This article provides steps to increase the maximum number of vNetwork Distributed Switch (vDS) ports designated for an ESXi 5.0/5.1 host.
Note: You may have to increase the maximum number of ports even if you have increased the maximum number of vNetwork Distributed Switch because a limit of 256 is set for ESXi hosts.
Symptoms:
When cloning a virtual machine that is part of a virtual Distributed Switch (vDS), you see this error:
Can not create DVPort port_number dvSwitch of VDS on the host-hostname fault.Dvs.Fault.summary