There are two ways to have packets go where no BGP routes are announced --
by adding bogus static or whatever routes or by pointing default. Both
are malicious. Note that accepting third party routes is also something
not generally welcomed. If you're not given routes you're _not_ expected
to send your packets. Consider that a "no trespassing" notice.
MCI has found an intereesting variant on this. Whenever MCI has
backbone problems in Chicago, DRA suddenly sees all sorts of inbound
traffic from MCI at mae-east and mae-west. DRA usually ends up sending
the outbound traffic back through CIX since MCI won't announce their
routes to DRA at mae-east and mae-west.
Backbones are _private_ property. As such the operators are in their
right to demand that others leave their equipment alone.
True, but who has deeper pockets when mistakes happen. If you are a
multi-billion dollar provider, and one of your engineers has a late
night routing 'oops', having an agreement already in place with other
providers can mitigate some of risk. Do I get to sue MCI for the
traffic they send DRA at mae-east and mae-west without an agreement?
In the mean time, consider all those routers at the exchange points
you don't peer with as potential legal lottery winners waiting for
the first wayward packet to violate your "no trespassing" notice.