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112
A
PPENDIX
Troubleshooting Hubs with Crossover Cable
A crossover cable can be used to isolate failures in these
components when hub performance or impedance settings
are in question.
1 Connect a file server and a client PC back to back with
a crossover cable to verify that the NIC and network
operating system are properly configured.
2 To make a crossover cable, connect TD+ to RD+ and
TD– to RD–.
The cable performs the crossover that is usually performed
by the hub.
crossover cable:
Figure 62 Straight-Through and Crossover Cable Pinouts
Straight-through
10BASE-T cable
1
2
3
4
5
6
7
8
If the file server and client PC function together as a
small network, then either the existing cabling or the hub
is failing.
I
I
I
B: C
C
ROSSOVER
ABLE
Figure 62
1 2 3 4 5 6 7 8
1
2
3
4
5
6
7
8
With a correct crossover connection, the LED lights.
With a straight-through connection, the LED does
not light.
With a polarity mismatch (that is, TD+ to RD– instead of
TD+ to RD+), the LED blinks.
T
T
ROUBLESHOOTING
shows the pinouts for the
Crossover
10BASE-T cable
1
TD+
TD–
2
3
RD+
4
5
RD–
6
7
8
IPS
1
TD+
2
TD–
3
RD+
4
5
6
RD–
7
8
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