TCP/IP Guide

ICMPv6 Router Advertisement and Router Solicitation Messages

At the highest level, we can separate IP devices into two groups: hosts and routers. Both participate in the use of the internetwork, but they have different roles. An important IP principle related to this division is that routers take care of routing—moving data between networks—while hosts generally don't need to worry about this job. Hosts rely on the routers on their local networks to facilitate communication to all other hosts except those on the local network.

The implications of this are clear: A host cannot really use an internetwork until it knows the identity of at least one local router and the method by which that router is to be used. In IPv4, a technique known as Router ...