One of the most lauded features of vSphere 4.1 is the built-in Active Directory authentication engine for ESXi hosts. It’s very easy to configure, and it works for both free ESXi installations as well as hosts managed by vCenter. The Active Directory-integrated security is configured in the Authentication Services section of each host (see Fig. 1).
So, while configuration is easy enough, I have confirmed with Microsoft that it’s not that easy to manage from a licensing perspective. As it turns out, enabling Active Directory-integrated security to the ESXi host creates a computer account for each host. It’s actually similar to what XenServer did in the 5.5 release, when Citrix added Active Directory authentication.