CCNP ROUTE: 5. OSPFv3

OSPFv2 - OSPFv3 comparison:

- The multicast addresses used by OSPFv3 of course differ, but they keep similar numbers compared to OSPFv2 - FF02::5, FF02::6
- OSPF uses IPv6’s inherent IPsec capabilities, rather than defining a separate authentication process.
- As with RIPng and EIGRP for IPv6, OSPFv3 does not require neighboring routers to be in the same subnet as a requirement for becoming neighbors. However, OSPFv3 does follow all other neighbor verification checks as compared with OSPFv2.
- Support for multiple instances of OSPF on a single link, whereas OSPFv2 supports only a single instance per link.
- OSPF uses the neighbor’s link local IPv6 address as the next-hop IP address.
- The RID is still based on IPv4 addresses. Like EIGRP for IPv6, a router must have a RID before OSPFv3 will work.

Note:  IOS does not support a network command for OSPFv3.

The following list shows the basic configuration steps, including the assignment of an IPv6 address to the interface.
Step 1. Enable IPv6 routing with the ipv6 unicast-routing global command.
Step 2. Create an OSPFv3 routing process using the ipv6 router ospf process-id global configuration command.
Step 3. Enable IPv6 on the interface, typically by configuring static IPv6 addresses as follows:
    - Configure an IPv6 unicast address on each interface, using the ipv6 address address/prefix-length [eui-64] interface command.
    - Configure the ipv6 enable command, which enables IPv6 and causes the router to derive its link local address.
Step 4. Enable OSPFv3 on the interface with the ipv6 ospf process-id area area-number interface subcommand.
Step 5. If no OSPF router ID has been automatically chosen, due to not having at least one working interface with a IPv4 address, configure an OSPF router ID with the router-id rid command in OSPFv3 configuration mode.

Note: Unlike a new EIGRP for IPv6 routing process, a newly created OSPFv3 routing process defaults to an administratively enabled state.

Let's consider routers R3, R6 and R7 in our topology. R6 and R7 will be considered being in Area 3 and R3 will be an ABR between Area 0 (the green area) and Area 3.

Step 1: We already have ipv6 routing enabled on all routers. Also, each interface has an IPv6 address already assigned. So steps 1 and 3 are covered.
!
ipv6 unicast-routing
!

Steps 2 and 5:

R3(config)#ipv6 router ospf 1
R3(config-rtr)#router-id 3.3.3.3

R6(config)#ipv6 router ospf 1
R6(config-rtr)#router-id 6.6.6.6

R7(config)#ipv6 router ospf 1
R7(config-rtr)#router-id 7.7.7.7

R3(config)#interface fastEthernet 0/0
R3(config-if)#ipv6 ospf 1 area 0
R3(config)#interface fastEthernet 0/1
R3(config-if)#ipv6 ospf 1 area 0              
R3(config)#interface serial 0/0
R3(config-if)#ipv6 ospf 1 area 3

R6(config)#interface fastEthernet 0/0
R6(config-if)#ipv6 ospf 1 area 3
R6(config)#interface serial 0/0
R6(config-if)#ipv6 ospf 1 area 3

R7(config)#interface fastEthernet 0/0
R7(config-if)#ipv6 ospf 1 area 3

OSPF is working and the neighborships are up:

R6#show ipv6 ospf neighbor

Neighbor ID     Pri   State           Dead Time   Interface ID    Interface
3.3.3.3           1   FULL/  -        00:00:39    6               Serial0/0
7.7.7.7           1   FULL/BDR        00:00:36    4               FastEthernet0/0

Verification commands on the ABR (R3):

R3#show ipv6 protocols
IPv6 Routing Protocol is "connected"
IPv6 Routing Protocol is "static"
IPv6 Routing Protocol is "ospf 1"
  Interfaces (Area 0):
    FastEthernet0/1
    FastEthernet0/0
  Interfaces (Area 3):
    Serial0/0
  Redistribution:
    None
   
R3#show ipv6 ospf interface brief
Interface    PID   Area            Intf ID    Cost  State Nbrs F/C
Fa0/1        1     0               5          10    DR    0/0
Fa0/0        1     0               4          10    DR    0/0
Se0/0        1     3               6          64    P2P   1/1

R3 learns about the subnet representing the link between R6 and R7:
R3#show ipv6 route ospf
IPv6 Routing Table - 9 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, IS - ISIS summary
       O - OSPF intra, OI - OSPF inter, OE1 - OSPF ext 1, OE2 - OSPF ext 2
       ON1 - OSPF NSSA ext 1, ON2 - OSPF NSSA ext 2
O   2003:0:0:1::/64 [110/74]
     via FE80::C205:13FF:FEE8:0, Serial0/0
   
R3#show ipv6 ospf database

            OSPFv3 Router with ID (3.3.3.3) (Process ID 1)

                Router Link States (Area 0)

ADV Router      Age         Seq#        Fragment ID  Link count  Bits
3.3.3.3         397         0x80000005  0            0           B

                Inter Area Prefix Link States (Area 0)

ADV Router      Age         Seq#        Prefix
3.3.3.3         412         0x80000001  2003::/64
3.3.3.3         349         0x80000001  2003:0:0:1::/64

                Link (Type-8) Link States (Area 0)

ADV Router      Age         Seq#        Link ID    Interface
3.3.3.3         437         0x80000001  5          Fa0/1
3.3.3.3         442         0x80000001  4          Fa0/0

                Intra Area Prefix Link States (Area 0)

ADV Router      Age         Seq#        Link ID    Ref-lstype  Ref-LSID
3.3.3.3         437         0x80000002  0          0x2001      0

                Router Link States (Area 3)

ADV Router      Age         Seq#        Fragment ID  Link count  Bits
3.3.3.3         355         0x80000002  0            1           B
6.6.6.6         277         0x80000004  0            2           None
7.7.7.7         269         0x80000002  0            1           None

                Net Link States (Area 3)

ADV Router      Age         Seq#        Link ID    Rtr count
6.6.6.6         277         0x80000001  4          2

                Inter Area Prefix Link States (Area 3)

ADV Router      Age         Seq#        Prefix
3.3.3.3         423         0x80000001  2000:0:0:2::/64
3.3.3.3         423         0x80000001  2000:0:0:3::/64

                Link (Type-8) Link States (Area 3)

ADV Router      Age         Seq#        Link ID    Interface
3.3.3.3         423         0x80000001  6          Se0/0
6.6.6.6         358         0x80000001  6          Se0/0

                Intra Area Prefix Link States (Area 3)

ADV Router      Age         Seq#        Link ID    Ref-lstype  Ref-LSID
3.3.3.3         425         0x80000001  0          0x2001      0
6.6.6.6         279         0x80000003  0          0x2001      0
6.6.6.6         279         0x80000001  4096       0x2002      4

Another useful command can be entered on one of the internal routers in Area 3 to find out who is the ABR:

R7#show ipv6 ospf border-routers

OSPFv3 Process 1 internal Routing Table

Codes: i - Intra-area route, I - Inter-area route

i 3.3.3.3 [74] via FE80::C205:13FF:FEE8:0, FastEthernet0/0, ABR, Area 3, SPF 1

Also, we can check on R7 if the expected routes (and route types) were learned via OSPF.
R7 should learn about the R3-R1, R3-R2 and R3-R6 subnets (links) - and it does:

R7#show ipv6 route ospf
IPv6 Routing Table - 7 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, IS - ISIS summary
       O - OSPF intra, OI - OSPF inter, OE1 - OSPF ext 1, OE2 - OSPF ext 2
       ON1 - OSPF NSSA ext 1, ON2 - OSPF NSSA ext 2
OI  2000:0:0:2::/64 [110/84]
     via FE80::C205:13FF:FEE8:0, FastEthernet0/0
OI  2000:0:0:3::/64 [110/84]
     via FE80::C205:13FF:FEE8:0, FastEthernet0/0
O   2003::/64 [110/74]
     via FE80::C205:13FF:FEE8:0, FastEthernet0/0

Note: Like OSPFv2, OSPFv3 can only summarize routes on ABRs and ASBRs, using the similar command area x range ipv6-prefix/length router subcommand.

Note: The concept and commands related to OSPF stub areas are literally identical, using commands such as area 3 stub.