Port Forwarding
Port Forwarding allows you to redirect a particular public
port to a computer on your LAN network. This helps
you host servers behind the NAT and Firewall.
In the example below, there is a FTP Server running
on port 21 on the LAN.
For security reasons, the Administrator would like to
provide this server to Internet connection on port 30.
Therefore then there is a connection from the Internet
on port 30, it will be forwarded to the computer with the
IP address 192.168.0.100 and changed to port 21.