Neighbor discovery allows hosts and routers to communicate with one another.
Neighbor discovery functions are used by IPv6 nodes (hosts or routers)
to discover the presence of other IPv6 nodes, to determine the link-layer
addresses of nodes, to find routers that are capable of forwarding IPv6 packets,
and to maintain a cache of active IPv6 neighbors. IPv6 nodes use these five
Internet Control Message Protocol version 6 (ICMPv6) messages to communicate
with other nodes:
- Hosts send these messages to request routers to generate router advertisements. A host sends an initial router solicitation when the host first becomes available on the network.
Router advertisement
- Routers send these messages either periodically or in response to a router solicitation. The information provided by router advertisements is used by hosts to automatically create global interfaces, and associated routes. Router advertisements also contain other configuration information used by a host such as maximum transmission unit and hop limit.
- Nodes send these messages to determine the link-layer address of a neighbor, or to verify that a neighbor is still reachable.
- Nodes send these messages in response to a neighbor solicitation or as an unsolicited message to announce an address change.
- Routers use these messages to inform hosts of a better first hop for a destination.
See RFC 2461 for more information about neighbor discovery and router discovery.
To view RFC 2461, see RFC Editor (www.rfc-editor.org/rfcsearch.html) 
.