what is it with people asking here, a wireless forum, about assistance for a DSL router (albeit a very solid and proven one)
I hate to sound blunt, but are you unable to find the manual and read it? If an idiot like me can configure an M1122, surely you'd be able to read the manual and do so as well...
I guess some questions have to be asked, does your m1122 have a firewall firmware or not? Have you checked out the NApT page?
http://www.nzdsl.co.nz/emulator/nokiamw112...2/localnapt.htm
You'll need to pinhole the ports that you need to use and point them at your internal IP address. You may need to create the same rules for UDP as you would for TCP. Then use a dynamicdns service to automate your external IP updates for your applications, or manually update your external IP settings using whatismyip.com
This is so that your applications advertise to their servers what your internet IP address is and what port your applications are listening on. Any return traffic hits the NApT table in the router and gets passed through to your PC.
basically speaking, of course.