Chapter 11 Network Address Translation (NAT)
SBG3500-N Series User’s Guide
208
11.3.1 Add New Application
This screen lets you create new NAT application rules. Click Add new application in the
Applications screen to open the following screen.
Figure 87 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 SBG3500-N Series 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 SBG3500-N Series's WAN port receives a response with a specific port number and
protocol ("open" port), the SBG3500-N Series 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 56 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 SBG3500-N Series automatically
configures the protocol, start, end, and map port number that define the service.
View Rule 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.
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