The import-route isis level-1 into level-2 command controls route leaking from Level-1 areas to Level-2 areas, which facilitates route management. The command needs to be configured on Level-1-2 routers connected to external areas.
The undo import-route isis level-1 into level-2 command disables route leaking from Level-1 areas to Level-2 areas.
By default, all the routing information (except information about default routes) is leaked from a Level-1 area to a Level-2 area.
import-route isis level-1 into level-2 [ filter-policy { acl-number | ip-prefix ip-prefix-name | route-policy route-policy-name } | tag tag | direct allow-filter-policy ] *
undo import-route isis level-1 into level-2 [ filter-policy { acl-number | ip-prefix ip-prefix-name | route-policy route-policy-name } | tag tag | direct allow-filter-policy ] *
| Parameter | Description | Value |
|---|---|---|
| filter-policy | Specifies the filtering policy to filter the imported routes. | - |
| acl-number | Specifies the number of the basic ACL. | The value is an integer ranging from 2000 to 2999. |
| ip-prefix ip-prefix-name | Specifies the prefix name of the IP address. Only the routes, which match the prefix, can be leaked from Level-1 to Level-2 area. | The name is a string of 1 to 169 case-sensitive characters, with spaces not supported. When double quotation marks are used around the string, spaces are allowed in the string. |
| acl6-number | Specifies the number of a basic ACL6. | The value is an integer ranging from 2000 to 2999. |
| route-policy route-policy-name | Specifies the name of the routing policy. | The name is a string of 1 to 40 case-sensitive characters, with spaces not supported. When double quotation marks are used around the string, spaces are allowed in the string. |
| tag tag | Indicates to assign the administrative tag value to the imported route. | It is an integer ranging from 1 to 4294967295. |
| direct allow-filter-policy | Indicates a filtering policy to filter the direct routes. If the parameter is configured, only the IS-IS Level-1 area direct routes that matches the filtering policy can leak to a Level-2 area. If the parameter is not configured, all Level-1 area direct routes will leak to a Level-2 area. |
- |
Usage Scenario
IS-IS is designed for a hierarchical network. This means that routes of Level-1 areas are leaked to Level-2 areas, whereas routes of Level-2 areas are not leaked to Level-1 areas.
The import-route isis level-1 into level-2 command can be run only on Level-1-2 routers to allow some or no Level-1 routes to be leaked to Level-2 areas.
For example, there are two Level-1-2 routers in a Level-1 area. You can run the import-route isis level-1 into level-2 command on one Level-1-2 router to allow some Level-1 routes to be leaked to the Level-2 area, and run the import-route isis level-1 into level-2 command on the other Level-1-2 router to allow the remaining Level-1 routes to be leaked to the Level-2 area. Then, traffic that is sent from the Level-2 area and destined for different network segments in Level-1 area will be forwarded to different Level-1-2 routers. This allows route selection to be controlled.
Prerequisites
IS-IS processes have been enabled.
Precautions
The import-route isis level-1 into level-2 [ filter-policy { acl-number | acl-name acl-name | ip-prefix-name | route-policy route-policy-name } ] [ tag tag ] command is used to configure the route leaking function in an IPv4 base topology or an IPv4 topology instance.
The import-route isis level-1 into level-2 [ filter-policy { acl6-number | acl6-name acl6-name | ipv6-prefix ipv6-prefix-name | route-policy route-policy-name } ] [ tag tag ] command is used to configure the route leaking function in an IPv6 topology instance.
The ipv6 import-route isis level-1 into level-2 command is used to configure the route leaking function in an IPv6 base topology.
Creating an ACL before it is referenced is recommended. If a nonexistent ACL is referenced using the command, all routes in the Level-1 area leak to the Level-2 area.
Creating an IP prefix list or route-policy before it is referenced is recommended. By default, nonexistent IP prefix lists or route-policies cannot be referenced using the command. If the route-policy nonexistent-config-check disable command is run in the system view and a nonexistent IP prefix list or route-policy is referenced using the current command, all routes in the Level-1 area leak to the Level-2 area.