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Duplicate MAC address – PowerShell Script to rescue

Today, in out office we were facing a interesting problem. Every now and then one of the VM will timeout. This was causing lot of issues. The VM was in production. This VM was created few days ago and everything was running fine. We were not sure what was causing the problem.
We looked at couple of things like ;-

  1. Network issue
  2. Switch issue
  3. May be the VMware tools had a problem this VM is using VMXNet3 adapter.
  4. Logged a call with VMware support and they wanted config logs for Networking switches – Network Manager was not at all happy when he heard that.

I just realized may be there might be a Duplicate MAC somewhere on the network that might be causing this problem. Here comes powershell to rescue. Did a google and found this nice script , from vNugglets which can tell us if there are any duplicate address on the network.

After running the script, we did find that there was indeed duplicate MAC address on the network which was causing this issue.
Thanks for the script it saved us lot of time.

On a side note :- I was wondering if there are duplicate MAC address across multiple VCenter Server, how are we going to troubleshoot that. Need to do some research to get answer to that question.

3 ResponsesLeave one →

  1. D-Day

     /  October 5, 2011

    Hello, vcpguy
    Good, glad that the "find duplicate MAC" script useful/helpful.
    As for your side note about finding duplicate MAC addresses across multiple vCenter servers — no problem:  thanks to the (default) behavior of the Connect-VIServer cmdlet, you can just connect to all of the vCenter servers that you want (at the same time), and then run the code to look for duplicate MAC addresses.
    We posted about that topic a while back at  Give it a read for more info.  Enjoy

  2. This is excellent man. i just tested it with different version of vCenter server one was vCenter 4.1 and the other was vCenter 5 and they both worked like charm.

    Thanks for your efforts.

  3. Cameron Spaziani

     /  October 21, 2011

    I don’t even know how I ended up here, but I thought this post was great. I don’t know who you are but certainly you’re going to a famous blogger if you aren’t already ;) Cheers!


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