HP procurve Installation Manual page 17

Installing the GL Modules
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Automatic Cable Sensing on Twisted Pair Ports:
When the ports for the 10/100-TX GL Module and the 100/1000-T GL Module
are in their default configuration, Auto , both modules automatically negotiate
whether the ports operate as MDI or MDI-X, depending on the cable type and
the connected device's operation. As a result, you can use either "straight-
through" or "crossover" twisted-pair cable for all network connections to
these modules.
On the 10/100-TX XL Module, this feature is identified as HP Auto-MDIX; on
the 100/1000-T XL Module, it is identified as Auto MDI/MDI-X and it is part
of the IEEE 802.3ab standard. Both features operate the same.
Operation of this feature depends on the port configurations being kept at Auto .
If the configuration is changed to one of the available fixed options though
(for example, 100-Full Duplex), the port operates as an MDI-X port. In that
case, to connect the module to another switch or hub, use a crossover cable;
to connect to an end node, use a straight-through cable.
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