Port forwarding, also referred to as port mapping, is a method of forwarding a network port from one network node to another. This technique can allow an external user to reach a port on a private IP address (inside a LAN) from the outside using a NAT-enabled router.
- forwarding of port 80 to run an HTTP webserver within private LAN from internet
- forwarding of port 22 to allow Secure Shell access within private LAN from internet
- forwarding of port 21 to allow FTP access within private LAN from internet
Port forwarding is not necessary with IPv6, because every IPv6-enabled device has a public IPv6 address.