Port forwarding is primarily used to segregate network traffic, optimize network speed and to permanently assign a network path for a specific protocol or network service. Generally, port forwarding uses well-known port numbers. It is typically implemented at a gateway router, which resides at a network’s boundary, to automate the process of identifying and transferring network packets to a destination port.

For example, suppose that a router receives a packet with an IP address and port number in the packet header. If the router is not configured with port forwarding, it will first resolve/identify the port before transmitting. However, if port forwarding is configured, it will automatically transfer the packet internally to the destination node. The whole process of port forwarding is transparent to all connected network clients.