The components used to establish a local area network (LAN) have a variety of functions. The common unifying theme among them is that they facilitate communication between two or more computers. LAN components are configurable in a variety of ways, but a LAN always requires the same basic components.
At the most basic level, a network card is a component that allows the computer to communicate across a network. This component is frequently built into the motherboard of today's computers, but it can also be a separate card for use in a PCI slot, or part of an external unit that connects to the computer via a USB port. Network cards are further categorized according to whether they operate on wired or wireless networks. However, some cards do support both wireless and wired networking.
Network cables are the physical lines used to carry information between computers in a wired LAN. The cables are labeled by their category and are commonly referred to as CatX--where X is the category number--cable. The most commonly used type in 2010 is Cat5, although other categories with different properties do exist.
A network hub acts as a centralized point for data transmission to computers in a LAN. When data from one computer reaches the hub it is broadcast to every computer in the network regardless of where the data is intended to go. Network bandwidth on LANs using a network hub is shared, which means that four computers on a hub will each get one-quarter the total bandwidth available on the hub.
An alternative to the network hub is the network switch. Switches represent a newer networking technology that assigns each computer in the network a specific MAC address. This allows LANs using a network switch to route information to individual computers. Because network switches do not broadcast to every computer on the network, they can simultaneously allot their full bandwidth to each computer.
Unlike switches and hubs, network routers are used to connect networks to one another, rather than connecting computers in a single network. Routers can connect groups of computers that are separated by a wall or by an ocean. They are most commonly found in the home, where they facilitate the connection of home computers to the Internet; however, they can be used to connect networks of any kind. Most modern network routers are actually combination units that contain a router and a network switch, in addition to a handful of other networking-related tools such as a DHCP server and a firewall.