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revert-time (Protocols Layer 2 Circuits)

 

Syntax

Hierarchy Level

Release Information

Statement introduced in Junos OS Release 10.2.

maximum option introduced in Junos OS Release 13.2.

Description

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

With the maximum option, specify a maximum reversion interval to add after the revert-time delay. If a revert-time delay is defined but a maximum timer is not defined, VCs are restored upon the revert-timer's expiration.

To reduce as much as possible the amount of traffic discarded, and potential data-path asymmetries observed during primary-to-backup transition periods, you can use this restoration timer. This restoration timer is activated when the backup path is performing as active, and then the primary path is restored. The goal is to avoid moving traffic back to the primary path right away, to make sure that the control plane's related tasks (such as IGP, LDP, RSVP, and internal BGP) have enough time to complete their updating cycle.

By enabling a gradual return of traffic to the primary path, you can ensure that the relatively-slow control-plane processing and updating does not have a negative impact on the restoration process.

The maximum option extends the revert timer’s functionality to provide a jittered interval over which a certain number of circuits can be transitioned back to the primary path. By making use of this maximum value, you can define a time interval during which circuits are expected to switch over. As a consequence, circuits’ effective transitions are scattered during restoration periods.

When making use of revert-time x maximum y statement, you can ensure that the corresponding circuit that is active is moved to the primary path within a time-slot (t1) such as that: x <= t1 <= y. In other words, by activating this statement, you can ensure the following:

  • VCs stay in the backup path for at least x seconds after the primary path comes back up.

  • VCs are moved back to the primary path before y seconds have elapsed.

  • y maximum value = x maximum value * 2 = 1200 seconds.

The ideal values for x and y will are conditioned to internal aspects of your network. For this reason, there are no default values for these settings. If no revert-time is set, the default behavior is non-revertive. That is, circuits are not returned to the primary path upon restoration. They are kept on the backup path.

Default

Without the revert-time statement, virtual circuit (VC) traffic is not transitioned to the primary path upon restoration of the primary path.

Options

seconds—Revert time in seconds.

Range: 0 through 600 seconds

maximum seconds—Number of seconds to delay path restoration after the revert-time delay.

Range: 0 through 1200 seconds

Required Privilege Level

routing—To view this statement in the configuration.

routing-control—To add this statement to the configuration.