Exhibit A

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/ Xxxxxx X. Xxxxxxxxxx
				Xxxxxx X. Xxxxxxxxxx, as General Partner or Managing Member or as Attorney-in-fact for the above-listed entities

Individuals:

Bandel X. Xxxxxx

Xxxxxx X. Xxxxxxxxx

Xxxxxx X. Xxxxxxxxxx

Xxxxxxx X. Xxxxxx

Xxx X. Xxxxxx

	By:		/s/ Xxxxxx X. Xxxxxxxxxx
				Xxxxxx X. Xxxxxxxxxx,
				Individually and as Attorney-in-fact for the above-listed individuals