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You can find bulk supplies of ethernet cable at many computer stores or
most electrical or home centers. You want UTP (Unshielded Twisted Pair)
ethernet cable of at least Category 5 (Cat 5). Cat 5 is required for
basic 10/100 functionality, you will want Cat 5e for gigabit (1000BaseT)
operation and Cat 6 or higher gives you a measure of future proofing.
You can also use STP (Shielded Twisted Pair) for extra resistance to
external interference but I won't cover shielded connectors. Bulk
ethernet cable comes in many types, there are 2 basic categories, solid
and braided stranded cable. Stranded ethernet cable tends to work better
in patch applications for desktop use. It is more flexible and resilient
than solid ethernet cable and easier to work with, but really meant for
shorter lengths. Solid ethernet cable is meant for longer runs in a
fixed position. Plenum rated ethernet cable must be used whenever the
cable travels through an air circulation space. For example, above a
false ceiling or below a raised floor. It may be difficult or impossible
to tell from the package or labelling what type of ethernet cable it is,
so peel out an end and investigate.
Inside the ethernet cable, there are 8 color coded wires. These wires
are twisted into 4 pairs of wires, each pair has a common color theme.
One wire in the pair being a solid or primarily solid colored wire and
the other being a primarily white wire with a colored stripe (Sometimes
ethernet cables won't have any color on the striped wire, the only way
to tell which is which is to check which wire it is twisted around).
Examples of the naming schemes used are: Orange (alternatively
Orange/White) for the solid colored wire and White/Orange for the
striped cable. The twists are extremely important. They are there to
counteract noise and interference. It is important to wire according to
a standard to get proper performance from the ethernet cable. The
TIA/EIA-568-A specifies two wiring standards for an 8-position modular
connector such as RJ45. The two wiring standards, T568A and T568B vary
only in the arrangement of the colored pairs. Tom writes to say
"...sources suggest using T568A cabling since T568B is the AT&T
standard, but the US Government specifies T568A since it matches USOC
cabling for pairs 1 & 2, which allows it to work for 1/2 line
phones...". Your choice might be determined by the need to match
existing wiring, jacks or personal preference, but you should maintain
consistency. I've shown both below for straight through cabling and just
T568B for crossover cabling.
The 8P8C modular connectors for Ethernet are often called RJ45 due to their physical ressemblance. The plug is an
8-position modular connector that looks like a large phone plug. There are a couple variations available. The
primary variation you need to pay attention to is whether the connector is intended for braided or solid wire. For
braided/stranded wires, the connector has sharp pointed contacts that actually pierce the wire. For solid wires,
the connector has fingers which cut through the insulation and make contact with the wire by grasping it from both
sides. The connector is the weak point in an ethernet cable, choosing the wrong one will often cause grief later.
If you just walk into a computer store, it's nearly impossible to tell what type of plug it is. You may be able to
determine what type it is by crimping one without a cable.
Modular connector jacks come in a variety styles intended for several
different mounting options. The choice is one of requirements and
preference. Jacks are designed to work only with solid ethernet cable.
Most jacks come labeled with color coded wiring diagrams for either
T568A, T568B or both. Make sure you end up with the correct one.
There are two basic ethernet cable pin outs. A straight through ethernet cable, which is used to connect to a hub
or switch, and a crossover ethernet cable used to operate in a peer-to-peer fashion without a hub/switch. Generally
all fixed wiring should be run as straight through. Some ethernet interfaces can cross and un-cross a cable
automatically as needed, a handy feature.
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