Configuring IPv6 IS-IS to Import External Routes
If devices in an IS-IS routing domain need to learn external routes, configure IS-IS on a Level-1-2 device of this routing domain to import external routes.
Context
If IS-IS is configured on a Level-1-2 device to advertise a default route, all traffic in IS-IS routing domains will be forwarded by this Level-1-2 device. This will burden this Level-1-2 device because no external route can be learned on the devices in the IS-IS routing domains.
If multiple Level-1-2 devices are deployed, optimal routes to other routing domains need to be selected. To ensure optimal routes are selected, all the other devices in the IS-IS routing domains must learn all or some external routes.
Routing policies can be configured to import or advertise external routes that meet specified conditions to the IS-IS routing domains.
Procedure
- Access the system view.
- Access the IS-IS process view.
isis [ process-id ]
- Configure IS-IS to import external IPv6 routes.
- If you want to set the cost for the imported route, run the ipv6 import-route { direct | static | { ospfv3 | ripng | isis } [ process-id ] | bgp [ permit-ibgp ] } | [ cost cost | tag tag | route-policy route-policy-name | { level-1 | level-2 | level-1-2 } ] * command to import the external ipv6 routes.
- If you want to keep the original cost for the imported route, run the ipv6 import-route { { ripng | isis | ospfv3 } [ process-id ] | bgp [ permit-ibgp ] | direct } inherit-cost [ tag tag | route-policy route-policy-name | [ level-1 | level-2 | level-1-2 ] ] * command to import the external ipv6 routes. When configuring IS-IS to retain the original cost value of the imported route, the source routes cannot be static.
IS-IS will advertise all imported external routes to an IS-IS routing domain by default.
If only some imported external routes need to be advertised, run the ipv6 filter-policy export command to set a filtering policy.
If an IS-IS device has a small routing table capacity, run the ipv6 import-route limit limit-number [ threshold-alarm upper-limit upper-limit-value lower-limit lower-limit-value ] { level-1 | level-2 | level-1-2 } command to set the maximum number of external routes that can be imported into an IS-IS routing domain.
- Filter the imported external IPv6 routes during the advertising to others.
ipv6 filter-policy { acl6-number | ipv6-prefix ipv6-prefix-name | route-policy route-policy-name } export [ protocol [ process-id ] ]