Configuring Redundant Pseudowires for Layer 2 Circuits and VPLS

A redundant pseudowire can act as a backup connection between PE routers and CE devices, maintaining Layer 2 circuit and VPLS services after certain types of failures. This feature can help improve the reliability of certain types of networks (metro for example) where a single point of failure could interrupt service for multiple customers. Redundant pseudowires cannot reduce traffic loss to zero. However, they provide a way to gracefully recover from pseudowire failures in such a way that service can be restarted within a known time limit.

For an overview of how redundant pseudowires work, see Redundant Pseudowires for Layer 2 Circuits and VPLS.

To configure pseudowire redundancy for Layer 2 circuits and VPLS, complete the procedures in the following sections:

Configuring Pseudowire Redundancy on the PE Router

You configure pseudowire redundancy on the PE router acting as the egress for the primary and standby pseudowires using the backup-neighbor statement.

To configure pseudowire redundancy on the PE router, include the backup-neighbor statement:

backup-neighbor {community name;psn-tunnel-endpoint address;standby;virtual-circuit-id number;}

For a list of hierarchy levels at which you can include this statement, see the statement summary for this statement.

The backup-neighbor statement includes the following configuration options:

community—Specifies the community for the backup neighbor.
psn-tunnel-endpoint—Specifies the endpoint address for the packet switched network (PSN) tunnel on the remote PE router. The PSN tunnel endpoint address is the destination address for the LSP on the remote PE router.
standby—Configures the pseudowire to the specified backup neighbor as the standby. When you configure this statement, traffic flows over both the active and standby pseudowires to the CE device. The CE device drops the traffic from the standby pseudowire, unless the active pseudowire fails. If the active pseudowire fails, the CE device automatically switches to the standby pseudowire.
virtual-circuit-id—Uniquely identifies the primary and standby Layer 2 circuits. This option is configurable for Layer 2 circuits only.

Configuring the Switchover Delay for the Pseudowires

To configure the time the router waits before switching traffic from the failed primary pseudowire to a backup pseudowire, include the switchover-delay statement:

switchover-delay milliseconds;

For a list of hierarchy levels at which you can include this statement, see the statement summary for this statement.

Configuring a Revert Time for the Redundant Pseudowire

You can specify a revert time for redundant Layer 2 circuit and VPLS pseudowires. When you have configured redundant pseudowires for Layer 2 circuits or VPLS, traffic is switched to the backup pseudowire in the event that the primary pseudowire fails. If you configure a revert time, when the configured time expires traffic is reverted back to the primary pseudowire, assuming the primary pseudowire has been restored.

To configure a revert time for redundant pseudowires, specify the time in seconds using the revert-time statement:

revert-time seconds;

For a list of hierarchy levels at which you can include this statement, see the statement summary for this statement.