A method of generating a routing table containing information as to the weighted distance between client's that use a resolver and each rack gateway, taking into account how traffic to each client can egress from the CDN AS. The routing table is generated from matrix multiplication of two matrices. One matrix contains information as to the proportion of each client's use of each resolver in a first autonomous system. The second matrix contains information as to the distance between each client and each rack, with respect to an egress gateway, in a second autonomous system. The resulting routing table is used to identify a gateway from which to serve content to a client.