Layer 3 hitless route purge

Layer 3 traffic is forwarded seamlessly during a failover, switchover, or OS upgrade when hitless management is enabled.

Some protocols support non-stop routing. On enabling non-stop routing, after switchover the management module quickly re-converge the protocol database. Whereas, some protocols support graceful restart, in which the protocol state is re-established with the help of neighboring devices. Once all the protocols converge the routes which were removed from the network during the convergence period, the routes are deleted from the devices. You can set the route purge timer per VRF instance. Configure the timer to set the duration for which the routes should be preserved after switchover. Once this period elapses, the route purging starts, if by then all other protocols have finished non-stop routing or graceful restart.

When switchover occurs, the route purge timer starts. If non-stop routing or graceful restart is also configured, the route validation and purging starts only when they are complete and the purge timer has elapsed. If for some reason more delay is expected in learning the routes, you can configure a larger period for the purge timer.