In recent years, along with diversification of services, there is a known technique used by a relay apparatus such as a mobile router for relaying communication between a terminal apparatus and a destination site by switching between a private network and a public network. The relay apparatus relays communication between the terminal apparatus and the destination site using a private network in view of security. This might increase communication load in the private network as a result.    Patent Literature 1: Japanese National Publication of International Patent Application No. 2008-504792    Patent Literature 2: Japanese Laid-open Patent Publication No. 2006-20031
To cope with this, the relay apparatus reduces processing load on a server on a private network side, by switching, for example, to the public network when the destination site has high reliability and to the private network when the destination site has low reliability. At this time, the relay apparatus has a list, a fully qualified domain name (FQDN) of a highly reliable destination site. In a case where an FQDN of the destination site included in a communication request from a terminal apparatus exists on the list, the relay apparatus relays communication between the terminal apparatus and the destination site using the public network instead of the private network.
On the relay apparatus, however, along with the increased number of sites to be used, the number of entries on the list also increases. This would increase processing load needed for list. As a result, control of processing might become difficult with a low-capability relay apparatus. In a case where determination of reliability of the destination site is executed on the management server side, increased number of terminals would cause high load, leading to an increase in cost to reduce the load on the server in the private network.