Does BGP use TCP or UDP? If TCP then we are in trouble. Almost everyone
has access to the Internet via BGP. The line IP address is usually made up
of a pair of addresses in the same subnet. You can IP spoof block all your
internal IP addresses but if you block the IP address of your BGP connection
to your BGP peer and BGP uses TCP, then the examples jbash gave out will
stop BGP updates as well.
-Hank