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Port Triggering
This page is used to configure port triggering for applications when the router is in NAT mode.
Some applications require that, when external devices connect to them, they receive data on a specific port or range of ports in order to function properly. The router must send all incoming data for that application only on the required port or range of ports.
Port triggering allows computers on the private network (LAN or DMZ) to request one or more ports to be forwarded to them. Unlike basic port forwarding which forwards ports to only one IP address, port triggering waits for an outbound request from the private network on one of the defined outgoing ports. It then automatically sets up forwarding to the IP address from where the request was made. When the application ceases to transmit data over the port, the router waits for a timeout interval and then closes the port or range of ports, making them available to other computers on the private network.

For example, if an IRC client on the private network makes a connection request through port 6667 and sends it's username information to the IRC server, the IRC server will send an IDENT verification packet on port 113 to check the authenticity of the IRC client. In NAT mode, the router will discard this packet since it doesn't know which computer to send the request on port 113 to. A Port Triggering rule can define port 6667 (or the range: 6660 to 7000) as the outgoing (trigger) port(s) and port 113 as the incoming (response) port.
Port Triggering Rules
This table lists the currently defined port triggering rules:
Name: Displays the user-defined name for this rule.
Enable: Displays the current status of the rule, i.e, whether it is Enabled or Disabled.
Protocol: Specifies whether the port uses the TCP or UDP protocol.
Outgoing Ports: Displays the port number or range of port numbers that will trigger this rule when a connection request for outgoing traffic is made. If the outgoing connection uses only one port, then both the Start Port and End Port fields will display the same port number.
Incoming Ports: Displays the port number or range of port numbers used by the remote system to respond to the request it receives. If the incoming connection uses only one port, then both the Start Port and End Port fields will display the same port number.
Add Port Triggering Rule
To add a Port Triggering rule, enter the following the fields and click Add.
Name: Specify an easily identifiable name for this rule.
Enable: Specify whether to Enable or Disable the rule.
Protocol: Specify whether the port uses the TCP or UDP protocol.
Outgoing Ports: Specify the port number or range of port numbers that will trigger this rule when a connection request from outgoing traffic is made. If the outgoing connection uses only one port, then specify the same port number in the Start Port and End Port fields.
Incoming Ports: Displays the port number or range of port numbers used by the remote system to respond to the request it receives. If the incoming connection uses only one port, then specify the same port number in the Start Port and End Port fields.
Edit: Click to modify the selected rule.
Select All: Select all the rules in the table.
Edit Port Triggering Rule
The following fields of an existing port triggering rule can be modified:
Enable: Specify whether to enable or disable the rule.
Protocol: Specify whether the port uses the TCP or UDP protocol.
Outgoing Ports: Specify the port number or range of port numbers that should trigger this rule when a connection request for outgoing traffic is made. If the outgoing connection uses only one port, then specify the same port number in the Start Port and End Port fields.
Incoming Ports: Displays the port number of range of port numbers used by the remote system to respond to the request it receives. If the incoming connection uses only one port, then specify the same port number in the Start Port and End Port fields.
Click Apply to save the settings when you are done changing them.
Click Reset to discard any changes and revert to the previous settings.
 

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