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Specifications
Twisted-Pair Cable/Connector Pin-Outs
N o t e
A-8
Twisted-Pair Cable/Connector Pin-Outs
The Auto-MDIX Feature: In the default configuration, "Auto", the fixed 10/100/
1000BASE-T ports on the switches all automatically detect the type of port on the
connected device and operate as either an MDI or MDI-X port, whichever is
appropriate. So for any connection, a straight-through twisted-pair cable can be
used—you no longer have to use crossover cables, although crossover cables can
also be used for any of the connections. (The 10/100/1000-T ports support the IEEE
802.3ab standard, which includes the "Auto-MDIX" feature.)
If you connect a switch twisted-pair port to another switch or hub, which typically
have MDI-X ports, the switch port automatically operates as an MDI port. If you
connect it to an end node, such as a server or PC, which typically have MDI ports,
the switch port operates as an MDI-X port. In all cases, you can use standard straight-
through cables or crossover cables.
If you use a correctly wired crossover cable, though, the switch will still be able to
automatically detect the MDI/MDI-X operation and link correctly to the connected
device.
Using Fixed Configurations. If the port configuration is changed to any of the fixed
configurations though, for example 100 Mb/s/full duplex, the port operates as MDI-
X only and the correct cable type must be used: for connections to MDI ports, such
as end nodes, use a straight-through cable; for connections to MDI-X ports, such as
on hubs and other switches, use a crossover cable.
Other Wiring Rules:
All twisted-pair wires used for 10 Mb/s, and 100 Mb/s operation must be twisted
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through the entire length of the cable. The wiring sequence must conform to
EIA/TIA 568-B (not USOC). See "Twisted-Pair Cable Pin Assignments" later
in this appendix for a listing of the signals used on each pin.
For 1000BASE-T connections, all four pairs of wires in the cable must be
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available for data transmission.
For 10 Mb/s connections to the ports, you can use Category 3, 4, or 5 unshielded
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twisted-pair cable, as supported by the IEEE 802.3 Type 10BASE-T standard.
For 100 Mb/s connections to the ports, use 100-ohm Category 5 UTP or STP
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cable only, as supported by the IEEE 802.3u Type 100BASE-TX
standard.
For 1000 Mb/s connections, 100-ohm Category 5e or better cabling is recom-
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mended.
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