User's Manual

12 Troubleshooting
152 APCD-LM043-4.0
Ethernet Cable Wiring
Table 37 provides troubleshooting tips related to problems that you may be having with
Ethernet cables.
Correct termination of an Ethernet cable is fundamental to preventing problems introduced by
crosstalk or noise. If a cable is incorrectly terminated, packet loss and network problems may
occur.
An Ethernet cable consists of eight wires, four of which are solid colored, and four of which
have white stripes (called tracers). Each solid-color wire and its corresponding color-striped
wire are twisted together and considered a pair (e.g. the solid-blue and white-blue wires
constitute one pair). The twisting of the wires prevents cross talk and the introduction of noise.
Only two of the four available pairs are actually used in data communications — one pair is
used for transmitting data and another pair for receiving data. If you look at the bottom of the
Ethernet plug (the metal contacts are visible from the bottom). The transmit pair uses pins 1
and 2, and the receive pair uses pins 3 and 6 (see Figure 48).
Figure 48 Ethernet Plug (Bottom View)
For a standard straight-through Ethernet cable, both plugs should be set up as follows:
• Pin1=WhiteGreen
•Pin2=Green
• Pin3=WhiteOrange
Table 37 Ethernet Cabling Problems
Symptom Potential Causes
• Unable to ping across a single
piece of Ethernet cable.
• Lose large-sized ping packets
acrossasinglepieceof
Ethernet cable.
• Ethernet cable wired wrong.
• Ethernet cable RJ-45 ends terminated incorrectly
or badly.
• Wrong cable type (crossover or straight-through)
used.
• Ethernet cable longer than 100 meters.
• Ethernet cable may be damaged, crimped, or
bent sharply.
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