This object specifies the identity of the virtual interface
whose state is to be monitored. Each port index is a
16-bit integer in big endian order. Default value
is 0 length octet string. If this object is configured
then the Preference Level of this interface will be adjusted
dynamically depending on the state of the Track Port.
The interface's Preference Level is reduced by value of
Preference Level parameter when the Track Port states first
changes from UP to DOWN. When the Track Port next comes up
the interface's Preference Level is increased by the amount
specified by the Preference Level.
The router VRRP virtual port track membership.