> No, systems will do a ping-pong if the routes point to each
> other...happens all the time.
Right, ISP A is responsible for net d, but happens to not have a route for
it at the time, so bounces it through the default route to upstream provider
B who says, "net d clearly belongs to ISP A" and bounces it back.
> In general its not a problem since a
> network that isn't in use generally won't have people trying to use it.
> Are you having a problem with this?
three words: "dial up network". Specifically 207.100.1.32/27, housing
giza.purplefrog.com, among others. When I dial in from home, there's a
route. When I'm not dialed in, there's no route, and you'll bounce between
icix and lw.net for days.
> In general if you see the ping-pong thing, its a routing problem
> somewhere, but not a network that is delegated but not in use. :)
In specific, it is exactly a network that is delegated and not in use.