You have to make 2 edits in the World_ .ini file, one top, one bottom, and 2 edits in the Game folder of the client. (one in internal.txt and one in serverlist)
Firewall should be offline, and PC hosting the database and Virtual Machine hosting the realm itself must have 2 different IP addresses.
If you use 192.168.150.1 for example as the WindowsXP SQL PC, your database will have the 192.168.150.1 IP
You can then assign 192.168.150.2 as Linux IP, with 192.168.150.1 as nameserver, broadcasting on 192.168.150.254.
Make sure the XP SQL PC does not use any gateway nor DNS.
After this, your clients should use IPs ranging from 192.168.150.3 onward, with a gateway of 150.1 and same DNS (I think this is even optional). You have to restart the realm after adjusting the server IP (192.168.150.2) in the WorldSrv INI file.
Should work.
@inter : How did you manage to upgrade to EP2 ? My client keeps crashing when I use the US client + files from clientfiles from my root folder.