The import-route isis level-1 into level-2 command configures route leaking from Level-1 areas to Level-2 areas.
The undo import-route isis level-1 into level-2 command prohibits route leaking from Level-1 areas to Level-2 areas.
By default, all Level-1 routing information, excluding information about default routes, is leaked to Level-2 areas.
import-route isis level-1 into level-2 [ filter-policy { acl-number | acl-name acl-name | 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 | acl-name acl-name | ip-prefix ip-prefix-name | route-policy route-policy-name } | tag tag | direct allow-filter-policy ] *
| Parameter | Description | Value |
|---|---|---|
| filter-policy | Specifies a filtering policy. | - |
| acl-number | Specifies the number of a basic ACL. | The value is an integer that ranges from 2000 to 2999. |
| acl-name acl-name | Specifies the name of a named ACL. | The value is a string of 1 to 64 case-sensitive characters without spaces. The value must start with a letter. |
| ip-prefix ip-prefix-name | Specifies the name of an IP prefix list. Only the routes that match the IP prefix can be leaked to Level-2 areas. | 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. |
| route-policy route-policy-name | Specifies the name of a route-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 | Specifies the administrative tag value of imported routes. | The value is an integer that ranges from 1 to 4294967295. |
| direct allow-filter-policy | Specifies the filtering policy to filter the direct routes. Only the IS-IS Level-1 area direct routing information that matches the filtering policy can be shared with the Level-2 area with this parameter, and all Level-1 area direct routing information will be shared with the Level-2 area without this parameter. |
- |
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.
Precautions
For an ACL, when the rule command is used to configure a filtering rule, the filtering rule is effective only with the source address range that is specified by the source parameter and with the time period that is specified by the time-range parameter.
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.