Router advertisements contain a list of subnet prefixes that is used to determine if a host is on the same link (on-link) as the router. The list of prefixes is also used for autonomous address configuration. Flags that are associated with the prefixes specify the intended uses of a particular prefix. Hosts use the advertised on-link prefixes to build and maintain a list that is used to decide when a packet's destination is on-link or beyond a router. A destination can be on-link even though the destination is not covered by any advertised on-link prefix. In such instances, a router can send a redirect. The redirect informs the sender that the destination is a neighbor.
Router advertisements, and per-prefix flags, enable routers to inform hosts how to perform stateless address autoconfiguration.