|A linkDown trap signifies that the sending
protocol entity recognizes a failure in one of
the communication links represented in the
agent's configuration. When a new config
command 'snmp-server trap link ietf' is set, the
varbind list is made of objects specified here.
Otherwise, the varbind list defined in the
previous version holds good. For sub-interfaces,
as there is no support for locIfReason, it will
be omitted from the trap message.