Exhibit 10.17

AMENDMENT NO. 3

TO

REGISTRATION RIGHTS AGREEMENT

AMENDMENT NO. 3 TO REGISTRATION RIGHTS AGREEMENT (this “Amendment”), dated as of
July 31, 2007, made among ITC^DeltaCom, Inc., a Delaware corporation (the
“Company”), and each person listed on the signature pages hereof under the
heading “WCAS Securityholders.”

WITNESSETH:

WHEREAS, the parties to this Amendment wish to amend the Registration Rights
Agreement, dated as of October 6, 2003 and amended as of December 4, 2003 and
July 26, 2005 (the “Agreement”), among the Company, the persons listed on the
signature pages thereof under the heading “WCAS Securityholders” and the other
parties to such agreement to facilitate the recapitalization transactions of the
Company to be consummated on the date hereof;

NOW, THEREFORE, in consideration of the premises and the mutual covenants and
conditions hereinafter set forth, and for other good and valuable consideration,
the receipt and sufficiency of which are hereby acknowledged, the parties hereby
agree as follows:

1. Effectiveness. This Amendment shall be effective as of the date hereof.

2. Definitions.

(a) Section 1 of the Agreement is hereby amended by adding, in the appropriate
alphabetical order, the following definition to such Section 1:

“Rights Offering” means a registration under the Securities Act of an offering
of Common Stock and rights to purchase Common Stock on substantially the terms
provided for in the Equity Purchase and Rights Offering Agreement, dated as of
July 16, 2007, as amended from time to time, among the Company and the other
Persons listed on the signature pages thereof.

(b) The definitions of “Excluded Registration,” “Registrable Securities” and
“TCP Registration Rights Agreement” set forth in Section 1 of the Agreement are
hereby amended and restated in their entirety to read as follows:

“Excluded Registration” means (i) a registration of Common Stock under the
Securities Act pursuant to a registration statement filed (a) on Form S-4 or
Form S-8 or any successor registration forms that may be adopted by the SEC or
(b) in connection with an exchange offer or an offering of securities solely to
existing stockholders of the Company (including, without limitation, the Rights
Offering) or employees of the Company or its subsidiaries, (ii) a Rule 144A
Resale Shelf Registration or (iii) a registration statement filed pursuant to
Section 3 of the TCP Registration Rights Agreement.”

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“Registrable Securities” means, collectively, (i) the shares of Common Stock
held by the Holders immediately prior to the Closing Date plus the shares of
Common Stock acquired by the Holders on or after the Closing Date (including,
without limitation, the shares of Common Stock issued or issuable upon
conversion of the Preferred Shares or upon exercise or exchange of the Warrants)
in accordance with the Governance Agreement (or otherwise following the
expiration of the Governance Agreement), (ii) the Preferred Shares, (iii) the
Warrants and (iv) any securities paid, issued or distributed in respect of any
shares of Common Stock referred to in clause (i) by way of stock dividend or
distribution or stock split or in connection with a combination of shares,
recapitalization, reorganization, merger, consolidation or otherwise. Without
limiting the generality of the foregoing, “Registrable Securities” shall include
the shares of Common Stock acquired by the Holders pursuant to or in accordance
with (a) the Stock Purchase Agreement, dated as of July 31, 2007, among the
Company and the other Persons listed on the signature pages thereof, (b) the
Exchange Agreement, dated as of July 31, 2007, among the Company, Interstate
FiberNet, Inc. and the other Persons listed on the signature pages thereof and
(c) the WCAS Exchange Agreement, dated as of July 31, 2007, among the Company
and the other Persons listed as the signature pages thereof. Securities shall
cease to be Registrable Securities in accordance with Section 2.

“TCP Registration Rights Agreement” means the Registration Rights Agreement,
dated as of July 26, 2005, as amended as of July 31, 2007, among the Company and
the other Persons listed on the signature pages thereof.

3. No Inconsistent Agreements; Most Favorable Provisions. The second sentence of
Section 15 of the Agreement is hereby amended and replaced in its entirety to
read as follows:

“The Holders agree for purposes of this Section 15 that the TCP Registration
Rights Agreement is not inconsistent with the rights of the Holders hereunder.”

4. Miscellaneous. This Amendment shall not constitute an amendment or
modification of any provision of the Agreement not expressly referred to herein.
Except as expressly set forth in this Amendment, the terms, provisions and
conditions of the Agreement shall remain unchanged and in full force and effect.
This Amendment may be executed in counterparts, all of which shall together
constitute a single agreement.

5. GOVERNING LAW. THIS AMENDMENT SHALL BE GOVERNED BY AND CONSTRUED IN
ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK WITHOUT GIVING EFFECT TO ITS
PRINCIPLES OR RULES OF CONFLICT OF LAWS TO THE EXTENT SUCH PRINCIPLES OR RULES
WOULD REQUIRE OR PERMIT THE APPLICATION OF THE LAWS OF ANOTHER JURISDICTION.

[signature pages follow]

 

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

 

COMPANY: ITC^DELTACOM, INC. By:  

/s/ Richard E. Fish, Jr.

Name:   Richard E. Fish, Jr. Title:   Executive Vice President and Chief
Financial Officer

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WCAS SECURITYHOLDERS: WCAS CAPITAL PARTNERS III, L.P. By:   WCAS CP III
Associates L.L.C., General Partner By:  

/s/ Jonathan M. Rather

Name:   Jonathan M. Rather Title:   Managing Member WELSH, CARSON, ANDERSON &
STOWE VIII, L.P. By:   WCAS VIII Associates LLC, General Partner By:  

/s/ Jonathan M. Rather

Name:   Jonathan M. Rather Title:   Managing Member WCAS INFORMATION PARTNERS,
L.P. By:   WCAS Info Partners, General Partner By:  

/s/ Jonathan M. Rather

Name:   Jonathan M. Rather Title:   Attorney-in-fact

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Individual investors and trusts: By:  

/s/ Jonathan M. Rather

  Jonathan M. Rather, as Attorney-in-fact for the individual investors listed
below:   Patrick J. Welsh   Russell L. Carson   Bruce K. Anderson   Andrew M.
Paul   Thomas E. McInerney   Robert A. Minicucci   Anthony J. de Nicola   Paul
B. Queally   D. Scott Mackesy   Sanjay Swani   James Matthews   Laura VanBuren  
Sean Traynor   John Almeida   Eric J. Lee   Jonathan M. Rather   IRA – f/b/o
James Matthews   IRA f/b/o Jonathan M. Rather Address of each of the WCAS
Securityholders Welsh, Carson, Anderson & Stowe 320 Park Avenue, Suite 2500 New
York, NY 10022

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/s/ Jill A. Hanau

Jill A. Hanau Other trusts: The Bruce K. Anderson 2004 Irrevocable Trust By:  

/s/ Mary Anderson

Name:  

Mary Anderson

Title:  

Trustee

The Patrick Welsh 2004 Irrevocable Trust By:  

/s/ Carol Welsh

Name:  

Carol Welsh

Title:  

Trustee

Patrick J. Welsh Tr UA 05 09 05 By:  

/s/ Patrick Welsh

Name:  

Patrick Welsh

Title:  

Trustee

Address of each of the WCAS Securityholders Welsh, Carson, Anderson & Stowe 320
Park Avenue, Suite 2500 New York, NY 10022