Configuring a Path Selection Revert Timer

Without a configured path selection revert timer, the router switches between a primary and secondary path immediately after the current working path goes down. A problem with this mode of operation is that it can cause flapping when the current path goes up and down frequently. Also, the LSP to which the route is switching traffic might be unstable, which causes the router to fail back to the current LSP almost immediately.

The path revert timer insures the stability of the LSP to which the traffic is switched by specifying the number of seconds that the LSP must be running before it carries traffic.

To configure a path selection revert timer for an LSP, complete the following steps using the revert-time command.

  1. Enable the device for configuration.
    device# configure
  2. Enable the MPLS router.
    device(config)# router mpls
  3. Enable and specify signaled label switched path (LSP).
    device(config-router-mpls)# lsp samplelsp
    In this example, samplelsp is the selected LSP.
  4. Configure revert timer.
    device(config-router-mpls-lsp-samplelsp)# revert-timer 10

    The timer-value value is the number of seconds that the router waits after the primary, or selected path comes up before traffic reverts to that path. in this example, the value is configured to 10 seconds.


The following example configures the path selection revert time to 10 seconds for LSP named 'samplelsp'.

device# configure terminal
device(config)# router mpls
device(config-router-mpls)# lsp samplelsp
device(config-router-mpls-lsp-samplelsp)# revert-timer 10

When deploying the revert-time command, consider the following: