vCenter Server and ESXi hosts that use Active Directory regularly validate users and groups against the Windows Active Directory domain. Validation occurs whenever the host system starts and at regular intervals specified in the vCenter Server settings.
For example, if user Smith was assigned permissions and in the domain the user’s name was changed to Smith2, the host concludes that Smith no longer exists and removes permissions for that user when the next validation occurs.
Similarly, if user Smith is removed from the domain, all permissions are removed when the next validation occurs. If a new user Smith is added to the domain before the next validation occurs, the new user Smith receives all the permissions the old user Smith was assigned.