Definition: port forwarding

Also called "port mapping," port forwarding is directing traffic from the outside world to the appropriate server inside a local TCP/IP network. Internet services are identified by a standard port number; for example, Web traffic uses port number 80. If the local network hosts a Web server that is accessible on the public Internet, the port forwarding panel in the router would be configured to direct Web/HTTP packets (port 80 traffic) to the IP address of the Web server in the local network (LAN). See TCP/IP port.

Ports are "opened" and "closed" in the firewall, which determines which types of traffic are allowed in or out. In a company, stand-alone commercial firewalls are used. In the home and small business, the firewall is built into the wireless router. For more details, see opening a port. See firewall, wireless router and port triggering.

Forward Web Traffic

If a company hosts its own website, the router adds the IP address of the Web server to all incoming port 80 packets (HTTP packets) from the Internet.

Forward Voice Over IP (VoIP) Traffic

Many companies use the Internet and their local network for telephone service. Because the outside world can "phone in" to the network, those packets must be directed to the company's digital PBX, which uses the SIP protocol. Depending on VoIP provider, the SIP port numbers vary. See SIP and SIP provider.