Network Cabling

A Quick Review of Cabling and Hubs

What you should know about Cabling and Hubs!

The two most popular types of network cabling are twisted-pair (also known as 10BaseT as shown on the left below) and thin coax (also known as 10Base2 as shown on the right). 10BaseT cabling looks like ordinary telephone wire, except that it has 8 wires inside instead of 4. Thin coax looks like the copper coaxial cabling that's often used to connect a VCR to a TV set.

10BaseT Cabling:

When 10BaseT cabling is used, a strand of cabling is inserted between each computer and a hub. If you have 5 computers, you'll need 5 cables. No cable can exceed 325 feet in length! Because the cables from all of the computers converge at a common point (normally a hub), a 10BaseT network forms a star configuration, or geometric design, when viewed from above. In the figure below, five computers are connected together with 10BaseT cabling and a hub.

A 10BaseT hub is basically a box with a row of 10BaseT jacks. Most hubs have 5, 8, 12, or 16 jacks, and some have even more. Most hubs also have an uplink port, which is a special 10BaseT or thin coax port that allows the hub to be connected to either (1) other hubs, or (2) a thin coax backbone (see below for information on backbones). By up-linking or stacking multiple hubs together, you can add additional computers to your network whenever you need them.

10BaseT cabling is available in different grades or categories. Some grades, or "cats", are required for Fast Ethernet networks, while others are perfectly acceptable for standard 10Mbps networks and happen to be less expensive as well. About 80% of the networks in the U.S. use standard unshielded twisted-pair (UTP) Category 5 10BaseT cabling because it offers a performance advantage over lower grades. If you are using a 10Mbps network, category 3 should be fine. If you plan on building a Fast Ethernet network at some time in the future, it is best to install Category 5 cabling right from the beginning.

	 		
10BaseT 
Category     What It's Used For
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   5	     Fast Ethernet (and everything below)
   4	     Networks other than Ethernet
   3	     10Mbps 10BaseT 
   2	     Alarms, telephone voice lines
   1	     Unknown (not rated for anything specific)

If possible, you should decide whether you will be using standard Ethernet or Fast Ethernet before you begin building your network. If you're not sure which technology you'll eventually use, choose Category 5 cabling. Remember, Fast Ethernet network adapters and hubs are not directly compatible with each other. It is possible to have both 10Mbps and 100Mbps segments on the same network, provided that you use a switching hub in between them that allows them to communicate.

We will discuss more about 10BaseT wiring configurations in our How to Wire a Network segment.

Thin Coax Cabling:

The geometric design that is formed when thin coax cabling is used is called a linear or backbone configuration. The reason for this is that thin coax is always arranged in a straight line of PCs, hubs and/or other devices. Thin coax networks always requires termination, which is the act of "plugging" the ends of the network. Instead of inserting an incoming thin coax cable directly into a computer, a T-connector is inserted instead, splitting the network adapter's input port into two separate ports. One port receives an incoming network cable; the other receives an outgoing network cable. If the PC is at the end of the network chain, a terminator plug is connected to the empty side of the T-connector.

Thin coax is only used with 10Mbps Ethernet networks. Fast Ethernet networks, which are 10 times faster than standard Ethernet, use category 5 10BaseT cabling.

The figure below shows three PCs connected together in a backbone configuration. Note that the backbone has termination at both ends, and each "T" connector plugs directly into a computer, where it allows for an incoming and outgoing connection. The maximum length for any thin coax segment is 607 feet.

Mixing 10BaseT & Coax:

Thin coax backbones and 10BaseT cabling & hubs can be connected together to allow for a wide variety of expansion options. In the example below, a thin coax backbone connects two 10BaseT hubs together, along with a computer in-between. Each hub, in turn, branches off to still more computers with 10BaseT cabling. Note that the ends of the thin coax backbone are terminated.

How to Pick Your Cabling:

There are two things to consider when deciding on the cable type you plan to use for your network.

1. How many PCs do you want to link together?
2. How long (in feet) is your network going to be?

Answering these two questions will determine the cabling that is best for you, and whether or not you'll need a hub.

Use thin coax cabling if you...
------------------------------------------------

have fewer than 10 PCs,
don't have any portable computers,
and don't plan to expand

Use 10BaseT cabling with a hub if you...
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have 16 or fewer PCs within a 325 foot radius of each other,
have portable computers,
and/or you plan to expand

Use both thin coax and 10BaseT together if...
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you have more than 16 computers,
or the radius of your workgroup is more than 300 feet

Common Problems and Some Solutions:

Here are some ways to avoid the most common cabling pitfalls that network installers face.

Avoid Interference
Network cabling can be run under floors, around office dividers, or over dropped ceilings. When planning your wiring layout, try to keep cables away from power outlets, florescent lighting fixtures, un-interruptible power supplies, and other sources of strong electromagnetic interference. Coiling up cables can also cause interference.
Thin Coax Cabling
When using thin coax cabling, you must always use a T-connector at each computer and termination at both ends of the network, even if you're only connecting a couple of computers together.
10BaseT Cabling
When using 10BaseT cabling, you must use a hub, even if you're only networking two computers together. Many first time network builders try and forego a hub and simply plug a 10BaseT cable between two computer network cards by using a cross-over cable. Such an installation is guaranteed to either (1) not work, or (2) be unreliable.

Need more on cabling? Click the "Go" button to review some interesting information from Cisco.

If you would rather move on to How to Wire Your Network, then click the "Next" button.