In a relay server, a routing group information sharing unit shares routing group information, which is prepared by grouping routing control points including at least two of a first relay server in a relay group, a second relay server in the relay group, a client terminal connected to the first relay server, and a client terminal connected to the second relay server. A routing session establishment unit establishes a routing session, which enables a communication packet to be routed via the routing control points, for each group indicated in the routing group information while referring to relay server information.