Using multiple Active Directory domains in VDI-in-a-Box 5.4
Multiple Active Directory (AD) domains are a must-have for most government organizations, and many businesses due to security needs, regulatory compliance requirements, or geographically distributed offices (http://technet.microsoft.com/en-us/library/cc780856(v=ws.10).aspx) whenever the Organizational Unit (OU) feature of AD is not adequate (http://social.technet.microsoft.com/Forums/windowsserver/en-US/064aa5c9-f040-45b6-b36a-38d1823c16a1/active-directory-design-multiple-domains-or-organizational-units, http://searchwindowsserver.techtarget.com/tip/Domains-vs-organizational-units-in-Active-Directory). VDI-in-a-Box requires you to configure one AD domain for both users and computers during its initial setup. Previous versions of VDI-in-a-Box allow you to optionally configure one additional AD domain only for computers (virtual desktops) as described in http://support.citrix.com/article/CTX136845.
Being able to specify only one AD domain for the users in VDI-in-a-Box is not a major limitation because VDI-in-a-Box does a look up of the Global Catalog (GC) if a user logs on with User Principal Name (UPN). See http://msdn.microsoft.com/en-us/library/windows/desktop/aa380525(v=vs.85).aspx for details of UPN. However, the limitation of one additional AD domain for computers (total up to 2 computer domains) can be limiting in certain scenarios.
To learn more, read the entire article here, Using multiple Active Directory domains in VDI-in-a-Box 5.4 – Citrix Blogs