IPv6 Intro: Routing with OSPFv3 for IPv6

Continuing on with our last lab, let's remove the RIPng config, and set up OSPFv3, instead. Here's the network diagram again, just so you don't have to jump back to the RIPng lab again:



Just like configuring RIPng, we will start by enabling IPv6 OSPF in the interface configurations. Once again, only R1 is shown, but the other routers are configured in exactly the same way:
R1(config)#int fa0/0
R1(config-if)#ipv6 ospf 42 area 0.0.0.0
R1(config-if)#int s0/0
R1(config-if)#ipv6 ospf 42 area 0.0.0.1
R1(config-if)#exit
R1(config)#do sho ipv6 route
IPv6 Routing Table - 8 entries
Codes: C - Connected, L - Local, S - Static, R - RIP, B - BGP
       U - Per-user Static route
       I1 - ISIS L1, I2 - ISIS L2, IA - ISIS interarea
       O - OSPF intra, OI - OSPF inter, OE1 - OSPF ext 1, OE2 - OSPF ext 2
LC  2001:C0:FFEE::1/128 [0/0]
     via ::, Loopback0
C   2001:C0:FFEE::1:0/125 [0/0]
     via ::, FastEthernet0/0
L   2001:C0:FFEE::1:1/128 [0/0]
     via ::, FastEthernet0/0
C   2001:C0:FFEE::1111:0/126 [0/0]
     via ::, Serial0/0
L   2001:C0:FFEE::1111:1/128 [0/0]
     via ::, Serial0/0
OI  2001:C0:FFEE::2222:0/126 [110/65]
     via FE80::CA03:3CFF:FEAE:0, FastEthernet0/0
L   FE80::/10 [0/0]
     via ::, Null0
L   FF00::/8 [0/0]
     via ::, Null0
R1(config)#

If this looks very familiar from the RIPng lab, it should. Any guesses on how to configure redistribution of connected networks?
R1(config)#ipv6 router ospf 42
R1(config-rtr)#router-id 10.254.254.1
R1(config-rtr)#redist conn
R1(config-rtr)#exit
R1(config)#

At this point, you might be scratching your head, wondering WHY I used an IPv4 address for the router ID. Actually...I didn't. The RFC for OSPF specifies that the router ID is a 32-bit, unique (at least within the AS) identifier. Since IPv4 addresses are ALSO 32-bit, unique identifiers, convention (and, unless a different router ID is specified in the config, Cisco's default behaviour) has set the loopback interface's IPv4 address as the router ID. I also chose to set an IPv4 address on the loopback interface, and I used it as the router ID in this lab. However, technically the OSPFv3 router ID is any random 32-bit number (see the footnote at the end of this lab for more).

After setting up redistribution, the routing table on R1 looks a little more populated:
R1(config)#do sho ipv6 route
IPv6 Routing Table - 12 entries
Codes: C - Connected, L - Local, S - Static, R - RIP, B - BGP
       U - Per-user Static route
       I1 - ISIS L1, I2 - ISIS L2, IA - ISIS interarea
       O - OSPF intra, OI - OSPF inter, OE1 - OSPF ext 1, OE2 - OSPF ext 2
LC  2001:C0:FFEE::1/128 [0/0]
     via ::, Loopback0
OE2  2001:C0:FFEE::2/128 [110/20]
     via FE80::CA03:3CFF:FEAE:0, FastEthernet0/0
OE2  2001:C0:FFEE::3/128 [110/20]
     via FE80::CA04:3CFF:FEAE:0, FastEthernet0/0
OE2  2001:C0:FFEE::4/128 [110/20]
     via FE80::CA00:3CFF:FEAE:0, Serial0/0
OE2  2001:C0:FFEE::5/128 [110/20]
     via FE80::CA03:3CFF:FEAE:0, FastEthernet0/0
C   2001:C0:FFEE::1:0/125 [0/0]
     via ::, FastEthernet0/0
L   2001:C0:FFEE::1:1/128 [0/0]
     via ::, FastEthernet0/0
C   2001:C0:FFEE::1111:0/126 [0/0]
     via ::, Serial0/0
L   2001:C0:FFEE::1111:1/128 [0/0]
     via ::, Serial0/0
OI  2001:C0:FFEE::2222:0/126 [110/65]
     via FE80::CA03:3CFF:FEAE:0, FastEthernet0/0
L   FE80::/10 [0/0]
     via ::, Null0
L   FF00::/8 [0/0]
     via ::, Null0
R1(config)#

There you go: we have a basic OSPFv3 (IPv6) configuration, sharing routes between each of the five routers in our network. We even set up three separate areas: the backbone, consisting of R1, R2 and R3; Area 1, consisting of R1 and R4; and Area 2, consisting of R2 and R5.

Footnote:
At this point, you may be wondering -- well, I am, anyway -- what OSPFv3 uses for a router ID if there are no IPv4 interfaces in use on the router, and there is no router ID specified in the OSPFv3 config. Let's find out, shall we?
R1(config)#int lo0
R1(config-if)#no ip addr
R1(config-if)#shut
R1(config-if)#no shut
R1(config-if)#no ipv6 router ospf 42
R1(config)#int fa0/0
R1(config-if)#ipv6 ospf 42 area 0.0.0.0
R1(config-if)#int s0/0
R1(config-if)#ipv6 ospf 42 area 0.0.0.1
R1(config-if)#exit
R1(config-if)#ipv6 router ospf 42
R1(config-rtr)# redistribute connected
R1(config-rtr)#exit
R1(config)#exit
R1#
00:36:49: %OSPFv3-4-NORTRID: OSPFv3 process 42 could not pick a router-id,
please configure manually
R1#sho ipv6 ospf neigh
%OSPFv3: Router process 42 is not running, please configure a router-id
R1#

Well, that's interesting! What happens if you don't have an IPv4 address on the loopback interface, but you have an IPv4 address on another interface?
R1(config-if)#int vlan 10
R1(config-if)#ip addr 10.254.254.1 255.255.255.252
R1(config-if)#no shut
R1(config-if)#no ipv6 router ospf 42
R1(config)#ipv6 router ospf 42
R1(config-rtr)#redist conn
R1(config-rtr)#exit
R1(config)#int fa0/0
R1(config-if)#ipv6 ospf 42 area 0.0.0.0
R1(config-if)#int s0/0
R1(config-if)#ipv6 ospf 42 area 0.0.0.1
R1(config-if)#exit
R1(config)#exit
R1#sho ipv6 ospf 42 neigh

Neighbor ID    Pri  State      Dead Time  Interface ID  Interface
10.254.254.2     1  FULL/BDR   00:00:39   4             FastEthernet0/0
10.254.254.3     1  FULL/DR    00:00:36   4             FastEthernet0/0
10.254.254.4     1  FULL/  -   00:00:38   5             Serial0/0
R1#

There you have it. If there is an IPv4 address configured anywhere on the router, OSPFv3 will use it for the router ID. If not, then you MUST configure a router ID in the OSPFv3 configuration.