Enabling and Configuring IS-IS for IPv6 Routing

When enabling IS-IS IPv6, you must create an IS-IS IPv6 routing process and assign it to specific interfaces rather than to networks. You can specify only a single IS-IS process per router.

Note: IS-IS obtains the router ID for routing processes using either the router ID configured using the ip router-id command or using the IPv4 address configured on the loopback interface. If you configure the router ID for IS-IS routing using both the ip-router-id command and also configure an IPv4 address on the loopback interface, the configured router ID takes precedence over the address of the loopback interface. In such a scenario, if you remove the router ID by using the no ip router-id command and also unconfigure all the IPv4 addresses from the interfaces, the IS-ISv6 adjacency is not reset and remains static. This behavior is expected because the router ID for IS-IS is not reset after you remove the all the IPv4 addresses of interfaces and the explicitly configured router ID.

Note: If you remove the last remaining IPv6 address from an interface, and no IS-IS IPv4 configuration exists, the IS-ISv6 neighbor adjacency is brought down. However, if an interface is present with an IPv4 address when you remove the last IPv6 address from the interface, the adjacency is not brought down because enabling IPv6 for the interface also enables IPv4 for that interface. In such a case, a reference to the IS-IS IPv4 routing process is still active.

To enable IS-IS routing, enter Global Configuration mode, and follow this procedure:

1. Access Global Configuration mode and specify an IPv6 license.
   host1(config)#license ipv6 license-value
2. Configure an IP address on the router to serve as the router ID.
   host1(config)#interface loopback0 host1(config-if)#ip address 10.6.5.4/32
3. Configure the lower-layer interfaces over which the IPv6 traffic flows.
   host1(config-if)#interface fastEthernet 1/0
4. Configure an IPv6 address on the interface.
   host1(config-if)#ipv6 address 2008::1/48
5. Specify the IS-IS IPv6 process to apply to the interface. Use the same tag name that you specify with the router isis command for the VR.
   host1(config-if)#ipv6 router isis floor12

   Repeat Steps 3–5 for all desired IPv6 interfaces.

6. Specify an IS-IS process globally for the VR. Use the same tag name that you specify with the ipv6 router isis command on the interface.
   host1(config)#router isis floor12
7. Configure a Network Entity Title (NET) for the routing process that specifies the ISO network address.
   host1(config-router)#net 47.0010.0000.0000.0000.0001.0001.1111.1111.1111.00
8. Create the IS-IS IPv6 address family for the interface.
   host1(config-router)#address-family ipv6 unicast
9. Configure any of the following desired IS-IS options for the address family: redistributing routes from other protocols, redistributing IS-IS IPv6 routes between levels, distributing level 2 routing information to level 1 routers throughout the IS-IS routing domain, summarizing IPv6 routes, applying a route map to modify routes before they are installed in the routing table,
   host1(config-router-af)#redistribute ospf level-1-2 host1(config-router-af)#redistribute isis level-2 into level-1 host1(config-router-af)#distribute-domain-wide host1(config-router-af)#summary-prefix 2001:2000::0/8 level-1 metric 10 tag 100 host1(config-router-af)#table-map ospfFilter
10. Exit the IS-IS IPv6 address family.
    host1(config-router-af)#exit-address-family

    Note: Enabling IPv6 for the interface also enables IPv4 for that interface. However, this interface does not participate in IS-IS IPv4 routing.

Summary Example