If you have only one router on the network and you want the network configuration server to specify its name automatically, ensure that the network client does not have a /etc/defaultrouter file.
To override the name of the default router provided by the network configuration server:
If you have multiple routers on the network, create /etc/defaultrouter on the network client, but leave it empty.
Creating /etc/defaultrouter and leaving it empty causes one of the two dynamic routing protocols to run: ICMP Router Discovery protocol (RDISC), or Routing Information Protocol (RIP). The system first runs the program in.rdisc, which looks for routers that are running the router discovery protocol. If it finds one such router, in.rdisc continues to run and keeps track of the routers that are running the RDISC protocol.
If the system discovers that routers are not responding to the RDISC protocol, it uses RIP and runs the daemon in.routed to keep track of them.