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Is there a way to find out the duplex setting of a NIC?

Is there a way to find out the duplex setting of a NIC? I have heard that a good way to determine the duplex setting of a switch is to set the PC's NIC to "auto," reboot, and see what settings the NIC has established. But there seems no easy way to see the settings.

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The method you described to determine the duplex setting of a network card is not totally correct, or could be for certain Windows versions. Setting the network card to 'auto' on Windows XP will have no effect as the setting will remain in 'auto' mode, without showing you the actual mode it is in. In other versions of the operating system it might work, but I am unsure.

The best way obviously is to check the switch you are connecting to as almost all network switches have led indicators that will show you the duplex mode your network card has been set to. In some cases, such as Cisco, you are also able to telnet into the switch and check the port status, obtaining a wealth of information for any required port.

Closing, I would suggest you visit sites such as and, searching for network tools which might be able to provide you with the information you require.

This was first published in September 2004

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