How Do I Set Up Port Forwarding?

Port mapping is a type of NAT. Its function is to translate the addresses on the public network into private addresses. The ADSL broadband router using routing has a dynamic or fixed public network IP. Computer sharing Internet. ^[1]

Port mapping is to map a port of the IP address of the host on the external network to a machine in the internal network to provide corresponding services. When a user accesses this port of the IP, the server automatically maps the request to a machine inside the corresponding LAN. There are dynamic and static port mappings. ^[2]

At present, many enterprises have built internal LANs. However, with the advent of the Internet era, the establishment of a LAN alone cannot meet the needs of many enterprises. More users need to publish information on the Internet or perform information retrieval. Intranet access to the Internet has become an urgent requirement for many enterprises. However, with the rapid development of the Internet, the shortage of IP addresses has become a very prominent problem. It is impossible for every computer in the enterprise to have a real IP address, so most corporate users access the Internet through a gateway or proxy server. The internal computer has only one IP address on the network. Although the advantages of doing so save IP address resources, there are many inconveniences because many of the corporate network is external. Because the computers on the network use a gateway and a proxy to access the Internet, Since there is no externally accessible IP address, these computers cannot be accessed by the outside world. It is also impossible to put all the servers of the enterprise on a computer acting as a proxy server, at this time port mapping will be used. ^[4]

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Users in a local area network cannot be actively connected by external users, which sometimes causes trouble. For example, a website built on your own machine is not accessible to external users. In this case, port mapping is used to transfer access from a certain port on the external network (usually by a broadband router) to a specified computer in the local area network. ^[6]

Port mapping and port forwarding are used to publish servers inside the firewall or client computers inside the firewall. Some routers also have port mapping and port forwarding functions. Port mapping is similar to, but not exactly the same as, port forwarding. Port mapping is to completely map a port on the external network to a designated port on an internal network address, and port forwarding is to completely forward traffic sent from a port on the external network to a designated port on an internal network address. Port mapping can realize two-way communication from the external network to the internal network and internal network to the external network, while mapping and forwarding can only realize one-way communication from the external network to the internal network. ^[8]

This can be done using a small tool called "PortMap". Install the software on the server, and then set the incoming port and the mapped IP and port. ^[9]

When Internet connection sharing is used, computers on the internal network use internal IP addresses and cannot be routed to the Internet. Therefore, without taking any measures, access and control of the internal network will not be achieved. At the same time, because different network services use different ports, for example, Web uses port 80, FTP uses port 21, and Rea streaming services use port 554. Therefore, if different ports are mapped to different IP addresses of the internal network on the router, when a host in the Internet accesses the local area network, different service requests can be forwarded to the corresponding server respectively, thereby achieving remote access and control. This is the meaning of port mapping. ^[10]

Therefore, the port mapping function has almost no effect on the network transmission rate, and its purpose is only to achieve Internet publishing of internal services, or for remote control of internal networks. ^[10]