A Router Solicitation (RS) is an ICMPv6 type 133 message that asks routers on the local link to identify themselves and provide network information. It is sent to the all-routers link-local multicast address ff02::2. section 21.1.3 section 21.1.2
Routers answer with Router Advertisement (RA) messages, typically sent to ff02::1. The advertisement can provide the network prefix and default-gateway information needed for Stateless Address Autoconfiguration (SLAAC). section 21.1.3 section 21.4
Remember the RS exchange:
- A host or Cisco router using SLAAC sends an RS to ff02::2. section 21.1.3
- A local router responds with an RA and also sends RAs periodically without receiving an RS. section 21.1.3
- The host combines the advertised prefix with a Modified EUI-64 interface identifier to generate its IPv6 address. section 21.4
Cisco SLAAC scenario
Configure a Cisco router interface with ipv6 address autoconfig. The router sends an RS; after receiving an RA advertising 2001:db8::/64, Cisco IOS uses Modified EUI-64 to create the interface address. section 21.1.3
Figure 21.3 R2 uses SLAAC to generate an IPv6 address. (1) Issue the ipv6 address autoconfig command. (2) R2 sends an RS message. (3) R1 responds with an RA message. (4) R2 combines the learned prefix with a Modified EUI-64 interface ID to make its IPv6 address.
Follow the four-step exchange from interface configuration through RS, RA, and IPv6 address generation. section 21.1.3
