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                                                                    Exhibit 10.5

                                 IFX CORPORATION

                             STOCK OPTION AGREEMENT

       THIS STOCK OPTION AGREEMENT (the "Agreement") is dated as of November
                                         ---------
10, 1998 (the "Grant Date") and is entered into between IFX CORPORATION, a
               ----------
Delaware corporation ("IFX"), and JOEL M. EIDELSTEIN ("Optionee"). In
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consideration of the mutual promises and covenants made herein, the parties
hereby agree as follows:

       1.    Defined  Terms.  Capitalized terms not otherwise defined herein
             --------------
shall have the same meaning ascribed to them in the Plan.

       2.    Grant of Option.
             ---------------

             (a)   Subject to the terms and conditions of the IFX 1998 Stock
Option and Incentive Compensation Plan (the "Plan"), a copy of which is attached
                                             ----
hereto and incorporated herein by this reference, IFX grants to Optionee an
option (the "Option") to purchase 300,000 shares (the "Shares") of IFX's common
             ------                                    ------
stock, $.02 par value (the "Common Stock"), at a price equal to $3.00 per share
                            ------------
(the "Option Price"). The Option Price has been determined by the Compensation
      ------------
Committee of the Board of Directors of IFX (the "Committee"), acting in good
                                                 ---------
faith, to be in excess of 150% of the fair market value of the Common Stock on
the Grant Date.

             (b)   The Option is intended to qualify as an incentive stock
option as defined in, and will be subject to, Section 422 of the Internal
Revenue Code of 1986, as amended (the "Code"), and all provisions of this
                                       ----
Agreement are to be construed in conformity with this intention. The failure of
all or any portion of the Option to qualify as an incentive stock option under
Section 422 of the Code shall not render invalid the Option or any portion of
the Option that fails to so qualify.

       3.    Term.  Except as otherwise provided herein, the Option shall be
             ----
valid for a term commencing on the Grant Date and ending 10 years after the
Grant Date (the "Termination Date").
                 ----------------

             (a)   Option Rights Upon Termination of Employment. If Optionee
ceases to be employed by IFX or any of its subsidiaries or affiliates
(collectively, the "Subsidiaries") for any reason other than death or for
                    ------------
"Cause" (as defined in the Plan), the Option shall be exercisable at any time
prior to the earlier of the termination date or the date three months after the
date of termination of employment.

             (b)   Option Rights Upon Termination for Cause. If Optionee's
                   ----------------------------------------
employment with IFX and/or its Subsidiaries is terminated for Cause, any
unexercised portion of the Option immediately shall be cancelled and thereafter
may not be exercised and Optionee shall forfeit all rights to any unexercised
portion of the Option.

             (c)   Option Rights Upon Death of Optionee. Following the death of
                   ------------------------------------
Optionee,
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the Option may be exercised by Optionee's personal representative or by the
distributee to whom Optionee's rights under the Option shall pass by will or by
the laws of descent and distribution, at any time prior to the earlier of the
Termination Date or the date six months after the date of Optionee's death.

       4.    Vesting.
             -------

             (a)   Standard Vesting. The Option may only be exercised to the
                   ----------------
extent vested. Any vested portion of the Option may be exercised at any time in
whole or from time to time in part. Vesting shall commence on the Grant Date and
Optionee shall vest in the Option according to the following schedule (each date
set forth below, a "Vesting Date"):
                    ------------

                                                       Cumulative
                                                       Percentage of
                  Vesting Date                         Option Vested
                  ------------                         -------------

                  Grant Date                                25%

                  January 1, 1999                           50%

                  January 1, 2000                           75%

                  January 1, 2001                           100%

Optionee must be employed by IFX or any Subsidiary on (a) the Grant Date, in
order to vest in any portion of the Option, and (b) on any Vesting Date, in
order to vest in the portion of the Option set forth in the chart above that
vests on such Vesting Date. No portion of the Option shall vest between Vesting
Dates; if Optionee ceases to be employed by IFX or any Subsidiary, then any
portion of the Option that is scheduled to vest on any Vesting Date after the
date Optionee's employment is terminated automatically shall be forfeited as of
the termination of employment. If Optionee's employment with IFX or any
Subsidiary is terminated for any reason, any portion of the Option which is not
then vested shall be immediately forfeited; provided, however, that a transfer
or reassignment of Optionee from IFX to any Subsidiary, or vice versa, shall not
                                                           ---- -----
constitute a termination of employment for purposes of this Agreement.

             (b)   Vesting Upon Change of Control.  Notwithstanding the
                   ------------------------------
provisions of Section 4(a) or anything contained in this Agreement or in the
Plan to the contrary, upon a Change in Control (as hereinafter defined) the
entire amount of the Option shall become 100% vested and immediately
exercisable. For purposes of this Agreement, "Change in Control" means the
                                              -----------------
occurrence of any one of the following events:

                (i)    any consolidation, merger or other similar transaction
       involving the Company, if the Company is not the continuing or surviving
       corporation, or which contemplates that all or substantially all of the
       business and/or assets of the Company will be controlled by another
       corporation;

                (ii)   any sale, lease, exchange or transfer (in one transaction
       or series of related

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       transactions) of all or substantially all of the assets of the Company;

                (iii)  approval by the shareholders of the Company of any plan
       or proposal for the liquidation or dissolution of the Company, unless
       such plan or proposal is abandoned within 60 days following such
       approval;

                (iv)   the acquisition by any "person" (as such term is used in
       Sections 13(d) and 14(d)(2) of the Exchange Act), or two or more persons
       acting in concert, of beneficial ownership (within the meaning of Rule
       13d-3 promulgated under the Exchange Act) of 50% or more of the
       outstanding shares of voting stock of the Company; provided, however,
                                                          --------  -------
       that for purposes of the foregoing, "person" excludes Lee S. Casty,
       International Technology Investments, LC or any of their affiliates; or

                (v)    if, during any period of 24 consecutive calendar months
       commencing on the date of this Agreement, those individuals (the
       "Continuing Directors") who either (i) were directors of the Company on
        --------------------
       the first day of each such period, or (ii) subsequently became directors
       of the Company and whose actual election or initial nomination for
       election subsequent to that date was approved by a majority of the
       Continuing Directors then on the board of directors of the Company, cease
       to constitute a majority of the board of directors of the Company.

       5.    Procedure for Exercise.  Exercise of the Option or a portion
             ----------------------
thereof shall be effected by the giving of written notice to IFX in accordance
the Plan and payment of the pro rata portion of the Option Price for the number
of Shares to be acquired pursuant to the exercise.

       6.    Payment for Shares. Payment of the Option Price (or portion
             ------------------
thereof) shall be made in cash or by such other method as may be permitted by
the Committee in accordance with the provisions of the Plan. No Shares shall be
delivered upon exercise of the Option until full payment has been made and all
applicable withholding requirements satisfied.

       7.    Options Not Transferable and Subject to Certain Restrictions.  The
             ------------------------------------------------------------
Option may not be sold, pledged, assigned or transferred in any manner without
the prior consent of the Committee, which may be given or withheld in its sole
discretion, other than by will or the laws of descent and distribution, or
pursuant to a qualified domestic relations order as defined in Section 414(p) of
the Code. During Optionee's lifetime, the Option may be exercised only by the
Optionee, a permitted assignee or by a legally authorized representative. In the
event of Optionee's death, the Option may be exercised by the distributee to
whom Optionee's rights under the Option shall pass by will or by the laws of
descent and distribution.

       8.    Acceptance of Plan.  Optionee hereby accepts and agrees to be bound
             ------------------
by all the terms and conditions of the Plan.

       9.    No Right to Employment.  Nothing herein contained shall confer upon
             ----------------------
Optionee any right to continuation of employment by IFX or any Subsidiary, or
interfere with the right of IFX or any Subsidiary to terminate at any time the
employment of Optionee. Nothing contained herein shall confer any rights upon
Optionee as a shareholder of IFX, unless and until Optionee

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actually receives Shares.

       10.   Compliance with Securities Laws.  The Option shall not be
             -------------------------------
exercisable and Shares shall not be issued pursuant to exercise of the Option
unless the exercise of the Option and the issuance and delivery of Shares
pursuant thereto shall comply with all relevant provisions of law including,
without limitation, the Securities Act of 1933, as amended (the "Securities
                                                                 ----------
Act"), the Securities Exchange Act of 1934, as amended, the rules and
---
regulations promulgated thereunder, and the requirements of any stock exchange
upon which Common Stock may then be listed, and shall be further subject to the
approval of counsel for IFX with respect to such compliance. If, in the opinion
of counsel for IFX, a representation is required to be made by Optionee in order
to satisfy any of the foregoing relevant provisions of law, IFX may, as a
condition to the exercise of the Option, require Optionee to represent and
warrant at the time of exercise that the Shares to be delivered as a result of
such exercise are being acquired solely for investment and without any present
intention to sell or distribute such Shares.

       11.   Adjustments.  Subject to the sole discretion of the Board of
             -----------
Directors, IFX may, with respect to any unexercised portion of the Option, make
any adjustments necessary to prevent accretion, or to protect against dilution,
in the number and kind of shares covered by the Option and in the applicable
exercise price thereof in the event of a change in the corporate structure or
shares of IFX; provided, however, that no adjustment shall be made for the
issuance of preferred stock of IFX or the conversion of convertible preferred
stock of IFX. For purposes of this Section 11, a change in the corporate
structure or shares of IFX includes, without limitation, any change resulting
from a recapitalization, stock split, stock dividend, consolidation, rights
offering, spin-off, reorganization or liquidation, and any transaction in which
shares of Common Stock are changed into or exchanged for a different number or
kind of shares of stock or other securities of IFX or another entity.

       12.   No Other Rights. Optionee hereby acknowledges and agrees that,
             ---------------
except as set forth herein, no other representations or promises, either oral or
written, have been made by IFX, any Subsidiary or anyone acting on their behalf
with respect to Optionee's right to acquire any shares of Common Stock, stock
options or awards under the Plan, and Optionee hereby releases, acquits and
forever discharges IFX, the Subsidiaries and anyone acting on their behalf of
and from all claims, demands or causes of action whatsoever relating to any such
representations or promises and waives forever any claim, demand or action
against IFX, any Subsidiary or anyone acting on their behalf with respect
thereto.

       13.   Severability.  Any provision of this Agreement (or portion thereof)
             ------------
that is deemed invalid, illegal or unenforceable in any jurisdiction shall, as
to that jurisdiction and subject to this Section 13, be ineffective to the
extent of such invalidity, illegality or unenforceability, without affecting in
any way the remaining provisions thereof in such jurisdiction or rendering that
or any other provisions of this Agreement invalid, illegal, or unenforceable in
any other jurisdiction.

       14.   Entire Agreement. This Agreement constitutes the entire agreement
             ----------------
between the parties concerning the subject matter hereof and supersedes all
prior and contemporaneous agreements, oral or written, between IFX and Optionee
relating to Optionee's entitlement to stock options, Common Stock or similar
benefits, under the Plan or otherwise.

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       15.   Amendment.  This Agreement may be amended and/or terminated at any
             ---------
time by mutual agreement of IFX and Optionee.

       16.   Governing Law. The construction and operation of this Agreement are
             --------------
governed by the laws of the State of Delaware (without regard to its conflict of
laws provisions).


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       This Agreement has been executed as of the date first written above.

                                               IFX CORPORATION




                                               By: /s/ Colleen M. Downes
                                                  -------------------------
                                                  Colleen M. Downes,
                                                  Chief Financial Officer



                                               /s/ Joel M. Eidelstein

                                               Joel M. Eidelstein


                                               Social Security Number

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