This setting controls how a port's Ethernet MDI/MDIX crossover wiring behaves: auto lets the port automatically detect and configure the correct rx/tx pairing, mdix forces standard switch-port wiring, and mdi forces the pattern normally used on a straight-through cable to a hub or another switch's uplink. An administrator overrides the automatic default when connecting to older equipment that doesn't support auto-MDIX and needs a specific crossover setting to link up correctly, and the setting works independently of any auto-negotiation configuration on the port. With the default value of auto, the port automatically figures out the correct crossover configuration for whatever cable and device is plugged in.