Symptoms:
VMware vCenter Server 4.0.x
VMware vCenter Server 5.1.x
VMware ESX 4.0.x
VMware ESXi 4.1.x Installable
VMware ESXi 4.1.x Embedded
VMware vSphere ESXi 5.5
VMware vCenter Server 5.0.x
VMware vSphere ESXi 5.1
VMware ESXi 4.0.x Installable
VMware ESXi 4.0.x Embedded
VMware vCenter Server 4.1.x
VMware vCenter Server 5.5.x
VMware ESX 4.1.x
VMware vSphere ESXi 5.0
This issue occurs if jumbo frames (MTU : 9000) is enabled for the vMotion vmkernel port group, but is not enabled on the physical switch.