PictureTel III ISA manual Troubleshooting Hubs with Crossover Cable

C	CROSSOVER CABLE
	TROUBLESHOOTING TIPS

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. Start with the following procedure to narrow the range of possible causes:

1Determine whether your equipment complies with the 10BASE-T standard.

This is particularly important for data concentrators (hubs or repeaters).

2Connect 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.

3Make 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.

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.

1Connect 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.