIACOM WISCONSIN LLC

                               By  MEDIACOM LLC, a Member

                               By:_________________________
                                  Name:
                                  Title:

                               ZYLSTRA COMMUNICATIONS CORP.

                               By:_________________________
                                  Name:
                                  Title:

                               THE CHASE MANHATTAN BANK,
                               individually and as Administrative Agent

                               By:_________________________
                                  Name:
                                  Title:

                               BANK OF MONTREAL

                               By:_________________________
                                  Name:
                                  Title:

                                 Amendment No. 2
                                 ---------------
<PAGE>

                                      -5-

                              FIRST UNION NATIONAL BANK

                              By:_________________________
                                 Name:
                                 Title:

                              CIBC INC.

                              By:_________________________
                                 Name:
                                 Title:

                              CREDIT SUISSE FIRST BOSTON

                              By:_________________________
                                 Name:
                                 Title:

                              By:_________________________
                                 Name:

                              DRESDNER BANK AG NEW YORK AND GRAND CAYMAN
                              BRANCHES

                              By:_________________________
                                 Name:
                                 Title:

                              By:_________________________
                                 Name:
                                 Title:

                                 Amendment No. 2
                                 ---------------
<PAGE>

                                      -6-

                              FLEET NATIONAL BANK

                              By:_________________________
                                 Name:
                                 Title:

                              MELLON BANK, N.A.

                              By:_________________________
                                 Name:
                                 Title:

                              PNC BANK, NATIONAL ASSOCIATION

                              By:_________________________
                                 Name:
                                 Title:

                              THE BANK OF NOVA SCOTIA

                              By:_________________________
                                 Name:
                                 Title:

                              SUNTRUST BANK, CENTRAL FLORIDA, N.A.

                              By:_________________________
                                 Name:
                                 Title:

                                 Amendment No. 2
                                 ---------------
<PAGE>

                                      -7-

                              BANK OF AMERICA, N.A.

                              By:__________________________
                                 Name:
                                 Title:

                              THE FUJI BANK, LIMITED

                              By:______________________________
                                 Name:
                                 Title:

                              MEES PIERSON CAPITAL CORP.

                              By:______________________________
                                 Name:
                                 Title:

                              UNION BANK OF CALIFORNIA, N.A.

                              By:______________________________
                                 Name:
                                 Title:

                              CITIBANK, N.A.

                              By:_____________________________
                                 Name:
                                 Title:

                                 Amendment No. 2
                                 ---------------
<PAGE>

                                      -8-

                              SOCIETE GENERALE

                              By:____________________________
                                 Name:
                                 Title:

                              GENERAL ELECTRIC CAPITAL CORPORATION

                              By:____________________________
                                 Name:
                                 Title:

                              CREDIT AGRICOLE INDOSUEZ

                              By:____________________________
                                 Name:
                                 Title:

                              By:____________________________
                                 Name:
                                 Title:

                              KZH SOLEIL LLC

                              By:____________________________
                                 Name:
                                 Title:

                              KZH SOLEIL-2 LLC

                              By:____________________________
                                 Name:
                                 Title:

                                 Amendment No. 2
                                 ---------------
<PAGE>

                                      -9-

                              FRANKLIN FLOATING RATE TRUST

                              By:____________________________
                                 Name:
                                 Title:

                              ELC (CAYMAN) LTD. 1999-III

                              By:____________________________
                                 Name:
                                 Title:

                                 Amendment No. 2
                                 ---------------

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