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Chapter 12 NAT
EMG1302-R10A User’s Guide
111
The following table describes the labels in this screen.
12.6 The NAT Trigger Port 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 EMG1302-R10A 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 EMG1302-R10A WAN port receives a response with a specific port number and protocol
(“open” port), the EMG1302-R10A 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 43 Configuration > Network > NAT > Port Forwarding
LABEL DESCRIPTION
Service Name Select User-Defined and type a name (of up to 31 printable characters) to identify this
rule in the first field next to Service Name. Otherwise, select a predefined service in
the second field next to Service Name. The predefined service name and port
number(s) will display in the Service Name and Port fields.
Service Protocol Select the protocol supported by this service. Choices are TCP_UDP, TCP, or UDP.
WAN Interface Select a WAN interface for which you want to configure port forwarding rules.
Port Range Type the first and last internal port number that identifies a service.
Translation Port
Range
Type the first and last external port number that identifies a service.
Server IP Address Type the inside IP address of the virtual server here.
Add Click Add to save the port forwarding rule.
# This is the number of an individual port forwarding server entry.
Status Shows the rule status.
Name This field displays a name to identify this rule.
Protocol This is the protocol used by this service.
WAN Interface This is the WAN interface of the rule.
WAN IP This is the WAN IP address of the incoming packets.
Port This is the internal port number that identifies the service.
Translation Port
Range
Type the first and last external port number that identifies a service.
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.
Click the Remove icon to delete a rule.
Apply Click Apply to save your changes back to the EMG1302-R10A.
Cancel Click Cancel to begin configuring this screen afresh.