ADSL Routers can be very troublesome for Nwn to host through them. Here's some thing I found out :-
1) Possibly, the SUREFIRE way to get any router to work with hosting nwn is to switch it to bridge mode. This works for my Alcatael Speedtouch pro. Bridge mode just makes the router transparent to the internet. However, anyone can access your pc because NAT is turned off. Another way to get a "bridged" mode, is to use a router which can define a DMZ.
(below applies to NAT enabled routers)
2) Bioware forums is chock full of router problems without a clear solution for all of them.
3) Some routers will just never work to host nwn on gamespy. It may work with Lord Elessar's technique but these servers will generally be able to be seen on gamespy but cannot joined easily. The older your modem is, the less likely it is to be able to handle the server's requests. (My modem is really clunky)
4) It seems a lot of NAT routers do work with nwn servers. You must make sure to open at least port 5121 as UDP and not TCP.
5) If opening port 5121 doesnt work, then u need to open all the other ports which nwnserver was unable to open on the router. There's a big list on bioware forums for this. The list specifies a range of 5121-5200 (i think) for the client ports, but if you just specify 5121 alone, it seems to work for most servers in this category.
(Tips on what to do if you do use bridging mode iare below)
6) You will need a firewall. Zonealarm doesnt work for me because somehow it lets people se the server on gamespy but not join it (maybe Lord Elessar's solution will work here?)
7) Other firewalls such as Sygate may work, I havent tested them. If any firewalls work for u guys, let me know!
The most secure firewall is possibly a separate linux box router.
Hope that helps. Additional comments really welcome!! (cos im trying to get my server up too)
regs
gashmo