Hyper V host server and guest server lose network connectivity.


  • Hi all

    I am running a 2008 R2 server with Hyper V. I have 5 virtual servers running on it. For the last 2 weeks the virtual servers and the host lose network connectivity. I have to physically reboot the host server to get the network access back.

    Let me know if you need more info?

    Thank you

    Friday, March 23, 2012 6:35 AM

All replies

  • It should be due to high usage of network...check out the url for ref..

    The network connection of a running Hyper-V virtual machine is lost under heavy outgoing network traffic on a Windows Server 2008 R2-based computer


    Exchange Queries

    Friday, March 23, 2012 7:36 AM
  • Hi thanks for the reply but I have already applied the hotfix discussed in KB974909. That also only applied to the guest os losing connectivity. I my case both the Host and guest lose connectivity. I have to logon to the console and restart the host server to get connectivity back. What I have done now is setup a second nic for the Virtual network switch and now if the VM's lose connection the HOST can still be access via the network. I still have to reboot the host to get the VM's to access the network again.


    Friday, March 23, 2012 8:33 AM
  • Hi,
    Let me have an analysis of your environment.
    1. You have one network adapter used for both virtual machines(External Virtual Network) and Hyper-V host management. And you encountered some networking lose issue with both virtual machines and Hyper-V host machine.
    2. You dedicated one network adapter for Hyper-V host machine, another one dedicate for virtual machines(External Virtual Network). In this case, only the virtual machines had networking lose issue.
    If there are any misunderstanding, please feel free to let me know.
    If above is true, you may try to disable TCP Offloading to see whether you can resolve the issue.

    Vincent Hu

    TechNet Community Support

    Friday, March 23, 2012 9:14 AM
  • Thank you Vincent

    Yes you are correct. Can you please tell me exactly were to disable the TCP Offloading? I now of the Parameter in the registry “HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\TCPIP\Parameters\DisableTaskOffload” is this the correct place?

    I thank you for your help.

    Friday, March 23, 2012 12:02 PM
  • Have you checked the settings of the physical NIC driver (on the hypervisor) and verified that any power management is disabled?

    Brian Ehlert
    Learn. Apply. Repeat.
    Disclaimer: Attempting change is of your own free will.

    Friday, March 23, 2012 2:50 PM
  • no.

    Do not disable "TCP Offload" that is actually TCP Chimney.

    Disable TCP Task Offload - these are a bunch of individual driver settings.

    But, you should not do this unless your guests are having problems or you applications are having problems - the big symptom is that the network appears slow.

    This symptom does not match your description.

    Brian Ehlert
    Learn. Apply. Repeat.
    Disclaimer: Attempting change is of your own free will.

    Friday, March 23, 2012 2:52 PM
  • Hi. Thank you Vincent and Brian.
    I have disabled TCP offload and left it for the weekend and the servers are still running. Even asked the users to hammer the system and it still stayed up.
    I will still monitor the servers but usually it only stayed up for 3 to 6 hours before the connection was lost and the host needed a reboot. Fingers crossed.

    Thanks again guys..

    Monday, March 26, 2012 11:12 AM