PORT FORWARDING

Port forwarding is the process that your router or firewall uses to sort the right kind of network data to the right port. Computers and routers use ports as a way to organize network data. Different types of data, such as web sites, file downloads, and online games, are each assigned a port number. By using port forwarding, the router or firewall sends the correct data to the correct place.

Port forwarding, also known as tunneling, is basically forwarding a network port from one node to the other. This forwarding technique allows an outside user to access a certain port (in a LAN) through a NAT (network address translation) enabled router.

Advantages of Port Forwarding

Port forwarding basically allows an outside computer to connect to a computer in a private local area network. Some commonly done port forwarding includes forwarding port 21 for FTP access, and forwarding port 80 for web servers. To achieve such results, operating systems like the Mac OS X and the BSD (Berkeley Software Distribution) will use the pre-installed in the kernel, ipfirewall (ipfw), to conduct port forwarding. Linux on the other hand would add iptables to do port forwarding.

Downsides of Port Forwarding

There are a few downsides or precautions to take with port forwarding.

* Only one port can be used at a time by one machine.
* Port forwarding also allows any machine in the world to connect to the forwarded port at will, and thus making the network slightly insecure.
* The port forwarding technology itself is built in a way so that the destination machine will see the incoming packets as coming from the router rather than the original machine sending out the packets.