Using Port Triggering - NETGEAR WGT624 v3 Reference Manual

Reference Manual for the 108 Mbps Wireless Firewall Router WGT624 v3
Some online games and videoconferencing applications are incompatible with NAT. The
WGT624 v3 wireless router is programmed to recognize some of these applications and to work
properly with them, but there are other applications that may not function well. In some cases, one
local computer can run the application properly if that computer's IP address is entered as the
default in the PORTS Menu. If one local computer acts as a game or videoconferencing host, enter
its IP address as the default.

Using Port Triggering

Port Triggering is an advanced feature that allows you to dynamically open inbound ports on the
basis of outbound traffic on different ports. This is an advanced feature that can be used for gaming
and other Internet applications.
Port Forwarding can typically be used to enable similar functionality, but it is static and has some
limitations. Ports will be open to traffic from the Internet until the port forwarding rule is removed.
Additionally, port forwarding does not work well for some applications when your WAN IP
address is assigned by DHCP, and is changed frequently. Port Triggering opens an incoming port
temporarily and does not require the server on the Internet to track your IP address if it is changed.
Port Triggering monitors outbound traffic. When the gateway detects traffic on the specified
outbound port, it remembers the IP address of the computer that sent the data and "triggers" the
incoming port. Incoming traffic on the triggered port is then forwarded to the triggering computer.
Once configured, operation is as follows:
• A computer makes an outgoing connection using a port number defined in the Port Triggering
table.
• This Router records this connection, opens the INCOMING port or ports associated with this
entry in the Port Triggering table, and associates them with the computer.
• The remote system receives the computer's request, and responds using a different port
number.
• This Router matches the response to the previous request, and forwards the response to the
computer.
• (Without Port Triggering, this response would be treated as a new connection request rather
than a response. As such, it would be handled in accordance with the Port Forwarding rules.)
Note: Only one computer can use a "Port Triggering" application at any time.
7-4
v3.0, December 2005
Advanced Configuration