Interface Tracking

Interface Tracking
One additional advantage of the preemption process is that it allows the selection of the active
router at arbitrary moments on a network without having to wait for formal elections. Thus if
a standby router receives a hello from the active router and the active router is lower than its
own configured priority, it will preempt and become active itself. By the same process, if an
active router receives a hello from a router with a higher priority; it will cease to remain active.
This leads to a rather clever situation where a router can be configured to track another interface,
with a view to reducing the standby priority on the standby interface should the other
interface fail. There is a default reduction of 10, but this is configurable, allowing for complex
scenarios to be created.