ZyXEL NBG-419N Guia Do Utilizador

 Chapter 15 Network Address Translation (NAT)

NBG-419N User’s Guide

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 NBG-419N 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 NBG-419N's WAN port 
receives a response with a specific port number and protocol ("incoming" port), 
the NBG-419N 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.

To change your NBG-419N’s trigger port settings, click Network > NAT > 
Advanced. The screen appears as shown.

Server IP 
Address

This field displays the inside IP address of the server.

Modify

Click the Edit icon to display and modify an existing rule setting in the 
fields under Add Application Rule. 

Click the Remove icon to delete a rule.

Apply

Click Apply to save your changes back to the NBG-419N.

Reset

Click Reset to begin configuring this screen afresh.

Table 58   Network > NAT > Application (continued)