Allied Telesis AT-S63 - Manual (Page 348)

Chapter 30: Virtual Router Redundancy Protocol
348 Section VII: Routing
Interface Monitoring
The virtual router can monitor certain interfaces to change the priority of
switches if the master switch loses its connection to the outside world.
This is known as interface monitoring. Interface monitoring reduces the
priority of the switch when an important interface connection is lost. The
reduction in priority causes a backup switch with a higher priority to take
over as the master switch and restore connectivity.
If a master switch loses its connection to the outside world, the connection
to the LAN is not affected. Advertisement packets are still sent by the
master and received by the backup switches, but the master is unable to
send data to other networks because its connection to the outside world
has been lost