I would like to know what duplex (half or full) my network card has negotiated with a switch when they are both set to auto configuration in Windows.

11 Answers 11


At command prompt:

powershell "Get-NetAdapter | SELECT name, fullduplex | where name -eq 'card name'"



Without looking at the switch, the only way it seems possible is if the windows driver for your NIC reports this information. To see if it does, go to Control Panel --> Administrator Tools --> Event Viewer. You then want to look at the System logs (in Windows7 this is under the Windows Logs tree). Once you found the System logs, click on Source at the top to use as the sorting criteria. Now look for your NIC driver, mine for example is b57nd60a. Scroll through all the entries that your NIC driver has made and if you're lucky you'll see what speed it negotiated at in the event report.

  • This is a pain in the ass, but it works, thanks. I sorted by Source, and found b57w2k (for a BroadCom chip) and then looked at the history of it configuring it self. Dec 23, 2009 at 23:35
  • +1. Worked for me. Searched for my NIC brand name (Marvell in this case) and jumped right to it. Mar 9, 2012 at 5:48

Type the following into command prompt:

wmic NIC where NetEnabled=true get Name, Speed

It should tell you.

  • 2
    Could you provide sample output?
    – Insane
    Oct 31, 2015 at 2:40
  • This worked great for me in Windows 10! Thanks. Dec 18, 2015 at 22:16
  • 1
    That doesn't appear to list whether or not it negotiated at full-duplex. Perhaps "get Name,Speed,AutoSense" gives that to you?
    – Wodin
    Apr 28, 2016 at 8:17

With Powershell run:

Get-NetAdapter | SELECT name, LinkSpeed, fullduplex | ft -autosize

enter image description here


Some cards (Intel for example) have a diagnostic suite that shows this information. This software is often not installed. Usually just the driver is installed and the diagnostic/management app is not. I believe the Intel app is called ProSet


This works in Windows 7, not sure about lower versions:

  1. Right click on the network card in Network Connections in the Control Panel
  2. Click Configure
  3. Click the Link Speed Tab
  4. Look at the Link status Window.

enter image description here

  • 6
    This one would work with lower versions of Windows but it is relevant only to certain network card drivers. Basic drivers and most drivers from other manufacturers than Intel will not show the information. Jan 24, 2014 at 9:36

Yes it's easy to see the speed 10/100/1000Mbps, windows tells you and the LEDs tell you, the person was asking about Full/Half duplex, which can be at any connection speed 10/100/1000Mbps.


The easiest way I can think of is to get a switch that has lights on the front or a management interface and simply take a look.

Other than that, I am not really aware of any software able to tell you.


There is no software-way to report the duplex mode negotiated(especially with a switch) because all of those things happen on the physical layer.

You will need some kind of measurement device to diagnose that electronically.

  • I waffled between serverfault and superuser, imo it's suitable for both, if the mod's think otherwise I wouldn't object. Dec 23, 2009 at 23:38
  • ethtool does it on Linux, so software interfaces to get to the info exists. Nov 26, 2018 at 8:13
  • It depend on OS driver model. If it in windows fully leaved on drivers, than OS no necessarily have such information. Feb 1, 2020 at 11:47

On my Windows 7 Platform -

  • List item

Type at the Windows 7 search bar Network and Sharing Center. Select - Network and Sharing Center

Change Adapter Settings

Right Click ( The LAN Lannetwrk Adapter) select Status it will show you the speed you have negotiated with the next network device up stream.

  • 1
    Link speed is unfortunately not the same as Duplex. It is possible to be Half Duplex 100mbps for example. Dec 11, 2014 at 2:22

There's no need to spend an hour in the event viewer :

Inside "Network Connections", right click -> "Status".

Here you can see "Speed".

step 1

step 2

  • 2
    Unfortunately Speed does not indicate the status of Duplex in ethernet on Windows. It is entirely possible to be 1.0 Gbps and half-duplex Aug 29, 2016 at 22:14
  • There's actually no such thing as half-duplex gigabit Ethernet. Nov 11, 2019 at 2:21
  • @NicolasMelay en.wikipedia.org/wiki/Gigabit_Ethernet half-duplex is a thing in 1000Base-T and unfortunately I have seen it in the wild due to cable damage and auto-negotiate. Which is what prompted this question originally. Oct 22, 2021 at 21:09

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