portforward.com has documentation on a good many number of routers, if your ISP didn't provide them for you. Basically what Gibstick has been telling you to do is to get onto your router and make it remember your MAC-Address (this is a unique identifier of your network-card in your PC) and make it always assign you the same LAN-IP-address - that way your portforwarding rules will forward to the correct box.
Oh, nearly forgot: you keep stating this in your threads - using the ICMP protocol (what the PING-program does) isn't the same as when the masterserver tells you it couldn't ping your gameserver - which it tries via the AssaultCube-info-protocol.
Oh, nearly forgot: you keep stating this in your threads - using the ICMP protocol (what the PING-program does) isn't the same as when the masterserver tells you it couldn't ping your gameserver - which it tries via the AssaultCube-info-protocol.