Relay server and relay communication system

A relay server, which is capable of communicating with a first relay server connected to a first network, the relay server functioning as a second relay server connected to a second network, the relay server comprising:

• a relay group information sharing unit that shares relay group information between the first relay server and the second relay server, the relay group information indicating that the first relay server and the second relay server constitute a relay group;
• a relay server information sharing unit that shares relay server information between the first relay server and the second relay server, the relay server information including activation information of the first relay server, activation information of the second relay server, activation/registration information of a client terminal connected to the first relay server, and activation/registration information of a client terminal connected to the second relay server;
• a VLAN device information sharing unit that shares VLAN device information between the first relay server and the second relay server, the VLAN device information including interface information of a plurality of client terminals capable of functioning as VLAN devices;
• a VLAN group creation unit that creates a plurality of VLAN groups by selecting at least some of the plurality of client terminals capable of functioning as VLAN devices by using the VLAN device information, and that creates VLAN group information by creating a virtual MAC address and a virtual IP address for each of the selected client terminals of each of the plurality of VLAN groups;
• a VLAN group information sharing unit that shares the VLAN group information among the first relay server, the second relay server, the client terminal connected to the first relay server, and the client terminal connected to the second relay server;
• a VLAN session establishment unit that allows a plurality of client terminals capable of functioning as the VLAN devices to function as VLAN terminals, and while referring to the relay server information, establish a VLAN session for each group indicated in the VLAN group information;
• and
• a VLAN connection function control unit that validates/invalidates a VLAN connection function for each group indicated in the VLAN group information, the VLAN connection function establishing a VLAN session between specific ones of the VLAN devices in different ones of the groups indicated in the VLAN group information;
• wherein
• the VLAN device information includes names of the client terminals, and a number of the interfaces of each of the client terminals that function as the VLAN terminals.