Chapter 9 Network Address Translation (NAT) Screens
P-662H/HW-D Series User’s Guide
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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.
For example:
1 Jane (A) 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). 
Click Network > NAT > Trigger Port to open the following screen. Use this screen to add 
and view trigger port rules configured on your ZyXEL Device.
Figure 89   Trigger Port   
The following table describes the labels in this screen.  
Table 57   Trigger Port 
LABEL DESCRIPTION
Service 
Name 
Type a unique name (up to 15 characters) for identification purposes. All characters 
are permitted - including spaces. 
Incoming 
Port Range 
The incoming port is a port (or a range of ports) that a server on the WAN uses when it 
sends out a particular service. The ZyXEL Device forwards the traffic with this port (or 
range of ports) to the client computer on the LAN that requested the service. 
Start Port  Type a port number or the starting port number in a range of port numbers. 
End Port  Type a port number or the ending port number in a range of port numbers. 
Trigger Port 
Range 
The trigger port is a port (or a range of ports) that causes (or triggers) the ZyXEL 
Device to record the IP address of the LAN computer that sent the traffic to a server on 
the WAN. 
Start Port  Type a port number or the starting port number in a range of port numbers. 
End Port  Type a port number or the ending port number in a range of port numbers. 
Add  Click this button to add a rule to the table below. 
#  Click this check box to enable the rule.