VRRP synchronization group
Interfaces in a VRRP synchronization group (“sync group”) are synchronized such that, if one of the interfaces in the group fails over to backup, all interfaces in the group fail over to backup. For example, in many cases, if one interface on a master router fails, the whole router fails over to a backup router. By assigning all the interfaces in a set of VRRP routers to a sync group, the failure of one interface triggers a failover of all the interfaces in the sync group to the backups that are configured for each interface in the sync group.
If you manually disable an interface that belongs in a VRRP sync group, whether the group is acting as the master or backup router, the state of the VRRP Finite State Machine (FSM) for each of the interfaces within the group changes to the fault state. A transition to the fault state is triggered by one of the following reasons:
- An interface has been administratively shut down.
- A media link failure has been detected.
- An interface hardware failure has been detected.
If the interfaces in the fault state remain in this state because they are not enabled, these interfaces remain in the fault state, thereby, terminating the router failover services that are available through the VRRP feature. For VRRP to function, you must have both master and backup VRRP routers.