What is a router?

A router is a device in computer networking that forwards data packets to their destinations, based on their addresses. The work a router does it called routing, which is somewhat like switching, but a router is different from a switch. The latter is simply a device to connect machines to form a LAN. A router allows connectivity to one or more computers, helping create a network. For home users, these are particularly useful for taking a single broadband internet account, and spreading it to at least two or more computers. Standard routers require the internet connection from a standalone modem, but modem-routers are increasing in popularity, which can be plugged into any broadband-enabled phone line, reducing cable clutter, and only taking up one power socket.

When data packets are transmitted over a network (say the Internet), they move through many routers (because they pass through many networks) in their journey from the source machine to the destination machine. Routers work with IP packets, meaning that it works at the level of the IP protocol. Each router keeps information about its neighbours (other routers in the same or other networks). This information includes the IP address and the cost, which is in terms of time, delay and other network considerations. This information is kept in a routing table, found in all routers. When a packet of data arrives at a router, its header information is scrutinized by the router. Based on the destination and source IP addresses of the packet, the router decides which neighbour it will forward it to. It chooses the route with the least cost, and forwards the packet to the first router on that route.

Each router has a configuration table, or routing table, containing information on which connections lead to certain groups of addresses, which connections have priority for usage, and rules for handling different kinds of traffic. A typical home/office router has a very small routing table, but the big routers that handle the main internet traffic can have huge complicated routing tables. Each time a router receives a packer of data it will attempt to send it along the best possible route to its destination, based on its routing table. If that connection is not currently available it will send it along the next best route. In this way, the routers that form the internet can reconfigure the paths packages take to work around any problems with the network.

Wireless routers have become more common. A wireless router does exactly the same job in the home as a regular wired (Ethernet) router, with the difference that a computer can be connected to it without needing to run Ethernet cable between the computer and the router. All you need is a wireless network adapter in each PC you want to connect, usually in the form of a card in your PCI slot (or a laptop's PCMCIA card slot) or an adapter for USB. Wireless routers generally have four ports to connect Ethernet cable as well, so computers can be connected by whatever means is most convenient - you might want to use a cable for your desktop PC which sits right next to the router, but use the wireless adapter in your laptop.

For home and business computer users who have high-speed Internet connections such as cable, satellite, or DSL, a router can act as a hardware firewall. This is true even if the home or business has only one computer. Many engineers believe that the use of a router provides better protection against hacking than a software firewall, because no computer Internet Protocol address are directly exposed to the Internet. This makes port scans (a technique for exploring weaknesses) essentially impossible. In addition, a router does not consume computer resources as a software firewall does. Commercially manufactured routers are easy to install, reasonably priced, and available for hard-wired or wireless networks.