For a simple way to tell if networks are hosed up...use the public, free route servers (!):
(You have to telnet into these..)
route-server.gt.ca
route-server.ip.att.net
route-server.exodus.net
route-server.gblx.net
route-views.oregon-ix.net
ner-routes.bbnplanet.net
sh ip bgp x.x.x.x tells you the AS-Paths that this router has learned the route.
sh ip bgp flap x.x.x.x tells you the flap statistics on a network
(Or just sh ip bgp flap for all networks)
etc..etc..