FIRST SUPPLEMENTAL INDENTURE

Exhibit 4.3

Execution Version

FIRST SUPPLEMENTAL INDENTURE

First Supplemental Indenture (this “Supplemental Indenture”), dated as of May 2, 2024, among Sprint Solutions Wireline LLC (the “Guaranteeing Subsidiary”), a subsidiary of Cogent Communications Group, LLC, a Delaware limited liability company (the “Company”), and Wilmington Trust, National Association, a national banking association organized and existing under the laws of the United States of America, as trustee (in such capacity, the “Trustee”), and as collateral agent (in such capacity, the “Collateral Agent”).

W I T N E S E T H

WHEREAS, each of the Company and the Guarantors (as defined in the Indenture referred to below) have heretofore executed and delivered to the Trustee and the Collateral Agent an indenture (the “Indenture”), dated as of May 7, 2021, providing for the issuance of a $500,000,000 aggregate principal amount of 3.500% Senior Secured Notes due 2026 (the “Notes”);

WHEREAS, the Indenture provides that, under certain circumstances, the Guaranteeing Subsidiary shall execute and deliver to the Trustee and the Collateral Agent a supplemental indenture pursuant to which the Guaranteeing Subsidiary shall unconditionally guarantee all of the Company’s Obligations under the Notes and the Indenture on the terms and conditions set forth herein and under the Indenture; and

WHEREAS, pursuant to Section 9.01 of the Indenture, the Trustee and the Collateral Agent are authorized to execute and deliver this Supplemental Indenture.

NOW THEREFORE, in consideration of the foregoing and for other good and valuable consideration, the receipt of which is hereby acknowledged, the parties mutually covenant and agree for the equal and ratable benefit of the Holders of the Notes as follows:

(1)            Capitalized Terms. Capitalized terms used herein without definition shall have the meanings assigned to them in the Indenture.

(2)            Agreement to be Bound. The Guaranteeing Subsidiary hereby becomes a party to the Indenture as a Guarantor and as such will have all of the rights and be subject to all of the obligations and agreements of a Guarantor under the Indenture.

(3)            Guarantee. The Guaranteeing Subsidiary agrees, on a joint and several basis with all the existing Guarantors, to Guarantee to each Holder of the Notes, the Trustee and the Collateral Agent all Obligations under the Indenture and the Notes pursuant to Article 13 of the Indenture.

(4)            No Recourse Against Others. No director, officer, employee, incorporator, stockholder, member, manager or partner of the Company, any Subsidiary or any direct or indirect parent of the Company, as such, will have any liability for any obligations of the Company or the Guarantors (including the Guaranteeing Subsidiary) under the Notes, any Note Guarantees, the Indenture, the Security Documents, the Intercreditor Agreement or any Supplemental Indenture or for any claim based on, in respect of, or by reason of, such obligations or their creation. Each Holder by accepting Notes waives and releases all such liability. The waiver and release are part of the consideration for issuance of the Notes and the Note Guarantees. The waiver may not be effective to waive liabilities under the federal securities laws, and it is the view of the SEC that such a waiver is against public policy.

(5)            Governing Law. THIS SUPPLEMENTAL INDENTURE WILL BE GOVERNED BY AND CONSTRUED IN ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK.

(6)            Counterparts. The parties may sign any number of copies of this Supplemental Indenture. Each signed copy shall be an original, but all of them together represent the same agreement. Delivery of an executed counterpart of a signature page to this Supplemental Indenture by facsimile, email or other electronic means shall be effective as delivery of a manually executed counterpart of this Supplemental Indenture.

(7)            Effect of Headings. The Section headings herein are for convenience only and shall not affect the construction hereof.

(8)            The Trustee and the Collateral Agent. Neither the Trustee nor the Collateral Agent shall be responsible in any manner whatsoever for or in respect of the validity or sufficiency of this Supplemental Indenture or for or in respect of the recitals contained herein, all of which recitals are made solely by the Guaranteeing Subsidiary and the Company.

(9)            Benefits Acknowledged. The Guaranteeing Subsidiary’s Note Guarantee is subject to the terms and conditions set forth in the Indenture. The Guaranteeing Subsidiary acknowledges that it will receive direct and indirect benefits from the financing arrangements contemplated by the Indenture and this Supplemental Indenture and that the guarantee and waivers made by it pursuant to this Note Guarantee are knowingly made in contemplation of such benefits.

(10)          Successors. All agreements of the Guaranteeing Subsidiary in this Supplemental Indenture shall bind its successors, except as otherwise provided in the Indenture. All agreements of the Trustee in this Supplemental Indenture shall bind its successors.

[Signature Pages Follow]

IN WITNESS WHEREOF, the parties hereto have caused this Supplemental Indenture to be duly executed, all as of the date first above written.

	COGENT COMMUNICATIONS GROUP, LLC
	By:	/s/ Xxxxx Xxxxxxxxx
		Name:	Xxxxx Xxxxxxxxx
		Title:	President and Chief Executive Officer
	SPRINT SOLUTIONS WIRELINE LLC
	By:	/s/ Xxxxx Xxxxxxxxx
		Name:	Xxxxx Xxxxxxxxx
		Title:	President and Chief Executive Officer
	WILMINGTON TRUST, National Association, as Trustee and Collateral Agent
	By:	/s/ Xxxxx Xxxxx
		Name:	Xxxxx Xxxxx
		Title:	Vice President

[Signature Page to First Supplemental Indenture (3.500% Notes)]