Stateless autoconfiguration for IPv6 is like a “mini-DHCP” server for IPv6. Routers running IPv6 can give the prefix of the network and a gateway address to clients looking for an IPv6 address. IPv6 uses the NDP (Neighbor Discovery Protocol) and one of the things this protocol offers is RS (Route Solicitation and (RA) Router Advertisement messages that help an IPv6 device to automatically configure an IPv6 address. Let’s take a look at a configuration example:

I’m going to use two routers to show you how stateless autoconfiguration works. R2 will have an IPv6 address and is going to send router advertisements. R1 will use this to configure it’s own IPv6 address.

R2(config)#ipv6 unicast-routing 
R2(config)#interface fastEthernet 0/0
R2(config-if)#ipv6 address 2001:1234::/64 eui-64

Besides configuring an IPv6 address we have to use the ipv6 unicast-routing command to make R2 act like a router. Remember this command since you need it for routing protocols as well.

R1(config)#interface fastEthernet 0/0
R1(config-if)#ipv6 address autoconfig

We need to enable ipv6 address autoconfig on R1 to make sure it generates its own IPv6 address.

R1#debug ipv6 nd 
ICMP Neighbor Discovery events debugging is on

R2#debug ipv6 nd 
ICMP Neighbor Discovery events debugging is on

We can use debug ipv6 nd to watch the whole process.