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5.1 | |
Cabling the LAN | |
| 5.1.5 | |
UTP implementation |
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EIA/TIA specifies an RJ-45 connector for
UTP cable. The letters RJ stand for
registered jack, and the number 45 refers to a specific wiring
sequence. The RJ-45 transparent end connector shows
eight colored wires. Four of the wires carry the voltage and are
considered “tip” (T1 through T4). The other four wires are grounded
and are called “ring” (R1 through R4). Tip and ring are terms that
originated in the early days of the telephone. Today, these terms
refer to the positive and the negative wire in a pair. The wires in
the first pair in a cable or a connector are designated as T1 and R1.
The second pair is T2 and R2, and so on.
The RJ-45 connector is the male
component, crimped on the end of the cable. When looking at the male
connector from the front, the pin locations are numbered 8 on the left
down to 1 on the right as seen in Figure
The jack is the female component in a
network device, wall outlet, or patch panel as
seen in Figure
For electricity to run between the
connector and the jack, the order of the wires must follow EIA/TIA-T568-A or T568-B standards, as shown in Figure
If the two RJ-45 connectors of a cable are
held side by side in the same orientation, the colored wires will be seen
in each. If the
order of the colored wires is the same at each end, then the cable is
straight-through as seen in Figure
With crossover, the RJ-45 connectors on
both ends show that some of the wires on one side of the cable are
crossed to a different pin on the other side of the cable. Figure
Figure
Use straight-through cables for the following cabling:
Use crossover cables for the following cabling:
Figure
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.
Figure
shows the punch-down connections at the back of the jack where the
Ethernet UTP cable connects. 
.
Identify the correct EIA/TIA category of cable to use for a connecting
device by determining what standard is being used by the jack on the
network device. In addition to identifying the correct EIA/TIA
category of cable, determine whether to use a straight-through cable
or a crossover cable. 
.
shows that pins 1 and 2 on one connector connect respectively to pins
3 and 6 on the other. 
shows the guidelines for what type of cable to use when
interconnecting Cisco devices. 
illustrates how a variety of cable types may be required in a given
network. The category of UTP cable required is based on the type
of Ethernet that is chosen. 
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