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                                                                   Exhibit 10.1

                              EMPLOYMENT AGREEMENT
                                       OF
                                  GEORGE LEBUS


        THIS EMPLOYMENT AGREEMENT ("Agreement") is made as of June 30, 2000
between National Telemanagement Corporation, a Texas corporation, and
wholly-owned subsidiary of Illuminet Holdings, Inc. ("Parent" or "Illuminet")
with its offices at 8828 Stemmons Freeway, Suite 212, Dallas, Texas 75247-3712
("Company") and George Lebus (the "Executive").

        WHEREAS, Company and the Executive desire to enter into this agreement
for the purpose of clearly, correctly and completely stating the terms of the
Executive's employment by Company;

        NOW, THEREFORE, in consideration of the foregoing premises and the
mutual covenants herein contained, Company and the Executive agree as follows:

        1. Employment. Company hereby employs the Executive and the Executive
hereby accepts such employment on the terms and conditions hereinafter set
forth.

        2. Term. Subject to the respective rights of Company and the Executive
under Paragraph 10 to terminate this employment, the Executive shall serve
Company for a period (the "Term of Employment") beginning on the date hereof and
shall continue for two years. Thereafter, the term shall automatically be
extended on an annual basis unless either party gives ninety (90) days advance
written notice of intention to terminate this Agreement.

        3. Duties. The Executive shall serve as President of Company and shall
report to and have such powers and duties as may be prescribed from time to time
by the Chief Executive Officer of Illuminet. During the Term of Employment the
Executive shall devote his full time, attention and efforts to the business of
Company and shall use his best efforts to promote the interests of Company at
all times. The Company agrees that without the consent of the Executive (i) he
will not be required to relocate his residence from the greater Dallas/Fort
Worth, Texas metropolitan area and (ii) his functional duties will not be
materially diminished from those customarily assigned to a person serving as the
senior executive of a division or operating subsidiary (with the understanding
that Illuminet may choose to centralize marketing, product development, human
resources, accounting and other non-operating functions).

        4. Compensation.

        (a)     Company agrees to pay the Executive for services rendered
                hereunder an annual base salary (exclusive of any bonus stock
                award, incentive payments, imputed income or similar items) of
                $215,000 during the first year of this Agreement. The salary
                shall be payable in twice a month installments in arrears less
                any sums
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                which may be required to be deducted or withheld under the
                provisions of law.

        (b)     The Executive shall be eligible for an annual increase in base
                salary, based on performance. The amount of the increase in base
                salary, if any, shall be determined by the Chief Executive
                Officer of Illuminet.

        (c)     The Executive shall be eligible to participate in the NTC
                Executive Bonus Program.

        5. Benefits. The benefits provided to the Executive in this Agreement
are all available employee benefits normally provided by Company to its
employees. The Executive may also participate in future benefits and incentive
plans as determined by the Chief Executive Officer of Illuminet.

        6. Expenses. Company shall reimburse the Executive for all reasonable
expenses incurred in connection with the performance of his duties for the
benefit of Company, within such limits and standards as may from time to time be
set by Company.

        7. Non-Competition and Confidentiality.

                (a)     The Executive acknowledges and agrees that during the
                        course of his employment by Company he has obtained or
                        will obtain access to certain information, know-how,
                        designs, formulas, processes, technology or other
                        matters relating to the business, research and design
                        activities, manufacturing processes, development,
                        products, and production, marketing, accounting or
                        engineering methods, customers and finances of the
                        Company and of Parent, not generally known by the public
                        or in the relevant industry ("Confidential Information")
                        and that because of such access, competition by him with
                        Company or Parent or disclosure of Confidential
                        Information could result in material damage to Company
                        or Parent and might cause it to suffer irreparable
                        damage.

                (b)     The Executive agrees that during the Term of Employment
                        and for a period of two years immediately following the
                        Term of Employment, the Executive shall not directly or
                        indirectly, as an owner, partner, employee, stockholder,
                        officer or director of any firm or business entity,
                        engage in any business activity in any state of the
                        continental United States, territory or foreign country
                        in which Company or Parent does business at the
                        conclusion of the Term of Employment that competes
                        directly with the business of Company or Parent or any
                        division or subsidiary thereof.

                (c)     The Executive acknowledges that his position with
                        Company is one of the highest trust and confidence both
                        by reason of his


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                        position and by reason of his access to and contact with
                        the trade secrets and Confidential Information of
                        Company and Parent. Both during the term of this
                        Agreement and thereafter, the Executive covenants and
                        agrees as follows:

                        (i)     he shall use his best efforts and exercise
                                utmost diligence to protect and safeguard the
                                trade secrets and Confidential Information of
                                Company and Parent;

                        (ii)    he shall not disclose any of such trade secrets
                                and Confidential Information, except as may be
                                required in the course of his employment with
                                Company and Parent or by law; and

                        (iii)   he shall not use, directly or indirectly, for
                                his own benefit or for the benefit of another,
                                any of such trade secrets and Confidential
                                Information.

                All files, records, documents, drawings, specifications,
                memoranda, notes, or other documents relating to the business of
                Company, whether prepared by the Executive or otherwise coming
                into his possession, shall be the exclusive property of Company
                and shall be delivered to Company and not retained by the
                Executive upon termination of his employment for any reason
                whatsoever or any other time upon request of Company.

                (d)     The Executive acknowledges and agrees that the
                        observance by him of his covenants contained in this
                        Paragraph 7 is so important to the continued success of
                        the business of Company and Parent that in the event of
                        a breach or threatened breach by the Executive of such
                        covenants Company and Parent will not have an adequate
                        remedy at law, and accordingly shall be entitled to
                        proceed in equity to obtain specific enforcement of such
                        covenants, including but not limited to injunctions
                        restraining the Executive from breaching such covenants,
                        and all without any requirement to post bond or other
                        security; provided that this sentence shall not be
                        construed as a waiver by Company or Parent of any other
                        remedies available to it for such breach or threatened
                        breach, including, but not limited to the recovery of
                        damages from the Executive.

                (e)     The prohibitions of this Paragraph 7 and any of its
                        provisions are severable, and a finding by any court
                        that any provision of this Paragraph 7 is unenforceable
                        shall not affect the validity of any other covenant set
                        forth herein. Additionally, should any court find that
                        the provisions of this Paragraph 7 are unenforceable,
                        the Executive and Company agree that the court may
                        modify the restrictions contained herein and prohibit
                        the Executive from engaging in such activities as the
                        court finds necessary to protect interests of the
                        Company and Parent.


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        8. Assignment of Intellectual Property.

                (a)     The Executive covenants and agrees that he will fully
                        inform Company of and disclose to Company all
                        inventions, designs, improvements, discoveries and
                        processes ("Discoveries") which he has now or may
                        hereafter have during his employment with the Company
                        and which pertain or relate to the business of the
                        Company or Parent or to any experimental work, products,
                        services or processes of Company or Parent in progress
                        or planned for the future, whether conceived by the
                        Executive alone or with others, and whether or not
                        conceived during regular working hours or in conjunction
                        with the use of any Company assets. All such Discoveries
                        shall be the exclusive property of Company whether or
                        not patent or trademark applications are filed thereon.

                (b)     The Executive shall assist the Company, at any time
                        during or after his employment, in obtaining patents on
                        all such Discoveries deemed patentable by Company or
                        Parent and shall execute all documents and do all things
                        necessary to obtain letters patent, vest Company or
                        Parent with full and exclusive title thereto, and
                        protect the same against infringement by others. If such
                        assistance takes place after his employment is
                        terminated the Executive shall be paid by Company at a
                        reasonable rate for any time actually spent in rendering
                        such assistance at the request of Company.

        9. Nonsolicitation. The Executive agrees that during the period of his
employment and for a period of two years immediately following the later of any
termination of his employment, whether voluntary or involuntary he will not,
either directly or indirectly, for himself or for any third party, solicit,
induce, recruit, or cause another person in the employ of Company to terminate
his/her employment for the purpose of joining, associating or becoming employed
with any business or activity. Company and the Executive specifically
acknowledge and agree that the foregoing covenants of the Executive in
Paragraphs 7, 8 and 9 are reasonable in content and scope and are given by the
Executive for adequate consideration.

        10. Termination. The Term of Employment or any renewal thereof may be
terminated by Company at any time or for any reason. Unless such termination is
on account of death or disability of the Executive or for good cause, Company
shall pay the Executive a "termination payment" as described below. Company
shall be deemed to have "good cause" to terminate the Executive's employment if
Company determines that the Executive

                (a)     has violated or failed to comply with Paragraph 7, 8 or
                        9, after, with respect solely to unintentional
                        violations or failures to comply, notice to the
                        Executive and his failure to correct, to the reasonable
                        satisfaction of Company, such unintentional violation or
                        failure within ten (10) days thereafter;


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                (b)     has refused or failed to perform the duties of his
                        position or other duties which have been assigned to
                        him, after notice to the Executive and his failure to
                        correct, to the reasonable satisfaction of the Company,
                        such refusal or failure within ten (10) days thereafter;
                        or

                (c)     has engaged in dishonesty, conduct detrimental to
                        Company's business or illegal conduct.

In the event of a termination for death, disability or good cause, Company shall
owe the Executive no further salary, benefits or other compensation of any kind
after Company provides notice to the Executive of termination. The obligations
of the Executive under Paragraphs 7, 8(b) and 9 shall survive any termination,
whether made by Company for any reason or by the Executive for any reason other
than a material breach by the Company of the terms hereof after written notice
by the Executive to the Company and the Company's failure to cure such breach
within ten (10) days thereafter.

"Termination Payment" means one year's annual base salary exclusive of any
current year bonus, stock award, incentive payments, imputed income or similar
items.

        11. Effectiveness of Agreement. This Agreement, including Paragraphs 7,
8 and 9, hereof, shall be binding upon and shall inure to the benefit of Company
and on any successors or assigns of Company, and any such successors or assigns
of Company shall be deemed substituted for Company under this Agreement. No
assignment by Company hereunder shall release Company from its obligations,
pursuant to Paragraph 4 hereof in the event Company's successor fails to satisfy
such obligations. No assignment hereof will release the Executive from his
obligations under Paragraphs 7, 8 and 9 hereof. For the purposes of this
Agreement, the term "successor" shall mean any person, firm, corporation or
other business entity which at any time, whether by merger, purchase,
liquidation or otherwise, shall acquire all or substantially all of the assets
of Company.

        12. Severability. The failure of any court to enforce any clause,
paragraph or provision of this Agreement shall not adversely affect the validity
or enforceability of any other clause or provision.

        13. Entire Agreement. This Agreement sets forth the entire agreement of
any parties with respect to the transactions contemplated hereby and supersedes
all prior agreements, arrangements and understandings with respect thereto
between Company and the Executive. No modification, amendment, addition to or
termination of this Agreement, nor waiver of any of its provisions shall be
valid or enforceable unless in writing and signed by both parties.

        14. Counterparts. This Agreement may be executed in any number of
counterparts, each of which shall be deemed an original and all of which
constitute one instrument.


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        15. Headings. The underlined headings herein are for convenience only
and shall not affect the interpretation of this Agreement.

        16. Governing Law. This Agreement shall be governed by and construed in
accordance with the laws of the State of Texas.

        17. Notice. Any notice to be delivered under this Agreement shall be
given in writing and delivered personally or by leaving the same at or by
sending the same first-class mail, postage prepaid:

                (a)     in the case of Company, at its principal executive
                        office at the time and to the current Chief Executive
                        Officer of Illuminet; and

                (b)     in the case of the Executive, at his personal address on
                        Company's records;

                (c)     in the case of either party, such other address as shall
                        have been notified in writing to the other of them for
                        the purposes of service hereunder.

        The Executive agrees to notify Company, in writing, of any change in
personal address since the date of this Agreement.


        IN WITNESS WHEREOF, each of the parties hereto has made and caused this
Agreement to be duly executed to be effective the day and year first above
written.

                                    NATIONAL TELEMANAGEMENT CORPORATION



                                    By: /s/ ROGER H. MOORE
                                       -----------------------------------------
                                       Roger H. Moore, Chief Executive Officer


                                       /s/ GEORGE LEBUS
                                       -----------------------------------------
                                       George Lebus