EXHIBIT 10.9

Voting Support and Standstill Agreement

This VOTING SUPPORT AND STANDSTILL AGREEMENT, dated as of July 13, 2007 (the “Agreement”), is by and between Arbinet-thexchange, Inc., a Delaware corporation (“Arbinet”), and the individuals and entities listed on Schedule A hereto (collectively, the “Stockholders”).

WHEREAS, the Stockholders are the beneficial owners of shares of common stock, par value $0.001 per share, of Arbinet (the “Common Stock”); and

WHEREAS, by letter dated March 19, 2007, Karen Singer, as trustee for the Singer Children’s Management Trust (the “Trust”), provided notice to Arbinet of her intention to nominate Shawn O’Donnell, Jill Thoerle, and Stanley Kreitman for election as directors of Arbinet at its 2007 annual meeting of stockholders (the “Stockholder Nomination”); and

WHEREAS, Arbinet has informed the Stockholders that it intends to provide for, among other matters, enlargement of the Board of Directors of Arbinet (the “Board”) from six (6) to nine (9) members and for the appointment of Shawn O’Donnell, Jill Thoerle, and Stanley Kreitman to the Board to fill the vacancies resulting therefrom.

NOW, THEREFORE, in consideration of the mutual covenants and agreements contained herein, and for other good and valuable consideration, the receipt and sufficiency of which is hereby acknowledged, the parties hereto hereby agree as follows:

Section 1. Representations.

(a) Binding Agreement: Authority . Arbinet hereby represents and warrants that this Agreement has been duly authorized, executed and delivered by Arbinet, and is a valid and binding obligation of Arbinet, enforceable against Arbinet in accordance with its terms. Each of the Stockholders represents and warrants that this Agreement has been duly authorized, executed and delivered by such Stockholder, and is a valid and binding obligation of such Stockholder, enforceable against such Stockholder in accordance with its terms.

(b) Share Ownership of Common Stock . Each of the Stockholders hereby represents and warrants that, as of the date hereof, it is the “beneficial owner” (as such term is hereinafter defined) of the shares of Common Stock set forth opposite its name on Schedule A hereto (the “Shares”), that neither it nor its Affiliates or Associates (as such terms are hereinafter defined) beneficially own, or have any rights, options or agreements to acquire or vote, any other shares of Common Stock, and that no person or entity other than itself or its Affiliates and Associates may be deemed the beneficial owner of the Shares set forth on Schedule A hereto.

(c) Defined Terms . For purposes of this Agreement, the term “Affiliate” and “Associate” shall have the respective meanings set forth in Rule 12b-2 promulgated by the Securities and Exchange Commission (the “SEC”) under the Securities Exchange Act of 1934, as

amended (the “Exchange Act”). For purposes of this Agreement, the terms “beneficial owner” and “beneficially own” shall have the same meanings as set forth in Rule 13d-3 promulgated by the SEC under the Exchange Act, except that a person shall also be deemed to be the beneficial owner of all shares of Common Stock that such person has the right to acquire pursuant to the exercise of any rights in connection with any securities or any agreement, regardless of when such rights may be exercised and whether they are conditional.

Section 2. Directors.

(a) Additional Directors . Arbinet agrees that as promptly as practicable (but in no event more than the second (2 ^nd ) business day) following the execution of this Agreement by the parties hereto, the Board will increase the size of the Board to nine (9) members and (i) appoint Shawn O’Donnell and Jill Thoerle (together with any successor nominees appointed by the Stockholders pursuant to this Agreement, the “Class III Nominees”) to fill the newly created directorships on the Board as Class III directors whose term shall expire at Arbinet’s 2007 annual meeting of stockholders, and (ii) appoint Stanley Kreitman to fill the newly created directorships on the Board as a Class II director whose term shall expire at Arbinet’s 2009 annual meeting of stockholders.

(b) Nominations . Arbinet agrees to nominate Michael J. Ruane, Shawn O’Donnell and Jill Thoerle for election as Class III directors of Arbinet at its 2007 annual meeting of stockholders, and use its reasonable best efforts to cause the election of such persons, each to serve for a three-year term ending upon the election of directors at Arbinet’s 2010 annual meeting of stockholders and until his or her successor is duly elected and qualified.

(c) Committees . Arbinet agrees to appoint (i) Shawn O’Donnell to the Compensation Committee of the Board, (ii) Jill Thoerle to the Audit Committee of the Board, and (iii) Stanley Kreitman to the Nominating and Corporate Governance Committee of the Board.

Section 3. Voting.

(a) 2007 Annual Meeting . The Stockholders, together with their Affiliates and Associates, will not submit any stockholder proposal (pursuant to Rule 14a-8 or otherwise), or any notice of nomination or other business under Arbinet’s Second Amended and Restated By-laws, and will not nominate or oppose directors for election at the 2007 annual meeting of stockholders of Arbinet. The Stockholders shall cause all Shares of Common Stock beneficially owned by them, and/or their Affiliates or Associates, as of the record date for the 2007 annual meeting of