I found interesting issue while testing W2k8 with KVM. I used bridged network with br0 interface.
<interface type='bridge'> <mac address='52:54:00:...'/> <source bridge='br0'/> <model type='e1000' /> </interface>
Windows server was not able to reach network. Network card was on-line, but ping was not working and network was not reachable.
Then I found PilotJLR’s solution. I just removed line with model type=’e1000′:
<interface type='bridge'> <mac address='52:54:00:...'/> <source bridge='br0'/> </interface>
Then I redefined virtual machine and start it again:
virsh define virtual.xml virsh start virtual