Port Forwarding

Port forwarding is the method that a firewall or router uses to sort the right network data that would go into a specific port. A computer normally uses ports to organize different kinds of network data.

Each web site, online game and file download has assigned port numbers. A port forwarding program allows either the firewall or the router to send the corresponding data to its correct port.

Directing the Flow of Data

Information that comes into the computer is filtered by the firewall. Anything unauthorized will not gain entry. Those allowed to enter will have to be sorted and assigned and sent to appropriate ports. This is where the port forwarding program comes in. It instructs and gives direction to the data flow.

Where it is Used

Port forwarding is extensively applied in computers with Internet connection. A computer has to have port forwarding within its system, especially if the IP address is a shared address among computer units. If a router is NAT-enabled, computers, whether connected by Ethernet or wireless, will make port forwarding within itself. Doing this will enable the router to share the Internet connection with multiple stations.

Types of Port Forwarding

There are two types of port forwarding variations: double port forwarding and reverse port forwarding.

  1. In double port forwarding, more than one router is
    often used by the network of computers. It is termed “double” in a sense that one router’s ports will forward it to another router within the network. The latter will again forward data to a host on the local area network (LAN).
  2. The reverse port forwarding is composed of a session server and a client. This is only necessary when access to a port behind the router is held up by the firewall.


When performing port forwarding, only one port is allowed to be used by a computer unit. Some consider it a somewhat unprotected move since incoming data packets are seen by the destination as sent by the router rather than the computer unit that sent it.