You need to do the DNS trick.
So, say the DNS name of your -external- ip is elkay.homeip.net (or whatever your dns name is from your ISP) and your internal IP of your eqemu server is 192.168.1.100. Make sure that LoginServer.ini refers to your external DNS name as well as your boot5zones.bat, etc
LoginServer.ini
Code:
...
worldaddress=elkay.homeip.net
...
boot5zones.bat (or whatever)
Code:
zone.exe . elkay.homeip.net 7001 192.168.1.100
On the machine you play eq from, put a hosts file (\windows\system32\drivers\etc\hosts) entry that points that name to the internal IP address of your server.
Code:
192.168.1.100 elkay.homeip.net
After that you should be good to go.