ZyXEL Communications P-334W - Manual (Page 160)

Prestige 334W User’s Guide
10-14 NAT Screens
receives a response with a specific port number and protocol ("incoming" port), the Prestige forwards the
traffic to the LAN IP address of the computer that sent the request. After that computer’s connection for that
service closes, another computer on the LAN can use the service in the same manner. This way you do not
need to configure a new IP address each time you want a different LAN computer to use the application.
10.6.1 Trigger Port Forwarding Example
The following is an example of trigger port forwarding.
Figure 10-7 Trigger Port Forwarding Process: Example
1. Jane requests a file from the Real Audio server (port 7070).
2. Port 7070 is a “trigger” port and causes the Prestige to record Jane’s computer IP address. The Prestige
associates Jane's computer IP address with the "incoming" port range of 6970-7170.
3. The Real Audio server responds using a port number ranging between 6970-7170.
4. The Prestige forwards the traffic to Jane’s computer IP address.
5. Only Jane can connect to the Real Audio server until the connection is closed or times out. The Prestige
times out in three minutes with UDP (User Datagram Protocol), or two hours with TCP/IP (Transfer Control
Protocol/Internet Protocol).
10.6.2 Two Points To Remember About Trigger Ports
1. Trigger events only happen on data that is going coming from inside the Prestige and going to the
outside.
2. If an application needs a continuous data stream, that port (range) will be tied up so that another
computer on the LAN can’t trigger it.
10.7 Configuring Trigger Port Forwarding
To change your Prestige’s trigger port settings, click SUA/NAT and the Trigger Port tab. The screen
appears as shown.