IPv6 SLAAC(er)

Promoted as a feature of IPv6, allows a device to connect to a network and receive an addresses without the administrative overhead of managing a DHCP.

But there are a few limitations that limit its usefulness in an enterprise environment:

• SLAAC only works with /64 subnets. No more, no less.
• SLAAC does not hand out DNS information (or any Windows domain specific info).

You get an address, a fixed subnet, and a default gateway. Period. This doesn't make it entirely useless, but definitely SLAAC is not a DHCP killer.

To enable a Cisco router to being making SLAAC announcements, all you need to do is configure an interface with an IPv6 address and a /64 subnet:

interface GigabitEthernet0/2
no ip address
duplex auto
speed auto
ipv6 address 2001:1890:1208:240::1/64

This line:

ipv6 address 2001:1890:1208:240::1/64

causes the router to begin making ND announcements which permit other devices to SLAAC themselves. We can verify announcements with a show ipv6 interface:

V6-R1-2911#sh ipv6 int gi0/1
GigabitEthernet0/1 is up, line protocol is up
IPv6 is enabled, link-local address is FE80::xxxx:xxxx:xxxx:xxxx
No Virtual link-local address(es):
Global unicast address(es):
   2001:xxxx:xxxx:xxxx::1, subnet is 2001:xxxx:xxxx:xxxx::/58
Joined group address(es):
   FF02::1
   FF02::2
   FF02::1:FF00:1
   FF02::1:FFFD:CCC1
MTU is 1500 bytes
ICMP error messages limited to one every 100 milliseconds
ICMP redirects are enabled
ICMP unreachables are sent
ND DAD is enabled, number of DAD attempts: 1
ND reachable time is 30000 milliseconds (using 30000)
ND advertised reachable time is 0 (unspecified)
ND advertised retransmit interval is 0 (unspecified)
ND router advertisements are sent every 200 seconds
ND router advertisements live for 1800 seconds
ND advertised default router preference is Medium
Hosts use stateless autoconfig for addresses.
V6-R1-2911#