The multi-homing-preference command configures the multi-homed priority for a VSI.
The undo multi-homing-preference command deletes multi-homed priority for a VSI.
By default, the multi-homed priority for a VSI is 0, which is the lowest priority.
| Parameter | Description | Value |
|---|---|---|
preference-value |
Specifies the multi-homed priority of a VSI. |
The value is an integer that ranges from 1 to 65535. A large value indicates a high priority. |
Usage Scenario
In CE dual-homed scenarios, run the multi-homing-preference command to specify a primary PE and a backup PE.
Prerequisites
Precautions
Currently, only Kompella VPLS supports the multi-homed priority for a VSI. In addition, only the dual-homed CE is supported.
At present, only one label block can be configured on the VSIs of the two dual-homed PEs. If you want to increase the range, run the undo site command to delete the existing site, and then specify a larger range. Only one AC can be configured for the VSIs of the dual-homed PEs.
If the VSIs of two PEs that the dual-homed CE accesses are Up, the PE with higher priority serves as the primary PE, while the PE with lower priority serves as the backup PE. The primary PE is responsible for forwarding the traffic of the CE, while the backup PE is responsible only for checking whether the VSI of the primary PE is Up. After the backup PE is selected, the VSI status of the backup PE turns Down. If the VSI status of the primary PE turns Down, the primary PE broadcasts Unreach packets. After the backup PE receives the Unreach packets, the backup PE judges that the primary PE is faulty. The backup PE then sends Reach packets to set up a PW with other PEs. The backup PE becomes a primary PE.
If the dual-homed priorities of the two PEs in dual-homed mode are the same, after a session is set up between the PEs, the PEs detect collision. At this time, the VSI of the PE with smaller router ID is Up, while the VSI of the PE with larger router ID is Down.
If a session is set up between PE1 with the priority being "a" and PE2 with the priority being "b", and a is larger than b, the VSI of PE1 is Up and that of PE2 is Down. At this time:
If the priority of PE1 is changed to "b" (the modification is permitted because PE1 does not have information about remote VCs on PE2), the VSI of PE1 remains Up, while the VSI of PE2 remains Down.
If the priority of PE2 is changed to "a", the modification is rejected and alarm information is displayed.
After the session turns Down, the PW of the PE with lower priority turns Up. The PW between the two PEs turns Up.