A. Sometimes you may experience a situation where you can't connect an ESX server to vCenter Server, or you can't connect directly to an ESX host using the vSphere Client. Perhaps you can't stop or start a virtual machine (VM), or a VM is shown as running when it actually isn't. Maybe you're getting the error message:
Virtual machine creation may fail because agent is unable to retrieve VM creation options from the host
In any of these cases, you might need to restart the management agent on the ESX host. You can do this from the host's Service Console with the commands
service mgmt-vmware restart service vmware-vpxa restart
Be cautious with these commands, as your Automatic Startup/Shutdown settings for VMs might force those VMs to restart. Setting your Automatic Startup/Shutdown settings to disabled first can prevent this restart from occurring.