How do I change my BT voyager router settings to allow me to host online games through gamespy?

I have a bt voyager 205 router and a zonealarm firewall, I've allowed gamespy and the game I want to run on zonealarm but my i.p address is still being altered by my router (I don't have any way to change my routers settings) and this is preventing me from hosting online games on gamespy..How do I change my BT voyager router settings to allow me to host online games through gamespy?
get help from the service provderHow do I change my BT voyager router settings to allow me to host online games through gamespy?
getting ps2's round router's firewalls is a pain. Bt voyager comes up again and again, in router problems.

If you dont get an answer, do as i do temporary...plug the ps2 directly into the modem. A problem if the router IS the modem, of course. with cable, i bypass my netgear router, and go direct, no firewall, no problems.

If you cant get help, (and bt are useless) OR you are worried, having opened up ports, and relaxed firewalls on the router to enable the ps2 ';carte balnche'; which it needs for operation, and are then worried about vunerabilities you may have opened for the computer, buy a separate simple Modem (for a broadband phone line) and switch between computer(router/wireless box) and ps2 (fixed simple box) manualy. A simple modem has no firewall, and lets your ps2 accept/send anything, which is cool, as ps2's cant be written to or pick up viruses! Then use a firewalled, complex router, for your pc network. Changing is just swapping a lan cable, and a modem';box'; power on/off reeboot.