Straight-through wiring, Crossover wiring – MRV Communications MR2228-S2C User Manual
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Table B-1. 10/100BASE-TX MDI and MDI-X Port Pinouts
Pin
MDI Signal Name
MDI-X Signal Name
1
Transmit Data plus (TD+)
Receive Data plus (RD+)
2
Transmit Data minus (TD-)
Receive Data minus (RD-)
3
Receive Data plus (RD+)
Transmit Data plus (TD+)
6
Receive Data minus (RD-)
Transmit Data minus (TD-)
4,5,7,8 Not used
Not used
Note: The “+” and “-” signs represent the polarity of the wires that make
up each wire pair.
Straight-Through Wiring
If the twisted-pair cable is to join two ports and only one of the ports has an
internal crossover (MDI-X), the two pairs of wires must be straight-through. (When
auto-negotiation is enabled for any RJ-45 port on this switch, you can use either
straight-through or crossover cable to connect to any device type.)
Crossover Wiring
If the twisted-pair cable is to join two ports and both ports are labeled with an “X”
(MDI-X) or neither port is labeled with an “X” (MDI), a crossover must be
implemented in the wiring. (When auto-negotiation is enabled for any RJ-45 port
on this switch, you can use either straight-through or crossover cable to connect
to any device type.)