While network cabling may not be the most exciting topic in the world, you’ll definitely need to understand the basics of different LAN media. The three main types of media found on LANs include coaxial cable, twisted pair, and fiber optics. In this section we’ll look not only at the properties of each but also maximum distances, signaling, and how cables are wired.
It really wasn’t all that long ago that coaxial cabling was the defacto standard for wiring LANs. On Ethernet LANs that used coaxial cable, individual computers were connected to the cable using devices such as BNC-T connectors or external transceivers. These connected to the system’s network card, and then to a run of cable that went to computers in either direction. At either end of this long segment, you were required to use a terminator that would absorb signals and prevent them from bouncing back down the wire and creating collisions.
Coaxial networks had a major downside. Since every system was connected to this same run of cable, a break or disruption at any point could bring down the network. Even as other wiring cabling standards became popular, coaxial cable was often used as backbone cabling between LANs. Its ability to span longer distances made it useful, even though the speeds at which data could be passed were fairly limiting by today’s standards.
While it’s not commonly used anymore, it is still important to know something about the two most popular types of coaxial cabling:
ThickNet. This type of coaxial cabling is used with Ethernet 10Base5 networks and is able to span distances of up to 500 meters. Originally used to directly connect computers, it eventually became popular in backbone implementations between LANs. Systems connected to the cable using an external transceiver unit than actually tapped directly into the wire. The transceiver was then connected to a network card using an Attachment Unit Interface (AUI) cable. You’ll learn more about external transceivers and AUI connections when we look at Cisco router ports.
ThinNet. A much thinner and more flexible type of coaxial cable, ThinNet is used on Ethernet 10Base2 networks and can span distances of up to 185 meters. This was usually the media of choice for connecting computers on a LAN. In ThinNet networks, computers connect to the network via a BNC-T connector attached to the network card.