The import-route isis level-2 into level-1 command configures route leaking from Level-2 areas to Level-1 areas.
The undo import-route isis level-2 into level-1 command prohibits route leaking from Level-2 areas to Level-1 areas.
By default, Level-2 routing information is not leaked to Level-1 areas.
import-route isis level-2 into level-1 [ filter-policy { acl-number | acl-name acl-name | ip-prefix ip-prefix-name | route-policy route-policy-name } | tag tag | direct { allow-filter-policy | allow-up-down-bit } * ] *
undo import-route isis level-2 into level-1 [ filter-policy { acl-number | acl-name acl-name | ip-prefix ip-prefix-name | route-policy route-policy-name } | tag tag | direct { allow-filter-policy | allow-up-down-bit } * ] *
| 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 specified IP prefix can be imported. |
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 |
Indicates the filtering policy to filter the direct routes. Only the IS-IS Level-1 area direct routing information that matches the filtering policy can leak to the Level-2 area with this parameter, and all Level-1 area direct routing information is available to the Level-2 area without this parameter. |
- |
direct allow-up-down-bit |
Indicates that the Up or Down bit is used during the leak of directs routes. If direct allow-up-down-bit is specified, the direct routes that have already leaked to the Level-1 area have the lowest priority and cannot leak back. |
- |
Usage Scenario
When multiple Level-1-2 switches in a Level-1 area are connected to a Level-2 area, Level-1 switches are unable to know the network topology of the Level-2 area, but forward traffic to the nearest Level-1-2 switch (based on the route with the smallest cost). For Level-2 switches, however, this route may not be the optimal one. Therefore, you need to allow some Level-2 routes to be leaked to the Level-1 area to help Level-1 switches select the optimal route for forwarding traffic to the Level 2 area.
To solve the preceding problem, IS-IS provides the route leaking function to enable Level-1 devices to choose the best path for traffic forwarding.
The import-route isis level-2 into level-1 command can be run only on Level-1-2 routers to allow all or some Level-2 routes to be leaked to the Level-1 area.
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-2 area leak to the Level-1 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.