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                                                                   Exhibit 10.18

Share Sale Agreement

between

IFX Corporation
as Vendor

and


Duncan Lawrie Offshore Services Limited in its capacity as
trustee for The IFX Group Trust
as Purchaser


relating to

the sale and purchase of the redeemable preference share in
IFX Limited

SIMMONS & SIMMONS

21 Wilson Street London EC2M 2TX
Tel: 020 7628 2020 / 7528 9292 Fax: 020 7628 2070 DX Box No 12

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                                                                   Exhibit 10.18


                                   CONTENTS

 1.  Definitions and Construction................................  1

 2.  Sale of Preference Share....................................  2

 3.  Consideration...............................................  3

 4.  Conditions..................................................  3

 5.  Completion..................................................  3

 6.  Waiver by the Vendor........................................  4

 7.  Warranties and representations..............................  4

 8.  Confidentiality.............................................  5

 9.  Provisions relating to this Agreement.......................  6

10.  Law and Jurisdiction........................................  8

                                       i
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                                                                   Exhibit 10.18

THIS AGREEMENT is dated August 24, 2000 and made


BETWEEN:
--------


(1)  IFX CORPORATION, (the "Vendor"), a corporation incorporated under the laws
     of the State of Delaware and whose registered office is at 707 Skokie
     Boulevard, Northbrook, Illinois 60062; and

(2)  Duncan Lawrie Offshore Services Limited, being a company incorporated in
     the Isle of Man with company number 44074C and registered office at 14-15
     Mount Havelock, Douglas, Isle of Man IM1 2QG in its capacity as trustee of
     THE IFX GROUP TRUST, being a trust constituted under the laws of Jersey
     (the "Purchaser").

Background:

The Vendor wishes to sell and the Purchaser wishes to acquire the single issued
redeemable preference share of US$1 in the Company on the terms of and subject
to such conditions to this Agreement.

THE PARTIES AGREE THAT:
-----------------------

1.   Definitions and Construction
     ----------------------------

1.1  In this Agreement where the context admits:


     "Admission" means admission to the Official List of the UK Listing
     Authority and admission to trading on the London Stock Exchange plc of the
     consideration shares to be allotted to the Purchaser under the Zetters
     Share Sale Agreement becoming effective;

     "Affiliate" means, in relation to a body corporate, any subsidiary or
     holding company of such body corporate, and any subsidiary of any such
     holding company for the time being;

     "Agreed Form" means in relation to any document, a document in the terms
     signed or initialled by or on behalf of the parties for identification;

     "Articles" means the Articles of Association of the Company;

     "Business Day" means a day (other than Saturday or Sunday) on which banks
     are open for ordinary banking business in London;

     "Company" means IFX Limited, a company incorporated in England and Wales
     (registered number 2876284) and whose registered office is at America
     House, 2 America Square, London EC3N 2LU;

     "Completion" means completion of the sale and purchase of the Preference
     Share in accordance with clause 5;

     "Completion Date" means the date upon which Completion takes place;

     "Consideration" means the consideration payable by the Purchaser for the
     Preference Share as set out in clause 3;

     "Deed of Termination and Waiver" means the deed in Agreed Form marked "B"
     attached to this Agreement;

                                       1
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                                                                   Exhibit 10.18


     "Director" means any director or officer of the Vendor or a member of the
     Vendor's Group since 01 January 1994 and "Directors" means each and all of
     them;

     "Encumbrance" includes any interest or equity of any person (including any
     right to acquire, option or right of pre-emption); any mortgage, charge,
     pledge, lien, assignment, hypothecation, security interest (including any
     created by law), title retention or other security agreement or
     arrangement; and any rental, hire purchase, credit sale or other agreement
     for payment on deferred terms;

     "First Share Sale Agreement" means the share sale agreement between the
     Vendor and the Purchaser, dated 30 June 1999 relating to the sale and
     purchase of 2,448,465 ordinary `A' shares in the Company;

     "Preference Share" means the single issued redeemable preference share of
     US$1 in the Company to be bought and sold pursuant to clause 2 of this
     Agreement;

     "Purchaser's Solicitors" means Simmons & Simmons of 21 Wilson Street,
     London EC2M 2TX;

     "Vendor's Attorneys" means Neal, Gerber & Eisenberg, Suite 2200, 2 N. La
     Salle Street, Chicago, Illinois 60602;

     "Vendor's Group" means the Vendor and each of its Affiliates from time to
     time;

     "Warranties" means the warranties and representations set out in clause 7;

     "Zetters Share Sale Agreement" means an agreement to be entered into
     between the Purchaser, other parties and Zetters Group plc (a company
     incorporated in England and Wales under registered number 853270 with its
     registered office at 86-88 Clerkenwell Road, London EC1P 12S) relating to
     the proposed sale and purchase of 4,896,929 ordinary shares of US$1 and a
     single redeemable preference share of US$1 in the share capital of the
     Company, where the total consideration payable to the Purchaser comprises:-

     (a)  8,717,949 ordinary shares in Zetters;

     (b)  (Pounds)3.9 million in cash; and

     (c)  the sterling equivalent of $469,406; and

     "Zetters Solicitors" means Herbert Smith of Exchange House, Primrose
     Street, London EC2A 2HS.

1.2  The headings and sub-headings and any contents pages are inserted for
     convenience only and shall not affect the construction of this Agreement.

2.   Sale of Preference Share

     Subject to the terms of this Agreement, the Vendor shall sell with full
     title guarantee and the Purchaser shall purchase, free from all
     Encumbrances and together with all rights now or hereafter attaching to the
     Preference Share including, for the avoidance of doubt, the dividend
     payable by the Company in respect of the Preference Share for the three
     months period ending on 30 September 2000.

                                       2
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                                                                   Exhibit 10.18

3.   Consideration

     The Consideration payable by the Purchaser to the Vendor for the Preference
     Share shall be the sum of US$2,400,000.

4.   Conditions

     Completion of the sale and purchase of the Preference Share is subject to
     the full and complete satisfaction of each and all of the conditions to
     completion set out in the Zetters Share Sale Agreement, save for any
     condition relating to the due and complete satisfaction of the conditions
     to this Agreement and any condition relating to Admission becoming
     effective.

5.   Completion

5.1  Date and place of Completion

     Completion shall take place at the offices of Simmons & Simmons, 21 Wilson
     Street, London EC2M 2TX on the date of completion of the Zetters Share Sale
     Agreement.

5.2  Vendor's obligations

     By no later than the day prior to the date of Completion the Vendor shall
     deliver or cause to be delivered to the Purchaser's Solicitors (all such
     documents to be held to the order of the Vendor's Attorney pending
     Completion):

     (A)  a signed class resolution evidencing the Vendor's consent to any
          variation of the rights attaching to the Preference Share by reason of
          the proposed resolution in the Agreed Form marked `A', to amend the
          Articles to delete Article 3.1(B)(v) of the Articles and replace it
          with the following:

               "(v) Transfers

                    The redeemable preference share shall be freely
                    transferable";

     (B)  (1)  a transfer of the Preference Share duly executed by the Vendor in
               favour of the Purchaser together with the relative share
               certificate;

          (2)  such waivers or consents as the Purchaser may reasonably require
               to enable the Purchaser to be registered as holder of the
               Preference Share;

          (3)  a duly executed Deed of Termination and Waiver effective on the
               Completion Date agreeing to the termination and waiver of any
               outstanding obligations and rights respectively, under the First
               Share Sale Agreement, including for the avoidance of doubt, the
               rights of the Vendor to additional consideration payments in the
               event of a Park Trust Adjustment Event (as defined therein) and
               rights of indemnification as provided for in section 1.4 of
               Article I and section 3.9 of Article III respectively thereof and
               any outstanding obligations and liabilities the Company may have
               to the Vendor, in Agreed Form marked `B'.

5.3  Purchaser's obligations

     By no later than the day prior to the date of Completion the Purchaser
     shall:-

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                                                                   Exhibit 10.18

(A)  deliver or cause to be delivered to the Vendor's Attorneys to be held to
     the order of the Purchaser's Solicitors a signed written shareholder
     resolution of the Company, in the Agreed Form marked `C';

(B)  deliver or cause to be delivered to the Vendor's Attorneys to be held to
     the order of the Purchaser's Solicitors a duly executed Deed of Termination
     and Waiver effective as at the Completion Date agreeing to the termination
     and waiver of any outstanding obligations and rights respectively, in
     Agreed Form marked "B"; and

(C)  pay or cause to be paid to the Vendor's Attorneys to be held to the order
     of Zetter's Solicitors the Consideration for the Preference Share as
     provided by clause 3 and in accordance with the payment provisions in
     clause 9.7.

5.4  Completion

     Completion shall take place upon Admission whereupon:-

     (A)  all documents delivered to the Purchaser's Solicitors pursuant to
          clause 5.2 shall cease to be held to the order of the Vendor's
          Attorneys; and

     (B)  the documents delivered to the Vendor's Attorney pursuant to sub-
          clause 5.3(B) and the payment made to the Vendor's Attorney pursuant
          to sub-clause 5.3(C) shall cease to be held to the order of the
          Purchaser's Solicitors and Zetters' Solicitors respectively.

5.5  Failure to complete

     If Completion does not take place on or before 31 October 2000, the
     provisions of this Agreement shall have no effect and no party shall have
     any rights or liabilities under them (without prejudice to the rights of
     any of the parties in respect of antecedent breaches).

6.   Waiver by the Vendor

     The Vendor waives any rights to any additional consideration payments under
     the First Share Sale Agreement arising from the occurrence of a Park Trust
     Adjustment Event (as defined in the First Share Sale Agreement) by reason
     of the Purchaser entering into the Zetters Share Sale Agreement.

7.   Warranties and representations

7.1  The Vendor hereby warrants and represents to and for the benefit of the
     Purchaser that:

     (A)  The Vendor has full power and authority to enter into and perform this
          Agreement, and may execute and deliver this Agreement and perform its
          obligations under this Agreement and this Agreement constitutes valid
          and binding obligations of the Vendor in accordance with its terms.

     (B)  The Vendor is the registered and sole beneficial owner of the
          Preference Share free from any Encumbrances.

     (C)  There is not outstanding any indebtedness or other liability (actual
          or contingent) owing by the Company to the Vendor or any member of the
          Vendor's Group or to any Director or any person connected with any of
          them, nor is there any indebtedness owing to the Company by any such
          person.

7.2  The Purchaser hereby warrants and represents to and for the benefit of the
     Vendor that it has full power and authority to enter into and perform this
     Agreement, and may execute

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                                                                   Exhibit 10.18

     and deliver this Agreement and perform its obligations under this Agreement
     and this Agreement constitutes valid and binding obligations of the
     Purchaser in accordance with its terms.

8.   Confidentiality
     ---------------

8.1  Confidentiality

     Each party:-

     (A)  shall treat as strictly confidential the provisions of this Agreement
          and the terms of the Zetters Share Sale Agreement as disclosed by the
          Purchaser to the Vendor and the process of their negotiation and all
          information about any other party obtained or received by it as a
          result of negotiating, entering into or performing its obligations
          under this Agreement ("Confidential Information"); and

     (B)  shall not, except with the prior written consent of each other party
          (which shall not be unreasonably withheld or delayed), publish or
          otherwise disclose to any person any Confidential Information.

8.2  Permitted disclosures

     Clause 8.1 shall not apply if and to the extent that the party disclosing
     Confidential Information can demonstrate that:

     (A)  such disclosure is required by law or by any securities exchange or
          regulatory or governmental body having jurisdiction over it (including
          but not limited to the London Stock Exchange plc, the Panel on
          Takeovers and Mergers and the Serious Fraud Office) and whether or not
          the requirement has the force of law; or

     (B)  such disclosure is to its professional advisers in relation to the
          negotiation, entry into or performance of this Agreement or any matter
          arising out of the same or, where the disclosing party is the
          Purchaser, is of information necessarily or reasonably disclosed to
          any person concerned with any transaction for financing the purchase
          of the Preference Share or the granting of security over the same or
          over the benefit of this Agreement, any other transaction dependent
          upon or relating to such purchase or any transaction involving the
          sale or other disposal of the Preference Share or the whole or any
          part of the issued share capital of the Company; or

     (C)  such disclosure is required to facilitate the satisfaction of any of
          the Conditions; or

     (D)  such disclosure is required in order to facilitate any assignment or
          proposed assignment of the whole or any part of the rights or benefits
          under this Agreement which is permitted by clause 9.1; or

     (E)  the Confidential Information concerned was lawfully in its possession
          (as evidenced by written records) prior to its being obtained or
          received as described in clause 8.1(A); or

     (F)  the Confidential Information concerned has come into the public domain
          other than through its fault or the fault of any person to whom such
          Confidential Information has been disclosed in accordance with clause
          8.1(B).

                                       5
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                                                                   Exhibit 10.18

8.3  Continuance of restrictions

     The restrictions contained in this clause 8 shall survive Completion and
     shall continue without limit of time.

9.   Provisions relating to this Agreement
     -------------------------------------

9.1  Assignment

     (A)  This Agreement shall be binding upon and enure for the benefit of the
          successors of the parties but shall not be assignable, save that the
          Purchaser may at any time assign all or any part of its rights and
          benefits under this Agreement and any agreement referred to herein,
          including, without limitation, any of the Warranties, to any
          transferee of the share capital of the Company or to any Affiliate of
          the Purchaser.

     (B)  Any such assignee may enforce any right or benefit assigned to it as
          if it had been named in this Agreement as the Purchaser, and may
          recover thereunder as if it had acquired the Preference Share for the
          consideration and upon the other terms of this Agreement and had
          thereby sustained all diminutions of value, losses and expenses in
          consequence of such acquisition as have been sustained by the
          Purchaser and any subsequent holder of such share capital, including
          itself, as if they were all one entity which had retained the
          ownership of such issued share capital throughout.

9.2  Whole agreement and variations

     (A)  This Agreement, together with any documents referred to in it
          (including for the avoidance of doubt the Deed of Termination and
          Waiver), constitutes the whole agreement between the parties relating
          to its subject matter and supersedes and extinguishes any prior
          drafts, agreements, and undertakings, whether in writing or oral,
          relating to such subject matter, except to the extent that the same
          are repeated in this Agreement.

     (B)  Each party acknowledges that it has not been induced to enter into
          this Agreement by any representation, warranty, promise or assurance
          save for those contained in this Agreement.

     (C)  No variation of this Agreement shall be effective unless made in
          writing and signed by each of the parties.

9.3  Agreement survives Completion

     The Warranties and all other provisions of this Agreement, in so far as the
     same shall not have been performed at Completion, shall remain in full
     force and effect notwithstanding Completion.

9.4  Rights etc cumulative and other matters

     (A)  The rights, powers, privileges and remedies provided in this Agreement
          are cumulative and are not exclusive of any rights, powers, privileges
          or remedies provided by law or otherwise.

     (B)  No failure to exercise nor any delay in exercising any right, power,
          privilege or remedy under this Agreement shall in any way impair or
          affect the exercise thereof or operate as a waiver thereof in whole or
          in part.

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                                                                   Exhibit 10.18

      (C)  No single or partial exercise of any right, power, privilege or
           remedy under this Agreement shall prevent any further or other
           exercise thereof or the exercise of any other right, power, privilege
           or remedy.

9.5   Further assurance

      At any time after Completion the Vendor shall, at the request and cost of
      the Purchaser, execute or procure the execution of such documents and do
      or procure the doing of such acts and things as the Purchaser may
      reasonably require for the purpose of vesting the Preference Share in the
      Purchaser or its nominees and giving to the Purchaser the full benefit of
      all the provisions of this Agreement.

9.6   Invalidity

      If any provision of this Agreement shall be held to be illegal, void,
      invalid or unenforceable under the laws of any jurisdiction, the legality,
      validity and enforceability of the remainder of this Agreement in that
      jurisdiction shall not be affected, and the legality, validity and
      enforceability of the whole of this Agreement in any other jurisdiction
      shall not be affected.

9.7   Payment to the Vendor

      Any payment falling to be made to the Vendor under any provision of this
      Agreement may be made by telegraphic transfer to the account of the
      Vendor's Attorneys, account no: 0980023788 account name: Neal Gerber &
      Eisenberg Client Funds, ABA no.: 271070801, reference: IFX Corporation.

9.8   Counterparts

      This Agreement may be executed in any number of counterparts, which shall
      together constitute one Agreement. Any party may enter into this Agreement
      by signing any such counterpart.

9.9   Costs

      Subject to clause 9.5, each party shall bear its own costs arising out of
      or in connection with the preparation, negotiation and implementation of
      this Agreement.

9.10  Notices

      (A)  Any notice or other communication required to be given under this
           Agreement or in connection with the matters contemplated by it shall,
           except where otherwise specifically provided, be in writing in the
           English language and shall be addressed as provided in clause 9.10(B)
           and may be:

           (1)  personally delivered, in which case it shall be deemed to have
                been given upon delivery at the relevant address; or

           (2)  if within the United Kingdom, sent by first class pre-paid post,
                in which case it shall be deemed to have been given two Business
                Days after the date of posting; or

           (3)  if from or to any place outside the United Kingdom, sent by pre-
                paid priority airmail, in which case it shall be deemed to have
                been given seven Business Days after the date of posting; or

           (4)  sent by fax, in which case it shall be deemed to have been given
                when despatched, subject to confirmation of uninterrupted
                transmission by a

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                                                                   Exhibit 10.18

                transmission report, provided that any notice despatched by fax
                after 17.00 hours (at the place where such fax is to be
                received) on any day shall be deemed to have been received at
                08.00 on the next Business Day.

      (B)  The addresses and other details of the parties referred to in clause
           9.10(A) are, subject to clause 9.10 (e):

           Name:                  IFX Corporation

           Address:               707 Skokie Boulevard

                                  5th Floor

                                  Northbrook

                                  Illinois 60062

           Fax number:            +1 305 574 7867


           Name:                  The IFX Group Trust

           For the attention of:  Mr Shaun Ridings

           Address:               c/o Duncan Lawrie Offshore Services Limited

                                  14/15 Mount Havelock

                                  Douglas

                                  Isle of Man

           Fax number:            + 44 1624 662 878

      Any party to this Agreement may notify the other parties of any change to
      its address or other details specified in clause 9.10(B), provided that
      such notification shall only be effective on the date specified in such
      notice or five Business Days after the notice is given, whichever is
      later.

10.   Law and Jurisdiction
      --------------------

10.1  English Law

      This Agreement shall be governed by, and construed in accordance with,
      English law.

10.2  Jurisdiction

      In relation to any legal action or proceedings to enforce this Agreement
      or arising out of or in connection with this Agreement ("Proceedings")
      each of the parties irrevocably submits to the exclusive jurisdiction of
      the English courts and waives any objection to Proceedings in such courts
      on the grounds of venue or on the grounds that the Proceedings have been
      brought in an inconvenient forum.

AS WITNESS the hands of the duly authorised representatives of the parties on
the date first before written.

                                       8
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                                                                   Exhibit 10.18

SIGNED by                              )
duly authorised for and on behalf of   )
IFX CORPORATION                        )
in the presence of:-                   Joel Eidelstein
                                       (Director)
Jose Leiman

Michael Shalom

Jak Bursztyn


SIGNED by                              )
for an on behalf of                    )
DUNCAN LAWRIE OFFSHORE                 )
SERVICES LIMITED                       )
in its capacity as trustee of          )
THE IFX GROUP TRUST                    )
in the presence of:-                   Shaun Ridings
                                       (Director)
Alan Molloy

                                       9