I have a cluster with proxmox 4.4. Three nodes, two IBM x3400 and a small PC. The two IBM host ceph data, the third is only monitor. I added another server, HP DL380 G7, installed Proxmox 5.2 on it and joined to the cluster (still not ceph). I will later upgrade the other servers. I have a problem with some Windows Server VMs, when I migrate them to the new server they start losing pings. A particular VM, with Win2008r2, loses 80% of pings. Linux VMs have no problems. If I migrate back the VM to IBM, it doesn't lose any ping. I tried to replace the virtual nic from E1000 to RTL3189. The node has 2 nics (NetXtreme BCM5709) in bonding. I tried to disconnect one cable to exclude problems with bonding. Any other suggestion?