SLAAC and DHCPv6
Stateless Address Autoconfiguration (SLAAC)
Dynamic Host Configuration Protocol v6 (DHCPv6)
The decision of how a client will obtain an IPv6 GUA depends on the settings within the RA message.
An ICMPv6 RA message includes three flags to identify the dynamic options available to a host, as follows:
- A flag – This is the Address Autoconfiguration flag. Use Stateless Address Autoconfiguration (SLAAC) to create an IPv6 GUA.
- O flag – This is the Other Configuration flag. Other information is available from a stateless DHCPv6 server.
- M flag – This is the Managed Address Configuration flag. Use a stateful DHCPv6 server to obtain an IPv6 GUA.
Using different combinations of the A, O and M flags, RA messages inform the host about the dynamic options available.
Enable IPv6 Routing
Although the router interface has an IPv6 configuration, it is still not yet enabled to send RAs containing address configuration information to hosts using SLAAC.
To enable the sending of RA messages, a router must join the IPv6 all-routers group using the ipv6 unicast-routing global config command, as show in the output.
Command to enable IPv6 Routing
R1(config)# ipv6 unicast-routing R1(config)# exit R1#