6 address autoconfig And here's the output of the show ipv6 interface interface-name command: R6#sho ipv6 int fo/o FastEtherneto/o is up, line protocol is up IPv6 is enabled, link-local address is FE80::214:6AFF:FEA2:D438 Global unicast address (es) AAAA: AAAA: AAAA: 1:214 : 6AFF FEA2:D438 subnet is AAAA:AAAA:AAAA:1::/64 [PRE] valid lifetime 2591981 preferred lifetime 604781 Joined group address (es): FF02: FF02:: FF02 : : 1: FFA2 : D438 MTU is 1500 bytes ICMP error messages limited to one every 100 milliseconds ICMP redirects are enabled ND DAD is enabled, number of DAD attempts: 1 ND reachable time is 30000 milliseconds Default router is FE80::212:43FF: FEB9 on FastEtherneto/o Not only does this router have a link-local address, but it also has a global unicast address and a default router configured. Where did it get all this information? It learned it from R1. Routers send out something called router advertisements in IPv6. These advertisements are sent in response to router solicitation messages. Though it's not strictly analogous, you can think of this a bit like DHCP. R6 learned that the prefix on this network is AAAA :AAAA:AAAA:1::/64, and since it's configured for autoconfig, it applied its EUI-64 host address to the prefix and configured an IPv6 address by itself. Let's assign an IPv6 address that's easier to read for our lab testing. I'll apply the host address of ::6 to the f0/0 interface on R6. Remember, this is in prefix AAAA AAAA:AAAA: with a subnet of : 1: R6(config)#int fo/o R6(config-if)#ipv6 address aaaa:aaaa:aaaa:1::6/64 A quick ping is in order to make sure we're configured properly. I'll ping the : :1 address on R1: R6#ping ipv6 aaaa:aaaa:aaaa:1::1 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to AAAA:AAAA:AAAA:1::1, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 0/157/788 ms Simple Router Configuration Success! Notice how we didn't have to specify an interface this time? That's because we've assigned a non-link-local network to the in