Using the Pre-empt Delay Timer (PDT)

To maintain availability of the default gateway router, the VRRP advertises a "virtual" router to the hosts. At least two other physical routers are configured to be virtual routers, but only one router provides the default router functionality at any given time. If the owner router or its VLAN goes down, the backup router takes over. When the owner router comes back on line (fail-back), it takes control of the VIP that has been assigned to it. It begins sending out VRRP advertisement packets at regular intervals. The backup router receives the VRRP advertisement packet and transitions to the backup state.