route loop-detect isis disable

Function

The route loop-detect isis disable command disables loop detection for imported routes.

The undo route loop-detect isis disable command enables loop detection for imported routes.

By default, loop detection is enabled for imported routes.

Format

route loop-detect isis disable

undo route loop-detect isis disable

Parameters

None

Views

System view

Default Level

2: Configuration level

Task Name and Operations

Task Name	Operations
isis	write

Usage Guidelines

Usage Scenario

When routes are imported to an IS-IS process, routing loops may occur. To prevent this problem, run the undo route loop-detect isis disable command to enable loop detection for imported routes. If the device detects that an imported route was advertised by itself, it encapsulates the route with a large link cost before advertising the route. After learning the route, other devices preferentially select another path to prevent routing loops.

Precautions

After the device enters the loop breaking state, it cannot automatically exit the routing loop state and the alarm cannot be automatically cleared. In this case, manual intervention is required. For example, after a routing policy or route tag is correctly configured, run the clear route loop-detect isis alarm-state command to exit the routing loop state and clear the alarm.
A single process supports loop detection for a maximum of 2000 routes. If more than 2000 routes are imported, routing loop detection is disabled automatically. The system checks the number of imported routes in the early morning every day. If the number of imported routes is less than 2000, the system automatically restores the routing loop detection function.
Summary and default routes do not support loop detection.
Loop detection is supported in the scenario where two IS-IS areas import routes from each other. If more than two IS-IS areas are involved, loop detection cannot be performed.
After a loop is detected during route import to IS-IS, if the original route advertisement is withdrawn, the loop persists. In this case, IS-IS reports a loop alarm, but the loop cannot be broken. Manual intervention is required.
If devices configured with route import to IS-IS has a system ID conflict in two IS-IS areas, loop detection may be falsely reported.
When the device advertises a large cost during the routing loop period, the apply cost command does not take effect in the routing policy.
When the IS-IS process that imports a route also calculates a route with the same prefix and the two routes implement inter-process route load balancing, loops cannot be detected.

Example

# Disable the function of loop-detect.

<HUAWEI> system-view
[~HUAWEI] route loop-detect isis disable