What is Port Forwarding and How Does It Work?
Port forwarding provides a way for a remote computer to connect to another computer that is inside a local area network (LAN) by forwarding a network port from one node to another node. When the network port is forwarded is provides a way for the remote user to access a specific port in the local area network (LAN) through a router that contains an (NAT) network address translation.
How Port Forwarding Works
Port forwarding allows access to a local area network by a remote user through forwarding ports that provide ftp access and web server access. The operating systems use a kernel or ipfirewall to carry out the port forwarding process.
There are several different ways that port forwarding is accomplished.
- Self Forwarding: Self forwarding is port forwarding that is accomplished on a local area network that has multiple computers connected to the network. Since all of the computers share the same IP address, the port forwarding must be conducted within each computer on its own system. If the local area network router has a network access translator then the computers that are connected to the router must also do port forwarding within their own system.
- Unix System Port Forwarding: Port forwarding can be accomplished with Unix systems however the port can only be accessed by the root administrator. This is a less common method of port forwarding due to the fact that using a root administrator poses risks to the system because the users will often take a detour to a higher port number to gain faster access to the server.
- Double Port Forwarding: Double port forwarding involves the use of multiple routers that join computers on a local area network. As a result, the ports on one router are forwarded to another router that acts as a gateway. The gateway router then forwards to a host on the local area network (LAN).
- Reverse Port Forwarding: This type of port forwarding involves the communication of several components which include the session server, session client, and session port. When the user establishes a connection the session server will connect to one of the session ports that are to be forwarded which will in turn, forward the port to the session client. Reverse port forwarding is used when access is required to a port that is protected behind a firewall.
While port forwarding is convenient, there are a few things to be aware of when using this type of technology. If you use port forwarding only one port can be used at a time and the machine that is receiving the port forwarding can only view the information as coming from the router instead of the original machine. Additionally, port forwarding can open up network access to other machines that may be able to find the port forwarding by gaining unauthorized access.