Port forwarding

Encyclopedia : P : PO : POR : Port forwarding

It is common to configure port forwarding on routers over a web interface. Here, the user is configuring port forwarding for a Conexant router using the Konqueror web browser. 10.0.0.3 and 10.0.0.5 are the private IPs on the LAN.

Port forwarding (sometimes referred to as tunneling) is the act of forwarding a network port from one network node to another. This technique can allow an external user to reach a port on a private IP address (inside a LAN) from the outside via a NAT-enabled router.

Port forwarding allows remote computers (e.g. public machines on the Internet) to connect to a specific computer within a private LAN.

For example:

• forwarding port 8000 on the router to a user's machine allows Shoutcast streaming
• forwarding ports 5000 through 6000 to a user's machine allows the use of Unreal Tournament

Some common caveats with port forwarding include:

• the need to forward the packets that come to the router's forwarded port as well as the need to rewrite them so that the machine to which the port is forwarded to can reply to the original source address, which in turn leads to
• the inability of the destination (private) machine to see the actual originator of the forwarded packets, and instead see them as if originating from the router

See also

• Network address translation
• Port triggering
• Secure Shell

External links

• [canyouseeme.org] - Tells you if your ports are forwarded properly (even ports under 1024)

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