ZyXEL Communications PMG5317-T20A - The Port Triggering Screen

Chapter 11 Network Address Translation (NAT)
PMG5317-T20A User’s Guide
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Figure 71 Network Setting > NAT > Applications: Add
The following table describes the labels in this screen.
11.4 The Port Triggering Screen
Some services use a dedicated range of ports on the client side and a dedicated range of ports on
the server side. With regular port forwarding you set a forwarding port in NAT to forward a service
(coming in from the server on the WAN) to the IP address of a computer on the client side (LAN).
The problem is that port forwarding only forwards a service to a single LAN IP address. In order to
use the same service on a different LAN computer, you have to manually replace the LAN
computer's IP address in the forwarding port with another LAN computer's IP address.
Trigger port forwarding solves this problem by allowing computers on the LAN to dynamically take
turns using the service. The GPON Device records the IP address of a LAN computer that sends
traffic to the WAN to request a service with a specific port number and protocol (a "trigger" port).
When the GPON Device's WAN port receives a response with a specific port number and protocol
("open" port), the GPON Device 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.
Table 49 Network Setting > NAT > Applications: Add
LABEL DESCRIPTION
WAN Interface Select the WAN interface that you want to apply this NAT rule to.
Server IP
Address
Enter the inside IP address of the application here.
Application
Category
Select the category of the application from the drop-down list box.
Application
Forwarded
Select a service from the drop-down list box and the GPON Device automatically configures
the protocol, start, end, and map port number that define the service.
View Rules Click this to display the configuration of the service that you have chosen in Application
Fowarded.
OK Click OK to save your changes.
Cancel Click Cancel to exit this screen without saving.