C
T
ROUBLESHOOTING
N
ETWORK
C
ONNECTION
P
ROBLEMS
This appendix provides information about using a crossover
cable to troubleshoot network problems when you know
that the 3C900B NIC is working, but you cannot send or
receive network traffic.
When you work with 10BASE-T cabling, concentrators,
and NICs from different vendors, it is possible to connect
everything but still have no communication between
file servers and workstations. When there are several
unknown variables, it is difficult to determine which
component is failing.
Eliminating Potential Causes of Problems
Follow these steps to narrow the range of possible causes
of some common problems:
1 Determine whether your equipment complies with
the 10BASE-T standard.
This is particularly important for data concentrators (hubs
or repeaters).
2 Connect a straight-through cable from the PC to
the hub.
The hub performs an internal crossover so that the signal
can go from TD+ to RD+ and TD– to RD–. When you look
at an RJ-45 connector from the front (that is, the opposite
side from where the wires enter the connector), pin 1 is
identified on the right-hand side when the metal contacts
are facing up.
3 Make sure that the TD+ and TD– wires are twisted
together, and that the RD+ and RD– wires are
twisted together.
Using wires from opposing pairs can cause signals to
be lost.
