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EXHIBIT 4.6

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REGISTRATION RIGHTS AGREEMENT

Dated as of March 25, 2003

among

IMPSAT FIBER NETWORKS, INC.,

IMPSAT S.A.

and

THE HOLDERS LISTED ON THE SIGNATURE PAGES HERETO



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REGISTRATION RIGHTS
AGREEMENT

THIS
REGISTRATION RIGHTS AGREEMENT (this Agreement) is made and entered
into as of March 25, 2003, among (i) IMPSAT FIBER NETWORKS, INC., a Delaware
corporation (the Company); (ii) IMPSAT, S.A., a corporation (sociedad
anonima) organized pursuant to the laws of the Republic of
Argentina (IMPSAT Argentina); (iii) the holders of the Companys 6% Senior Guaranteed
Convertible Notes due 2011  Series A and B guaranteed by IMPSAT Argentina
(collectively, the Notes), listed on the Schedule of Holders attached hereto
as Exhibit A (the Schedule of Holders); (iv) the holders of shares (the
Common Shares) of the Companys common stock, par value $.01 per share (the
Common Stock), listed on the Schedule of Holders; and (v) the holders of
warrants to purchase shares of Common Stock (the Warrants and, collectively
with the Notes and the Common Shares, the Securities) listed on the Schedule
of Holders.

RECITALS:

WHEREAS, on June 11, 2002, the Company filed a petition under Chapter 11
of title 11 of the United States Code, 11 U.S.C. §§ 101-1330, as amended (the
Bankruptcy Code), in the United States Bankruptcy Court for the Southern
District of New York (the Bankruptcy Court); and

WHEREAS, by order dated December 16, 2002, entered by the Bankruptcy Court
pursuant to section 1129 of the Bankruptcy Code, the Bankruptcy Court confirmed
the Companys Plan of Reorganization dated October 23, 2002, as amended (the
Plan); and

WHEREAS, the Plan provides, among other things, for (i) the issuance by
the Company of the Securities held by each Holder (as defined herein) in
discharge of pre-existing indebtedness of the Company to such Holder, and (ii)
the execution and delivery of this Agreement by the parties hereto.

NOW, THEREFORE, in consideration of the foregoing, the parties hereto
agree as follows:

1.      Definitions. As used in this Agreement, the following capitalized
defined terms shall have the following meanings:



| |                                                                                                                                                                  
| | -----------------------------------------------------------------------------------------------------------------------------------------------------------------
| | 1933
Act shall mean the Securities Act of 1933, as amended from
time to time.                                                                                  
|
| | 1934
Act shall mean the Securities Exchange Act of 1934, as
amended from time to time.                                                                         
|
| | Adverse
Effect shall have the meaning set forth in Section 2(d).                                                                                               
|
| | Common
Shares shall have the meaning set forth in the preamble.                                                                                                
|
| | Common
Share Equivalents shall mean, as to any Holder, all Common
Shares that are issued and outstanding to such Holder and all shares of
Common Stock that are





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| |                                                                                                                                                                                                                                                                                                                                                                                                                                
| | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
| | issuable upon the exchange, exercise or conversion of any other of
the Registrable Securities held by such Holder. The number of Common
Share Equivalents owned by a Holder shall equal the sum of the number of
issued and outstanding Common Shares owned by such Holder plus the number
of shares of Common Stock issuable upon the exchange, exercise or
conversion of any other Registrable Security owned by such Holder.
|
| | Common Stock shall have the meaning set forth in the preamble.                                                                                                                                                                                                                                                                                                                                                               
|
| | Company shall have the meaning set forth in the preamble and shall
also include the Companys successors; provided that, where this
Agreement pertains in any manner to the Notes (including for purposes of
Section 4), Company shall mean IMPSAT Fiber Networks, Inc. and IMPSAT
Argentina, jointly and severally.                                                                                                       



| |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              
| | -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
| | Conversion Shares shall have the meaning set forth in the
definition of Registrable Securities.                                                                                                                                                                                                                                                                                                                                                                                                                            
|
| | Holder shall mean a holder of Registrable Securities.                                                                                                                                                                                                                                                                                                                                                                                                                                                                      
|
| | Indenture shall mean the indentures relating to the Notes dated as
of March 25, 2003 among the Company, IMPSAT Argentina and The Bank of New
York.                                                                                                                                                                                                                                                                                                                                                                         
|
| | Majority Holders shall mean the Holders of a majority of the total
Common Share Equivalents.                                                                                                                                                                                                                                                                                                                                                                                                                               
|
| | Notes shall have the meaning set forth in the Preamble.                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|
| | Person shall mean an individual, partnership, limited liability
company, corporation, trust or unincorporated organization, or a
government or agency or political subdivision thereof, or any other
entity.                                                                                                                                                                                                                                                                                                               
|
| | Prospectus shall mean the prospectus included in a Registration
Statement, including any preliminary prospectus, and any such prospectus
as amended or supplemented by any prospectus supplement (including a
prospectus supplement with respect to the terms of the offering of any
portion of the Registrable Securities covered by a Shelf Registration
Statement), and all other amendments and supplements to such prospectus,
in each case, including all material, if any, incorporated by reference
therein.       
|
| | Purchased Shares shall mean any shares of Common Stock purchased
after the date hereof and held by a Holder to whom Securities were issued
pursuant to the Plan.                                                                                                                                                                                                                                                                                                                                                           
|
| | Registrable Securities shall mean (i) the Securities issued under
the Plan, (ii) the shares of Common Stock issued or issuable upon
conversion of the Notes issued under the Plan (the Conversion Shares),
(iii) any Purchased Shares included in a Shelf Registration Statement by
a post-effective amendment pursuant to Rule 462(b) under the 1933 Act in
accordance with Section 2(a), (iv) the shares of Common Stock issued or
issuable upon exercise of the Warrants issued under the Plan (the
Warrant Shares),

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| |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  
| | -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
| | (v) any shares of capital stock issued or issuable with respect to
any Securities, Conversion Shares or Warrant Shares referenced in the
immediately preceding clauses (i) through (iv) as a result of any stock
split, stock dividend, recapitalization, exchange or similar event or
otherwise, without regard to any limitations on conversions of the Notes
or the exercise of the Warrants, and (vi) any shares of capital stock of
any entity issued in respect of the capital stock referenced in the
immediately preceding clauses (i) through (v) as a result of a merger,
consolidation, sale of assets, sale or exchange of capital stock or other
similar transaction; provided, however, that any securities described in
the preceding clauses (i) through (vi) shall not be Registrable
Securities (A) when a Registration Statement with respect to such
securities shall have been declared effective under the 1933 Act and such
securities shall have been disposed of pursuant to such Registration
Statement, (B) when such securities have been sold in accordance with
Rule 144 (or any successor provision) promulgated under the 1933 Act, (C)
the Company has delivered a new certificate or other evidence of
ownership for such securities not bearing a legend restricting further
transfer and such securities may be resold under Rule 144(k) under the
1933 Act, or (D) when such securities shall have ceased to be
outstanding.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                
|
| | Registrable Common Securities shall mean any shares of Common
Stock (excluding any Purchased Shares), Conversion Shares and Warrant
Shares that are Registrable Securities.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|
| | Registration Expenses shall mean the following expenses incident
to performance of or compliance by the Company with this Agreement: (i)
all SEC, stock exchange or National Association of Securities Dealers,
Inc. registration, listing and filing fees (including fees of any
qualified independent underwriter in connection with an Underwritten
Offering); (ii) all fees and expenses incurred in connection with
compliance with state securities or blue sky laws (including reasonable
fees and disbursements of counsel for any underwriters or Holders in
connection with blue sky qualification of any of the Registrable
Securities); (iii) all expenses of any Persons in preparing or assisting
in preparing, word processing, printing and distributing any Registration
Statement, any Prospectus, any amendments or supplements thereto, any
underwriting agreements, securities sales agreements and other documents
relating to the performance of and compliance with this Agreement; (iv)
all fees and disbursements relating to the qualification of the Indenture
under applicable securities laws; (v) the fees and disbursements of the
Trustee and its counsel, the transfer agent, registrar and/or depositary
(including the Depository Trust Company) for the Common Stock; (vi) the
fees and disbursements of counsel for the Company and, in the case of a
Shelf Registration Statement, the fees and disbursements of one counsel
for the Holders (which counsel shall be selected by the Majority
Holders); and (vii) the fees and disbursements of the independent public
accountants of, and any special experts retained by, the Company,
including, the expenses of any special audits or comfort letters
required by or incident to such performance and compliance, but excluding
fees and expenses of counsel to the underwriters (other than fees and
expenses set forth in clause (ii) above) or the Holders (other than such
fees and expenses of counsel for the Holders permitted under clause (vi)
above) and underwriting discounts and commissions and transfer taxes, if
any, relating to the sale or disposition of Registrable Securities by a
Holder.

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| |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
| | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
| | Registration Statement shall mean any registration statement of
the Company (including any Shelf Registration Statement) filed pursuant
to this Agreement under the 1933 Act, and all amendments and supplements
to any such Registration Statement, including post-effective amendments
(including pursuant to Rule 462(b) under the 1933 Act), in each case
including the Prospectus contained therein, all exhibits thereto and all
material incorporated by reference therein.                                                                        
|
| | SEC shall mean the Securities and Exchange Commission.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|
| | Securities shall have the meaning set forth in the preamble.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              
|
| | Shelf Registration shall mean a registration effected pursuant to
Section 2(a) hereof.                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|
| | Shelf Registration Statement shall mean a shelf registration
statement of the Company pursuant to the provisions of Section 2(a) of
this Agreement that covers all of the Registrable Securities on an
appropriate form under Rule 415 under the 1933 Act (or any similar rule
that may be adopted by the SEC) and all amendments and supplements to
such registration statement, including post-effective amendments, in each
case including the Prospectus contained therein, all exhibits thereto and
all material incorporated by reference therein.
|
| | Trustee shall mean the trustee with respect to the Notes under the
Indenture.                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|
| | Underwriter shall have the meaning set forth in Section 3 hereof.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         
|
| | Underwritten Offering shall mean a registration in which
Registrable Securities are sold to an Underwriter for reoffering to the
public.                                                                                                                                                                                                                                                                                                                                                                                                                  
|
| | Warrants shall have the meaning set forth in the preamble.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                
|
| | Warrant Shares shall have the meaning set forth in the definition
of Registrable Securities.                                                                                                                                                                                                                                                                                                                                                                                                                                                              

2.      Registration Under the 1933 Act.

(a)      As soon as practicable, but in no event later than 60 days after the
date hereof, the Company shall file a Shelf Registration Statement providing
for the sale by the Holders of all of the Registrable Securities and shall use
its best efforts to cause such Shelf Registration Statement to be declared
effective by the SEC as soon as thereafter practicable but in any event not
later than 90 days following such filing. The Company agrees to use its best
efforts to keep the Shelf Registration Statement continuously effective until
the Holders shall no longer hold any Registrable Securities or such shorter
period that will terminate when all of the Registrable Securities covered by
the Shelf Registration Statement have been sold pursuant to the Shelf
Registration Statement. The Company further agrees (i) to supplement or amend
the Shelf Registration Statement if required by the rules, regulations or
instructions applicable to the registration form used by the Company for such
Shelf Registration Statement or by the 1933 Act

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or by any other rules and regulations thereunder for shelf registration or
if reasonably requested by a Holder with respect to information relating to
such Holder and (ii) if the Company receives written notice from any Holder
after the date on which such Shelf Registration Statement has become effective
that such Holder desires to include some or all of its Purchased Shares in such
Shelf Registration Statement, to use its reasonable best efforts to so include
such Purchased Shares as promptly as practicable by a post-effective amendment
to such Shelf Registration Statement pursuant to Rule 462(b) under the 1933
Act, and, in each such case, to use its best efforts to cause any such
amendment to become effective and such Shelf Registration Statement to become
usable as soon as thereafter practicable. The Company shall give all Holders
written notice of such proposed post-effective amendment to the Shelf
Registration Statement as soon as practicable (but in any event not less than
five business days before the anticipated filing date of such amendment), and
such Holders may thereupon include some or all of their Purchased Shares in the
Shelf Registration Statement under such post-effective amendment by making a
written request therefor to the Company (which request must be received by the
Company not later than five business days after receipt by such Holder of the
Companys notice); provided, however, that, if the maximum aggregate offering
price of all Purchased Shares requested by all Holders for inclusion in such
Shelf Registration pursuant hereto would exceed the limitations imposed by Rule
462(b) under the 1933 Act, the total number of such Purchased Shares to be so
included shall be reduced in compliance with such limitations, pro rata based
on the ratio that all shares of Common Stock held by each such Holder bears to
the total number of shares of Common Stock held by all such Holders. The
Company agrees to furnish to the Holders copies of any such supplement or
amendment promptly after its being used or filed with the SEC.

(b)      The Company shall pay all Registration Expenses in connection with the
registration pursuant to Section 2(a). Each Holder shall pay all underwriting
discounts and commissions and transfer taxes, if any, relating to the sale or
disposition of such Holders Registrable Securities in an Underwritten Offering
pursuant to the Shelf Registration Statement.

(c)      A Shelf Registration Statement pursuant to Section 2(a) hereof shall
not be deemed to have become effective unless it has been declared effective by
the SEC; provided, however, that, if, after it has been declared effective, the
offering of Registrable Securities pursuant to a Shelf Registration Statement
is interfered with by any stop order, injunction or other order or requirement
of the SEC or any other governmental agency or court, such Registration
Statement will be deemed not to have become effective during the period of such
interference until the offering of Registrable Securities pursuant to such
Registration Statement may legally resume. The Company shall be deemed not to
have used its best efforts to keep the Shelf Registration Statement effective
during the requisite period if it takes any action that would result in Holders
of Registrable Securities covered thereby not being able temporarily to offer
and sell such securities during that period, unless (i) such action is required
by (and is the only course of action available to comply with) applicable law
or is taken by the Company in good faith and for valid business reasons (not
including avoidance of the Companys obligations hereunder), including the
acquisition or divestiture of assets, so long as the Company promptly
thereafter complies with the requirements of Section 3(j) hereof, if
applicable, and (ii) the Company gives written notice thereof to such Holders
describing in reasonable detail the reasons for and nature of such action and
the period during which such Holders ability to offer and sell Registrable
Securities is suspended.

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(d)      If at any time after the date hereof the Company proposes to file a
Registration Statement with respect to an offering of Common Stock for the
account of the Company or any Person other than a Holder of Registrable Common
Securities (except a registration pursuant to Section 2(a) or on Form S-4 or
Form S-8 or any successor form), in each case, that is to be underwritten on a
firm commitment or best efforts basis, then the Company shall give written
notice of such proposed filing to the Holders of Registrable Common Securities
as soon as practicable (but in any event not less than 20 business days before
the anticipated filing date of such registration), describing in reasonable
detail the proposed registration (including, to the extent practicable, the
number of securities proposed to be registered, the proposed date of filing of
such Registration Statement, any proposed means of distribution, any proposed
managing underwriters and a good faith estimate of the proposed range of
offering prices), and shall offer such Holders the opportunity to register such
number of Registrable Common Securities as each such Holder may request. Upon
the written request of any Holder, which must be received by the Company not
later than 10 business days after receipt by such Holder of the Companys
notice, to register any of such Holders Registrable Common Securities, the
Company will use its reasonable best efforts to cause such Registrable Common
Securities to be included in such Registration Statement proposed to be filed
by the Company on the same terms and conditions as the Common Stock being
registered; provided, however, that if the managing underwriters for the
offering advise the Company in writing that the inclusion of such Registrable
Common Securities would adversely affect the price or success of the offering
(an Adverse Effect), and the Company notifies the Holder thereof in writing
of such advice, then (i) the number of Registrable Common Securities to be
included in such Registration Statement shall be reduced to an amount which, in
the judgment of such managing underwriters, would eliminate such Adverse Effect
or (ii) if no such reduction would, in the judgment of such managing
underwriters, eliminate such Adverse Effect, then the Company shall have the
right to exclude all such Registrable Common Securities from such Registration
Statement provided no other securities are included for the account of any
Person other than the Company or the Person that initiated such registration;
and provided, further, that the Company shall not be required to include any
Registrable Common Securities in any such Registration Statement under this
Section 2(d) unless the Holder thereof furnishes to the Company such
information about such Holder as the Company reasonably requests for inclusion
in or in connection with such Registration Statement. Any partial reduction in
the number of Registrable Common Securities to be included in such Registration
Statement pursuant hereto shall be effected pro rata based on the ratio that
any Holders Registrable Common Securities bears to the total number of
Registrable Common Securities requested to be included in such Registration
Statement. Any Holder of Registrable Common Securities shall have the right to
withdraw its request for inclusion of such securities in any such Registration
Statement pursuant to this Section 2(d) by giving written notice to the Company
of its request to withdraw prior to the earlier of the execution of any
underwriting agreement or custody agreement with respect to such registration,
and such withdrawal shall be irrevocable. The Company shall have the right to
postpone, suspend or withdraw any registration pursuant to this Section 2(d)
without obligation to any Holder of Registrable Common Securities.

3.      Registration Procedures. In connection with the obligations of the
Company with respect to the Registration Statement pursuant to Section 2(a)
hereof, the Company shall as expeditiously as possible, as applicable:

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(a)      prepare and file with the SEC a Registration Statement (i) on the
appropriate form under the 1933 Act, which (x) shall be selected by the
Company, (y) shall be available for the sale of the Registrable Securities by
the selling Holders thereof and (z) shall comply as to form in all material
respects with the requirements of the applicable form and the rules and
regulation of the SEC (including with respect to containing all financial
statements required by the SEC to be filed therewith, and (ii) not containing
any untrue statement of a material fact or omitting to state a material fact
required to be stated therein or necessary to make the statements therein (in
the case of any related Prospectus, in light of the circumstances under which
they were made) not misleading; and use its best efforts to cause such
Registration Statement to become effective and remain effective in accordance
with Section 2 hereof;

(b)      prepare and file with the SEC such amendments, post-effective
amendments and supplements to each Registration Statement as may be necessary
to keep such Registration Statement effective as required under Section 2 and
to comply with the provisions of the 1933 Act with respect to the disposition
of all Registrable Securities covered by such Registration Statement until the
earlier of such time as all of such Registrable Securities have been disposed
of in accordance with the intended methods of disposition by the Holders;

(c)      furnish to each Holder and to each Underwriter of an Underwritten
Offering of Registrable Securities, if any, without charge, as many copies of
each Prospectus, including each preliminary prospectus and any summary
prospectus, and any amendment or supplement thereto and such other documents
(including any documents incorporated by reference therein) as such Holder or
Underwriter may reasonably request, in order to facilitate the public sale or
other disposition of the Registrable Securities; and the Company consents to
the use of such Prospectus and any amendment or supplement thereto and any such
document in accordance with applicable law by each of the selling Holders of
Registrable Securities and any such Underwriters in connection with the
offering and sale of the Registrable Securities covered by and in the manner
described in such Prospectus or any amendment or supplement thereto in
accordance with applicable law;

(d)      use its best efforts to register or qualify the Registrable Securities
under all applicable state securities or blue sky laws of such jurisdictions
as any Underwriter of an Underwritten Offering of Registrable Securities or any
Holder of Registrable Securities covered by a Registration Statement shall
reasonably request in writing, to continue such qualification in effect in such
jurisdiction for as long as permissible pursuant to the laws of such
jurisdiction, or for as long as any Holder requests or until all of such
Registrable Securities are sold, whichever is shortest, to cooperate with such
Holder and Underwriter in connection with any filings required to be made with
the National Association of Securities Dealers, Inc. and do any and all other
acts and things that may be reasonably necessary or advisable to enable such
Holder to consummate the disposition in each such jurisdiction of such
Registrable Securities owned by such Holder; provided, however, that the
Company shall not be required to (i) qualify as a foreign corporation or as a
dealer in securities in any jurisdiction where it would not otherwise be
required to qualify but for this Section 3(d), (ii) file any general consent to
service of process or (iii) subject itself to material taxation in any such
jurisdiction if it is not so subject; and use its reasonable best efforts to
obtain all other approvals, consents, exemptions, or authorizations from

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such securities regulatory authorities or governmental agencies as may be
necessary to enable such Holders to consummate the disposition of such
Registrable Securities;

(e)      notify promptly each Holder and, if requested by any such Holder,
confirm such advice in writing (i) of the filing of a Registration Statement,
Prospectus and any amendment or supplement thereto, and with respect to a
Registration Statement or any post-effective amendment thereto, when the same
has become effective, (ii) of any comments by the SEC with respect to such
Registration Statement or any request by the SEC or any state securities
authority for amendments or supplements to a Registration Statement and
Prospectus or for additional information after the Registration Statement has
become effective, (iii) of the issuance by the SEC or any state securities
authority of any stop order suspending the effectiveness of a Registration
Statement or the initiation of any proceedings by any Person for that purpose,
(iv) if, between the effective date of a Registration Statement and the closing
of any sale of Registrable Securities covered thereby, the representations and
warranties of the Company contained in any underwriting agreement, securities
sales agreement or other similar agreement, if any, relating to the offering
cease to be true and correct in all material respects or if the Company
receives any notification with respect to the suspension of the qualification
of the Registrable Securities for sale in any jurisdiction or the initiation of
any proceeding for such purpose, (v) upon discovery that, or upon the happening
of any event as a result of which, the Prospectus included in such Registration
Statement contains an untrue statement of a material fact or omits to state any
material fact required to be stated therein or necessary to make the statements
therein, in light of the circumstances under which they were made, not
misleading and (vi) of any determination by the Company that a post-effective
amendment to a Registration Statement would be appropriate;

(f)      make every reasonable effort to obtain the withdrawal of any order
suspending the effectiveness of a Registration Statement (or the lifting of any
suspension of the qualification (or exemption from qualification) of any
Registrable Securities for sale in any jurisdiction) at the earliest possible
moment and provide immediate notice to each Holder of the withdrawal of any
such order (or the lifting of any such suspension);

(g)      furnish to each Holder, without charge, at least one conformed copy of
each Registration Statement and any post-effective amendment thereto (without
documents incorporated therein by reference or exhibits thereto, unless
requested);

(h)      cooperate with the selling Holders of Registrable Securities to
facilitate the timely preparation and delivery of certificates representing
Registrable Securities to be sold and not bearing any restrictive legends and
enable such Registrable Securities to be in such denominations (in the case of
the Notes, consistent with the provisions of the Indenture) and registered in
such names as the selling Holders may reasonably request at least one business
day prior to the closing of any sale of Registrable Securities;

(i)      upon the occurrence of any event contemplated by clause (v) of Section
3(e) hereof, use its best efforts promptly (subject to its obligations under
Section 3(j)) to prepare and file with the SEC (and deliver to each Holder) a
supplement, amendment or post-effective amendment to a Registration Statement
or the related Prospectus or any document incorporated therein by reference or
file any other required document so that, as thereafter delivered to the

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purchasers of the Registrable Securities, such Prospectus will not contain
any untrue statement of a material fact or omit to state a material fact
necessary to make the statements therein, in light of the circumstances under
which they were made, not misleading. The Company agrees to notify the Holders
to suspend use of the Prospectus as promptly as practicable after the
occurrence of such an event, and the Holders hereby agree to suspend use of the
Prospectus immediately thereafter until the Company has amended or supplemented
the Registration Statement or related Prospectus or document to correct such
misstatement or omission and delivered to the Holders the Registration
Statement, Prospectus or document, as then amended and supplemented;

(j)      a reasonable time prior to the filing of any Registration Statement,
any Prospectus, or any document which is to be incorporated by reference into a
Registration Statement or a Prospectus after the initial filing of a
Registration Statement pursuant to Section 2(a), provide copies of such
document to the Holders, provide the Holders and their counsel with an adequate
opportunity to review and comment on such Registration Statement (and reflect
in the Registration Statement all such comments the Holders may reasonably
make) and make such of the representatives of the Company as shall be
reasonably requested by the Holders or their counsel available for discussion
of such document, and not at any time file or make any amendment to the
Registration Statement, any Prospectus, or any document that is to be
incorporated by reference into a Registration Statement or a Prospectus, of
which the Holders and their counsel shall not have previously been advised and
furnished a copy or to which the Holders or their counsel shall reasonably
object;

(k)      cause the Indenture to be qualified under the Trust Indenture Act of
1939, as amended (the TIA), in connection with the registration of the
Registrable Securities, cooperate with the Trustee and the Holders to effect
such changes to the Indenture as may be required for the Indenture to be so
qualified in accordance with the terms of the TIA and execute, and use their
best efforts to cause the Trustee to execute, all documents as may be required
to effect such changes and all other forms and documents required to be filed
with the SEC to enable the Indenture to be so qualified in a timely manner;

(l)      make available for inspection by representatives of the Holders of the
Registrable Securities, any Underwriter participating in any disposition
pursuant to a Shelf Registration Statement, and any attorneys and accountants
or other agents designated by the Holders or Underwriters, at reasonable times
and in a reasonable manner, all financial and other records, pertinent
documents and properties of the Company and its subsidiaries, and cause the
officers, directors and employees of the Company to supply all information
reasonably requested by any such representative, Underwriter, attorney or
accountant in connection with such Shelf Registration Statement;

(m)      use its best efforts to cause all Registrable Common Securities to be
listed on any securities exchange or any automated quotation system on which
the Common Stock is then listed;

(n)      if reasonably requested by any Holder of Registrable Securities
covered by a Registration Statement, (i) promptly incorporate in a Prospectus
supplement or post-effective amendment such information with respect to such
Holder as such Holder reasonably requests to

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be included therein and (ii) make all required filings of such Prospectus
supplement or such post-effective amendment as soon as the Company has received
notification of the matters to be incorporated in such filing;

(o)      enter into such customary agreements (including underwriting
agreements in customary form, in the case of an Underwritten Offering, which
may include such standard lock-up obligations as may be reasonably requested
by the managing Underwriters) and take all such other actions in connection
therewith (including those requested by the Holders of a majority in Common
Share Equivalents of the Registrable Securities being sold) in order to
expedite or facilitate the disposition of such Registrable Securities pursuant
to a Shelf Registration Statement, including, an Underwritten Offering, and in
such connection, (i) to the extent possible, make such representations and
warranties to the Holders and any Underwriters of such Registrable Securities
with respect to the business of the Company and its subsidiaries, the
Registration Statement, Prospectus and documents incorporated by reference or
deemed incorporated by reference, if any, in each case, in form, substance and
scope as are customarily made by issuers to underwriters in underwritten
offerings and confirm the same if and when requested, (ii) obtain opinions of
counsel to the Company (which counsel and opinions, in form, scope and
substance, shall be reasonably satisfactory to the Holders and such
Underwriters) addressed to each selling Holder and Underwriter of Registrable
Securities, covering the matters customarily covered in opinions requested in
underwritten offerings, (iii) obtain comfort letters from the independent
certified public accountants of the Company (and, if necessary, any other
certified public accountant of any subsidiary of the Company, or of any
business acquired by the Company for which financial statements and financial
data are or are required to be included in the Registration Statement)
addressed to each selling Holder and Underwriter of Registrable Securities,
such letters to be in customary form and covering matters of the type
customarily covered in comfort letters in connection with underwritten
offerings, (iv) use its reasonable best efforts to make such road show
presentations and otherwise engage in such reasonable marketing support in
connection with any Underwritten Offering, including making its management
available for such purpose if so requested by the Underwriters for such
offering, and (v) deliver such documents and certificates as may be reasonably
requested by the Holders of a majority in Common Share Equivalents of the
Registrable Securities being sold or the Underwriters, and that are customarily
delivered in underwritten offerings, to evidence the continued validity of the
representations and warranties of the Company made pursuant to clause (i) above
and to evidence compliance with any customary conditions contained in an
underwriting agreement;

(p)      comply with all applicable rules and regulations of the SEC, and make
available to its security holders, as soon as reasonably practicable but no
later than fifteen (15) months after the effective date of the Registration
Statement, an earnings statement covering a period of twelve (12) months
beginning after the effective date of the Shelf Registration Statement, in a
manner which satisfies the provisions of Section 11(a) of the 1933 Act and Rule
158 thereunder; and

(q)      use its best efforts to take all other steps necessary to effect the
registration of such Registrable Securities contemplated hereby.

10



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The Company may require each Holder of Registrable Securities to furnish
to the Company such information regarding such Holder and the proposed
distribution by such Holder of such Registrable Securities as the Company may
from time to time reasonably request in writing.

Each Holder agrees that, upon receipt of any notice from the Company of
the happening of any event of the kind described in Section 3(e)(v) hereof,
such Holder will forthwith discontinue disposition of Registrable Securities
pursuant to a Shelf Registration Statement until such Holders receipt of the
copies of the supplemented or amended Prospectus contemplated by Section 3(i)
hereof, and, if so directed by the Company, such Holder will deliver to the
Company (at the Companys expense) all copies in its possession, other than
permanent file copies then in such Holders possession, of the Prospectus
covering such Registrable Securities current at the time of receipt of such
notice. Each Holder further agrees that, upon receipt of any notice from the
Company of the happening of any event of the kind described in the last
sentence of Section 2(c), such Holder shall forthwith discontinue disposition
of Registrable Securities pursuant to a Registration Statement until expiration
of the suspension period indicated in such notice. The Company may give notice
of any event of the kind described in Section 3(e)(v) and/or in the last
sentence of Section 2(c) not more than three times during any 365-day period
and any such suspensions may not exceed 30 days for each suspension (or 90 days
in the aggregate in any such period).

The Holders of Registrable Securities covered by a Shelf Registration
Statement who desire to do so may sell such Registrable Securities in an
Underwritten Offering. In any such Underwritten Offering, the investment
banker or investment bankers and manager or managers (the Underwriters) that
will administer the offering will be selected by the Holders of a majority in
Common Share Equivalents of the Registrable Securities included in such
offering.

4.      Indemnification and Contribution.

(a)      The Company agrees to indemnify and hold harmless each Holder and each
Person, if any, who controls such Holder within the meaning of Section 15 of
the 1933 Act and Section 20 of the 1934 Act, or is under common control with,
or is controlled by, such Holder, from and against all losses, claims, damages,
liabilities and expenses (including any legal or other expenses reasonably
incurred by any such Holder or Person in connection with defending or
investigating any such action or claim, as such expenses are incurred) arising
out of or based on any untrue statement or alleged untrue statement of a
material fact contained in any Registration Statement pursuant to which
Registrable Securities were registered under the 1933 Act or in any Prospectus,
or in any amendment or supplement thereto, including all documents (if any)
incorporated therein by reference, or arising out of or based on any omission
or alleged omission to state therein a material fact required to be stated
therein or necessary to make the statements therein (in the case of any such
Prospectus, in light of the circumstances under which they were made) not
misleading; provided, however, that the foregoing indemnity shall not inure to
the benefit of any of the foregoing parties to the extent, but only to the
extent, that such untrue statement or alleged untrue statement or omission or
alleged omission was made (x) in any Prospectus delivered by any such party (1)
if prior to such delivery by such party, the Company shall have complied with
its obligations under Section 3(e), (c) and (i) of this Agreement, to

11



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provide such party with prompt notification of such untrue statement or
omission and to furnish to such party copies of an amended or supplemented
Prospectus, and (2) if delivered by such party (after receipt thereof from the
Company) within the time (if any) required by the 1933 Act, such amended or
supplemented Prospectus would have cured such untrue statement or omission
contained in the Prospectus delivered by such party or (y) in any such
Registration Statement or Prospectus (or amendment or supplement) in reliance
upon and in conformity with written information relating to any such party
furnished to the Company by such party expressly for use therein. For the
avoidance of doubt, the parties hereto acknowledge and agree that, in any suit,
action or proceeding in which the Company asserts that, under the foregoing
clauses (x) and (y) of this Section 4(a), the foregoing indemnity does not
inure to the benefit of any of such foregoing parties the Company shall bear
the evidentiary burden of establishing such assertion in accordance with the
normal, civil burden of proof by a preponderance of the evidence. In
connection with any Underwritten Offering permitted by Section 3, the Company
will also indemnify the Underwriters, if any, selling brokers, dealers and
similar securities industry professionals participating in the distribution,
their officers and directors and each Person who controls such Persons (within
the meaning of the 1933 Act and the 1934 Act) to the same extent as provided
above with respect to the indemnification of the Holders, if requested in
connection with any Registration Statement. This indemnity shall be in
addition to any liability the Company may otherwise have.

(b)      Each Holder agrees, severally and not jointly, to indemnify and hold
harmless the Company, the other Holders, and each of their respective
directors, officers who sign the Registration Statement and each Person, if
any, who controls the Company and any other Holder within the meaning of
Section 15 of the 1933 Act and Section 20 of the 1934 Act to the same extent as
the foregoing indemnity from the Company to the Holders, but only with
reference to information relating to such indemnifying Holder furnished to the
Company in writing by such Holder expressly for use in any Registration
Statement (or any amendment thereto) or any Prospectus (or any amendment or
supplement thereto).

(c)      In case any proceeding (including any governmental investigation)
shall be instituted involving any Person in respect of which indemnity may be
sought pursuant to either paragraph (a) or paragraph (b) above, such Person
(the indemnified party) shall promptly notify the Person against whom such
indemnity may be sought (the indemnifying party) in writing and the
indemnifying party, upon request of the indemnified party, shall retain counsel
reasonably satisfactory to the indemnified party to represent the indemnified
party and any others the indemnifying party may designate in such proceeding
and shall pay the fees and disbursements of such counsel related to such
proceeding; provided, however, that the failure to notify the indemnifying
party shall not relieve the indemnifying party of any liability that it may
have to the indemnified party hereunder (except to the extent that the
indemnifying party is materially prejudiced or otherwise forfeits substantive
rights or defenses by reason of such failure). In any such proceeding, any
indemnified party shall have the right to retain its own counsel, but the fees
and expenses of such counsel shall be at the expense of such indemnified party
unless (i) the indemnifying party and the indemnified party shall have mutually
agreed to the retention of such counsel, (ii) the named parties to any such
proceeding (including any impleaded parties) include both the indemnifying
party and the indemnified party and representation of both parties by the same
counsel would be inappropriate due to actual or

12



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potential differing interests between them or (iii) the indemnifying party
fails to assume the defense of such action reasonably promptly with counsel
reasonably satisfactory to the indemnified party. It is understood that the
indemnifying party shall not, in connection with any proceeding or related
proceedings in the same jurisdiction, be liable for (A) the fees and expenses
of more than one separate firm (in addition to any local counsel) for all
Holders and all Persons, if any, who control any Holders within the meaning of
Section 15 of the 1933 Act and Section 20 of the 1934 Act, and (B) the fees and
expenses of more than one separate firm (in addition to any local counsel) for
the Company, its directors, its officers who sign the Registration Statement
and each Person, if any, who controls the Company within the meaning of such
Sections, and that all such fees and expenses shall be reimbursed as they are
incurred. In such case involving the Holders and such Persons who control
Holders, such firm shall be designated in writing by the Holders of a majority
of the Registrable Securities (being) sold. In all other cases, such firm
shall be designated by the Company. The indemnifying party shall not be liable
for any settlement of any proceeding effected without its written consent
(which shall not be unreasonably withheld), but if settled with such consent or
if there be a final judgment adverse to the indemnified party, the indemnifying
party agrees to indemnify the indemnified party from and against any loss or
liability by reason of such settlement or judgment. Notwithstanding the
foregoing sentence, if at any time an indemnified party shall have requested an
indemnifying party to reimburse the indemnified party for fees and expenses of
counsel as contemplated by this Section 4(c), the indemnifying party agrees
that it shall be liable for any settlement of any proceeding effected without
its written consent if (i) such settlement is entered into more than 30 days
after receipt by such indemnifying party of the aforesaid request and (ii) such
indemnifying party shall not have reimbursed the indemnified party for such
fees and expenses of counsel in accordance with such request prior to the date
of such settlement. No indemnifying party shall, without the prior written
consent of the indemnified party (which shall not be unreasonably withheld),
effect any settlement of any pending or threatened proceeding in respect of
which such indemnified party is or could have been a party and indemnity could
have been sought hereunder by such indemnified party, unless such settlement
includes an unconditional release of such indemnified party from all liability
on claims that are the subject matter of such proceeding.

(d)      If the indemnification provided for in paragraph (a) or paragraph (b)
of this Section 4 is unavailable to an indemnified party or insufficient in
respect of any losses, claims, damages, liabilities or expenses incurred by an
indemnified party, then each indemnifying party under such paragraph, in lieu
of indemnifying such indemnified party thereunder, shall contribute to the
amount paid or payable by such indemnified party as a result of such losses,
claims, damages, liabilities or expenses in such proportion as is appropriate
to reflect the relative fault of the indemnifying party or parties on the one
hand and of the indemnified party or parties on the other hand in connection
with the statements or omissions that resulted in such losses, claims, damages,
liabilities or expenses, as well as any other relevant equitable
considerations. The relative fault of the Company and the Holders shall be
determined by reference to, among other things, whether the untrue or alleged
untrue statement of a material fact or the omission or alleged omission to
state a material fact relates to information supplied by the Company or by the
Holders and the parties relative intent, knowledge, access to information and
opportunity to correct or prevent such statement or omission. The Holders
respective obligations to contribute pursuant to this Section 4(d) are several
in proportion to the respective number of Registrable Securities of such Holder
that were registered pursuant to a Registration Statement. No Person

13



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guilty of fraudulent misrepresentation (within the meaning of Section
11(f) of the 1933 Act) shall be entitled to contribution from any Person who
was not guilty of such fraudulent misrepresentation.

The Company and each Holder agree that it would not be just or equitable
if contribution pursuant to this Section 4(d) were determined by pro rata
allocation or by any other method of allocation that does not take account of
the equitable considerations referred to in paragraph above. The amount paid
or payable by an indemnified party as a result of the losses, claims, damages,
liabilities and expenses referred to in paragraph above shall be deemed to
include, subject to the limitations set forth above, any legal or other
expenses reasonably incurred by such indemnified party in connection with
investigating or defending any such action or claim.

(e)      Notwithstanding any other provision of this Section 4, no Holder shall
be required to indemnify or contribute with respect to any sale of any of
Registrable Securities any amount in excess of the total amount received by
such Holder from the sale of such Registrable Securities (less underwriting
discounts and sale commissions). The remedies provided for in this Section 4
are not exclusive and shall not limit any rights or remedies which may
otherwise be available to any indemnified party at law or in equity.

The indemnity and contribution provisions contained in this Section 4
shall remain operative and in full force and effect regardless of (i) any
termination of this Agreement, (ii) any investigation made by or on behalf of
any Holder or any Person controlling any Holder, or by or on behalf of the
Company, its officers or directors or any Person controlling the Company, and
(iii) any sale of Registrable Securities pursuant to Section 2.

5.      Rule 144. The Company covenants that so long as any Registrable
Securities remain outstanding it shall (a) file any reports required to be
filed by it under the 1934 Act and (b) take such further action as each Holder
may reasonably request (including providing any information necessary to comply
with Rule 144 under the 1933 Act), all to the extent required from time to time
to enable such Holder to sell Registrable Securities without registration under
the 1933 Act within the limitation of the exemptions provided by (i) Rule 144
under the 1933 Act, as such rule may be amended from time to time, or
Regulation S under the 1933 Act or (ii) any similar rules or regulations
hereafter adopted by the Commission. The Company shall, upon the request of
any Holder, deliver to such Holder a written statement as to whether it has
complied with such requirements. The Company shall not, after the date hereof,
grant any registration rights which conflict with or impair, or have any
priority over, the registration rights granted herein.

6.      Miscellaneous.

(a)      No Inconsistent Agreements. The Company has not entered into, and on
or after the date of this Agreement shall not enter into, any agreement that is
inconsistent with the rights granted to the Holders in this Agreement or
otherwise conflicts with the provisions hereof. The rights granted to the
Holders hereunder do not in any way conflict with and are not inconsistent with
the rights granted to the holders of the Companys other issued and outstanding
securities under any such agreements.

14



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(b)      Amendments and Waivers. The provisions of this Agreement, including
the provisions of this sentence, may not be amended, modified or supplemented,
and waivers or consents to departures from the provisions hereof may not be
given unless the Company has obtained the written consent of Holders of at
least a majority in Common Share Equivalents of the outstanding Registrable
Securities affected by such amendment, modification, supplement, waiver or
consent; provided, however, that no amendment, modification, supplement, waiver
or consents to any departure from the provisions of Section 4 hereof shall be
effective as against any Holder of Registrable Securities unless consented to
in writing by such Holder.

(c)      Notices. All notices and other communications provided for or
permitted hereunder shall be made in writing by hand-delivery, registered
first-class mail, telex, telecopier, or any courier guaranteeing overnight
delivery (i) if to a Holder, at the most current address given by such Holder
to the Company by means of a notice given in accordance with the provisions of
this Section 6(c), which address initially is, with respect to the Holders of
the Securities, the address set forth on the Schedule of Holders, and (ii) if
to the Company, initially at the Companys address set forth in the Plan and
thereafter at such other address, notice of which is given in accordance with
the provisions of this Section 6(c).

All such notices and communications shall be deemed to have been duly
given: at the time delivered by hand, if personally delivered; five business
days after being deposited in the mail, postage prepaid, if mailed; when
answered back, if telexed; when receipt is acknowledged, if telecopied; and on
the second succeeding business day if timely delivered to an air courier
guaranteeing overnight delivery.

Copies of all such notices, demands, or other communications shall be
concurrently delivered by the Person giving the same to the Trustee, at the
address specified in the Indenture.

(d)      Successors and Assigns. This Agreement shall inure to the benefit of
and be binding upon the successors, assigns and transferees of each of the
parties, including, without limitation and without the need for an express
assignment, subsequent Holders; provided that nothing herein shall be deemed to
permit any assignment, transfer or other disposition of any Registrable
Securities that are Notes in violation of the terms of the applicable
Indenture.

(e)      Counterparts. This Agreement may be executed in any number of
counterparts and by the parties hereto in separate counterparts, each of which
when so executed shall be deemed to be an original and all of which taken
together shall constitute one and the same agreement.

(f)      Headings. The headings in this Agreement are for convenience of
reference only and shall not limit or otherwise affect the meaning hereof. In
this Agreement, the words include, includes, and including shall be
deemed to be followed by the phrase without limitation and the words
herein, hereof, and hereunder, and words of similar import, shall be
construed to refer to this Agreement in its entirety and not to any particular
provision hereof unless the context otherwise requires.

(g)      GOVERNING LAW; CONSENT TO JURISDICTION. THIS AGREEMENT SHALL BE
GOVERNED BY AND CONSTRUED IN ACCORDANCE

15



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WITH THE LAWS OF THE STATE OF NEW YORK, WITHOUT REGARD TO THE PRINCIPLES
OF CONFLICTS OF LAW THEREOF.The parties hereto irrevocably submit to the
exclusive jurisdiction of any state or federal court sitting in the County of
New York, in the State of New York over any suit, action or proceeding arising
out of or relating to this Agreement or the affairs of the Company. To the
fullest extent they may effectively do so under applicable law, the parties
hereto irrevocably waive and agree not to assert, by way of motion, as a
defense or otherwise, any claim that they are not subject to the jurisdiction
of any such court, any objection that they may now or hereafter have to the
laying of the venue of any such suit, action or proceeding brought in any such
court and any claim that any such suit, action or proceeding brought in any
such court has been brought in an inconvenient forum.

(h)      Remedies. Without limiting the remedies available to the Holders, the
Company acknowledges that any failure by the Company to comply with its
obligations under this Agreement may result in material irreparable injury to
the Holders for which there is no adequate remedy at law, that it will not be
possible to measure damages for such injuries precisely and that, in the event
of any such failure, any Holder shall be entitled to injunctive relief or the
enforcement of other equitable remedies, without bond or other security, to
compel performance and to prevent breaches of this Agreement by the Company and
specifically to enforce the terms and provisions hereof (including Section 2),
in addition to any other remedy to which they may be entitled, at law or in
equity.

(i)      Severability. In the event that any one or more of the provisions
contained herein, or the application thereof in any circumstance, is held
invalid, illegal or unenforceable, the validity, legality and enforceability of
any such provision in every other respect and of the remaining provisions
contained herein shall not be affected or impaired thereby.

[remainder of page blank; signature page follows]

16



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SIGNATURES TO
REGISTRATION RIGHTS AGREEMENT

IN WITNESS WHEREOF, the parties have executed this Agreement as of the
date first written above.

| |  |                             |  |        |  |                                    
| |  | --------------------------- |  | ------ |  | -----------------------------------
| |  | IMPSAT FIBER NETWORKS, INC.
| |  |                             |  |        |  |                                    
| |  | By:                         |  |       
| |  |                             |  | Name:  |  | Héctor Alonso                      
| |  |                             |  | Title: |  | Executive Vice President and       
| |  |                             |  |        |  | Chief Financial Officer            
| |  |                             |  |        |  |                                    
| |  | By:                         |  |       
| |  |                             |  | Name:  |  | Guillermo V. Pardo                 
| |  |                             |  | Title: |  | Senior Vice President, Corporate   
| |  |                             |  |        |  | Finance and Treasury, and Secretary
| |  |                             |  |        |  |                                    
| |  | IMPSAT S.A.                
| |  |                             |  |        |  |                                    
| |  | By:                         |  |       
| |  |                             |  | Name:  |  |                                    
| |  |                             |  | Title: |  |                                    
| |  |                             |  |        |  |                                    
| |  | By:                         |  |       
| |  |                             |  | Name:  |  |                                    
| |  |                             |  | Title: |  |                                    





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##### 



SIGNATURES TO
REGISTRATION RIGHTS AGREEMENT
(Continued)

Confirmed and accepted as of the date first above written:

|                                       |  |        |  |                                       |  |       
|-------------------------------------- |  | ------ |  | ------------------------------------- |  | ------
|MORGAN STANLEY & CO. INCORPORATED     
|                                       |  |        |  |                                       |  |       
|By:                                    |  |       
|                                       |  | Name: 
|                                       |  | Title:
|                                       |  |        |  |                                       |  |       
|NORTEL NETWORKS LIMITED               
|                                       |  |        |  |                                       |  |       
|By:                                    |  |       
|                                       |  | Name: 
|                                       |  | Title:
|                                       |  |        |  |                                       |  |       
|WRH PARTNERS GLOBAL SECURITIES, L.P.  
|                                       |  |        |  |                                       |  |       
|                                       |  | By:    |  | WRH Partners Global Securities, Inc.,
|                                       |  |        |  | its General Partner                  
|                                       |  |        |  |                                       |  |       
|                                       |  |        |  | By:                                   |  |       
|                                       |  |        |  |                                       |  | Name: 
|                                       |  |        |  |                                       |  | Title:
|                                       |  |        |  |                                       |  |       
|W.R. HUFF ASSET MANAGEMENT CO., L.L.C.
|                                       |  |        |  |                                       |  |       
|By:                                    |  |       
|                                       |  | Name: 
|                                       |  | Title:





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EXHIBIT A

SCHEDULE OF HOLDERS

Date of this Schedule of Holders: March 25, 2003

|                                      |  |                                          
|------------------------------------- |  | -----------------------------------------
|Holder                                |  | Securities Held                          
|                                      |  |                                          
|                                     
|Morgan Stanley & Co. Incorporated     |  | 2,884,659 shares of Common Stock         
|                                      |  |                                          
|Nortel Networks Limited               |  | $15,938,000 Series B 6% Senior Guaranteed
|                                      |  | Convertible Notes due 2011               
|                                      |  |                                          
|                                      |  | Warrants exercisable for up to 2,667,975 
|                                      |  | shares of Common Stock                   
|                                      |  |                                          
|WRH Partners Global Securities, L.P.  |  | Series A 6% Senior Guaranteed Convertible
|                                      |  | Notes due 2011 in the aggregate principal
|                                      |  |                                          
|W.R. Huff Asset Management Co., L.L.C |  | amount received pursuant to the Plan