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                                                                    Exhibit 10.1

                           Effective 11 September 2001

                              CARRIER 1 UK LIMITED

                           CARRIER1 INTERNATIONAL S.A.

                                     - AND -

                             ROBERT MICHAEL MCTIGHE

THIS EMPLOYMENT AGREEMENT (the "Agreement") is dated 27 September, 2001 and is
effective as of 11 September 2001

BETWEEN:-

(1)   CARRIER 1 UK LIMITED whose registered office is at 6 Harbour Exchange
      Square, London, E149GE (the "COMPANY"), which is the employer under this
      Agreement;

(2)   CARRIER1 INTERNATIONAL S.A., c/o Carrier1 International GmbH,
      Militarstrasse 36, 8004 Zurich ("CARRIER1 SA"), which is a Luxembourg
      societe anonyme and the parent of the Company; and

(3)   ROBERT MICHAEL MCTIGHE (the "EXECUTIVE"), who is the employee under this
      Agreement.

WHEREAS, the Executive has previously served as a senior executive in the
telecommunications and technology sectors and the Company and Carrier1 SA desire
to secure the services of the Executive as Chief Executive Officer and member of
the Board of Directors; and

WHEREAS, in order to induce the Executive to accept employment, and to address
certain forfeitures that will arise as a result of the Executive's termination
of employment with his current employer, the Company has agreed to provide the
remuneration set forth herein (and object to the terms and conditions hereof): -

THE PARTIES AGREE AS FOLLOWS: -

1.    DEFINITIONS

      In this Agreement unless the context otherwise requires:-

"AFFILIATED COMPANY" as to the Company means a company that directly or
indirectly, through one or more intermediaries, controls, is controlled by, or
is under common control with, the Company, including a subsidiary of the
Company, a company of which the Company is a subsidiary, or another subsidiary
of a company of which the Company is also a subsidiary, where the term "control"
(including the terms "controlled by" and "under common control with") means the
possession, directly or indirectly, of the power to direct or cause the
direction of the management policies of a company, whether through the ownership
of voting securities, by contract or credit arrangement, as trustee or executor,
or otherwise;

"BOARD" means the board of directors from time to time of the Company;

"BUSINESS DAY" means any day other than a Saturday, a Sunday, a holiday or a
vacation day;

"CARRIER1 SA BOARD" means the board of directors from time to time of Carrier1
SA;
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"CHANGE OF CONTROL" means the first to occur of the following: (i) the
consummation of a single transaction or series of related transactions as a
result of which a "person" or "group" (within the meaning of Section 13(d) or
14(d)(2) under the Exchange Act) becomes the ultimate "beneficial owner" (as
defined in Rule 13d-3 under the Exchange Act) of more than 35% and such
ownership represents a greater percentage of the total voting power of the
Voting Stock of Carrier1 SA, on a fully diluted basis, than is held by Permitted
Holders on such date, (ii) consummation of a merger or consolidation as a result
of which the Persons who own voting equity securities of the Company or Carrier1
SA prior to such transaction(s) shall own less than 65% of the voting securities
of the surviving Person or its direct or indirect parent, or (iii) the sale or
other disposition of all or substantially all of the assets of Carrier1 SA
(determined on a consolidated basis);

"CREATIVE WORK" means any work in which copyright or unregistered design right
may subsist in any media (including but not limited to electronic materials);

"EVENT OF DEFAULT" means an act that constitutes an Event of Default hereunder
as set forth in Clause 10;

"GROUP COMPANY" means the Company and its affiliated companies, and "Group"
means all of such companies taken together;

"INTELLECTUAL PROPERTY" means patents, trade marks and service marks, rights in
designs, trade or business names, copyrights (including rights in computer
software), whether or not registered and including applications for (and the
right to apply for) registration of any such thing, and all rights or forms of
protection of a similar nature or having equivalent or similar effect to any of
these which may subsist anywhere in the world for the full period thereof and
all extensions or renewals thereof;

"INVENTION" means any invention, idea, discovery, development, writing, design,
drawing, improvement or innovation whether or not patentable or capable of
registration;

"KEY EMPLOYEE" means any person who has or had responsibility for or is or was
involved in: any policy-making function, preparation or presentation of
financial statements; obtaining or maintaining government or third party
consents, approvals, licenses or similar activities, or complying with
applicable laws and regulations; communicating with securityholders; identifying
or executing business or strategic opportunities in internet, voice,
infrastructure or other telecommunications products or services whether with
potential customers or other companies; maintaining or creating relationships
with customers; acquiring, constructing or maintaining telecommunications
networks, data centers, or any other technology; and formation or administration
of employment, customers and other contracts; in each case, as an employee or
consultant of the Company or any other Group Company in the period of 12 months
prior to the Termination Date (for the avoidance of doubt, it being agreed that
the Executive's secretarial assistant shall not be treated as a Key Employee);

"LIMITED VICARIOUS LIABILITY" means any liability that is based on acts of the
Company, Carrier1 SA or any member of the Group for which Executive is
responsible solely as a

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result of his office(s) with the Company and Carrier1 SA, provided that (A) he
was not directly involved in such acts and either had no prior knowledge of such
intended actions or promptly acted reasonably and in good faith to attempt to
prevent the acts causing such liability or (B) he did not have a reasonable
basis to believe that a law was being violated by such acts;

"PERMITTED HOLDERS" means any of the following: any of Providence Equity
Partners L.P., Providence Equity Partners II L.P., Providence Equity Partners
III L.P., Providence Equity Partners IV L.P., Providence Operating Partners IV
L.P., Providence Growth Investors L.P., Primus Capital Fund IV L.P., Primus
Capital Fund V L.P., Primus Executive Fund L.P. and Primus Executive Fund V L.P.
and any of the respective Affiliates or successors of the foregoing.

"PERSON" means any natural person, corporation, limited liability company,
partnership, limited partnership, firm, joint venture, association, joint-stock
company, trust, business trust, unincorporated organization, governmental or
regulatory body, or other entity of whatever nature.

"VOTING STOCK" means, with respect to any person, capital stock of Carrier1 SA
of any class or kind ordinarily having the power to vote for the election of
directors, managers or other voting members of the governing body of such
person.

"TERMINATION DATE" means the date of effectiveness of termination of the
Appointment.

2.    APPOINTMENT

2.1   TERM. The Company shall engage the Executive and the Executive shall serve
      the Company as provided herein (the "APPOINTMENT"). The Appointment shall
      commence on the date the Executive commences full time employment with the
      Company (the "COMMENCEMENT DATE"), which shall be no later than 1 October
      2001, and shall continue unless and until terminated as provided in Clause
      5. The Executive shall use his reasonable best efforts to commence
      employment as soon as possible after the date hereof.

2.2   APPOINTMENT. During the Appointment, the Executive shall be employed as
      the Chief Executive Officer of the Company and of Carrier1 SA. Effective
      as of the Commencement Date, the Executive shall be named to serve as a
      member of the Carrier1 SA Board and the Board. Thereafter during the
      Appointment, the Company shall nominate the Executive for, and support his
      election to, serve as a member of the Board and the Carrier1 SA Board
      during the Appointment. If there is a chairman of the Carrier1 SA Board,
      who is also an employee of the Group, the Executive shall be such
      chairman.

2.3   EFFECT OF PREVIOUS EMPLOYMENT. No previous employment counts as part of
      the Executive's continuous employment with the Company.

2.4   NO CONFLICTS. The Executive represents that (i) he is entering into this
      Agreement voluntarily and that his employment hereunder and compliance
      with the terms and

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      conditions hereof will not conflict with or result in the breach by him of
      any agreement to which he is a party or by which he may be bound, (ii)
      except for his agreement with Cable & Wireless plc (a copy of which he has
      heretofore provided to the Company), he is not and will not be bound by
      any noncompetition, nonsolicitation or other similar covenant or
      agreement, and (iii) in connection with his employment with the Company he
      will not use any confidential or proprietary information he may have
      obtained in connection with employment with any prior employer.

3.    DUTIES AND RESPONSIBILITIES

3.1   GENERAL. The Executive shall report solely to the Board and the Carrier1
      SA Board. The Executive shall be the most senior executive of the Company
      and Carrier1 SA with ultimate responsibility for the business of all Group
      Companies, together with the services and staff directly related thereto.
      Subject to the supervision and direction of the Board and the Carrier1 SA
      Board, the Executive shall have broad discretion and authority to manage
      and direct the day-to-day affairs and operations of all Group Companies,
      including with respect to the strategic direction of all Group Companies
      and the hiring and termination of any one or more employees of the Group
      Companies. All operating, staff, other executives, and divisions of all
      Group Companies shall report solely to Executive, either directly to
      Executive or indirectly to Executive through subordinates of Executive who
      report to Executive. In addition, the Executive shall have such other
      duties consistent with the Executive's titles and positions as the Board
      or the Carrier1 SA Board specifies from time to time, which may include
      serving as an officer or director or otherwise performing services for any
      Group Company. In so acting, the Executive shall devote such time and
      attention to the duties assigned to him as may be required for the
      performance of such duties as an employee of the Company and well and
      faithfully serve the Company and the Group and use his best endeavours to
      promote the interests of the Company and the Group and obey all reasonable
      and lawful directions given to him by or under the authority of the Board
      or the Carrier1 SA Board, it being understood that the Executive shall
      devote substantially all his working time and attention to the performance
      of such duties and the fulfillment of such commitments (other than (i)
      vacation time and absence for sickness or similar disability, (ii) to the
      extent that it does not interfere with the performance of the Executive's
      duties hereunder such reasonable time as may be devoted to service in a
      non-executive capacity on not more than three corporate boards of
      directors as the Carrier1 SA Board shall from time to time approve (such
      approval not to be unreasonably withheld), it being understood that such
      approval is given with respect to the three corporations listed on
      Schedule A hereto, and (iii) such reasonable time as may be necessary from
      time to time for managing his personal financial affairs and the
      fulfillment of his civic responsibilities, in each case subject to Clause
      3.2).

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3.2   RESTRICTIONS. During the Appointment the Executive shall:-

      (a)   comply with all material written Company employment-related policies
            that have been provided to him;

      (b)   not do anything that would cause him to be disqualified from holding
            any office as a director, chief executive officer, or any other
            office with the Company or any Group Company;

      (c)   not, except as a representative of the Company or with the prior
            written approval of the Board, whether directly or indirectly, paid
            or unpaid, (i) be engaged or concerned in the conduct of any other
            actual or prospective business or profession, (ii) be or become an
            employee, agent, partner, member, consultant, director or officer of
            any other company or firm or (iii) assist or have any financial
            interest in any other business or profession that may interfere,
            conflict or compete with the proper performance of the Executive's
            obligations to the Company.

3.3   PLACE OF WORK. The Executive shall be required in pursuance of his duties
      hereunder:-

      (a)   to work at 6 Harbour Exchange Square, London, E149GE or such other
            places within the United Kingdom as the Company may require; and

      (b)   to travel to such places inside or outside the United Kingdom by
            such means and on such occasions as may from time to time be
            required in connection with the Executive's performance of services
            hereunder.

3.4   WORKING HOURS. The normal business hours of the Company are 9.00 a.m. to
      5.00 p.m. Monday to Friday and shall apply to the Executive provided that
      the Executive shall work such further hours as may be necessary for the
      proper discharge of his duties and he shall not be entitled to receive any
      additional remuneration for work outside normal business hours.

4.    REMUNERATION AND BENEFITS

4.1   BASE SALARY. During the Appointment, the Company shall pay the Executive a
      base salary at the annual rate of (pound)UK450,000. The Board shall review
      Executive's base salary annually during the Appointment and, in its sole
      discretion, may change such base salary from time to time based upon the
      performance of Executive, the financial condition of the Company,
      prevailing industry salary levels and such other factors as the Board
      shall consider relevant, provided that the annual base salary may not be
      decreased. (The annual base salary payable to Executive under this Clause
      4.1 from time to time shall hereinafter be referred to as the "BASE
      SALARY"). The Base Salary shall be payable in accordance with the
      Company's standard payroll practices, but no less frequently than calendar
      monthly in arrears on the last working day of each month.

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4.2   ANNUAL BONUS OPPORTUNITY. The Executive shall participate in the Company's
      annual incentive bonus program. The Executive's target annual bonus at
      achievement of 100% of the objectives established by the Board and the
      Carrier1 SA Board shall be 50% of his Base Salary ("OTE BONUS"), and the
      actual bonus paid based upon performance may range from 0% to 75% of Base
      Salary (or higher) depending on such performance relative to the
      objectives established by the Board and the Carrier1 SA Board, provided
      that for the portion of the Company's fiscal year ending 31 December 2001
      during the Appointment, the Executive's annual bonus shall be not less
      than 50% of Base Salary for such period. The Executive's annual bonus
      shall be paid at the time the Company customarily pays annual bonuses to
      its executives.

4.3   REPLACEMENT AWARD.

      (a)   In order to address certain forfeitures that the Executive will face
            upon termination of his employment with his prior employer, the
            Executive shall receive the following:-

            (i)   prior to the Commencement Date, the Company shall pay the
                  Executive(pound)UK 694,020; and

            (ii)  upon the 24-month and 36-month anniversary of the Commencement
                  Date the Executive commences full-time employment with the
                  Company, the Company shall pay the Executive (pound)UK
                  1,388,041, in each case subject to the Executive's continuous
                  employment with the Company through such payment date (except
                  as provided in Clause 5.2(b)).

(b)   In order to secure the obligations of the Company under this Clause 4.3,
      on or before the Commencement Date, the Company shall establish a standby
      letter of credit (the "Letter of Credit") in favor of the Executive, in
      form and substance reasonably satisfactory to the Executive, in the amount
      of(pound)UK 2,776,082 and that shall provide that the Executive may draw
      upon the Letter of Credit in the amounts and at the times (and subject to
      the terms and conditions) provided for in Clause 4.3(a), 4.4(c) and 4.4(d)
      upon certification delivered to the issuing bank (with a copy to the
      Company pursuant to Clause 11 hereof) signed by the Executive under
      penalties of perjury certifying that the conditions set forth in this
      Agreement to the Executive's right to draw such amount have been satisfied
      in full. If the Letter of Credit is scheduled to expire before amounts
      payable with respect thereto have been satisfied in full or the
      obligations with respect thereto have been extinguished in accordance with
      the terms of this Agreement, and the Company has failed to provide a
      renewal or replacement letter of credit, the bank issuing such Letter of
      Credit shall notify the Executive no later than 60 days prior to such
      expiration.

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      (c)   If the Executive voluntarily terminates employment other than for
            Good Reason before the first anniversary of the Commencement Date,
            the Executive shall be obligated to repay to the Company 100% of the
            amounts paid pursuant to Clause 4.3(a). If the Executive voluntarily
            terminates employment other than for Good Reason after the first
            anniversary of the Commencement Date and before the second
            anniversary of the Commencement Date, the Executive shall be
            obligated to repay to the Company 50% of the amounts paid pursuant
            to Clause 4.3(a).

      (d)   If the employment is terminated by the Company (other than as a
            result of an Event of Default or as a result of the Executive's
            death or Disability) or by the Executive for Good Reason, the
            Executive shall be entitled to retain the amounts previously paid to
            him pursuant to Clause 4.3(a) and any remaining amounts that he is
            entitled to draw down under the Letter of Credit.

4.4   STOCK OPTION AWARD.

      (a)   Effective as of September 11, 2001, the Executive will receive a
            special one-time award of options to purchase 1,200,000 Carrier1 SA
            ordinary shares (it being understood that the foregoing number shall
            be appropriately adjusted to reflect any reverse stock split, stock
            split, stock dividend or other similar item any time after August 6,
            2001). Such stock option grant shall have an exercise price per
            ordinary share of $1.10 (it being understood that the price shall be
            appropriately adjusted to reflect any reverse stock split, stock
            split, stock dividend or other similar item), shall generally have a
            term of 10 years and, except as otherwise expressly provided herein,
            shall be granted pursuant to an option agreement in the form
            attached hereto as Exhibit A.

      (b)   The options provided for in this Clause 4.4 shall vest 25% on the
            first anniversary of the Commencement Date and thereafter shall vest
            in 6 equal semi-annual installments on the succeeding 6-month
            anniversaries of the Commencement Date, in each case subject to the
            Executive's continuous employment through such dates.

      (c)   Notwithstanding the foregoing, if a Change of Control occurs and the
            Executive is not offered the position of Chief Executive Officer of
            the surviving company (the parent company if such parent company is
            publicly traded and owns more than 50% of the surviving company)
            following such Change of Control, the Executive may elect no later
            than 30 days prior to the Change of Control either (i) payment of
            any unpaid amounts provided for under Clause 4.3(a)(ii), to be -
            paid promptly following such Change of Control, or (ii) vesting
            effective upon the Change of Control of all of the remaining
            unvested options granted pursuant to this Clause 4.4 held by the
            Executive at such time, provided that the Executive will not be
            entitled to make this election if, after the announcement of or
            entering into the transaction that would constitute the Change of
            Control but prior to the consummation of the Change of Control, the
            Appointment has terminated for

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            any reason other than a termination by the Company where no Event of
            Default has occurred or by the Executive for Good Reason.

      (d)   If the Appointment is terminated by the Company (other than as a
            result of an Event of Default or as a result of the Executive's
            death or Disability) or by the Executive for Good Reason (other than
            in the circumstances where preceding Clause 4.4(c) applies) , the
            Executive may elect no later than 30 days prior to the Termination
            Date (or, in the case of a termination by the Company on summary
            notice, within 20 days following such Termination Date) either (i)
            payment of any unpaid amounts provided for under Clause
            4.3(a)(ii), to be paid promptly following such termination, or (ii)
            vesting effective upon the Termination Date of that number of
            options granted pursuant to this Clause 4.4 that would have vested
            within the 12 months following such termination, in each case
            assuming the Executive had remained employed with the Company
            through such date.

      (e)   If the Executive makes an election pursuant to Clause 4.4(c) or
            4.4(d) for options to vest instead of receiving unpaid amounts under
            Clause 4.3(a)(ii), the Letter of Credit may be cancelled and any
            remaining amounts in escrow or otherwise supporting such Letter of
            Credit shall be paid over to the Company. If, pursuant to Clause
            4.4(c) or 4.4(d), the Executive draws down remaining amounts under
            the Letter of Credit such action shall be deemed an irrevocable
            election with respect thereto (in lieu of vesting of options).

      (f)   Coincident herewith, the Executive and the other parties thereto
            shall enter into a Stockholders Agreement that will provide for
            certain registration rights and the right (and obligation) to
            participate in sales by certain shareholders of Carrier1 SA, in each
            case subject to the terms and conditions set forth therein,
            substantially in the form attached as Exhibit A.

4.5   BENEFITS, PERQUISITES AND EXPENSES.

      (a)   BENEFITS. During the Appointment, the Executive shall be eligible to
            participate, to the extent made generally available by the Company
            to its senior executives, in (i) each welfare benefit plan sponsored
            or maintained by the Company, - including, without limitation,
            hospitalization, disability, life and health insurance and (ii)
            other benefit arrangements, whether now existing or established
            hereafter, and to the extent that the Executive is eligible to
            participate in any such plan under the generally applicable
            provisions thereof. During the Appointment, the Company shall
            provide the Executive with (i) term life insurance equal to 4 times
            his Base Salary and OTE Bonus (in each case - as of the date
            hereof), (ii) disability insurance, (iii) medical insurance for him
            and his family and (iv) shall contribute to its pension plan (a copy
            of which has heretofore been provided to the Executive) for the
            benefit of the Executive each month such amounts as shall be equal
            to 10 % per annum of his Base Salary and OTE bonus. If and to the

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            extent that such contributions shall not be capable of being made to
            an Inland Revenue approved scheme because of the application of
            Inland Revenue limits on contributions or benefits the Company shall
            contribute any excess amounts to an unapproved retirement benefits
            scheme or plan for the benefit of the Executive. For the avoidance
            of doubt it is confirmed that the Executive shall not be required to
            contribute to any pension plan or scheme whether approved or
            unapproved.

      (b)   HOLIDAYS.

            (i)   During the Appointment, the Executive shall be entitled to up
                  to 25 days paid holiday each year, accruing ratably each
                  calendar month consistent with Company policy for all senior
                  executives; provided that unused holiday time shall not be
                  carried over to subsequent years, and no payment will be due
                  with respect to such unused days. In addition, the Executive
                  will be entitled to statutory and other public holidays in
                  force in the United Kingdom.

            (ii)  If either party gives notice to terminate the Appointment, the
                  Company may require the Executive to take any accrued but
                  unused holiday entitlement during the notice period, and the
                  Executive shall not receive additional compensation for any
                  accrued but unused holiday entitlement upon termination.

      (c)   PERQUISITES. During the Appointment, the Executive shall be entitled
            to participate in all perquisite programs maintained by the Company
            for its senior executives, on a basis that is commensurate with the
            Executive's position and duties with the Company hereunder, in
            accordance with the terms thereof, as the same may be amended and in
            effect from time to time.

      (d)   BUSINESS EXPENSES. During the Appointment, the Company shall pay or
            reimburse the Executive for reasonable, ordinary and necessary
            out-of-pocket business expenses incurred by the Executive in the
            performance of his duties, subject to the Company's policies in
            effect from time to time with respect to travel, entertainment and
            other expenses, including without limitation, requirements with
            respect to reporting and documentation of such expenses.

5.    TERMINATION

5.1   TERMINATION OF APPOINTMENT.

      (a)   BY THE COMPANY OR BY THE EXECUTIVE. The Appointment may be
            terminated by either the Executive or the Company by giving to the
            other party written notice not less than twelve weeks prior to the
            Termination Date (such period being referred to herein as the notice
            period). Notwithstanding the foregoing, the Company reserves the
            right to pay the Executive salary in lieu of part or all of the
            notice of termination to which the Executive is otherwise

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            entitled hereunder. Such payment shall extinguish all obligations of
            the Company to the Executive in respect of that part of the notice
            period to which it relates.

      (b)   BY COMPANY WHERE EVENT OF DEFAULT HAS OCCURRED. The Company may
            terminate the Appointment upon an Event of Default in accordance
            with Clause 10. Any delay by the Company in exercising such right to
            terminate the Appointment shall not constitute a waiver thereof.

      (c)   BY THE EXECUTIVE FOR GOOD REASON. The Executive may terminate the
            Appointment for Good Reason within 90 days of the Executive becoming
            aware of the occurrence of a Good Reason Event (other than in the
            case of item (vii) below) by giving the Company not less than 30
            days prior written notice of the Termination Date (or, in the case
            of item (vii) below, at any time prior to the expiration of the
            Letter of Credit), unless such circumstances are fully corrected
            prior to the date of termination specified in such written notice.
            Any such written notice shall set forth in reasonable detail the
            Good Reason Event. For these purposes, a "GOOD REASON EVENT" means
            the occurrence of any of the following circumstances without the
            Executive's consent: (i) any material diminution of the Executive's
            positions, duties or responsibilities of Appointment as provided in
            Clause 2.2 (except in each case in connection with the termination
            of the Executive's employment as a result of an Event of Default or
            Disability or as a result of the Executive's death, or temporarily
            as a result of Executive's illness or other absence); (ii) removal
            of, or the non-reelection of, the Executive from officer or director
            positions with the Company or Carrier1 SA specified herein; (iii)
            requiring Executive's principal place of business to be located
            other than in the London Metropolitan region; (iv) a reduction in
            the Executives remuneration specified herein; (v) any material
            breach by the Company of any provision of this Agreement; (vi) any
            appointment of any person who is an employee of the Group as
            chairman of the Carrier1 SA Board (other than the Executive); or
            (vii) any notice of expiration of the Letter of Credit, unless all
            amounts payable with respect thereto have been satisfied or the
            Company's obligations with respect thereto have been extinguished in
            accordance with the terms of this Agreement.

      (d)   DEATH OR DISABILITY. The Appointment shall terminate automatically
            upon the death of the Executive, and the Board may terminate the
            Appointment upon a determination of the Disability of the Executive.
            For these purposes, a "DISABILITY" of the Executive means a physical
            or mental disability that prevents or is reasonably expected to
            prevent the performance by the Executive of his duties hereunder for
            180 days in any 365 day period. In the event of any dispute, the
            determination of the Executive's Disability shall (i) be made by an
            independent physician who is reasonably acceptable to the Company
            and the Executive (or his representative), (ii) be final and binding
            on the parties hereto and (iii) be made taking into account such
            competent medical evidence as shall be presented to such independent
            physician by the

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            Executive and/or the Company or by any physician or group of
            physicians or other competent medical experts employed by the
            Executive and/or the Company to advise such independent physician.

5.2   REMUNERATION UPON TERMINATION.

      (a)   REMUNERATION APPLICABLE TO ANY TERMINATION. In the event of any
            termination, the Executive (or his estate, beneficiary or legal
            representative, as the case may be) shall be entitled to receive
            accrued Base Salary through the Termination Date and any other
            amounts or benefits payable under any applicable plan, program or
            policy of the Company (determined in accordance with the terms
            thereof).

      (b)   TERMINATION OTHER THAN AS A RESULT OF AN EVENT OF DEFAULT. If the
            Appointment is terminated by the Executive for Good Reason or by the
            Company other than as a result of an Event of Default on the part of
            the Executive, the Executive (or his estate, beneficiary or legal
            representative, as the case may be) shall, subject to the
            Executive's continued compliance with Clause 6, 7 and 8 be entitled
            to receive:-

            (i)   the Executive's Base Salary for 12 months following the
                  Termination Date (less any amounts paid pursuant to the second
                  sentence of Clause 5.1(a) in lieu of the notice period) plus,
                  when annual bonuses are otherwise payable, an amount equal to
                  the OTE Bonus (provided that if the termination occurs
                  following a Change of Control, such amounts shall be paid in a
                  lump sum promptly following such termination of employment);
                  and

            (ii)  continued medical benefits for 12 months following the
                  Termination Date for the Executive and his eligible family
                  members, on the same terms and conditions as in effect
                  immediately before such termination; and

            (iii) the items that may be provided for in Clause 4.4(c) or 4.4(d),
                  if applicable.

      (c)   TERMINATION WHERE EVENT OF DEFAULT HAS OCCURRED; TERMINATION BY THE
            EXECUTIVE OTHER THAN FOR GOOD REASON. Notwithstanding anything
            herein to the contrary, in the event that the Appointment terminates
            and there has been an Event of Default by the Executive, or the
            Executive voluntarily terminates the Appointment other than for Good
            Reason, the Executive shall not be entitled to any remuneration
            other than as expressly provided for in Clause 5.2(a).

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6.    DISCLOSURE, USE AND PUBLICATION OF BUSINESS INFORMATION

6.1   DISCLOSURE. Without prejudice to his common law duties, the Executive
      shall not (except in the proper course of his duties, as required by law
      or as authorised by the Board) use or communicate to any person (and shall
      use his best endeavours to prevent the use or communication of) any trade
      or business secrets or other confidential, non-public or proprietary
      information of or relating to the Company or any other member of the Group
      (including but not limited to details of actual or potential customers,
      clients, consultants, suppliers, networks, facilities, designs, products,
      product applications, trade arrangements, terms of business, operating
      systems, marketing strategies, manufacturing processes, pricing and fee
      arrangements and structures and financial information, research and
      development activities, Creative Work, Intellectual Property or Invention)
      which he may have created, developed, received or obtained while in the
      service of the Company or any other Group Company, except to the extent
      the Executive is required to do so in connection with any judicial,
      regulatory or other similar proceeding or investigation. If the Executive
      shall be required by law (whether by court order, subpoena or otherwise)
      to communicate any such information to a court, governmental agency or any
      other person, the Executive shall use his best efforts to consult with the
      other members of the Board prior to responding to any such order, subpoena
      or other requirement. These restrictions shall continue to apply after the
      termination of the Appointment howsoever arising without limit in time and
      shall include information in the public domain for so long as the
      Executive is in a position to use such information more readily than
      others who have not worked for the Company or any other Group Company.

6.2   RECORDS. The Executive shall not (i) during the Appointment make (other
      than for the benefit of the Group) any record (whether on paper, computer
      memory, disk or otherwise) relating to any matter within the scope of the
      business of the Group Companies or their customers, clients, consultants
      and suppliers or concerning any of its or their dealings or affairs or
      (ii) either during the Appointment or at any time thereafter use or permit
      to be used any such records other than for the benefit of the Group, it
      being agreed by the parties that all such records (and copies thereof)
      shall be the property of the relevant member of the Group and shall be
      handed over to any other member of the Board by the Executive on the
      termination of the Appointment or (at the request of the Board) at any
      time during its term.

6.3   PUBLICATION. The Executive shall not during the Appointment or at any time
      thereafter either directly or indirectly publish any opinion, fact or
      material on any matter connected with or relating to the business of any
      member of the Group or their customers, clients, consultants or suppliers
      (whether confidential or not) without the prior approval of the Board.

                                       12
<Page>

7.    OBLIGATIONS UPON TERMINATION

Upon termination of the Appointment howsoever arising the Executive shall,
except as otherwise reasonably determined in good faith (with the advice of
counsel) by the Executive to be required by applicable law:-

7.1   at any time or from time to time thereafter upon the request of the Board
      (i) immediately resign in writing without claims of any kind as a director
      of and from all other offices held in the Company and membership of any
      organisation and any directorship or other office in any other company
      acquired by reason of or in connection with the Appointment or any
      employment or service agreement with any other Group Company, and any
      authority, power or proxy to vote held by the Executive in any such
      company (including but not limited to any appointment as an alternate
      director), (ii) acknowledge in writing that he has no claims of any kind
      arising from his office, membership or appointment and (iii) consent in
      writing to the revocation of any such authority, power or proxy, and
      should he fail to do so the Company is hereby irrevocably appointed to be
      the Executive's attorney in his name and on his behalf to execute any
      documents and to do any things necessary or requisite to give effect to
      this Clause 7.1.

7.2   deliver to the Board (or, as to documents and property of any other member
      of the Group, to the board of directors or other similar governing body of
      such other member of the Group):-

      (a)   all documents (including but not limited to correspondence, lists of
            clients or customers, plans, drawings, accounts and other documents
            of whatsoever nature and all copies thereof, whether on paper,
            computer memory, disk or otherwise) containing confidential or other
            business information referred to in Clause 6.1 or 6.2 or made or
            compiled or acquired by the Executive during the Appointment and
            concerning the business, finances or affairs of the Company or any
            other member of the Group or any of its or their partners, members,
            shareholders, directors, officers, employees, customers, clients,
            consultants or suppliers; and

      (b)   all other property of the Company or any other member of the Group;

7.3   transfer (without payment) to the Company or as the Company may direct any
      qualifying shares held by the Executive solely in his capacity as a
      director of a member of the Group; and

7.4   except as provided in Clause 5.2, have no rights as a result of this
      Agreement or any other terms of the Executive's employment with the
      Company, or any alleged breach of this Agreement or such terms, to any
      compensation under or in respect of any share option, bonus or long term
      incentive plans in which he may participate or have received grants or
      allocations at or before the date the Appointment terminates. Any rights
      which he may have under such schemes shall be exclusively governed by the
      rules of such schemes.

                                       13
<Page>

8.    RESTRICTIONS AFTER TERMINATION

8.1   RESTRICTIONS. The Executive covenants to the Company (for itself and for
      each other Group Company) that he shall not for the following periods
      after the Termination Date howsoever arising, save with the prior written
      consent of the Board, directly or indirectly, either alone or jointly with
      or on behalf of any person, firm, company or entity and whether on his own
      account or as principal, partner, member, shareholder, director, officer,
      employee, consultant or in any other capacity whatsoever:-

      (a)   for 12 months following the Termination Date employ, engage or offer
            to employ, engage or solicit the employment or engagement of, induce
            the termination of employment of or otherwise interfere with the
            relationship of the Company or any other Group Company with any Key
            Employee (whether or not such person would commit any breach of
            their contract of employment or engagement by reason of leaving the
            service of their employer); or

      (b)   at any time after the Termination Date disparage or otherwise make
            any statement that is damaging to the business or reputation of the
            Company or any other member of the Group or the business or
            prospects thereof, or any partner, member, shareholder, director,
            officer or employee of any member of the Group, or any of Providence
            Equity Partners L.P., Providence Equity Partners II L.P., Primus
            Capital Fund IV Limited Partnership, Primus Executive Fund Limited
            Partnership, or any affiliated company of any thereof, or any
            partner, member, shareholder, director, officer or employee of any
            thereof.

8.2   RESTRICTIONS SEPARATE AND INDEPENDENT. Each of the obligations contained
      in this Clause 8 constitutes an entire separate and independent
      restriction on the Executive, despite the fact that they may be contained
      in the same phrase, and if any part is found to be unenforceable the
      remainder will remain valid and enforceable.

8.3   MODIFICATIONS AS NECESSARY. Although such restrictions are considered by
      the parties to be fair and reasonable in the circumstances, it is agreed
      that if any such restrictions should be judged to be void or ineffective
      for any reason but would be treated as valid and effective if part of the
      wording thereof were deleted or the periods thereof reduced in scope, such
      restrictions shall apply with such modifications as may be necessary to
      make them valid and effective.

8.4   OTHER MEMBERS OF GROUP. The Executive agrees that he will at the request
      of the Company and at no cost to him enter into a direct agreement with
      any and each other member of the Group under which he will accept
      restrictions corresponding to the restrictions contained in this Clause 8
      (or such as will be appropriate in the circumstances) in relation to such
      member of the Group.

                                       14
<Page>

9.    DISCIPLINARY AND GRIEVANCE PROCEDURE

9.1   APPLICABLE RULES. There are no disciplinary rules applicable to the
      Executive except as provided in this Agreement.

9.2   REDRESS OF GRIEVANCES. Any application for the purpose of seeking redress
      of any grievance relating to the Executive's employment under this
      Agreement shall be made as provided elsewhere herein.

10.   EVENTS OF DEFAULT

10.1  The Executive shall have committed an act that constitutes an Event of
      Default hereunder if he shall at any time during the Appointment:-

      (a)   engage in gross misconduct, fraud, willful misconduct or gross
            negligence, or act with bad faith or reckless disregard of his duty
            to the Company in performing services hereunder or his duty to any
            other member of the Group;

      (b)   be convicted of or enter a plea of guilty or no contest to (i) any
            criminal offence that shall constitute a felony, or that shall be
            punishable by imprisonment for a period of one year or longer
            (whether or not such punishment is imposed on him), or for which a
            term of imprisonment of any duration shall be imposed on him (other
            than an offence under any road traffic legislation in the United
            Kingdom or elsewhere for which a fine or other non-custodial penalty
            is imposed on him) or (ii) any offence under any regulation or
            legislation relating to insider dealing or any other relevant
            legislation, rules or regulations which may apply to the Executive,
            the Company or any other member of the Group; provided that in
            either case of subsection (i) or (ii), Limited Vicarious Liability
            shall be excluded; or

      (c)   do anything of a similar nature which does or may bring the Company
            or any other member of the Group into disrepute or causes or may
            result in serious injury to the Company or any other member of the
            Group.

      If an act, or a failure to act, that was done, or omitted to be done, by
      the Executive in good faith and with a reasonable belief that Executive's
      act, or failure to act, was in the best interests of the Company or was
      required by applicable law or administrative regulation, such breach shall
      not constitute an Event of Default if, within thirty (30) days after the
      Executive is given written notice of such breach that specifically refers
      to this Clause, the Executive cures such breach in full.

10.2  SUSPENSION. The Company may at any time and upon written notice approved
      by not less than a75% majority of the Carrier1 SA Board (excluding, for
      these purposes, the Executive), suspend the Executive for a period of up
      to three months for the purposes of investigating any allegation of
      misconduct or neglect against the Executive that may constitute an Event
      of Default and during this period the Executive shall not (except with the
      prior written approval of the Board) attend any premises of or contact any
      employee (other than any director),

                                       15
<Page>

      customer, client, consultant or supplier of the Company or any other
      member of the Group. The Company and Carrier1 SA will use their reasonable
      best efforts to maintain any such suspension or investigation
      confidential.

10.3  The Company may not terminate the Appointment for an Event of Default
      unless:

      (a)   A meeting of the Carrier1 SA Board shall be called for the stated
            purpose of determining whether Executive's acts or omissions
            constitute an Event of Default and, if so, whether to terminate the
            Appointment for an Event of Default;

      (b)   no fewer than 20 days prior to the date of such meeting, the Company
            provides Executive and each member of the Carrier1 SA Board with
            written notice (the "NOTICE OF CONSIDERATION") of its intent to
            consider termination of the Appointment for an Event of Default,
            including (i) a description setting forth in reasonable detail the
            specific reasons which form the basis for such consideration, (ii)
            the date, time and location of such meeting of the Carrier1 SA
            Board, and (iii) Executive's rights under Clause 10.3(c) below;

      (c)   Executive shall have the opportunity, if he so elects, to appear
            before the Carrier1 SA Board in person and, at Executive's option,
            with legal counsel, and to present to the Carrier1 SA Board a
            response to the Notice of Consideration;

      (d)   the Appointment may be terminated for an Event of Default only if
            (i) the acts or omissions specified in the Notice of Consideration
            did in fact occur and do constitute an Event of Default as defined
            in this Agreement, (ii) the Carrier1 SA Board makes a specific
            determination by at least 75% of the members of the Carrier1 SA
            Board (excluding for these purposes the Executive) to such effect
            and to the effect that the Appointment should be terminated for an
            Event of Default and (iii) the Company thereafter provides Executive
            with a written notice which setting forth in reasonable detail the
            basis of such termination of Appointment for an Event of Default and
            which notice shall be consistent with the reasons set forth in the
            Notice of Consideration; and

      In the event that the existence of an Event of Default shall become an
      issue in any action or proceeding between the parties, the Company shall,
      notwithstanding the determination referenced in Clause 10.3(d) above, have
      the burden of establishing by a preponderance of the evidence that the
      actions or omissions specified in the Notice of Consideration did in fact
      occur and do constitute an Event of Default and that the Company has
      satisfied the substantive and procedural requirements of this Clause.

11.   NOTICES

Any notice to be given hereunder in writing may be given by either party by
personal delivery or post or by fax addressed to the other party at (in the case
of the Company) its

                                       16
<Page>

registered office at such time and (in the case of the Executive) his last known
place of residence, in each case with copies to the persons indicated below, and
any such notice given by personal delivery or fax shall be deemed to have been
given at the time at which the notice was delivered personally or transmitted or
if given by post would be delivered in the ordinary course of post.

Carrier One, LLC                                 Carrier1 International GmbH
901 Fleet Center                                 36 Militarstrasse
50 Kennedy Plaza                                 Zurich, Switzerland
Providence RI 02903                              Attention: General Counsel
USA                                              Facsimile: 41 1297-2601
Attention: Glenn M. Creamer                      Telephone: 41 1297-2600
Facsimile: (401) 751-1790
Telephone: (401) 751-1700

Sonnenschein Nath & Rosenthal                    Debevoise & Plimpton
8000 Sears Tower                                 919 Third Avenue
Chicago, IL 60606                                New York, NY 10022
USA                                              USA
Attention: Roger C. Siske                        Attention: Paul D. Brusiloff
Facsimile: (312) 876-7934                        Facsimile: (212) 909-6836
Telephone: (312) 876-8000                        Telephone: (212) 909-6000

12.   GENERAL PROVISIONS

12.1  ENTIRE AGREEMENT. This Agreement contains the entire understanding between
      the parties with respect to the subject matter hereof.

12.2  PROPER LAW. Any dispute, controversy, proceeding or claim of whatever
      nature arising out of or relating to, or breach of, this Agreement or any
      other terms of the Executive's employment with the Company shall be
      governed by, and this Agreement and such terms shall be construed in all
      respects in accordance with, English law.

12.3  LEGAL FEES AND LATE PAYMENTS.

      (a)   If the Executive prevails as to at least one material aspect (after
            exhaustion of all available judicial remedies) of a material claim
            asserted by him to obtain any benefit or enforce any right accorded
            to the Executive or to defend any claim against the Executive
            brought by the Company under this Agreement, the Company shall
            reimburse the Executive upon submission of an itemized bill for all
            reasonable legal fees and other expenses reasonably incurred by him
            in connection therewith.

      (b)   If either of the parties fails to pay any amount provided under this
            Agreement, such party shall pay to the other party interest,
            compounded monthly, on such amount from the date payment of such
            amount should otherwise have been made to the actual date of
            payment, at a rate equal to the prime commercial lending rate plus
            2% announced by THE WALL STREET

                                       17
<Page>

            JOURNAL on the date such amount is due or, if no such rate shall be
            announced on such date, the immediately prior date on which The Wall
            Street Journal announced such a rate.

12.4  WITHHOLDING AND OFFSETS. The Executive acknowledges that any payment made
      to him under this Agreement may be subject to income tax and national
      insurance contributions or other applicable taxes or social charges and
      that the Company may withhold amounts in respect of such taxes,
      contributions or other charges from any such payment.

12.5  CERTAIN EXPENSES. The Company shall pay for the reasonable costs, fees and
      expenses incurred by Executive's tax and legal advisor in connection with
      the negotiation and execution of this Agreement.

12.6  NO CONTRACTING-OUT CERTIFICATE. A contracting-out certificate is not in
      force in respect of the Executive's employment.

12.7  COLLECTIVE AGREEMENTS. There is no collective agreement which directly
      affects the Executive's employment.

12.8  CONSTRUCTION.

      (a)   HEADINGS. The headings in this Agreement are inserted for
            convenience only and shall not affect its construction.

      (b)   STATUTORY PROVISIONS. Any reference to a statutory provision shall
            be construed as a reference to any statutory modification or
            reenactment thereof (whether before or after the date hereof) for
            the time being in force.

12.9  INDEMNIFICATION. The Company shall indemnify and hold harmless the
      Executive to the greatest extent permitted under applicable law as the
      same now exists or may hereafter be amended (but, in the case of any such
      amendment, only to the extent that such amendment permits the Company to
      provide broader indemnification than was permitted prior to such
      amendment) and the Company's by-laws as such exist on the date of this
      Agreement if Executive was, is, or is threatened to be made, a party to
      any pending, completed or threatened action, suit, arbitration, alternate
      dispute resolution mechanism, investigation, administrative hearing or any
      other proceeding whether civil, criminal, administrative or investigative,
      and whether formal or informal, by reason of the fact that Executive is or
      was, or had agreed to become, a director, officer, employee, agent, or
      fiduciary of the Company, any other member of the Group or any other
      entity which Executive is or was serving at the request of the Company
      ("PROCEEDING"), against all expenses (including all reasonable attorneys'
      fees of legal counsel selected by the Company, retainers, court costs,
      transcripts, fees of experts, witness fees, travel expenses, duplicating
      costs, printing and binding costs, telephone charges, postage, delivery
      service fees, and all other reasonable disbursements or expenses
      customarily required in connection with asserting or defending claims)
      ("EXPENSES") and all claims, damages, liabilities and losses

                                       18
<Page>

      (including judgments; fines; liabilities under the applicable taxation
      laws, employment laws or the Employee Retirement Income Security Act of
      1974, as amended, for damages, excise taxes or penalties; damages, fines
      or penalties arising out of violation of any law related to the protection
      of the public health, welfare or the environment; and amounts paid or to
      be paid in settlement) incurred or suffered by Executive or to which
      Executive may become subject for any reason. A Proceeding shall not
      include any proceeding to the extent it concerns or relates to a matter
      described in Clause 12.3.

      (a)   ADVANCEMENT OF EXPENSES AND COSTS. All Expenses incurred by or on
            behalf of Executive in defending or otherwise being involved in a
            Proceeding shall be paid by the Company in advance of the final
            disposition of a Proceeding, including any appeal therefrom, within
            30 days after the receipt by the Company of a statement or
            statements from Executive requesting such advance or advances from
            time to time. Such statement or statements shall evidence the
            Expenses incurred by Executive in connection therewith, together
            with supporting invoices, receipts and other documentation. Any
            Expenses paid by Executive shall be deemed reasonable unless the
            Company establishes before a court of competent jurisdiction by
            clear and convincing evidence, that such Expenses are not
            reasonable.

      (b)   EFFECT OF CERTAIN PROCEEDINGS. The termination of any Proceeding by
            judgment, order, settlement or conviction, or upon a plea of nolo
            contendere or its equivalent, except, in each case, to the extent
            that the terms thereof expressly so provide, shall not, of itself
            (i) adversely affect the rights of Executive to indemnification, or
            (ii) create a presumption that Executive did not meet any particular
            standard of conduct or have any particular belief or that a court
            has determined that indemnification or contribution is not permitted
            by applicable law.

      (c)   OTHER RIGHTS TO INDEMNIFICATION. Executive's rights of
            indemnification and advancement of Expenses provided by this Clause
            12.9 shall not be deemed exclusive of any other rights to which
            Executive may now or in the future be entitled under applicable law,
            the certificate of incorporation, by-laws, agreement, vote of
            stockholders, or resolution of the Board, or other provisions of
            this Agreement or any other agreement, or otherwise.

      (d)   REPRESENTATIONS. The Company represents and warrants that this
            Clause 12.9 does not conflict with or violate its certificate of
            incorporation or by-laws, and agree that the Company will not amend
            its certificate of incorporation or by-laws in a manner that would
            limit the rights of Executive hereunder. The Company represents that
            the execution, delivery and performance of this Agreement has been
            duly and validly authorized by the Board.

      (e)   SURVIVAL OF INDEMNITY. Notwithstanding anything in this Agreement to
            the contrary, this Clause 12.9 shall survive any termination of the
            relationship of Executive with the Company and shall be binding on,
            and inure to the benefit

                                       19
<Page>

            of the successors and assigns of the Company and the successors,
            assigns, heirs and personal representatives of Executive.

12.10 D&O INSURANCE. The Company shall provide directors and officers insurance
      coverage to Executive during the period beginning on the Commencement Date
      and ending on the sixth anniversary of the Termination Date not less than
      the highest coverage level offered to any other senior executive or
      director of Carrier1 SA, in accordance with the coverage terms as in
      effect from time to time.

12.11 COUNTERPARTS. This Agreement may be executed in more than one counterpart,
      each of which shall be deemed an original, but all such counterparts when
      executed shall constitute one and the same agreement.

12.12 MODIFICATIONS. No modification, variation or amendment to this Agreement
      shall be effective unless such modification, variation or amendment is in
      writing and has been signed by or on behalf of both parties.

                                       20
<Page>

IN WITNESS whereof this Agreement has been executed as a deed as of the date
first above written.

Signed as a deed and delivered by          )
ROBERT MICHAEL MCTIGHE in the              )
presence of:-                              )    /s/ Robert Michael McTighe
                                                --------------------------------

Witness name:                                   /s/  Teresa Vega
                                                --------------------------------

Witness address:
                                                --------------------------------

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

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

Signed as a deed by, CARRIER 1 UK           )
LIMITED, acting by its attorney,            )
Carrier1 International, S.A., acting by its     /s/  Glenn Creamer
                                                --------------------------------

authorized officer in the presence of:          /s/ Mark A. Pelson
                                                --------------------------------

Witness name:                                   /s/ Kristine Brodeur
                                                --------------------------------

Witness address:
                                                --------------------------------

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

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

Signed as a deed by, CARRIER1               )
INTERNATIONAL, S.A.                         )
                                                /s/ Glenn Creamer
                                                --------------------------------

                                                /s/ Mark A. Pelson
                                                --------------------------------
<Page>

                                                                      Schedule A

1.    Alliance and Leicester Bank plc

2.    Pace Micro Technologies plc

3.    Red M Communications Ltd.

4.    European Telecom plc(1)

--------

(1) The Executive currently serves on the Board of European Telecom plc.
However, the parties agree that the Executive will resign from that Board prior
to October 1, 2001.<Page>

                          CARRIER 1 INTERNATIONAL S.A.
                                OPTION AGREEMENT

      This OPTION AGREEMENT, effective as of September 11, 2001, is by and among
Carrier 1 UK Limited (the "EMPLOYER"), Robert Michael McTighe (the "EXECUTIVE")
and Carrier 1 International S.A., a Luxembourg SOCIETE ANONYME (the "COMPANY").

                              W I T N E S S E T H:

      WHEREAS, the Employer is a subsidiary of the Company; and

      WHEREAS, the Executive has not previously been employed by the Company or
any of its affiliates; and

      WHEREAS, as an inducement essential to the Executive's entering into the
Employment Agreement with the Employer, dated as of the date hereof (the
"EMPLOYMENT AGREEMENT"), the Employer and the Company have agreed to grant the
Options (as defined below) covering the Option Shares (as defined below),
pursuant to, and subject to, the terms and conditions set forth in this
Agreement; and

      WHEREAS, pursuant to the Carrier 1 International S.A. Master Option
Agreement, the Company has agreed to make certain options available to the
Employer in order to enable the Employer to carry out its obligations under this
Agreement.

      NOW THEREFORE, in consideration of the mutual agreements herein contained,
the parties hereto agree as follows:

1. CERTAIN DEFINITIONS.

      As used in this Agreement, the terms "APPOINTMENT," "BOARD," "CARRIER1 SA
BOARD," "CHANGE OF CONTROL," "COMMENCEMENT DATE," "DISABILITY," "EVENT OF
DEFAULT," "GROUP COMPANY," "PERSON" and "TERMINATION DATE," shall each have the
respective meanings assigned to such terms in the Employment Agreement.

2. GRANT OF OPTION.

      Effective as of the date hereof, the Employer grants to Executive, subject
to the terms and conditions set forth herein, the right and option (the
"OPTIONS") to purchase from the Employer 1,200,000 of the ordinary shares of the
Company (the "OPTION SHARES" and each ordinary share of the Company, a "SHARE")
at a purchase price equal to US$1.10 per Share plus the amount of any capital
duty payable by the Company, the Employer or the Executive in respect of the
issuance of such Option Shares (not to exceed the amount of such capital duty
that would be payable upon a direct issuance by

<Page>

the Company of the Option Shares to the Executive) (the "EXERCISE PRICE") . The
number of Option Shares and the Exercise Price are subject to adjustment
pursuant to Section 7.2.

3.    VESTING AND EXERCISABILITY

3.1   IN GENERAL. Except as otherwise expressly provided in this Option
      Agreement, and subject to the continuous employment of the Executive with
      the Employer or one or more other Group Companies until the applicable
      vesting date, the Options shall become vested and exercisable as to 25% of
      the Option Shares on the twelve-month anniversary of the Commencement Date
      and as to the remainder of the Option Shares in six equal installments on
      each of the six next succeeding six-month anniversaries of the
      Commencement Date. Except as provided in Clause 3.2 below, if the
      Executive's employment with the Employer or one or more other Group
      Companies terminates, any portion of the Options that have not vested on
      or prior to the effective date of such termination shall be cancelled for
      an aggregate payment for all such unvested portion of US$1.00 to the
      Executive.

3.2   CERTAIN TERMINATIONS OF EMPLOYMENT. Notwithstanding anything in Clause 3.1
      to the contrary:-

      (a)   if a Change of Control occurs and the Executive is not offered the
            position of Chief Executive Officer of the surviving company (the
            parent company if such parent company is publicly traded and owns
            more than 50% of the surviving company) following such Change of
            Control and the Executive has elected accelerated vesting of the
            Options pursuant to Clause 4.4(c) of the Employment Agreement, then
            effective immediately prior to the Change of Control, any Options
            then held by the Executive and that have not vested previously in
            accordance with Clause 3.1 shall vest in full, provided that the
            Options shall not so vest if, after the announcement of or entering
            into the transaction that would constitute the Change of Control but
            prior to the consummation of the Change of Control, the Appointment
            has terminated for any reason other than a termination by the
            Company where no Event of Default has occurred or by the Executive
            for Good Reason; and

      (b)   if the Appointment of the Executive is terminated by the Company
            (other than as a result of an Event of Default or as a result of the
            Executive's death or Disability) or by the Executive for Good Reason
            (other than in the circumstance where the preceding Clause 3.2(a)
            applies) and the Executive has elected accelerated vesting of the
            Options pursuant to Clause 4.4(d) of the Employment Agreement,
            effective as of the Termination Date, the Options shall immediately
            vest and become exercisable as to that number of Option Shares that
            would have become vested and exercisable pursuant to

                                       2
<Page>

            Clause 3.1 within the twelve-month period following the Termination
            Date (notwithstanding such termination of the employment).

3.3   BOARD DISCRETION. The Board in its sole discretion, with the consent of
      the Carrier1 SA Board, may accelerate the vesting or exercisability of all
      or any portion of the Options, at any time and from time to time.

4.    EXERCISE

4.1   Once vested in accordance with the provisions of this Option Agreement,
      the Options may be exercised at any time and from time to time prior to
      the date such options terminate as provided for in Section 5 by giving
      written notice to the Employer at its principal office address, or to such
      transfer agent as the Employer shall designate. Such notice shall identify
      the Option being exercised and specify the number of Shares as to which
      this Option is being exercised, accompanied by full payment of the
      purchase price therefor either (a) in United States dollars in cash or by
      check, (b) through delivery of Shares that have been owned by the
      Executive for at least six months and having a fair market value equal as
      of the date of the exercise to the cash exercise price of the Option, (c)
      by any combination of (a) and (b) above. Options may only be exercised
      with respect to full ordinary shares. No fractional ordinary shares shall
      be issued.

5.    TERMINATION OF OPTIONS

5.1   NORMAL EXPIRATION DATE. The Options shall expire on the tenth (10th)
      anniversary of the Commencement Date, subject to earlier termination as
      provided in Clause 5.2 or 6 below.

5.2   EFFECT OF TERMINATION OF EMPLOYMENT.

      (a)   TERMINATION UPON DEATH OR DISABILITY. If the Executive ceases to be
            employed by the Employer and all other Group Companies by reason of
            his death or Disability, the Executive (or his personal
            representative, estate or beneficiary, as applicable) shall have the
            right to exercise the Options for that number of Option Shares that
            have vested in accordance with Section 3 on or prior to the
            Termination Date until the specified expiration date of the Options
            provided for in Clause 5.1.

      (b)   TERMINATIONS BY THE EMPLOYER OTHER THAN WHERE EVENT OF DEFAULT HAS
            OCCURRED. If the Employer (and any other Group Company then
            employing the Executive) terminates the Executive's employment
            (other than as a result of his death or Disability or where an Event
            of Default has occurred), or the Executive terminates for Good
            Reason, the Executive (or his personal representative, estate or
            beneficiary, as applicable) shall have the right,

                                       3
<Page>

            subject to Clause 5.2(e), to exercise the Options for the number of
            Option Shares that have vested in accordance with Section 3 on or
            prior to the Termination Date until the earlier of (i) the specified
            expiration date of the Options provided for in Clause 5.1 or (ii) 24
            months from the Termination Date.

      (c)   TERMINATIONS BY THE EXECUTIVE OTHER THAN FOR GOOD REASON. If the
            Executive voluntarily terminates employment with the Employer (or
            other Group Companies then employing the Executive) other than for
            Good Reason, then Executive shall have the right to exercise the
            Options for the number of Option Shares that have vested in
            accordance with Section 3 until the earlier of (i) the specified
            expiration date of the Options provided for in Clause 5.1 or (ii) 30
            days from the Termination Date.

      (d)   EVENT OF DEFAULT. If an Event of Default has occurred, the Options,
            whether or not vested, shall immediately be cancelled for an
            aggregate payment for all such Options of US$1.00 to the Executive
            and neither the Executive nor any person claiming through the
            Executive shall have any further rights with respect thereto.

      (e)   VIOLATION OF POST-TERMINATION OBLIGATIONS. Notwithstanding anything
            herein to the contrary, if the Executive breaches any of his
            obligations under any of Clauses 6, 7 or 8 of his Employment
            Agreement, any outstanding Options shall immediately be cancelled
            for an aggregate payment of US$1.00 to the Executive and neither the
            Executive nor any person claiming through the Executive shall have
            any further rights with respect thereto.

6.    CHANGE OF CONTROL

      In the event of a Change of Control, the Employer, under the instruction
from the Carrier1 SA Board (as constituted immediately prior to the consummation
of the transaction constituting the Change of Control) shall either: (i) make
appropriate provision for the continuation of this Options by substituting on an
equitable basis for the Option Shares then subject to this Option either (a) the
consideration payable with respect to the outstanding Shares in connection with
the Change of Control or (b) equity securities of the surviving corporation in
such Change of Control (or a direct or indirect parent thereof); or (ii) upon
written notice to Executive, provide that the Options must be exercised, to the
extent exercisable, within a specified number of days of the date of such
notice, at the end of which period the Options shall terminate; or (iii)
terminate the Options in exchange for a cash payment equal to the excess of the
fair market value of the Option Shares subject to this Option (to the extent
then exercisable) over the Exercise Price thereof.

                                       4
<Page>

7.    MISCELLANEOUS PROVISIONS

7.1   NON-TRANSFERABILITY OF OPTIONS. The Options may be exercised only by the
      Executive or, following his death, by the Executive's estate. The Options
      are not assignable or transferable, in whole or in part, and it may not,
      directly or indirectly, be offered, transferred, sold, pledged, assigned,
      alienated, hypothecated or otherwise disposed of or encumbered (including
      without limitation by gift, operation of law or otherwise) other than by
      will or by the laws of descent and distribution to the estate of the
      Executive upon the Executive's death.

7.2   ADJUSTMENTS. The number, class and exercise price of any outstanding
      Options (and the number of shares subject to outstanding Options), shall
      be adjusted by the Board, upon the instruction of the Carrier1 Board, if
      and to the extent necessary or appropriate to reflect any stock dividend,
      stock split, reverse stock split or share combination of, or extraordinary
      cash dividend on, the Shares or recapitalization, reorganization, merger,
      consolidation, split-up, spin-off, combination, exchange of shares or
      other similar event on or after the date hereof.

7.3   NO RIGHTS AS STOCKHOLDER. The Executive shall not have the rights of a
      shareholder with respect to the Option Shares until the date on which the
      Options Shares are recorded in his or her name in the share registry of
      the Company following exercise hereof and no adjustments shall be made for
      distributions, dividends or similar rights for which the record date is
      before the date such Share is issued.

7.4   NO RIGHT TO CONTINUED EMPLOYMENT. Nothing in this Option Agreement shall
      interfere with or limit in any way the right of the Employer or any Group
      Company to terminate the Executive's employment at any time, or confer
      upon the Executive any right to continued employment.

7.5   MODIFICATION OF OPTIONS. The Employer, under the instruction from the
      Carrier1 SA Board, shall have the authority to effect, at any time and
      from time to time, with the written consent of Executive, the modification
      of the terms of this Option Agreement.

7.6   COMPLIANCE WITH LAW AND REGULATIONS. The Options and the obligation of the
      Employer to sell and deliver Shares hereunder shall be subject to all
      applicable laws, rules and regulations of any jurisdiction and to such
      approvals by any government or regulatory agency as may be required. The
      Employer shall not be required to issue or deliver any certificates for
      Shares prior to (i) the listing of such Shares on any stock exchange on
      which the Shares may then be listed, and (ii) the completion of any
      registration or qualification of such Shares under any applicable law, or
      any rule or regulation of any government body. No Shares

                                       5
<Page>

      shall be issued upon exercise of any Options granted hereunder, if such
      exercise would result in a violation of applicable law, including
      applicable securities laws.

7.7   WITHHOLDING TAXES. Executive acknowledges and agrees that the Employer and
      the other Group Companies have the right to require from the Executive or
      to deduct from payments of any kind otherwise due to Executive any
      foreign, federal, state or local taxes of any kind required by law to be
      withheld with respect to the exercise of the Options hereunder. The
      Employer in its discretion may condition the exercise of the Options on
      the Executive's making satisfactory arrangements for such withholding. For
      the avoidance of doubt, each of the Employer, on the one hand, and the
      Executive, on the other, shall bear and pay their respective National
      Insurance contributions imposed in connection with the Executive's
      exercise of the Options.

7.8   ADS. Upon written request of the Executive, the Company will use its good
      faith, commercially reasonable best efforts to facilitate deposit by the
      Executive of the Option Shares in exchange for American Depository Shares
      with respect to the Shares (the "ADS's"), if at the time of such request
      such ADS's are then maintained and available. The Company shall pay all
      expenses, fees and charges for receiving deposit of the Shares and issuing
      ADS's.

7.9   ASSIGNMENT. The Employer may assign all or any part of its rights and
      obligations under this Agreement to the Company or any other Group
      Company.

7.10  NOTICES. Any notice hereunder shall be made as provided in the Employment
      Agreement.

7.11  GOVERNING LAW; JURISDICTION.

      (a)   This Option Agreement shall be construed and administered in
            accordance with and governed by the laws of Luxembourg. In the event
            of any conflict or inconsistency between the provisions of this
            Agreement, the terms of this Agreement shall govern.

      (b)   The courts of England have exclusive jurisdiction to hear and decide
            any suit, action or proceedings, and to settle any disputes, which
            may arise out of or in connection with this Option Agreement
            (respectively, "PROCEEDINGS" and "DISPUTES") and for this purpose
            each party irrevocably submits to the jurisdiction of the Courts of
            England. Each party irrevocably waives any objection which it might
            at any time have to the courts of England being nominated as the
            forum to hear and decide any Proceedings and to settle any disputes
            and agrees not to claim that the courts of England are not a
            convenient or appropriate forum.

                                       6
<Page>

7.12  SIGNATURES. This Agreement is made in three copies, each of which shall be
      considered as an original and each of the three parties acknowledges
      having received a copy.

      IN WITNESS WHEREOF, the Employer has caused this Option Agreement to be
executed by its duly authorized officer and the Executive has executed this
Option Agreement as of the date hereof.

                                        EXECUTIVE

                                        /s/ Robert Michael McTighe
                                        ---------------------------------------

                                        CARRIER 1 UK LIMITED, acting by its
                                        attorney, Carrier 1 International S.A.,
                                        acting by its authorized officers

                                        By: /s/ Glenn Creamer
                                            -----------------------------------
                                            Title:

                                        By: /s/ Mark A. Pelson
                                            -----------------------------------
                                            Title:

                                        CARRIER 1 INTERNATIONAL S.A.

                                        By: /s/ Glenn Creamer
                                            -----------------------------------
                                            Title:

                                        By: /s/ Mark A. Pelson
                                            -----------------------------------
                                            Title:

                                       7

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