How a Machine Determines if It Is a Router

The /etc/rc2.d/S69inet startup script, which runs when the machine boots, determines whether a machine is a router or a host. This decision also determines whether the routing protocols (RIP and RDISC) should run in router mode or host mode.

The /etc/rc2.d/S69inet script concludes that a machine is a router if the following two conditions exist:

• More than one /etc/hostname.interface file exists.

• More than one interface was configured “up” by the ifconfig command. See the ifconfig(1M) man page.

If only one interface is found, the script concludes that the machine is a host. See Configuring Both Router Network Interfaces. An interface that is configured by any means other than an /etc/hostname.interface file is not considered.