<PAGE>

                                                                     Exhibit 4.2
                                                                     -----------




                         REGISTRATION RIGHTS AGREEMENT


                                     among


                               IFX CORPORATION,

                        UBS CAPITAL AMERICAS III, L.P.,

                               UBS CAPITAL LLC,

                  INTERNATIONAL TECHNOLOGY INVESTMENTS, LLC,

                                      and

                                 LEE S. CASTY

                            dated as June 15, 2000
<PAGE>

                         REGISTRATION RIGHTS AGREEMENT
                         -----------------------------

     THIS REGISTRATION RIGHTS AGREEMENT (this "Agreement") is entered into as of
June 15, 2000, among IFX Corporation, a Delaware corporation (the "Company"),
UBS Capital Americas III, L.P., a Delaware limited partnership, and UBS Capital
LLC, a Delaware limited liability company, (collectively "UBS" and together with
their successors and assigns, the "Investor Stockholders"), INTERNATIONAL
TECHNOLOGY INVESTMENTS, LC, a Nevada limited liability company ("ITI"), and LEE
S. CASTY, individually ("Casty").

                                   RECITALS
                                   --------

     WHEREAS, the Company and the Investor Stockholders have entered into the
IFX Corporation Preferred Stock Purchase Agreement, of even date herewith (the
"Stock Purchase Agreement"), pursuant to which the Investor Stockholders will
purchase shares (the "Preferred Shares") of newly issued Series A Convertible
Preferred Stock, par value $1.00 per share, of the Company ("Series A Preferred
Stock");

     WHEREAS, in connection with the Stock Purchase Agreement, the Company has
agreed to grant the Investor Stockholders the registration rights described
herein;

     WHEREAS, the Company, Emerging Networks, Inc., ITI and Casty were parties
to a Subscription and Joint Venture Agreement, dated as of November 23, 1998, as
amended, providing, inter alia, for registration rights, which Subscription and
                    ----- ----
Joint Venture Agreement is being terminated as of the date hereof; and

     WHEREAS, in connection with the termination of such agreement, the Company
has agreed to grant ITI and Casty the registration rights described herein;

     NOW THEREFORE, the parties hereto, in consideration of the foregoing and
the mutual covenants and agreements hereinafter set forth, hereby agree as
follows:

     1. Certain Definitions.  As used herein, the following terms shall have the
        -------------------
following meanings:

     "Commission" means the Securities and Exchange Commission or any other
federal agency then administering the federal securities laws.

     "Common Shares" means shares of Common Stock held by ITI and Casty and
their permitted assigns under Section 13(b) or the Investor Stockholders.

     "Common Stock" means the common stock, par value $0.02 per share, of the
Company and any securities issued in respect thereof, or in substitution
therefor, in connection with any stock split, dividend or combination, or any
reclassification, recapitalization, merger, consolidation exchange or other
similar reorganization.

     "Conversion Shares" means shares of Common Stock issued or issuable upon
conversion of the Preferred Shares or any other Convertible Securities held by
the Investor Stockholders.
<PAGE>

          "Convertible Securities" shall mean (i) any rights, options or
warrants to acquire Common Stock or any capital stock of the Company or any
Subsidiary, including the shares of Series A Preferred Stock to be issued
hereunder, and (ii) any notes, debentures, shares of preferred stock or other
securities, options, warrants or rights, which are convertible or exercisable
into, or exchangeable for, Common Stock or any capital stock of the Company or
any Subsidiary.

     "Exchange Act" means the Securities Exchange Act of 1934, as amended, or
any similar federal statute, and the rules and regulations promulgated
thereunder.

     "Initial Closing" has the meaning assigned to such term in the Stock
Purchase Agreement.

     "Registration Expenses" means the expenses so described in Section 8.

     "Restricted Stock" means the Conversion Shares and Common Shares, excluding
Conversion Shares and Common Shares which have been (a) registered under the
Securities Act pursuant to an effective registration statement filed thereunder
and disposed of in accordance with the registration statement covering them or
(b) publicly sold pursuant to Rule 144 under the Securities Act.

     "Securities Act" means the Securities Act of 1933, as amended, or any
similar federal statute, and the rules and regulations promulgated thereunder.

     "Selling Expenses" shall mean the expenses so described in Section 8.

     2.   Restrictive Legend.  Each certificate representing Preferred Shares,
          ------------------
Conversion Shares or Common Shares shall, except as otherwise provided in this
Section 2 or in Section 3, be stamped or otherwise imprinted with a legend
substantially in the following form:

          "THIS SECURITY HAS NOT BEEN REGISTERED UNDER THE SECURITIES
          ACT OF 1933 OR ANY STATE SECURITIES LAWS AND MAY NOT BE
          TRANSFERRED OR OTHERWISE DISPOSED OF UNLESS IT HAS BEEN
          REGISTERED UNDER SUCH ACT AND ALL SUCH APPLICABLE LAWS OR AN
          EXEMPTION FROM REGISTRATION IS AVAILABLE."

A certificate shall not bear such legend if in the opinion of counsel
satisfactory to the Company (it being agreed that each of Neal, Gerber &
Eisenberg and Kaye, Scholer, Fierman, Hays & Handler, LLP shall be satisfactory)
the securities represented thereby may be publicly sold without registration
under the Securities Act and any applicable state securities laws.

     3.   Removal of Legend.  Each certificate for Preferred Shares,
          -----------------
Conversion Shares or Common Shares transferred shall bear the legend set forth
in Section 2, except that such certificate shall not bear such legend if (i)
such transfer is in accordance with the provisions of Rule 144 (or any other
rule permitting public sale without registration under the Securities Act) or
(ii) in the opinion of counsel satisfactory to the Company (it being agreed that
either of Neal,

                                       2
<PAGE>

Gerber & Eisenberg or Kaye, Scholer, Fierman, Hays & Handler, LLP shall be
satisfactory) the transferee and any subsequent transferee would be entitled to
transfer such securities in a public sale without registration under the
Securities Act.

     4.   Required Registration.  (a) At any time after the earlier of (i) 180
          ---------------------
days following the consummation of a Qualified Public Offering (as defined in
the Stock Purchase Agreement) and (ii) the first anniversary of the Initial
Closing, the Investor Stockholders holding Restricted Stock constituting at
least 66 2/3% of the total shares of Restricted Stock held by Investor
Stockholders then outstanding, ITI or Casty may request the Company to register
under the Securities Act all or any portion of the shares of Restricted Stock
held by such requesting holder or holders for sale in the manner specified in
such notice, provided that the shares of Restricted Stock for which registration
             --------
has been requested shall have a reasonably anticipated aggregate price to the
public which is at least $15,000,000 (the "Minimum Offering Price"); provided
                                                                     --------
further that neither ITI nor Casty shall request such registration prior to a
-------
Qualified Public Offering without the consent of UBS. The only securities which
the Company shall be required to register pursuant hereto shall be shares of
Common Stock, provided, however, that, in any underwritten public offering
              --------  -------
contemplated by this Section 4 or Sections 5 and 6, the holders of Preferred
Shares shall be entitled to sell such Preferred Shares to the underwriters for
conversion and sale of the shares of Common Stock issued upon conversion
thereof. Notwithstanding anything to the contrary contained herein, the Company
shall not be required to file any registration statement under this Section 4,
within such period of time after the effective date of any earlier registration
statement relating to an underwritten public offering (other than a registration
statement on Form S-3 or any successor thereto relating to the resale of
securities of the Company acquired in connection with an acquisition or similar
transaction (each, an "Acquisition Registration Statement")) as shall be
determined in good faith by the managing underwriter of an underwritten public
offering, provided that such time period shall not exceed 180 days.

     (b)  Following receipt of any notice under this Section 4, the Company
shall immediately notify all holders of Restricted Stock from whom notice has
not been received and shall use its reasonable best efforts to register under
the Securities Act, for public sale in accordance with the method of disposition
specified in such notice from requesting holders, the number of shares of
Restricted Stock specified in such notice (and in all notices received by the
Company from other holders within 30 days after the giving of such notice by the
Company). If such method of disposition shall be an underwritten public
offering, the Company shall designate the underwriter(s) of such offering,
subject to the approval by the holders of a majority of the shares of Restricted
Stock, including the approval of holders of at least 66 2/3% of the shares of
Restricted Stock proposed to be sold by Investor Stockholders, to be sold in
such offering (such approval not to be unreasonably withheld or delayed). If the
managing underwriter advises the Company in writing that in such underwriter's
good faith determination the marketing factors require a limitation of the
amount of Restricted Stock to be underwritten in such registration, the Company
shall (to the extent that the managing underwriter believes that such securities
can be sold in such offering without having an adverse effect upon the marketing
of such offering) register in such registration (i) first, the Restricted Stock
                                                    -----
proposed to be sold by the parties participating in the demand registration of
Restricted Stock under this Section 4, pro rata based upon the number of shares
                                       --- ----
of Restricted Stock proposed to be sold by such holders; provided that until at
least 50% of the Restricted Stock held by the Investor Stockholders determined
on a fully

                                       3
<PAGE>

diluted basis after the Subsequent Closing (as defined in the Stock Purchase
Agreement) is registered and sold, the Investor Stockholders shall be entitled
to have included in any registration under this Section 4 at least 50% of the
Restricted Stock proposed to be included in such registration, and (ii) second
                                                                        ------
securities held by the Company. The Company shall be obligated to register
Restricted Stock pursuant to this Section 4, in the case of registrations
requested by the Investor Stockholders, on two occasions only, and in the case
of each of ITI and Casty on three occasions only, provided, however, that such
                                                  --------  -------
obligation shall be deemed satisfied only when a registration statement covering
all shares of Restricted Stock specified in demand notices delivered pursuant to
Section 4(a), for sale in accordance with the method of disposition specified by
the requesting holders, shall have become effective and, if such method of
disposition is a firm commitment underwritten public offering, all such shares
designated in the notice shall have been sold pursuant thereto.

     (c)  The Company shall, subject to Section 4(b), be entitled to include in
any registration statement referred to in this Section 4 for sale in accordance
with the method of disposition specified by the requesting holders, shares of
Common Stock to be sold by the Company for its own account.

     5.   Incidental Registration.  If the Company at any time (other than
          -----------------------
pursuant to Section 4 or Section 6) proposes to register any of its securities
under the Securities Act for sale to the public, whether for its own account or
for the account of other security holders or both (except with respect to
registration statements on Forms S-4, S-8 or another form not available for
registering the Restricted Stock for sale to the public), each such time it will
give written notice to all holders of outstanding Restricted Stock of its
intention so to do. Upon the written request of any such holder, received by the
Company within 30 days after the giving of any such notice by the Company, to
register any of its Restricted Stock, the Company will use its reasonable best
efforts to cause the Restricted Stock as to which registration shall have been
so requested to be included in the securities to be covered by the registration
statement proposed to be filed by the Company, all to the extent requisite to
permit the sale or other disposition by the holder of such Restricted Stock so
registered. In the event that any registration pursuant to this Section 5 shall
be, in whole or in part, an underwritten public offering of Common Stock, and
the managing underwriter advises the Company in writing that in such
underwriter's good faith determination the marketing factors require a
limitation of the amount of Restricted Stock to be underwritten in such
registration then (a) if such registration is a primary registration on behalf
of the Company, the Company shall (to the extent that the managing underwriter
believes that such securities can be sold in such offering without having an
adverse effect upon the marketing of such offering) register in such
registration (i) first, the Company securities which the Company proposes to
                 -----
sell in such registration, (ii) second, the Restricted Stock held by Investor
                                ------
Stockholders which they propose to sell in such registration on a pro rata basis
                                                                  --- ----
based upon the number of shares of Restricted Stock owned by such holders, (iii)
third, Restricted Stock held by ITI and Casty which they propose to sell in such
-----
registration on a pro rata basis based upon the number of shares of Restricted
                  --- ----
Stock owned by such holders and (iv) fourth, securities held by other parties
                                     ------
eligible for inclusion in such registration statement on a pro rata basis based
                                                           --- ----
upon the amount of securities held by them, and (b) if such registration is a
secondary registration, the Company shall (to the extent that the managing
underwriter believes that such securities can be sold in such offering without
having an adverse effect upon the marketing of such offering) register in such
registration (i) first, the Restricted Stock held by Investor Stockholders which
                 -----

                                       4
<PAGE>

they propose to sell in such registration on a pro rata basis based upon the
                                               --- ----
number of shares of Restricted Stock owned by such holders, (ii) second, the
                                                                 ------
Restricted Stock held by ITI and Casty which they propose to sell in such
registration on a pro rata basis based upon the number of shares of Restricted
                  --- ----
Stock owned by such holders and (iii) third, the securities held by other
                                      -----
parties eligible for inclusion in such registration on a pro rata basis based
                                                         --- ----
upon the amount of securities held by them. Notwithstanding the foregoing
provisions, the Company may withdraw any registration statement referred to in
this Section 5, without thereby incurring any liability to the holders of
Restricted Stock other than for the payment of Registration Expenses in
accordance with Section 8.

     6.   Registration on Form S-3.  If at any time (i) one or more Investor
          ------------------------
Stockholders, ITI or Casty requests that the Company file a registration
statement on Form S-3 or any successor thereto for a public offering of all or
any portion of the shares of Restricted Stock held by such requesting holder or
holders, the reasonably anticipated aggregate price to the public of which would
exceed $2,500,000, provided that the Restricted Stock for which registration has
been requested constitutes at least 10% of the total shares of Restricted Stock
then outstanding held by Investor Stockholders, if such registration is
requested by one or more Investor Stockholders, or at least 10% of the total
shares of Restricted Stock then outstanding held by ITI or Casty, as the case
may be, if such registration is requested by ITI or Casty, and (ii) the Company
is a registrant entitled to use Form S-3 or any successor thereto to register
such shares, then the Company shall use its reasonable best efforts to register
under the Securities Act on Form S-3 or any successor thereto, for public sale
in accordance with the method of disposition specified in such notice, the
number of shares of Restricted Stock specified in such notice.  Whenever the
Company is required by this Section 6 to use its reasonable best efforts to
effect the registration of Restricted Stock, each of the procedures and
requirements of Section 4 (including but not limited to the requirement that the
Company notify all holders of Restricted Stock from whom notice has not been
received and provide them with the opportunity to participate in the offering)
shall apply to such registration, provided, however, that each of the Investor
                                  --------  -------
Stockholders (considered as a group), ITI and Casty may only request and obtain
two registrations on Form S-3 under this Section in any calendar year, provided,
                                                                       --------
further, that no request may be made by a party under this Section 6 within 180
-------
days after the effective date of any other registration statement filed by the
Company pursuant to this Section on behalf of such party, and provided further,
                                                              -------- -------
however, that the requirements contained in Section 4(a) (other than the
-------
requirements as to a Minimum Offering Price) shall apply to any registration on
Form S-3 which may be requested and obtained under this Section 6.

     7.   Registration Procedures.  If and whenever the Company is required by
          -----------------------
the provisions of Sections 4, 5 or 6 to use its reasonable best efforts to
effect the registration of any shares of Restricted Stock under the Securities
Act, the Company will, as expeditiously as possible:

     (a)  prepare and file with the Commission a registration statement (which,
other than in the case of an underwritten public offering pursuant to Section 4,
may be on Form S-3 or any successor thereto if the Company is a registrant
entitled to use such Form) with respect to such securities and use its
reasonable best efforts to cause such registration statement to become and
remain effective for the period of the distribution contemplated thereby
(determined as hereinafter provided);

                                       5
<PAGE>

     (b)  prepare and file with the Commission such amendments and supplements
to such registration statement and the prospectus used in connection therewith
as may be necessary to keep such registration statement effective for the period
specified in paragraph (a) above and comply with the provisions of the
Securities Act with respect to the disposition of all Restricted Stock covered
by such registration statement in accordance with the sellers' intended method
of disposition set forth in such registration statement for such period;

     (c)  furnish to each seller of Restricted Stock and to each underwriter
such number of copies of the registration statement and the prospectus included
therein (including each preliminary prospectus) as such persons reasonably may
request in order to facilitate the public sale or other disposition of the
Restricted Stock covered by such registration statement;

     (d)  use its reasonable best efforts to register or qualify the Restricted
Stock covered by such registration statement under the securities or "blue sky"
laws of such jurisdictions as the sellers of Restricted Stock or, in the case of
an underwritten public offering, the managing underwriter reasonably shall
request, provided, however, that the Company shall not for any such purpose be
         --------  -------
required to qualify generally to transact business as a foreign corporation in
any jurisdiction where it is not so qualified or to consent to general service
of process in any such jurisdiction;

     (e)  list the Restricted Stock covered by such registration statement with
any securities exchange on which the Common Stock of the Company is then listed;

     (f)  immediately notify each seller of Restricted Stock and each
underwriter under such registration statement, at any time when a prospectus
relating thereto is required to be delivered under the Securities Act, of the
happening of any event of which the Company has knowledge as a result of which
the prospectus contained in such registration statement, as then in effect,
includes an untrue statement of a material fact or omits to state a material
fact required to be stated therein or necessary to make the statements therein
not misleading in light of the circumstances then existing;

     (g)  as soon as practicable upon the occurrence of any event contemplated
by Section 7(f), prepare and file a supplement or post-effective amendment to
such registration statement or the prospectus contained in such registration
statement, or any document incorporated therein by reference, or file any other
required document so that, as thereafter delivered to the purchasers of the
shares of Restricted Stock covered thereby, the prospectus contained in such
registration statement will not contain any untrue statement of a material fact
or omit to state a material fact necessary to make the statements therein, in
the light of the circumstances under which they were made, not misleading;
provided, however, that the obligation to prepare and file any such supplement,
--------  -------
post-effective amendment or other document shall be suspended (a "Suspension")
if the Company shall furnish to the holders a certificate signed by the
President of the Company stating that in the good faith judgment of the Board of
Directors of the Company, it would be seriously detrimental to the Company and
its stockholders for such registration to be effected at such time due to any
pending material financing, acquisition or corporate reorganization or other
material corporate development involving the Company or any of its subsidiaries;
provided further, that the Company shall only be permitted to effectuate one (1)
-------- -------
Suspension in any twelve

                                       6
<PAGE>

(12) month period and any such suspension will be lifted by the Company as soon
as practicable and will not, in any event, extend for more than 60 days with
respect to any such specified event;

     (h)  if the offering is underwritten and at the request of any seller of
Restricted Stock, use its reasonable best efforts to furnish on the date that
Restricted Stock is delivered to the underwriters for sale pursuant to such
registration: (i) an opinion dated such date of counsel representing the Company
for the purposes of such registration, addressed to the underwriters and to such
seller, stating that such registration statement has become effective under the
Securities Act and that (A) to the best knowledge of such counsel, no stop order
suspending the effectiveness thereof has been issued and no proceedings for that
purpose have been instituted or are pending or contemplated under the Securities
Act, (B) the registration statement, the related prospectus and each amendment
or supplement thereof comply as to form in all material respects with the
requirements of the Securities Act (except that such counsel need not express
any opinion as to financial statements contained therein) and (C) to such other
effects as reasonably may be requested by counsel for the underwriters or by
such seller or its counsel and (ii) a letter dated such date from the
independent public accountants retained by the Company, addressed to the
underwriters and to such seller, stating that they are independent public
accountants within the meaning of the Securities Act and that, in the opinion of
such accountants, the financial statements of the Company included in the
registration statement or the prospectus, or any amendment or supplement
thereof, comply as to form in all material respects with the applicable
accounting requirements of the Securities Act, and such letter shall
additionally cover such other financial matters (including information as to the
period ending no more than five business days prior to the date of such letter)
with respect to such registration as such underwriters reasonably may request;
and
     (i)  make available for inspection by each seller of Restricted Stock, any
underwriter participating in any distribution pursuant to such registration
statement, and any attorney, accountant or other agent retained by such seller
or underwriter, all financial and other records, pertinent corporate documents
and properties of the Company, and cause the Company's officers, directors and
employees to supply all information reasonably requested by any such seller,
underwriter, attorney, accountant or agent in connection with such registration
statement.

     Upon receipt of any notice from the Company of any event of the kind
described in Section 7.3(f), each seller of Restricted Stock (x) promptly will
discontinue disposition of any shares of Restricted Stock pursuant to such
registration statement until such seller of Restricted Stock has received copies
of the supplemented or amended prospectus contemplated by Section 7(g) (it being
understood that such discontinuance shall be deemed a Suspension subject to the
limitations on Suspensions set forth in Section 7(g)), (y) thereafter, will
utilize and distribute only such supplemented or amended prospectus, and (z) if
so directed by the Company, will deliver to the Company all copies of the
prospectus covering such shares of Restricted Stock in such party's possession
at the time of receipt of such suspension notice.

     For purposes of Section 7(a) and 7(b), the period of distribution of
Restricted Stock in a firm commitment underwritten public offering shall be
deemed to extend until each underwriter has completed the distribution of all
securities purchased by it, and the period of distribution of Restricted Stock
in any other registration shall be deemed to extend until the earlier of the
sale of all Restricted Stock covered thereby and 180 days following
effectiveness of registration.

                                       7
<PAGE>

     In connection with each registration hereunder, each seller of Restricted
Stock will furnish to the Company in writing such information with respect to
itself and the proposed distribution by it as reasonably shall be necessary in
order to assure compliance with federal and applicable state securities laws,
and will notify the Company promptly upon the happening of any event during the
period any registration statement is effective that makes any statement
regarding such seller made in a registration statement or the prospectus
contained therein untrue in any material respect or which requires the making of
any changes in a registration statement or the prospectus contained therein in
order to make the statements therein regarding such seller, in light of
circumstances under which they were made, not misleading.

     In connection with each registration pursuant to Sections 4, 5 or 6
covering an underwritten public offering, the Company and each seller agree to
enter into a written agreement with the managing underwriter selected in the
manner herein provided in such form and containing such provisions as are
customary in the securities business for such an arrangement between such
underwriter and companies of the Company's size and investment stature.

     8.   Expenses. All expenses incurred by the Company in complying with
          --------
Sections 4, 5 and 6, including, without limitation, all registration and filing
fees, printing expenses, fees and disbursements of counsel and independent
public accountants for the Company, fees and expenses (including counsel fees)
incurred in connection with complying with state securities or "blue sky" laws,
fees of the National Association of Securities Dealers, Inc., transfer taxes,
fees of transfer agents and registrars, costs of insurance and reasonable fees
and disbursements of one counsel for the sellers of Restricted Stock, but
excluding any Selling Expenses, are called "Registration Expenses". If ITI
and/or Casty are the only parties (other than the Company) selling Restricted
Stock pursuant to a registration statement described herein, "Registration
Expenses" shall not include the fees and disbursements of counsel for such
sellers of Restricted Stock. All underwriting discounts and selling commissions
applicable to the sale of Restricted Stock are called "Selling Expenses".

     The Company will pay all Registration Expenses in connection with each
registration statement under Sections 4, 5 or 6.

     9.   Indemnification and Contribution. (a) In the event of a registration
          --------------------------------
of any of the Restricted Stock under the Securities Act pursuant to Sections 4,
5 or 6, the Company will indemnify and hold harmless each seller of such
Restricted Stock thereunder, each underwriter of such Restricted Stock
thereunder and each of their respective officers, directors, employees,
partners, agents or other person, if any, who controls such seller or
underwriter within the meaning of the Securities Act, against any losses,
claims, damages or liabilities, joint or several, to which such seller,
underwriter or controlling person may become subject under the Securities Act or
otherwise, insofar as such losses, claims, damages or liabilities (or actions in
respect thereof) arise out of or are based upon any untrue statement or alleged
untrue statement of any material fact contained in any registration statement
under which such Restricted Stock was registered under the Securities Act
pursuant to Sections 4, 5 or 6, any preliminary prospectus or final prospectus
contained therein, or any amendment or supplement thereof, or arise out of or
are based upon the omission or alleged omission to state therein a material fact
required to be stated therein or necessary to make the statements therein not
misleading, and will reimburse

                                       8
<PAGE>

each such seller, each such underwriter and each such controlling person for any
legal or other expenses reasonably incurred by them in connection with
investigating or defending any such loss, claim, damage, liability or action,
provided, however, that the Company will not be liable in any such case if and
--------  -------
to the extent that any such loss, claim, damage or liability arises out of or is
based upon an untrue statement or alleged untrue statement or omission or
alleged omission so made in conformity with information furnished by any such
seller, any such underwriter or any such controlling person in writing
specifically for use in such registration statement or prospectus and, provided
                                                                       --------
further, however, that the Company will not be liable to any such person or
-------  -------
entity with respect to any such untrue statement or omission or alleged untrue
statement or omission made in any preliminary prospectus that is corrected in
the final prospectus filed with the Commission pursuant to Rule 424(b)
promulgated under the Securities Act (or any amendment or supplement to such
prospectus) if the person asserting any such loss, claim, damage or liability
purchased securities but was not given a copy of the final prospectus (as
amended or supplemented) at or prior to the written confirmation of the sale of
such securities to such person in any case where such delivery of the final
prospectus (as amended or supplemented) is required by the Securities Act,
unless such failure to deliver the final prospectus (as amended or supplemented)
was a result of the Company's failure to provide such prospectus (as amended or
supplemented).

     (b)  In the event of a registration of any of the Restricted Stock under
the Securities Act pursuant to Sections 4, 5 or 6, each seller of such
Restricted Stock thereunder, severally and not jointly, will indemnify and hold
harmless the Company, each person, if any, who controls the Company within the
meaning of the Securities Act, each officer of the Company who signs the
registration statement, each director of the Company, each underwriter and each
person who controls any underwriter within the meaning of the Securities Act,
against all losses, claims, damages or liabilities, joint or several, to which
the Company or such officer, director, underwriter or controlling person may
become subject under the Securities Act or otherwise, insofar as such losses,
claims, damages or liabilities (or actions in respect thereof) arise out of or
are based upon any untrue statement or alleged untrue statement of any material
fact contained in the registration statement under which such Restricted Stock
was registered under the Securities Act pursuant to Sections 4, 5 or 6, any
preliminary prospectus or final prospectus contained therein, or any amendment
or supplement thereof, or arise out of or are based upon the omission or alleged
omission to state therein a material fact required to be stated therein or
necessary to make the statements therein not misleading, and will reimburse the
Company and each such officer, director, underwriter and controlling person for
any legal or other expenses reasonably incurred by them in connection with
investigating or defending any such loss, claim, damage, liability or action,
provided, however, that such seller will be liable hereunder in any such case if
--------  -------
and only to the extent that any such loss, claim, damage or liability arises out
of or is based upon an untrue statement or alleged untrue statement or omission
or alleged omission made in reliance upon and in conformity with information
pertaining to such seller, as such, furnished in writing to the Company by such
seller specifically for use in such registration statement or prospectus, and
provided, further, however, that the liability of each seller hereunder shall be
--------  -------  -------
limited to the proportion of any such loss, claim, damage, liability or expense
which is equal to the proportion that the public offering price of the shares
sold by such seller under such registration statement bears to the total public
offering price of all securities sold thereunder, but not in any event to exceed
the net proceeds received by such seller from the sale of Restricted Stock
covered by such registration statement.

                                       9
<PAGE>

     (c)  Promptly after receipt by an indemnified party hereunder of notice of
the commencement of any action, such indemnified party shall, if a claim in
respect thereof is to be made against the indemnifying party hereunder, notify
the indemnifying party in writing thereof, but the omission so to notify the
indemnifying party shall not relieve it from any liability which it may have to
such indemnified party other than under this Section 9 and shall only relieve it
from any liability which it may have to such indemnified party under this
Section 9 if and to the extent the indemnifying party is prejudiced by such
omission.  In case any such action shall be brought against any indemnified
party and it shall notify the indemnifying party of the commencement thereof,
the indemnifying party shall be entitled to participate in and, to the extent it
shall wish, to assume and undertake the defense thereof with counsel
satisfactory to such indemnified party, and, after notice from the indemnifying
party to such indemnified party of its election so to assume and undertake the
defense thereof, the indemnifying party shall not be liable to such indemnified
party under this Section 9 for any legal expenses subsequently incurred by such
indemnified party in connection with the defense thereof other than reasonable
costs of investigation and of liaison with counsel so selected, provided,
                                                                --------
however, that, if the defendants in any such action include both the indemnified
-------
party and the indemnifying party and the indemnified party shall have reasonably
concluded, based on advice of counsel, that there may be reasonable defenses
available to it which are different from or additional to those available to the
indemnifying party or if the interests of the indemnified party reasonably may
be deemed to conflict with the interests of the indemnifying party, the
indemnified party shall have the right to select a separate counsel and to
assume such legal defenses and otherwise to participate in the defense of such
action, with the reasonable expenses and fees of such separate counsel and other
reasonable expenses related to such participation to be reimbursed by the
indemnifying party as incurred.

     (d)  In order to provide for just and equitable contribution in
circumstances in which the indemnity agreement provided for in Sections 9(a) and
9(b) above is for any reason held to be unenforceable by the indemnified party
although applicable in accordance with its terms, the Company and each holder of
Restricted Stock exercising rights under this Agreement shall contribute to the
aggregate losses, claims, damages and liabilities of the nature contemplated by
such indemnity agreement incurred by the Company and such holder, (i) in such
proportion as is appropriate to reflect the relative fault of the Company on the
one hand and such holder on the other, in connection with the statements or
omissions which resulted in such losses, claims, damages or liabilities or (ii)
if the allocation provided by clause (i) above is not permitted by applicable
law, in such proportion as is appropriate to reflect not only the relative fault
of, but also the relative benefits to, the Company on the one hand and such
holder on the other, in connection with the statements or omissions which
resulted in such losses, claims, damages or liabilities, as well as any other
relevant equitable considerations.  The relative benefits to the indemnifying
party and indemnified party shall be determined by reference to, among other
things, the gross proceeds received by the indemnifying party and indemnified
party in connection with the offering to which such losses, claims, damages or
liabilities relate.  The relative fault of the indemnifying party and
indemnified party shall be determined by reference to, among other things,
whether the action in question, including any untrue or alleged untrue statement
of a material fact or omission or alleged omission to state a material fact, has
been made by, or relates to information supplied by, the indemnifying party or
the indemnified party, and the parties' relative intent, knowledge, access to
information and opportunity to correct or prevent such action.  The parties
hereto agree that it would not be just or equitable if contribution

                                      10
<PAGE>

pursuant to this Section 9(d) were determined by pro rata allocation or by any
other method of allocation which does not take account of the equitable
considerations referred to in the immediately preceding sentence.
Notwithstanding the provisions of this Section 9(d), each holder of Restricted
Stock exercising rights under this Agreement shall not be required to contribute
any amount in excess of the amount of the gross proceeds to such holder from
sales of the Restricted Stock of such holder under a registration statement.

     Notwithstanding the foregoing, no person guilty of fraudulent
misrepresentation (within the meaning of Section 11(f) of the Securities Act)
shall be entitled to contribution from any person who was not guilty of such
fraudulent misrepresentation.  For purposes of this Section 9(d), each person,
if any, who controls a holder of Restricted Stock within the meaning of Section
15 of the Securities Act shall have the same rights to contribution as such
holder, and each director of the Company, each officer of the Company who signed
a registration statement and each person, if any, who controls the Company
within the meaning of Section 15 of the Act shall have the same rights to
contribution as the Company.

     10.  Changes in Common Stock or Preferred Stock. If, and as often as, there
          ------------------------------------------
is any change in the Common Stock or the Preferred Stock by way of a stock
split, stock dividend, combination or reclassification, or through a merger,
consolidation, reorganization or recapitalization, or by any other means,
appropriate adjustment shall be made in the provisions hereof so that the rights
and privileges granted hereby shall continue with respect to the Common Stock or
the Preferred Stock as so changed.

     11.  Rule 144 Reporting.  With a view to making available the benefits of
          ------------------
certain rules and regulations of the Commission which may at any time permit the
sale of the Restricted Stock to the public without registration, the Company
agrees to:

     (a)  make and keep public information available, as those terms are
understood and defined in Rule 144 under the Securities Act;

     (b)  use its reasonable best efforts to file with the Commission in a
timely manner all reports and other documents required of the Company under the
Securities Act and the Exchange Act; and

     (c)  furnish to each holder of Restricted Stock forthwith upon request a
written statement by the Company as to its compliance with the reporting
requirements of such Rule 144 and of the Securities Act and the Exchange Act, a
copy of the most recent annual or quarterly report of the Company, and such
other reports and documents so filed by the Company as such holder may
reasonably request in availing itself of any rule or regulation of the
Commission allowing such holder to sell any Restricted Stock without
registration.

     12.  Representations and Warranties of the Company.  The Company
          ---------------------------------------------
represents and warrants to the Investor Stockholders, ITI and Casty as follows:

     (a)  The execution, delivery and performance of this Agreement by the
Company have been duly authorized by all requisite corporate action on its part
and will not violate any provision of law, any order of any court or other
agency of government, the Certificate of Incorporation or By-laws each, as
amended, of the Company or any provision of any indenture,

                                      11
<PAGE>

agreement or other instrument to which it or any or its properties or assets is
bound, conflict with, result in a breach of or constitute (with due notice or
lapse of time or both) a default under any such indenture, agreement or other
instrument or result in the creation or imposition of any lien, charge or
encumbrance of any nature whatsoever upon any of the properties or assets of the
Company, except where the foregoing would not reasonably be expected to have a
material adverse effect on the Company or its business.

     (b)  This Agreement has been duly executed and delivered by the Company and
constitutes the legal, valid and binding obligation of the Company, enforceable
against the Company in accordance with its terms.

     13.  Miscellaneous.

     (a)  Except as otherwise provided herein, no modification, amendment or
waiver of any provision of this Agreement shall be effective against the Company
or any other party unless such modification, amendment or waiver is approved in
writing by the Company and the holders of at least 66 2/3% of the outstanding
shares of Restricted Stock held by each of the Investor Stockholders, ITI and
Casty, provided that any modification, amendment or waiver which would adversely
       --------
affect any party hereto in a manner which is different from the manner the other
parties hereto are affected shall also require the approval of such party. The
failure of any party to enforce any of the provisions of this Agreement shall in
no way be construed as a waiver of such provisions and shall not affect the
right of such party thereafter to enforce each and every provision of this
Agreement in accordance with its terms.

     (b)  This Agreement shall bind and inure to the benefit of and be
enforceable by the parties hereto and their respective heirs, personal
representatives, successors and permitted assigns. This Agreement and the rights
of the parties hereunder may not be assigned by any party hereto without the
prior written consent of the other parties, except as otherwise provided herein.
The Investor Stockholders may assign their rights and obligations hereunder to a
transferee of Restricted Stock, provided that such transferees agree in writing
                                --------
to be bound by the provisions of this Agreement. ITI and Casty may assign their
rights and obligations hereunder to a transferee of Restricted Stock, provided
that each such transferee of ITI and Casty and any subsequent transferee shall,
together with ITI or Casty, as the case may be, be deemed one person for
purposes of this Agreement, and any right or notice hereunder on behalf of such
person may only be delivered by ITI or by Casty (personally, or through his
personal representatives) and, provided, further, that ITI or Casty, as the case
                               --------  -------
may be, shall provide notice of any such assignment to the other parties hereto,
and any such transferee must agree in writing to be bound by the provisions of
this Agreement.

     (c)  All notices required or permitted hereunder shall be in writing and
shall be deemed effectively given: (i) upon personal delivery to the party to be
notified; (ii) when sent by confirmed facsimile if sent during normal business
hours of the recipient, if not, then on the next business day; (iii) five days
after having been sent by registered or certified mail, return receipt
requested, postage prepaid; or (iv) one business day after deposit with a
nationally recognized overnight courier, specifying next day delivery, with
written verification of receipt. All communications shall be sent, with respect
to the Company and the Investor Stockholders, to their respective addresses
specified in the Stock Purchase Agreement (or at such other address as

                                      12
<PAGE>

any such party may specify by like notice) and, with respect to any other party,
to the address of such party as shown in the stock record books of the Company
(or at such other address as any such party may specify to all of the above by
like notice).

     (d)  Except as otherwise expressly set forth herein, this document, the
Stock Purchase Agreement, the Certificate (as defined in the Stock Purchase
Agreement) and the Stockholders Agreement embody the complete agreement and
understanding among the parties hereto with respect to the subject matter hereof
and supersede and preempt any prior understandings, agreements or
representations by or among the parties, written or oral, that may have related
to the subject matter hereof in any way.

     (e)  This Agreement shall be governed by and construed and enforced in
accordance with the internal laws of the State of New York without regard to the
principles of conflicts of law thereof. Each party hereto hereby irrevocably
submits to the nonexclusive jurisdiction of the courts of the state of New York
and of the United States of America sitting in the City of New York, Borough of
Manhattan, for the adjudication of any dispute hereunder or in connection
herewith or with any transaction contemplated hereby or discussed herein, and
hereby irrevocably waives, and agrees not to assert in any suit, action or
proceeding, any claim that it is not personally subject to the jurisdiction of
any such court, that the venue thereof may not be appropriate, that such suit,
action or proceeding is improper or that this Agreement or any of the documents
referred to in this Agreement may not be enforced in or by said courts, and each
party hereto irrevocably agrees that all claims with respect to such suit,
action or proceeding may be heard and determined in such a New York state or
federal court. Each party hereby irrevocably waives personal service of process
and consents to process being served in any such suit, action or proceeding by
mailing a copy thereof to such party in the manner provided in Section 12(b) of
the Stock Purchase Agreement and agrees that such service shall constitute good
and sufficient service of process and notice thereof. Nothing contained herein
shall be deemed to limit in any way any right to serve process in any manner
permitted by law. EACH PARTY HEREBY IRREVOCABLY WAIVES ANY RIGHT IT MAY HAVE,
AND AGREES NOT TO REQUEST, A JURY TRIAL FOR THE ADJUDICATION OF ANY DISPUTE
HEREUNDER OR IN CONNECTION HEREWITH OR ARISING OUT OF THIS AGREEMENT OR ANY
TRANSACTION CONTEMPLATED HEREBY.

     (f)  The obligations of the Company to register shares of Restricted Stock
under Section 4, 5 or 6 shall terminate at the time at which all Restricted
Securities are eligible for resale pursuant to Rule 144(k) under the Securities
Act.

     (g)  If requested in writing by the Company and the underwriters for an
underwritten public offering of securities of the Company, each holder of
Restricted Stock who is a party to this Agreement shall agree not to sell
publicly any shares of Restricted Stock or any other shares of Common Stock
(other than shares of Restricted Stock or other shares of Common Stock being
registered in such offering), without the consent of the Company and such
underwriters, for such period requested by the underwriters (not to exceed 180
days) following the effective date of the registration statement relating to the
Qualified Public Offering (as defined in the Stock Purchase Agreement) or 90
days following the effective date of a registration statement relating to any
other offering; provided, however, that all persons entitled to registration
                --------  -------
rights with respect to shares of Common Stock who are not parties to this
Agreement, all persons holding 5% or more

                                      13
<PAGE>

of the capital stock of the Company on a fully diluted basis and all executive
officers and directors of the Company shall also have agreed not to sell
publicly their Common Stock under the circumstances and pursuant to the terms
set forth in this Section 13(g).

     (h)  Notwithstanding the provisions of Section 7(a), the Company's
obligation to file a registration statement, or cause such registration
statement to become and remain effective, shall be suspended for a period not to
exceed 90 days in any 12-month period if the Company shall furnish to the
holders a certificate signed by the President of the Company stating that in the
good faith judgment of the Board of Directors of the Company, it would be
seriously detrimental to the Company and its stockholders for such registration
to be effected at such time due to any pending material financing, acquisition
or corporate reorganization or other material corporate development involving
the Company or any of its subsidiaries; provided, however, that any suspension
                                        --------  -------
effectuated by the Company under this Section 13(h) shall be deemed a Suspension
subject to the limitation on the number of Suspensions permitted in any twelve
month period under Section 7(g) hereof.

     (i)  The Company shall not grant to any third party any registration rights
more favorable than or inconsistent with any of those contained herein, so long
as any of the registration rights under this Agreement remains in effect.

     (j)  Whenever possible, each provision of this Agreement shall be
interpreted in such manner as to be effective and valid under applicable law,
but if any provision of this Agreement is held to be invalid, illegal or
unenforceable in any respect under any applicable law or rule in any
jurisdiction, such invalidity, illegality or unenforceability shall not affect
any other provision or any other jurisdiction, but this Agreement shall be
reformed, construed and enforced in such jurisdiction as if such invalid,
illegal or unenforceable provision had never been contained herein.

     (k)  The titles of the sections and subsections of this Agreement are for
convenience of reference only and are not to be considered in construing this
Agreement.

     (l)  This Agreement may be executed in any number of counterparts, each of
which shall be an original, but all of which together shall constitute one
instrument. This Agreement may be executed by facsimile signature(s).

                                      14
<PAGE>

     IN WITNESS WHEREOF, the parties have executed this REGISTRATION RIGHTS
AGREEMENT as of the date set forth in the first paragraph hereof.

                                    IFX CORPORATION

                                    By:/s/ Joel Eidelstein
                                       --------------------------------------
                                       Name:  Joel Eidelstein
                                       Title: President

                                    UBS CAPITAL AMERICAS III, L.P
                                    By: UBS Capital Americas (LA-Advisors), LLC

                                    By:/s/ Charles W. Moore
                                       --------------------------------------
                                       Name:  Charles W. Moore
                                       Title: Principal

                                    By:/s/ Marc Unger
                                       --------------------------------------
                                       Name:  Marc Unger
                                       Title: Chief Financial Officer

                                    UBS CAPITAL LLC

                                    By:/s/ George Duarte
                                       --------------------------------------
                                       Name:  George Duarte
                                       Title: Attorney-in-Fact

                                    By:/s/ Marc Unger
                                       --------------------------------------
                                       Name:  Marc Unger
                                       Title: Attorney-in-Fact

                                    INTERNATIONAL TECHNOLOGIES
                                      INVESTMENTS, LLC

                                    By:/s/ Michael Shalom
                                       --------------------------------------
                                       Name:  Michael Shalom
                                       Title: Manager

                                       /s/ Lee S. Casty
                                       --------------------------------------
                                       Lee S. Casty

                                      15