With my linksys router, if you go to 192.168.1.1, go into the config, select apps/gaming, then select dmz to your ip - prolly 192.168.1.100. DMZ forwards all ports to whatever ip you select.
if you shut off and there are other computers on the network, when you restart you will get a new ip address, and you will have to change the dmz address. At my house, the other users are rarely on and I am always on, so in over a year I have only fixed my ip address maybe 10 times. Sounds like alot, but it only takes a couple of seconds, no big deal, ymmv
edit - the linksys router assigns ips starting at 192.168.1.100. So your ip address will only change if you log off, then the others users log off, and then someone logs back on before you do. So if you were originally 192.168.1.100, logged off, everyone else logged off, then one person logs back on before you, he is 192.168.1.100, then you would be 192.168.1.101, and so on.