OSPFv3

Understand

OSPFv3 was defined for IPv6; address-family extensions also support IPv4. Router IDs remain 32-bit. Control communication uses IPv6 link-local addresses even for IPv4 AF, so enable IPv6 on participating links. IPv4 forwarding still needs IPv4 interface addressing.

V3 separates topology and prefixes: router/network LSAs describe topology; link-LSAs convey link-local information and prefixes; intra-area-prefix LSAs associate prefixes with topology. Scope is encoded in LSA types. Link-LSAs are link-local; router/network records are area-local. Do not apply v2 LSA numbers mechanically.

This recipe targets IOS XE OSPFv3 address-family syntax: router ospfv3, address-family and ospfv3 interface commands. Older ipv6 router ospf / ipv6 ospf commands are a different configuration family. Do not mix them. V3 authentication is explicit: IPsec-based mechanisms and authentication trailers have platform-specific configuration and support.

Lab setup

Use a fresh lab for this lesson; changes from other lessons are not cumulative. All outputs are illustrative excerpts, not recorded router tests. Transit cost is explicitly 10 and Loopback0 cost is 1. Interface names may vary by image.

Loopback0 is 10.255.0.<router number>/32; area assignments: R1: area 0, R2: area 0.

configure terminal
hostname R1
router ospf 1
 router-id 10.255.0.1
 passive-interface Loopback0
 exit
interface Loopback0
 ip address 10.255.0.1 255.255.255.255
 ip ospf 1 area 0
 ip ospf cost 1
 exit
interface GigabitEthernet1
 ip address 192.0.2.1 255.255.255.252
 ip ospf network point-to-point
 ip ospf cost 10
 ip ospf 1 area 0
 no shutdown
 exit
end

configure terminal
hostname R2
router ospf 1
 router-id 10.255.0.2
 passive-interface Loopback0
 exit
interface Loopback0
 ip address 10.255.0.2 255.255.255.255
 ip ospf 1 area 0
 ip ospf cost 1
 exit
interface GigabitEthernet1
 ip address 192.0.2.2 255.255.255.252
 ip ospf network point-to-point
 ip ospf cost 10
 ip ospf 1 area 0
 no shutdown
 exit
end

Apply

Keep the pair baseline’s IPv4 addresses, then remove the v2 process and apply the replacements. Each AF has separate adjacency and routing state. IPv6 transit is 2001:db8:12::/64; loopbacks are 2001:db8:1::1/128 and 2001:db8:2::1/128. This isolated first v3 lab has no authentication.

R1 · replace v2 with OSPFv3 address families

configure terminal
no router ospf 1
ipv6 unicast-routing
router ospfv3 1
 router-id 10.255.0.1
 address-family ipv6 unicast
  passive-interface Loopback0
 exit-address-family
 address-family ipv4 unicast
  passive-interface Loopback0
 exit-address-family
 exit
interface GigabitEthernet1
 ipv6 address FE80::1 link-local
 ipv6 address 2001:DB8:12::1/64
 ospfv3 network point-to-point
 ospfv3 cost 10
 ospfv3 1 ipv6 area 0
 ospfv3 1 ipv4 area 0
 exit
interface Loopback0
 ipv6 address 2001:DB8:1::1/128
 ospfv3 cost 1
 ospfv3 1 ipv6 area 0
 ospfv3 1 ipv4 area 0
end

R2 · replace v2 with OSPFv3 address families

configure terminal
no router ospf 1
ipv6 unicast-routing
router ospfv3 1
 router-id 10.255.0.2
 address-family ipv6 unicast
  passive-interface Loopback0
 exit-address-family
 address-family ipv4 unicast
  passive-interface Loopback0
 exit-address-family
 exit
interface GigabitEthernet1
 ipv6 address FE80::2 link-local
 ipv6 address 2001:DB8:12::2/64
 ospfv3 network point-to-point
 ospfv3 cost 10
 ospfv3 1 ipv6 area 0
 ospfv3 1 ipv4 area 0
 exit
interface Loopback0
 ipv6 address 2001:DB8:2::1/128
 ospfv3 cost 1
 ospfv3 1 ipv6 area 0
 ospfv3 1 ipv4 area 0
end

Verify and interpret

R1# show ospfv3 neighbor
          OSPFv3 1 address-family ipv4 (router-id 10.255.0.1)
Neighbor ID     Pri State   Interface
10.255.0.2        0 FULL/-  GigabitEthernet1
          OSPFv3 1 address-family ipv6 (router-id 10.255.0.1)
Neighbor ID     Pri State   Interface
10.255.0.2        0 FULL/-  GigabitEthernet1

The same router ID appears in both AF contexts. IPv6 Full alone does not prove IPv4 AF operation.

R1# show ipv6 route 2001:DB8:2::1/128 | include Routing entry|via
Routing entry for 2001:DB8:2::1/128
  via FE80::2, GigabitEthernet1
R1# show ip route 10.255.0.2 | include Routing entry|via
Routing entry for 10.255.0.2/32
  * 192.0.2.2, via GigabitEthernet1
R1# ping ipv6 2001:DB8:2::1 source Loopback0
!!!!!
R1# ping 10.255.0.2 source Loopback0
!!!!!

IPv6 uses a link-local next hop plus interface; IPv4 still needs IPv4 forwarding addresses. These filtered excerpts focus on next hops. OSPFv3 host-prefix metrics can be zero, so do not mechanically add the configured loopback cost as in the v2 examples; inspect the actual prefix LSA and route metric. Use show ip route ospfv3 for the IPv4 AF protocol-filtered view on this platform.

If the image rejects these commands, use its documented supported syntax or select a supporting image. Validate an explicit v3 security mechanism before deployment; IPv6 does not automatically enable authentication.

Technical references

OSPFv2 standard · Router configuration guide · OSPFv3 standard · OSPFv3 address families