Chapter 3: Advanced Configuration
Port Triggers Web Page
Some Internet activities, such as interactive gaming, require that a PC on the WAN side of your gateway be able to originate connections during the game with your game playing PC on the LAN side. You could use the Advanced...Forwarding page to construct a forwarding rule during the game, and then remove it afterwards (to restore full protection to your LAN PC) to facilitate this. Port Triggering is an elegant mechanism that does this work for you, each time you play the game.
Fig.29 
Port Triggering works as follows. Imagine you want to play a particular game with PCs somewhere on the Internet. You make one time effort to set up a Port Trigger for that game, by entering into Trigger Range the range of destination ports your game will be sending to, and entering into Target Range the range of destination ports the other player (on the WAN side) will be sending to (ports your PC’s game receives on). Application programs like games publish this information in user manuals. Later, each time you play the game, the gateway automatically creates the forwarding rule necessary (see Advanced...Forwarding discussion above). This rule is valid until 10 minutes after it sees game activity stop. After 10 minutes, the rule becomes inactive until the next matched outgoing traffic arrives.
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