Error Joining ESXi To Windows Domain

I was trying to join 2 new ESXi 4.1 hosts to our AD domain and encountered the following errors.

The error message “Errors in Active Directory operations.” does not provide much clue.

I have make sure that the DNS settings on both hosts are correct and valid.  I have also make sure that the time on both hosts are in synch with the AD.

After a few attempts, I figured out that the error was caused by the format of the user name used to join the domain.

Using down level logon name (e.g. NetBIOS_Domain_Name\username) such as the one below will not work.

I will need to use the user principal name format (e.g. username@upn_suffix) such as the one below.

It is that simple.