Virtual Machine Goes Unreachable after vMotion or reboot

Hi Folks,

We are running newly configured VMware ESXi 5 node cluster. Each server having 6 NICs in which 2 NICs dedicated for Management and vMotion. Rest connnected to trunk ports for multi VLAN communication. In vSwitch 2 we have configured one port group for each VLAN with total 5 VLANs.

We observed our Virtual machines becomes unreachable from network if;

-DRS vMotion the VM

-Manual vMotion

-VM rebooted

Also this occurs randomly not on any particular machine and this is intermedient problem which doesn't not occurs all time but most time.

Please help me understand this issue and for the resolution of the same. Also if this is physical network issue how can I justify it?

Thank you,

Karthi.