Figure 130 Trigger Port Forwarding Process: Example - ZyXEL Communications ZyWALL 2Plus User Manual

For example:

Figure 130 Trigger Port Forwarding Process: Example

1 Jane's computer, labeled J in the figure, requests a file from the Real Audio server (port
7070) labeled S in the figure.
2 Port 7070 is a "trigger" port and causes the ZyWALL to record Jane's computer IP
address. The ZyWALL 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 ZyWALL 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 ZyWALL times out in three minutes with UDP (User Datagram Protocol) or two
hours with TCP/IP (Transfer Control Protocol/Internet Protocol).
To change your ZyWALL's trigger port settings, click ADVANCED > NAT > Port
Triggering. The screen appears as shown.
Chapter 14 Network Address Translation (NAT)
ZyWALL 2 Plus User's Guide
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