I was talking with a photocopier technician the other day, and he asked if I still carried a cross-over cable. I informed him that I haven’t carried one with me for a few years now since most newer computers and peripherals support automatic negotiations. I always carry a 6ft cable with me in case I need to connect my laptop to a client’s network. The “Need” for cross over cables has ended a long time ago.
You would normally need a crossover cable unless;
Automatic MDI/MDI-X Configuration is specified as an optional feature in the 1000BASE-T standard, meaning that straight-through cables will usually work between Gigabit capable interfaces. This feature eliminates the need for crossover cables, obsoletes the uplink/normal ports and manual selector switches found on many older hubs and switches, 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.
Even for legacy 10/100 devices, many NICs, switches and hubs 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.