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RJ-45 Cabling Pinouts (Copper NIC Only)

Troubleshooting Hubs

A crossover cable can be used to identify the type of failure when hub performance or

connectivity is in question.

To use a crossover cable:

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.

RJ-45 Cabling Pinouts (Copper NIC Only)

The following illustration compares the cabling pinouts for straight-through and crossover

cables on the 3CR990B-97 NIC.

If the file server and client PC function together as a small network, then either the

existing cabling or the hub is failing.

When a crossover cable is used, the LED on the NIC functions differently than it would

under normal operating conditions. For example, with a correct crossover connection, the

LED lights, whereas with a straight-through connection, the LED does not light. If you

make a crossover cable and the polarity is mismatched (that is, TD+ to RD– instead of TD+

to RD+), the LED blinks.

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HP Embedded Firewall Series Manuel d'utilisateur Page 63