A network system comprises routers (704 and 705) connected through a network, pseudo-redundant configuring means (702 and 703) connected with the individual routers for communications with a redundant protocol, and interlocking control means (701) connected with the pseudo-redundant configuring means (702 and 703). When a server (716) is a backup server and keeps a standby state, the pseudo-redundant configuring means (703) issues a signal for keeping the standby state, to the router (705). When the server is switched between the standby state and an active state, the interlocking control means (701) sends an instruction for switching the standby state and the active state, to the pseudo-redundant configuring means (702 and 703).