So what exactly is a "router"?

As our homes and offices become more and more connected to the Internet and the World Wide Web, we also have more and more devices that we want to connect. Some of these are connected by Ethernet cable while there are more and more wireless devices, from smartphones to laptops to printers, that we run on our networks.

A typical North American home office is connected to the Internet via the phone company or the cable TV provider. While using different mechanisms to facilitate the connection, both provide high speed Internet through their end-point devices (an ADSL modem from the phone company; a cable modem from your TV provider). Each device connected to the Internet must have a unique address (the "IP address") and your provider will allocate one or two of these addresses to your connection (depending on the package they offer). The challenge of how we can connect multiple devices with only one or two IP addresses is solved by use of a device called a "router".

Simply put, a router is a device that connects two networks together - your provider's network and your home or small office network. It does this by connecting the provider's modem to the external ("WAN" for Wide Area Network) side of the router. The internal (or "LAN"; Local Area Network) side of the router provides a set of IP addresses that are private to your network (and, in fact, cannot be used on the public Internet). Most small home and office routers use a range of IP addresses of the form 192.168.x.1. The "x" is dependent on the maker of the router - for example, Linksys/Cisco routers are addressed 192.168.1.1, while D-Link devices use 192.168.0.1. The router itself uses the .1 address, while other devices are allocated addresses somewhere between 192.168.x.2 and 192.168.x.254. From this you can see that these devices can support a considerable number of connected systems.

The vast majority of routers on sale in 2010 support both wired and wireless devices. The number of wired ports is usually 4 or 5, depending on the design of the router, and can therefore impact on the number of wired devices you can connect - more on this later. On the wireless side, the primary restrictions are distance and location. The newer Wireless N devices have a stronger signal than the previous generation Wireless G devices; however, if the device you want to connect is an older one, having a Wireless N router won't provide any advantage. If your home or office has concrete walls or floors, these will reduce the strength of signal, so you may have to consider device placement carefully. 

The router has built-in intelligence that translates the internal IP address to the external one - and more importantly, manages the communication so that when you connect to a Web site, the page gets delivered correctly to your computer even though you don't have a public IP address.

Des Dougan is Principal of Dougan Consulting Group, which provides technology support services to small businesses in the Metro Vancouver area.  Des has over 30 years experience in the computer business and can be contacted here and via @ddougan on Twitter.