Port Mapping

WinRoute performs NAT, which makes the protected network inaccessible from outside. Using port mapping, public services like a WWW server or an FTP server, and others running on your private network may become accessible from the Internet.

How Port Mapping Works

Each packet received from the outside network (from the Internet) is checked whether its attributes (that is the protocol, destination port, and destination IP address) comply with an entry in the port mapping table (Protocol, Listen Port, Listen IP). If the arriving packet meets the desired criteria, the packet is modified and routed to the IP address within the protected network defined as the "Destination IP" in the table's entry and to the port defined as "Destination port".

portmapschema

For example if you run a telnet server at internal IP 192.168.1.4 and you want to allow users from the Internet to access it. There will be requests from Internet users coming to your WinRoute computer on the external IP address that is equal to the DNS record for your web server www.yourdomain.com. As all requests to the telnet server are coming on port 23 you will set up port mapping saying that all TCP communication on port 23 will be diverted to the internal IP address 192.168.1.4.