Setting the Rapid Switchover Stale Timer

Use the Rapid Switchover Stale Timer to set the amount of time that you want route and neighbor table entries to be re-added to the Forwarding Information Base on the active management module after a failover has occurred.

Layer 3 applications and protocols rely on existing routing information in the FIB. They restart and operate as if the switch performed a quick reset.

When a failover occurs, the interface modules and the fabric modules continue forwarding Layer 3 traffic based on the information in the FIB. The transitioning standby management module marks all routes in the FIB as “stale”. The routing protocols restart, re-establish their neighbors and reconverge. As the routes are added in again, the route’s stale designation is removed. After the Rapid Switchover Stale Timer expires, the remaining stale route entries are removed. Multicast flows are also removed; the multicast application re-adds the flows after failover completes.

Syntax

redundancy rapid-switchover <0-2147483647>

Allows configuration of a timer (in seconds) for Layer 3 forwarding of packets when Nonstop switching is configured for redundancy. After failover, the route and neighbor entries in the Forwarding Information Base (FIB) on the active management module are marked as stale. As new routes are added, the stale flag is reset. This continues for the number of seconds indicated by the timer, after which all remaining stale entries (entries not re-added) are removed.

A setting of zero indicates that no Layer 3 Nonstop switching behavior is wanted.

When the switch fails over, the FIB entries and corresponding hardware entries are removed. Default: 90 seconds

To display information about stale FIB routes, enter the show tech route stale command. The VLAN ID and IP route are shown, as well as other information used only for technical support.