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                                EXHIBIT 10.51

General Release, Covenant Not to Sue and Agreement, dated as of January 1, 2000,
               between ICG communications, Inc. and John Kane.

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              GENERAL RELEASE, COVENANT NOT TO SUE AND AGREEMENT

     This GENERAL RELEASE, COVENANT NOT TO SUE AND AGREEMENT (this "Agreement")
is by and between ICG COMMUNICATIONS, INC., a Delaware corporation (which
entity, together with its parents, subsidiaries and affiliates is referred to
herein as the "Company"), and John Kane ("Employee").

     WHEREAS, the Company and Employee agree to terminate the employment
relationship between them; and

     WHEREAS, the Company and Employee agree to settle and release all actual
and potential claims they may have against one another arising out of or in
connection with the employment of Employee by the Company, the terms and
conditions of Employee's employment, the termination of such employment and any
other action, event or matter prior to the date of this Agreement; and

     WHEREAS, Employee has substantial knowledge of the Company's operations,
customers, vendors, suppliers and other proprietary and confidential
information, and the Company desires for Employee to agree to protect such
confidential information from disclosure and to make certain other covenants and
agreements with the Company.

     NOW, THEREFORE, in consideration of the mutual promises, covenants and
agreements contained herein and for other good and valuable consideration, the
parties agree as follows:

     1.   TERMINATION OF EMPLOYMENT RELATIONSHIP. This Agreement evidences the
termination of the employment relationship between Employee and the Company
effective as of January 1, 2000 ("Termination Date"). Employee shall return all
property in the possession of Employee which is owned by the Company upon the
Termination Date.

     2.   RESIGNATION OF POSITIONS. Employee does hereby resign from all officer
and director positions with the Company effective as of the Termination Date.

     3.   TERMINATION OF AGREEMENTS. As of the Termination Date, the Employment
Agreement between Employee and Company dated as of May 19, 1999, as amended, and
all other agreements between Company and Employee (excepting solely the
agreements relating to the stock options referred to in Section 4.4 below and
Exhibit A hereto) are terminated and all rights thereunder are rescinded and
superseded by the terms and conditions of this Agreement. For the avoidance of
doubt, insurance coverage of Employee under the Company's applicable Directors'
& Officers' policies, if any, shall be excepted from this Section 3.

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     4.   PAYMENT TO EMPLOYEE.

          4.1  Conditioned upon the full execution of this Agreement, and the
lapse of the seven (7) day period described in Section 12 below, the Company
shall pay Employee on or before January 13, 2000 the total sum of One Million
Nine Hundred Thirty-One Thousand Two Hundred Seventy-One and 57/100 Dollars
($1,931,271.57), less applicable withholding taxes and other governmental
obligations. This amount represents severance in the amount of $931,271.57, less
applicable withholding taxes and other governmental obligations, a bonus in the
amount of $750,000, less applicable taxes and governmental obligations, for his
services in connection with the sale of ICG Fiber Optic Technologies, Inc. and a
bonus in the amount of $250,000, less applicable taxes and governmental
obligations, for his services in connection with the sale of ICG Satellite
Services, Inc.

          4.2  The Company will permit Employee to continue participation in the
Company's Medical/Dental/Vision benefit plans at Employee's present level
through and including January 31, 2000, at which time all such benefits shall be
terminated. At that time, Employee may be eligible to continue appropriate
coverage pursuant to COBRA, subject to COBRA rules and provisions. Conditioned
upon the full execution of this Agreement, and the lapse of the seven (7) day
period described in Section 12 below, the Company shall pay Employee the net sum
of Eight Thousand Four Hundred Dollars and 00/100 Dollars ($8,400.00) on or
before January 13, 2000, which represents the approximate equivalent of 12
months' payments for coverage under COBRA. It is Employee's responsibility to
pay these amounts and to obtain the appropriate coverage if the Employee so
desires.

          4.3  No additional time for vacation or sick leave or personal time
shall accrue after Termination Date. Employee's participation in the 401(k) and,
if applicable, 401(k) Wrap, and Employee Stock Purchase Plan shall cease as of
the Termination Date. Employee's participation in the Company benefit programs
for Basic Life Insurance, Accidental Death and Dismemberment Insurance ("AD&D"),
Dependent Life Insurance, Short Term Disability benefits, Long Term Disability
Insurance, and any participation in the Flexible Spending Cafeteria Plan,
Voluntary Life Insurance, Voluntary AD&D, Pre-Paid Legal Insurance and Employee
Assistance Program, and all other Company programs and benefits will terminate
as of the Termination Date, subject to continuation rights, if any, required by
law. Notwithstanding the foregoing, the Company will transfer to Employee the
life insurance policy it has taken out on his life to the extent permitted by
the terms of the policy. Employee shall be solely responsible for making premium
payments on such policy.

          4.4  Conditioned upon the full execution of this Agreement and the
lapse of the seven (7) day period described in Section 12 below, the Company
will fully vest all stock options granted to Employee under the Company's Stock
Option Plans that are unvested as of the Termination Date. A summary of such
unvested options and all other options granted to Employee is set forth on the
Personnel Option Status attached as Exhibit A hereto. Employee will be entitled
to exercise existing stock options for a period of six (6) months after the
Termination Date in accordance with the plans and agreements relating to such
options. Any

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options not exercised prior to July 1, 2000 shall terminate and Employee shall
have no rights as to options not exercised prior to such date.

          4.5  Conditioned upon the full execution of this Agreement and the
lapse of the seven (7) day period described in Section 12 below, the Company
will not enforce its right to seek reimbursement of $280,000, which was loaned
by the Company to Employee and evidenced by Promissory Note dated August 6, 1999
in the principal amount of $200,000 and Promissory Note dated December 10, 1999
in the principal amount of $80,000 and such Promissory Notes shall be cancelled.
The Company shall provide copies of such notes marked "cancelled" to Employee.

          4.6  No other amounts except those specified in Sections 4 and 5 will
be owing to or paid to Employee, including, without limitation, any bonus
payments earned or to be earned prior to or after the Termination Date.

     5.   OTHER PAYMENTS. The consideration described above in Section 2 is
separate from the payment by the Company to Employee of accrued and unused
vacation pay of 295.25 hours in the amount of Sixty Thousand Three Hundred
Twenty-Eight and 43/100 Dollars ($60,328.43) and regular salary or wages for
work performed through the Termination Date, less applicable withholding taxes
and obligations ("Other Payments"). Employee's receipt of the Other Payments is
not conditioned upon signing this Agreement. Employee shall receive all Other
Payments to which Employee is entitled regardless of whether Employee signs this
Agreement.

     6.   COOPERATION CLAUSE. Upon reasonable request, the Employee shall make
himself available to the Company to furnish full and truthful information
concerning any event which took place during Employee's employment. Upon
reasonable request, as deemed necessary by the Company, the Employee shall make
himself available to the Company to furnish full and truthful consultations
concerning any potential or actual litigation. Employee shall furnish the
information as soon as is practical after a request from the Company is
received. The Company shall reimburse Employee for the reasonable cost of all
Employee's travel, lodging, meals and any loss of compensation suffered by
Employee from his current employer as a result of time spent furnishing
information under this clause.

     7.   NON-COMPETE AND NON-INTERFERENCE.

          7.1  For a period of twelve (12) months after the Termination Date,
Employee shall not, directly or indirectly, own, manage, operate, control, be
employed by, or participate in the ownership, management, operation or control
of, a business that is engaged in the same business as the Company within any
area constituting, during the term of Employee's employment or at the time
Employee's employment is terminated, a Relevant Area. A "Relevant Area" shall be
defined for the purposes of this Agreement as any area located within, or within
fifty (50) miles of, the legal boundaries or limits of any city within which the
Company

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is engaged in business or in which the Company has publicly announced or
privately disclosed to Employee that it plans to engage in business.

          7.2. For a period of two (2) years after the Termination Date,
Employee shall not (i) directly or indirectly cause or attempt to cause any
employee of the Company or any of its affiliates to leave the employ of the
Company or any affiliate, (ii) in any way interfere with the relationship
between the Company and any employee or between an affiliate and any employee of
the affiliate, or (iii) interfere or attempt to interfere with any transaction
in which the Company or any of its affiliates was involved prior to the
Termination Date.

          7.3  Employee agrees that, because of the nature and sensitivity of
the information to which he was privy and because of the nature and scope of the
Company's business, the restrictions contained in this Section 7 are fair and
reasonable.

     8.   CONFIDENTIAL INFORMATION.

          8.1  The relationship between the Company and Employee is one of
confidence and trust. This relationship and the rights granted and duties
imposed by this Section shall continue until a date ten (10) years from the
Termination Date.

          8.2  As used in this Agreement (i) "Confidential Information" means
information disclosed to or acquired by Employee about the Company's plans,
products, processes and services, including information relating to research,
development, inventions, manufacturing, purchasing, accounting, engineering,
marketing, merchandising, selling, pricing, tariffed or contractual terms,
customer lists and prospect lists and other market information, with respect to
any of the Company's business activities; and (ii) "Inventions" means any
inventions, discoveries, concepts and ideas, whether patentable or not,
including, without limitation, processes, methods, formulas, and techniques (as
well as related improvements and knowledge) that are based on or related to
Confidential Information, that pertain in any manner to the Company's
technology, expertise or business and that are made or conceived by Employee,
either solely or jointly with others, and while employed by the Company or
within six (6) months after the Termination Date, whether or not made or
conceived during working hours or with the use of the Company's facilities,
materials or personnel.

          8.3  Employee agrees that he shall at no time disclose any
Confidential Information to any person, firm or corporation to any extent or for
any reason or purpose or use any Confidential Information for any purpose other
than the conduct of the Company's business.

          8.4  Any Confidential Information that was directly or indirectly
originated, developed or perfected to any degree by Employee during the term of
his employment by the Company shall be and remain the sole property of the
Company and shall be deemed trade secrets of the Company.

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          8.5  Upon the Termination Date, Employee or his legal representative
shall deliver to the Company all originals and all duplicates and/or copies of
all documents, records, notebooks, and similar repositories of or containing
Confidential Information then in his possession, whether prepared by him or not.

          8.6  Employee agrees that the covenants and agreements contained in
this Section 8 are fair and reasonable and that no waiver or modification of
this Section or any covenant or condition set forth herein shall be valid unless
set forth in writing and duly executed by the parties hereto.

     9.   INJUNCTIVE RELIEF. Upon a material breach or threatened material
breach by Employee of any of the provisions of Sections 7 or 8 of this
Agreement, the Company shall be entitled to an injunction restraining Employee
from such breach. Nothing herein shall be construed as prohibiting the Company
from pursuing any other remedies for such breach or threatened breach, including
recovery of damages from Employee.

     10.  NON-DISPARAGEMENT. Employee agrees that Employee will not make any
false, disparaging or misleading statements to any person or entity regarding
the Company or any of its officers, directors or employees. The Company agrees
that it will not condone the making of any false, disparaging or misleading
statements to any person or entity regarding Employee.

     11.  RELEASE. Employee hereby releases and forever discharges the Company,
and the Company's affiliates, subsidiaries, parents, successors, assigns and
other affiliated entities, past and present, and each of them, as well as its
and their officers, directors, attorneys, managers, agents and employees
("Releasees") from all claims, known or unknown, which Employee ever had or now
has or may hereafter claim to have had prior to the date of this Agreement with
respect to Employee's employment with the Company, the terms and conditions of
Employee's employment, the termination of Employee's employment and any other
action, event or matter. These claims may include, but are not limited to,
claims based on (a) violations of Title VII of the Civil Rights Act of 1964, the
Civil Rights Act of 1991, the Americans with Disabilities Act, the Age
Discrimination in Employment Act, and the Employee Retirement Income Security
Act; (b) any and all claims under Colorado statutory or decisional law,
including, but not limited to, the Colorado Anti-Discrimination Act, pertaining
to employment discrimination or harassment, wrongful discharge or breach of
public policy; and (c) state, federal or common law relating to breach of
express or implied contract, wrongful termination, employment discrimination or
harassment, emotional distress, privacy rights, fraud or misrepresentation. The
Company hereby releases and forever discharges Employee from all claims, known
or unknown, which the Company ever had or now has or may hereafter claim to have
had prior to the date of this Agreement against Employee with respect to
Employee's employment with the Company, the terms and conditions of Employee's
employment, the termination of Employee's employment and any other action, event
or matter.

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     12.  REVIEW. Employee acknowledges that Employee has been advised by the
Company to consult with an attorney to receive independent legal advice with
respect to the ramifications and the advisability of entering into and executing
this Agreement. Employee has twenty-one (21) days after the date this Agreement
is tendered to Employee to sign this Agreement. Employee agrees to read and
understand this Agreement prior to signing it. Employee will have seven (7) days
following signing the Agreement to revoke it, and the Agreement will not become
effective until the seven (7) day revocation period has expired. Such revocation
must be in writing and received by the Company prior to the end of the
revocation period.

     13.  NO ADMISSIONS. Nothing in this Agreement, including the payment of any
sum by the Company, constitutes an admission by the Company of any legal wrong
in connection with the employment or termination of Employee.

     14.  COVENANT NOT TO SUE. Employee covenants and agrees that Employee will
never, individually or with any other person, commence, aid, prosecute, or cause
or permit to be commenced or prosecuted, any lawsuit, charge or other proceeding
against any Releasee based upon any claim which Employee has released in this
Agreement. This Agreement shall be deemed breached immediately upon the
commencement or prosecution of any such lawsuit or proceeding. In the event of
any breach of this Section, the aggrieved Releasee shall be entitled to recover
from Employee not only the amount of any judgment which may be awarded against
that Releasee, but also all such other damages, costs and expenses as may be
incurred by that Releasee, including attorney's fees and expenses, in defending
against or seeking to stop any lawsuit or proceeding brought by Employee in
violation of this covenant not to sue or other terms of this Agreement.

     15.  CONFIDENTIALITY. Except as required by an order of a court of law, the
parties agree not to disclose or publicize the terms of this Agreement, or to
assist others to disclose or publicize the terms of this Agreement. This non-
disclosure Agreement applies to the parties, their attorneys, agents, officials,
managers, employees and spouses as well as to the named parties.

     16.  AGREEMENT UNDERSTOOD. By freely, knowingly and voluntarily executing
this Agreement, both parties confirm that they have had the opportunity to have
this Agreement explained to them by attorneys. The Company is relying on its own
judgment and on the advice of its attorneys and not upon any recommendation of
Employee or Employee's agents, attorneys, or other representatives. Employee is
relying on Employee's own judgment and on the advice of Employee's attorneys, if
Employee has chosen to engage counsel, and not upon any recommendations by the
Company or its directors, officers, employees, agents, attorneys, or other
representatives. By voluntarily executing this Agreement, both parties confirm
their competence to understand and do hereby accept the terms of this Agreement
as resolving fully all differences, disputes and claims that may exist within
the scope of the Agreement.

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     17.  GOVERNING LAW. This Agreement shall be construed and enforced in
accordance with, and the validity and performance hereof shall be governed by,
the laws of the State of Colorado.

     18.  SEVERABILITY. In the event that any one or more of the provisions of
this Agreement shall for any reason be held to be invalid or unenforceable, the
remaining provisions of this Agreement shall be unimpaired, and shall remain in
effect and be binding upon the parties.

     19.  AMENDMENTS. No amendment, waiver, change or modification of any of the
terms, provisions or conditions of this Agreement shall be effective unless made
in writing and signed or initialed by the parties or by their duly authorized
agents. Waiver of any provision of this Agreement shall not be deemed a waiver
of future compliance therewith and such provision shall remain in full force and
effect.

     20.  SUCCESSORS AND TRANSFEREES. This Agreement shall be binding upon and
inure to the benefit of each of the parties' successors, assigns, heirs, and
transferees.

     21.  COUNTERPARTS. This Agreement may be executed in any number of
counterparts, each of which shall be deemed to be an original, but all of which
together shall constitute one and the same instrument, and in making proof
hereof, it shall not be necessary to produce or account for more than on such
counterpart.

     22.  COSTS, EXPENSES, AND ATTORNEYS' FEES. In the event any claim, default
or violation is asserted by a party to this Agreement regarding any of the terms
or conditions of this Agreement, the party may enforce this instrument by
appropriate action, and should any of the parties prevail in such litigation
that prevailing party shall recover all costs, expenses, and reasonable
attorneys' fees incurred in such litigation.

     23.  FINAL AGREEMENT. This Agreement sets forth the entire understanding of
the parties and supersedes any and all prior written or oral agreements,
arrangements or understandings related to the subject matter described herein,
and no written or oral representation, promise, inducement or statement of
intention has been made by either party which is not embodied herein.

     This Agreement is dated as of the 1st day of January, 2000.



                                           /s/ John Kane
                                           -------------------------------------
                                           John Kane, EMPLOYEE
                                           Date of signing by Employee: 12/23/99
                                                                        --------

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WITNESSED BY:

/s/ Harry R. Herbst
-------------------------------
Name: Harry R. Herbst
     --------------------------



                                            ICG COMMUNICATIONS, INC.



                                            By: /s/ Don Teague
                                              ----------------------------------
                                            Name: Don Teague
                                                 -------------------------------
                                            Title: Executive Vice President
                                                  ------------------------------

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