ZyXEL Communications P-334U - Manual (Page 121)

P-334U/P-335U User’s Guide
Chapter 9 Network Address Translation (NAT) 121
9.5.1 Trigger Port Forwarding Example
The following is an example of trigger port forwarding.
Figure 75 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 ZyXEL Device to record Jane’s computer IP
address. The ZyXEL Device 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 ZyXEL Device 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 ZyXEL Device times out in three minutes with UDP (User Datagram Protocol),
or two hours with TCP/IP (Transfer Control Protocol/Internet Protocol).
9.5.2 Two Points To Remember About Trigger Ports
1 Trigger events only happen on data that is going coming from inside the ZyXEL Device
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.
9.6 NAT Advanced Screen
To change your ZyXEL Device’s trigger port settings, click Network > NAT > Advanced.
The screen appears as shown.
Note: Only one LAN computer can use a trigger port (range) at a time.