KB974909: Heavy Outgoing Network Traffic Causes Hyper-V Network Outages

Microsoft released a patch for Windows Server 2008 R2 Hyper-V host servers.  It fixes a problem where VM’s are experiencing heavy outgoing network traffic loads.  This can cause the virtual NIC to fail and the only way to fix it (otherwise) is to restart the VM.

“Consider the following scenario:

  • You install the Hyper-V role on a computer that is running Windows Server 2008 R2.
  • You run a virtual machine on the computer.
  • You use a network adapter on the virtual machine to access a network.
  • You establish many concurrent network connections, or there is heavy outgoing network traffic.
  • In this scenario, the network connection on the virtual machine may be lost. Additionally, the network adapter is disabled.

Note: You have to restart the virtual machine to recover from this issue.”

This hotfix applies to

  • Windows Server 2008 R2 Datacenter
  • Windows Server 2008 R2 Enterprise
  • Windows Server 2008 R2 Standard

It requires the host to be rebooted.

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