112
A
PPENDIX
B: C
ROSSOVER
C
ABLE
T
ROUBLESHOOTING
T
IPS
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.
Figure 62
shows the pinouts for the
crossover cable:
Figure 62
Straight-Through and Crossover Cable Pinouts
If the file server and client PC function together as a
small network, then either the existing cabling or the hub
is failing.
■
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.
1
2
3
4
5
6
7
8
1
2
3
4
5
6
7
8
Straight-through
10BASE-T cable
1 2 3 4 5 6 7 8
1
2
3
4
5
6
7
8
1
2
3
4
5
6
7
8
Crossover
10BASE-T cable
TD+
RD+
RD+
TD+
TD–
TD–
RD–
RD–
Book Page 112 Monday, June 7, 1999 8:55 AM
