[libvirt-users] Windows 2008r2 guest tcp retransmit hangs

Hi, I'm currently investigating a problem with our windows 2008r2 guest on centos 6 hosts. The issue is that the windows system sometimes sees a SYN packet for a tcp connection but doesn't respond. Three seconds later the retransmitted packet arrives and this time windows decides to proceed normally with the connection. This is with the virtio drivers but I have now switched to the e1000 driver where the problem also occurs but not quite as badly as with virtio which leads me to speculate that the driver isn't really the problem but only affects whatever the real issue is. Also this does not happen when the systems primary IP is addressed directly but only when an IP on the loopback device is addressed through a load-balancer. I've also provisioned a linux guest on the same host and put that into the load balancer as well but there everything is fine. Has anyone run into this and can provide a pointer in the right direction? Regards, Dennis