Fortunately, formally listing all of the internal IP ranges is a solved problem: http://www.ietf.org/rfc/rfc1918.txt http://www.ietf.org/rfc/rfc1918.txt http:

Fortunately, formally listing all of the internal IP ranges is a solved problem: http://www.ietf.org/rfc/rfc1918.txt http://www.ietf.org/rfc/rfc1918.txt http://www.ietf.org/rfc/rfc4193.txt http://www.ietf.org/rfc/rfc4193.txt I have a feeling that IPv6 is going to be a lot more complex than simply blocking FC00::/7. I seem to recall that one of the benefits of IPv6 was that NAT-ing would be a thing of the past and every system would have a public address.