User's Manual

Chapter 16 Network Address Translation (NAT)
NBG6515 User’s Guide
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16.5 NAT Advanced 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 NBG 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's WAN port receives a response with a specific port number and protocol ("incoming" port),
the NBG 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’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.
Application Rules Summary
# This is the number of an individual port forwarding server entry.
Active This icon is turned on when the rule is enabled.
Name This field displays a name to identify this rule.
Port This field displays the port number(s).
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.
Reset Click Reset to begin configuring this screen afresh.
Table 59 Network > NAT > Application (continued)
LABEL DESCRIPTION