Address Assignment Using SLAAC
The most common method for IPv6 client address assignment is SLAAC, which provides simple plug-and-play connectivity, where clients self-assign an address based on the IPv6 prefix.
SLAAC is configured as follows:
A host sends a Router Solicitation message.
The host waits for a Router Advertisement message.
The host take the first 64 bits of the IPv6 prefix from the Router Advertisement message and combines it with the 64 bit EUI-64 address (in the case of Ethernet, this is created from the MAC address) to create a global unicast message. The host also uses the source IP address, in the IP header, of the Router Advertisement message, as its default gateway.
Duplicate Address Detection is performed by the IPv6 clients to ensure that random addresses that are picked do not collide with other clients.
The choice of algorithm is up to the client and is often configurable.
The last 64 bits of the IPv6 address can be learned by using one of the following algorithms:
The following Cisco IOS configuration commands from a Cisco-capable IPv6 router are used to enable SLAAC addressing and router advertisements:
ipv6 unicast-routing interface Vlan20 description IPv6-SLAAC ip address 192.168.20.1 255.255.255.0 ipv6 address FE80:DB8:0:20::1 linklocal ipv6 address 2001:DB8:0:20::1/64 ipv6 enable end