VPXA.log is not sufficient. Can we also take a look at /var/log/vmkernel.log, var/log/hostd.log, /var/log/vmkwarning.log on the ESXi host that we are failing to add to vCenter? Also as per KB Using NAT between the vCenter Server system and ESXi/ESX hosts (1010652) , using NAT between vCenter and ESXi host is unsupported.