In a functioning cluster, the primary unit keeps all subordinate unit routing tables up to date and synchronized with the primary unit. After a failover, because of these routing table updates the new primary unit does not have to populate its routing table before being able to route traffic. After a failover the new primary unit rebuilds its routing table, but having the synchronized routes already available means the table is rebuilt much faster than if no route information was available.

This section describes how clusters handle dynamic routing failover and also describes how to use CLI commands to control the timing of routing table updates of the subordinate unit routing tables from the primary unit.