A host generates an ICMP router solicitation message in response to a missing default gateway. This message is sent via multicast and it is the first step in the router discovery process. A local router will respond with a router advertisement identifying the default gateway for the local host. Figure identifies the frame format and Figures gives an explanation of each field.

Web Links ICMP Router-Discovery Protocol (IDRP) http://www.cisco.com/en/US/products/sw/ iosswrel/ps1831/ products_configuration_guide_ chapter09186a00800d97f7.html#xtocid15