Router discovery lets an IPv6 host automatically find routers on its local network and learn configuration information such as the network prefix and default gateway. It is an NDP function rather than an IPv4 ARP function. section 21.1 section 21.1.3
NDP router discovery uses two ICMPv6 message types:
- Router Solicitation (RS), ICMPv6 type 133, asks routers on the local link to identify themselves through the all-routers multicast address ff02::2. section 21.1.3
- Router Advertisement (RA), ICMPv6 type 134, provides router and network information, typically through the all-nodes multicast address ff02::1. section 21.1.3
- SLAAC uses the learned prefix to help a host generate its own IPv6 address without a central address-assignment server. section 21.1.3
Cisco SLAAC sequence
On a Cisco router, configure an interface with ipv6 address autoconfig. The router sends an RS, receives an RA containing a prefix such as 2001:db8::/64, and combines that prefix with a Modified EUI-64 interface identifier to form its IPv6 address. section 21.1.3
