Exhibit 99A

Exhibit A

Agreement of Reporting Persons

Each of the undersigned hereby agrees that the Amendment No. 1 to Schedule 13D filed on the date hereof with respect to the shares of Common Stock of Cogent Communications Group, Inc. has been filed on behalf of the undersigned.

Signature

Dated: April 6, 2004

Entities:

Oak Investment Partners IX, Limited Partnership

Oak Associates IX, LLC

Oak IX Affiliates Fund – A, Limited Partnership

Oak IX Affiliates Fund, Limited Partnership

Oak IX Affiliates, LLC

Oak Management Corporation

By:	/s/ Edward F. Glassmeyer
		Edward F. Glassmeyer, as General Partner or Managing Member or as Attorney-in-fact for the above-listed entities

Individuals:

Bandel L. Carano

Gerald R. Gallagher

Edward F. Glassmeyer

Fredric W. Harman

Ann H. Lamont

By:	/s/ Edward F. Glassmeyer
		Edward F. Glassmeyer,
		Individually and as Attorney-in-fact for the above-listed individuals