(Optional) Configuring a Revertive Switchover Policy

Context

Revertive switching policies are classified into the following types:

Immediate revertive switchover: When the primary PW recovers from a fault, the local PE switches traffic back to the primary PW immediately and notifies the peer PE on the secondary PW of the fault. In FRR mode, the local PE notifies the peer PE on the secondary PW of the recovery after a delay of resume-time. In PW redundancy master/slave mode, the parameter resume-time is not supported.

This revertive switchover applies to scenarios in which users hope traffic to be restored as soon as possible.
Delayed revertive switchover: When the primary PW recovers from a fault, traffic is switched back to the primary PW after a period specified by delay-time. After traffic is switched back, the local device immediately notifies the peer device on the secondary PW of the fault. If resume-time is configured in FRR mode, the local device notifies the peer device on the secondary PW of the recovery after a delay of resume-time.

On a large-scale network, packet loss caused by incomplete route convergence may occur during the switchback. To prevent this problem, configure traffic to be switched back after a delay.
None revertive switchover: When the primary PW recovers from a fault, traffic is not switched back to the primary PW until the secondary PW becomes faulty.

If you do not want traffic to be frequently switched between the primary and secondary PWs, you can use the non-revertive switchover.

By default, the delayed revertive switchover is performed.

A revertive switchover policy is configured on a PE. On an asymmetric network, if the active PW is faulty, the PE, to which a CE is connected through a single link, switches traffic. When the active PW is restored, configure a revertive switchover policy on this PE. The PE then processes traffic based on the configured revertive switchover policy.

Perform the following operations on the PE (where traffic is switched to) to which the CE is connected through a single link.

Procedure

Run system-view
The system view is displayed.
Run interface interface-type interface-number
The AC interface view is displayed.
Run mpls l2vpn reroute { { delay delay-time | immediately } [ resume resume-time ] | never }
A revertive switchover policy is configured.

For an asymmetric network with ACs of the Ethernet type, if the notification of physical layer faults function is configured on the interface of a PE connected to a CE, you are not advised to use the immediate revertive switchover policy, because this policy may lead to network flapping and traffic loss. Delayed revertive switchover is recommended and delay-time must be greater than or equal to 30 seconds.

On a network where CEs are asymmetrically connected to PEs, the secondary PW cannot transmit data when the primary and secondary paths work normally. On a CE in the dual-homed site, if the interface of the secondary PW borrows the IP address of the interface of the primary PW, you cannot configure revertive switchover.