SUPPLEMENTAL INDENTURE

Exhibit 4.1

SUPPLEMENTAL INDENTURE

Dated September 10, 2009

among

GC IMPSAT HOLDINGS I PLC,

as Issuer,

the parties named as guarantors herein,

as Guarantors,

and

WELLS FARGO BANK, NATIONAL ASSOCIATION,

as Trustee,

to the

INDENTURE

dated February 14, 2007

governing

$225,000,000 Aggregate Principal Amount of

9.875% Senior Notes due 2017

TABLE OF CONTENTS

SUPPLEMENTAL INDENTURE, dated as of September 10, 2009 (the “ Supplemental Indenture ”), among GC IMPSAT HOLDINGS I PLC, a public limited company organized and existing under the laws of England and Wales (the “ Company ”), the parties named on the signature page hereto as guarantors (the “ Guarantors ”) and WELLS FARGO BANK, NATIONAL ASSOCIATION, as trustee (the “ Trustee ”).

RECITALS

WHEREAS, the Company and the Guarantors heretofore have executed and delivered to the Trustee an Indenture, dated February 14, 2007 (the “ Indenture ”), providing for the issuance of $225,000,000 in aggregate principal amount of the Company’s 9.875% Senior Notes due 2017 (the “ Notes ”);

WHEREAS, Section 9.02 of the Indenture provides that the Company, the Guarantors and the Trustee, at any time and from time to time, may amend or supplement the Indenture or the Notes with the consent of the Holders of at least a majority in principal amount of the Notes then outstanding (determined in accordance with Section 2.08 of the Indenture), other than with respect to certain enumerated items which are not included in the Proposed Amendments (as defined below);

WHEREAS, the Company and the Guarantors have duly authorized the execution and delivery of this Supplemental Indenture;

WHEREAS, the Company has offered to purchase (the “ Tender Offer ”) any and all of the outstanding Notes upon the terms and subject to the conditions set forth in the Company’s Offer to Purchase and Consent Solicitation Statement, dated August 24, 2009 (the “ Statement ”), and the accompanying Letter of Transmittal and Consent, as the same may be further amended, supplemented or modified;

WHEREAS, the Tender Offer is conditioned upon, among other things, the proposed amendments (the “ Proposed Amendments ”) to the Indenture as described in the Statement and set forth in Section 1.01 of this Supplemental Indenture having been executed and delivered, with the operation of such Proposed Amendments being subject to the acceptance by the Company of all Notes validly tendered pursuant to the Tender Offer;

WHEREAS, the Company has received and delivered to the Trustee the consents from at least a majority in aggregate principal amount of Notes outstanding (the “ Requisite Consents ”) to effect the Proposed Amendments under the Indenture;

WHEREAS, all other acts and proceedings required by law, by the Indenture and by the amended and restated articles of incorporation and by-laws of the Company and by the applicable governing documents of each Guarantor to execute and deliver this Supplemental Indenture, in accordance with its terms, have been duly done and performed;

NOW, THEREFORE, in consideration of the premises and the covenants and agreements contained herein, and for other good and valuable consideration the receipt of which is hereby acknowledged, and for the equal and proportionate benefit of the holders of the Notes, the Company, the Guarantors and the Trustee hereby agree as follows:

ARTICLE I.

AMENDMENTS TO THE INDENTURE

Section 1.01 Deletion of Certain Provisions

Pursuant to the terms of the Statement and the receipt of the Requisite Consents:

(a) the Indenture is hereby amended to delete each of the following sections, or clauses of sections, in its entirety and, in the case of each such section or clause, insert in lieu thereof the phrase “[Intentionally Omitted]”:

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