Statement introduced in Junos OS Release 12.2 for EX Series switches.
Support for SRX Series devices introduced in Junos OS Release 15.1x49.D80.
You must configure media dependent interface (MDI) properties for a 10-Gigabit Ethernet interface on a copper network port of an EX4550 switch to ensure that both sides of the link are compatible.
MDI refers to the IEEE standard for the interface to an unshielded twisted pair (UTP) cable. Twisted-pair Ethernet standards are such that the majority of cables can be wired "straight-through" (pin 1 to pin 1, pin 2 to pin 2 and so on), but others may need to be wired in the "crossover" form (receive to transmit and transmit to receive).
For most ports, the switch can automatically detect the required connection type and can therefore configure the interface appropriately. However, the switch cannot automatically detect whether the connection type of a 10-Gigabit Ethenet interface on a copper network port is straight-through or crossover.
Therefore, you must set the MDI properties of the local interface of a 10-Gigabit Ethernet interface on a copper network port to ensure that it will work correctly with the other side of the link. When you set this configuration on an interface, you must also disable auto-negotiation and set the speed to 100m.
This configuration does not apply to management Ethernet or console interfaces and it does not apply to 1-Gigabit copper ports.
The proper setting depends both on the type of cable and the setting that is being used on the other side of the link:
For crossover cables—Set the polarity to match the other side of the link. Specify mdi for the switch interface if mdi is being used on the other side of the link; specify mdix if mdix is being used on the other side of the link.
For straight cables—Set the polarity to be the opposite of the other side link. Specify mdi for the switch interface if mdix is being used on the other side of the link; specify mdix if mdi is being used on the other side of the link.
One of the following modes:
Required Privilege Level
interface—To view this statement in the
interface-control—To add this statement to the configuration.