How to check the interface duplex mode of an AR router

Duplex modes:
- Half-duplex: An interface can either receive or send data at one time. The maximum transmission distance is also limited.
- Full duplex: An interface can receive and send data simultaneously. The maximum throughput can be twice of the interface rate. In addition, the transmission distance is not limited.

You can run the display interface ethernet brief command to check the brief information about the Ethernet interface of a router, including the physical state, auto-negotiation method, duplex mode, rate, and average bandwidth utilization rate in the receiving and sending directions in the recent period of the interface.

In the displayed information, the Duplex column indicates the duplex mode of the interface, which can be one of the following modes:
? full: Indicates that the interface works in full-duplex mode.
? half: Indicates that the interface works in half-duplex mode.
? In auto-negotiation mode, you can run the auto duplex command to configure the duplex mode of an interface.
? In non-auto negotiation mode, you can run the duplex command to configure the duplex mode of an interface.

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