Prerequisites for Adding hosts to vCenter
Verify that you have sufficient permissions to create a host object.
Verify that a Datacenter, folder, or cluster exists in the inventory.
Obtain the user name and password for an account with administrative privileges on the host.
Verify that hosts behind a firewall are able to communicate with the vCenter Server system and all other hosts through port 902 or other custom-configured port.
Verify that all NFS mounts on the host are active.
When you Enable Lockdown Mode, it disables remote access for the administrator account and vCenter Server takes control of this host. Selecting this check box ensures that the host is managed only through vCenter Server. You can perform certain management tasks while in lockdown mode by logging into the local console on the host.