Jazz Jackrabbit 2 Online

i have troubles using my new router,
after 30 seconds of play-time my connexion is timed out
i have got a new connexion over adsl with a router and a hardware-firewall in one when i had my old connexion evrything worked fine but now since i got the new one...

OS = win98
router = e-tech see here,hereandhere pictures of the router part
router service ip: http://192.168.1.254
i know that i have to forward the ports 10052 to 10054 tcp and udp but what about ip's forwarding can i leave these blanco? also i want to use jj2 on two computers who are on the same router is that a problem? also for playing on two computers using lan network and internet play at the same time, is that a problem?

please help me, msn + mail = scatman@wct.zzn.com