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virsh 0.9.10 Enterprise Linux 6.3 I have a Windows 7 guest running on the KVM host and am frequently seeing 25% loss when pinging other boxes on the same subnet. The first ping request times out, and the others usually succeed. How would I go about troubleshooting possible packet drop or errors on a Windows guest? I did ifconfig on the KVM host and see no dropped or error packets.

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Just some thoughts:

  1. disable tso and lso on the host
  2. set the bridge DELAY=0
  3. use the virtio network card in the VM
  4. If bonding is in use, try a different mode
dyasny
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    I would love to hear some more in depth explanations for those 4 suggestions if you don't mind. –  Apr 10 '13 at 13:08
  • 1. buggy drivers, especially bnx2 in conjunction with some bcom firmware versions can cause weird issues. 2. This is especially important with live migration, but if a VM comes up and down often, it can also play a role in a network coming up in time. 3. this is best practice, virtio is PV and performs much better than e1000/rtl. 4. some bonding modes are known to not work with bridges at all (0 and 6), others, have been observed to cause network issues with different switches – dyasny Apr 10 '13 at 14:11