Automatic MDI/MDI-X Configuration is specified as an optional feature in the 1000BASE-T standard[1], meaning that straight-through cables will often work between Gigabit capable interfaces. This feature eliminates the need for crossover cables, making obsolete the uplink/normal ports and manual selector switches found on many older hubs and switches and greatly reducing installation errors. Note that although Automatic MDI/MDI-X is generally implemented, a crossover cable would still be required in the occasional situation that neither of the connected devices has the feature implemented and enabled. Prior to the 1000Base-T standard, using a crossover cable to connect a device to a network accidentally, usually meant wasted time troubleshooting the resulting lack of connection, but with this standard in place, that is no longer a concern.
Modern switches automatically apply an internal crossover when necessary. Besides the eventually agreed upon Automatic MDI/MDI-X, this feature may also be referred to by various vendor-specific terms including: Auto uplink and trade, Universal Cable Recognition and Auto Sensing.