In Ethernet networking, Twisted Pair that used a port must be connected accordingly that the Transmit pair on one end is connected to the Receive pair on the other end, and vice versa. For the correct duplex setting; it is important to have the correct cable type defined for each port. Connections between particular devices, for example; switch-to-switch, switch-to-host, switch-to-router, router-to-router devices and router-to-host; required the use of exact cable types (crossover or straight-through).
What is Auto-MDIX.?
Auto-MDIX is a function that every port on the switch will automatically detect the Ethernet cable type being used (straight-through or crossover) and adjust to make a link over that cable. Most switch devices now support the MDIX auto interface configuration command in the CLI to enable the automatic medium-dependent interface crossover (auto-MDIX) feature.
When this feature is enabled; the switch automatically detects the type of cable attached to the port and configures the interfaces accordingly. so, if this function is enabled we can use either a crossover or a straight-through cable for connections to a copper 10/100/1000 port on the switch, anyway of the type of device on the other end of the connection.Most of the new switches by default enable the auto-MDIX feature.