I have 4 ESXi 5.5.0, 2403361 servers in cluster, running 50 virtual machine. Yesterday 2 of my VM was not able to communicate via the network. I restarted the two VM's, but still same problem. I then moved one of the VM to another host, then the VM suddenly replied on ping. I then moved the VM backed to the host it was originally (when it not answered on ping), and network was still OK..... Can anyone explain this for me... ?
It happens due to host OS firewall service also. Indeed disconnection \ reconnecting vNIC and checking changing/resetting vLAN tagging helps however firewall service is culprit if that does not resolve issue and repetitive behaviour is observed.
If this is still reproducible, it would be interesting to see whether the VMs can communicate with other VMs on the same host (same vSwitch)!? If this is the case there might be an issue with either one of the vmnics assigned to the vSwitch, or even an issue (e.g. ARP table, allowed VLAN) on the physical switch.