ZyXEL Communications P-320W, User Manual

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P-320W User’s Guide
Chapter 8 Network Address Translation (NAT) 107
Figure 60 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).
8.4.2 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.
8.5 Trigger Port Forwarding Screen
To change your Prestige’s trigger port settings, click the NAT link under Network and the
Trigger Port tab. The screen appears as shown.
Note: Only one LAN computer can use a trigger port (range) at a time.