Most networks consist of two major zones—the local area network (LAN) and the wide area network (WAN). A LAN is the internal network, whether it is a house with two computers or a high-rise office building with thousands doesn’t matter. The WAN is the network outside the LAN; this is both other internal networks and the full Internet. A WAN port is the portal by which information passes back and forth between the LAN and the WAN.
Most users will find a WAN port on a network router. A common home router has one WAN port and four LAN ports. Some routers refer to them as an uplink (for the WAN port) and wired connections (for LAN ports). This port take in information from a high-speed Internet source, such as a cable modem, and splits it to multiple machines inside the home network. While the majority of home routers have four LAN ports, there can be as few as zero or an unlimited amount, although rarely more than eight.
These five ports all appear as rectangular holes on the back of the device. Each of them is designed to have a network cable plugged into it. The WAN port generally sits apart from the other ports to make it easier to identify, but it otherwise looks the same as the LAN ports.
The important difference in the two port types is inside the router. The WAN port takes in information from the outside network or the Internet. The information is filtered through the router’s internal firewall and routing system. Then the information is sent to the proper LAN port or out over a wireless connection to a wireless source.
In addition to the routing and firewall abilities, routers also include switching functions. This allows computers that are connected through the LAN ports only to communicate with each other. This switching function bypasses the router’s standard firewall, and the computers are all on the same network. Users can use this function to connect multiple routers to one another to increase the size of their network.
If they were to connect multiple routers together using the WAN port, they could have multiple internal networks that operate independently of one another. For instance, the high-speed information comes to a single router, and that router then has connections from its LAN ports to three other routers where it plugs into their WAN ports. These internal networks would contain independent information and have no more of a connection to one another than they have to a network in a different building.