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Hyper-V Virtual Networking Chicken and the Egg

Virtual networking is very interesting.  I ran into the issue with applying an external virtual switch to an interface within Hyper-V Server 2008 R2 when still using that interface to access the server.  This seems obvious, but since the cards can sometimes grab DHCP, you may find yourself in this predicament.   The error I received was:

“error applying new virtual network changes”, with “binding to external Ethernet… failed”.  “Cannot bind to … because it is already bound to another virtual network”.

To fix it I opened the command prompt on Hyper-V Server 2008 R2 and ran:

  1. netcfg -u vms_pp
  2. netcfg -l c:windowswinsxsamd64_wvms_pp.inf_31bf3856ad364e35_6.1.7600.16385_
    none_beda85050b13680cwvms_pp.inf -c p -i vms_pp

Have a good day.



Nathan Lasnoski is the Director of Concurrency’s Solutions, a Datacenter MVP and a recognized leader in Core Infrastructure Design, SharePoint Infrastructure, Virtualization, and Unified Communications technologies.

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  • Nathan Lasnoski
  • http://YourWebsite john

    I did step one and step 2 failed. This killed my whole hyperv cluster communication. Live migration wont work no more. What can i do to reverse.


  • http://YourWebsite john

    I have fixed it my self. Your step are dangerous. Thanks God its fixed now.