Once upon a time, Sam Varshavchik <mrsam(a)courier-mta.com> said:
I defy anyone to identify a tangible benefit that comes from
removing a static IP address from a port when it loses carrier, and
installing one only once a carrier is present.
It is useful for systems with multiple interfaces, for example a desktop
with wired and wifi, and different preference default routes out both
(so if the wired goes down, traffic can still go out over the wifi).
Anything acting like a router also needs this behavior, typically in
conjuction with dynamic routing protocols.
Chris Adams <linux(a)cmadams.net>