ZyXEL Communications P-2812HNU-51c User Manual page 164

Chapter 8 Network Address Translation (NAT)
port), the P-2812HNU-51c 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.
For example:
Figure 72 Trigger Port Forwarding Process: Example
Jane requests a file from the Real Audio server (port 7070).
1
Port 7070 is a "trigger" port and causes the P-2812HNU-51c to record Jane's
2
computer IP address. The P-2812HNU-51c associates Jane's computer IP address
with the "open" port range of 6970-7170.
The Real Audio server responds using a port number ranging between 6970-7170.
3
The P-2812HNU-51c forwards the traffic to Jane's computer IP address.
4
Only Jane can connect to the Real Audio server until the connection is closed or
5
times out. The P-2812HNU-51c times out in three minutes with UDP (User
Datagram Protocol) or two hours with TCP/IP (Transfer Control Protocol/Internet
Protocol).
164
Jane's
Computer
Real Audio Server
P-2812HNU-51c User's Guide