CYRUSONE LP CYRUSONE FINANCE CORP. AND EACH OF THE GUARANTORS PARTY HERETO 6.375% SENIOR NOTES DUE 2022 __________________ THIRD SUPPLEMENTAL INDENTURE DATED AS OF MARCH 17, 2017 __________________ WELLS FARGO BANK, N.A. Trustee

This THIRD SUPPLEMENTAL INDENTURE, dated as of March 17, 2017 (this “Third Supplemental Indenture”), is entered into by and between CyrusOne LP, a Maryland limited partnership (the “Company”), and CyrusOne Finance Corp., a Maryland corporation (“Finance Corp.”, and together with the Company, the “Issuers”), the Persons listed on Exhibit A hereto (the “Guarantors”) and Wells Fargo Bank, N.A., as trustee under the Indenture referred to below (the “Trustee”).

WHEREAS, the Issuers, the Guarantors thereto and the Trustee entered into the Indenture, dated as of November 20, 2012 (the “Original Indenture,” as supplemented by the First Supplemental Indenture, dated as of July 1, 2015 (the “First Supplemental Indenture”) and the Second Supplemental Indenture, dated as of July 2, 2015 (the “Second Supplemental Indenture”) and as further amended or supplemented from time to time, the “Indenture”), providing for the issuance of 6.375% Senior Notes due 2022 in an aggregate principal amount equal to $625,000,000 (the “Notes”);

NOW, THEREFORE, for and in consideration of the mutual covenants contained herein and in the Indenture and for other good and valuable consideration, the receipt and sufficiency of which are herein acknowledged, the Issuers, the Guarantors and the Trustee hereby agree, for the equal and ratable benefit of all Holders, as follows:

Section 1.01    To Be Read With the Original Indenture.

This Third Supplemental Indenture is supplemental to the Original Indenture, and the Original Indenture (as supplemented by the First Supplemental Indenture and the Second Supplemental Indenture) and this Third Supplemental Indenture shall hereafter be read together and shall have effect, so far as practicable, with respect to the Notes as if all the provisions of the Original Indenture (as supplemented by the First Supplemental Indenture and the Second Supplemental Indenture) and this Third Supplemental Indenture were contained in one instrument.

Section 1.02    Capitalized Terms.

All capitalized terms used but not defined in this Third Supplemental Indenture shall have the meanings ascribed to such terms in the Original Indenture (as supplemented by the First Supplemental Indenture and the Second Supplemental Indenture).

Section 3.01    Ratification of Indenture.

Section 3.03    Governing Law.

THE INTERNAL LAW OF THE STATE OF NEW YORK WILL GOVERN AND BE USED TO CONSTRUE THIS THIRD SUPPLEMENTAL INDENTURE, THE NEW NOTES AND THE NOTE GUARANTEES WITHOUT GIVING EFFECT TO APPLICABLE PRINCIPLES OF CONFLICTS OF LAW TO THE EXTENT THAT THE APPLICATION OF THE LAWS OF ANOTHER JURISDICTION WOULD BE REQUIRED THEREBY.

Section 3.04    Counterparts.

The parties may sign any number of copies of this Third Supplemental Indenture. Each signed copy will be an original, but all of them together represent the same agreement. The exchange of signed copies of this Supplemental Indenture by emailed portable document format (.pdf) shall constitute effective execution and delivery of this Supplemental Indenture as to the parties hereto and such copies may be used in lieu of the original Supplemental Indenture for all purposes. Signatures of the parties hereto transmitted by portable document format (.pdf) shall be deemed to be their original signatures for all purposes.

Section 3.05    Trustee.

The Trustee shall not be responsible in any manner whatsoever for or in respect of the validity or sufficiency of this Third Supplemental Indenture or for or in respect of the recitals contained herein, all of which recitals are made solely by the Issuers and the Guarantors.