I'm not sure if you have seen this or if it answers your question, but take a look at
http://www.phex.org/wiki/index.php/C...rivate_Network which explains two differnt ways to set up a private network.
I'm not sure if that appies also to LANs.
Let us know if that helped
This might also help
http://gnutellaforums.com/showthread...860#post262860
but you will have seen that as you double posted ........