What is Port Forwarding
Port Forwarding is used to take packets (can be data packets) destined for a specific port (i.e. TCP or UDP port) and machine, and then forwards the packets to a different port or a machine. This is done in such a way that the network clients cannot see that the Port Forwarding is taking place. They connect to a port on a machine when in actual the packets are being redirected somewhere else.
The packets that the user needs to redirect are passed through the machine. If Port Forwarding is used to forward a port to somewhere else, everything will work fine by default. The packets go directly to the machine and are then redirected or forwarded.
Port Forwarding is also referred to as Tunneling. It is used for intercepting traffic bound for certain IP combinations and redirecting to a different IP or port. This may only be accomplished by an application running on destination host or by intermediate hardware (e.g. router, proxy server etc…)
Port Forwarding is basically used to keep unwanted traffic out of the network. It also allows the administrator to use the IP address for all external communications on the Internet. It is done while dedicating multiple servers and that too with different IP’s and ports internally. It is useful in such cases when a home network user wants to run a Web Server, an FTP Server and a gaming server on one network only. A single public IP address on the router is set up to translate the requests to the proper server on internal network. This is basically used to hide all the services running on the network, using only IP address to complete multiple tasks and dis allowing all the services that the firewall is not related to.
Using Port Forwarding, the public IP addresses can be preserved and servers and clients can also be protected from unwanted access. The services which are running as well as the servers which are on the network are also hidden. This limits the access to the network and from the network. It provides an extra layer of security at the network and acts as a benefit of being transparent to the end users. Port Forwarding can be performed with as well as without router.
One of the main disadvantages of Port Forwarding is that only one port can be used at a time by one machine.