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Appendix E: Twisted-Pair Cabling
There are different grades, or “categories,” of twisted-pair cabling. Category 5
is the most reliable and most highly recommended. Category 3 is a good sec-
ond choice. Straight-through cables are used for connecting computers to a
hub. Crossover cables are used for connecting a hub to another hub (there is an
exception: some hubs have a built-in uplink port that is crossed internally; this
allows you to link or connect hubs together with a straight-through cable
instead).
You can buy pre-made Category 5 cables, or cut and crimp your own. Category
5 cables can be purchased or crimped
as either straight-through or crossover.
Inside a Category 5 cable are eight
thin, color-coded wires inside that run
from one end of the cable to the other.
All eight wires are used. In a straight-
through cable, wires 1, 2, 3, and 6 at
one end of the cable are also wires 1,
2, 3, and 6 at the other end. In a
crossover cable, the order of the wires
change from one end to the other: wire
1 becomes 3, and 2 becomes 6. See
Figures E-3 and E-4 on the next page
for more detailed information on
straight-through and crossover
cabling.
To determine which
wire is wire number 1,
hold the cable so that the
end of the plastic RJ-45 tip
(the part that goes into a wall jack first) is facing away
from you. Face the clip down so that the copper side faces
up (the springy clip will now be parallel to the floor).
When looking down on the copper side, wire 1 will be on
the far left.
110
• Straight-Through Cabling
• Cross-Over Cabling
Crimping Your Own Network Cables
Figure E-3
Figure E-4
Figure E-1
Figure E-2