The dcdiag utility is built into Windows Server 2008 R2 and Windows Server 2008. The tool analyzes the state of domain controllers in a forest or enterprise and reports any problems to help in troubleshooting. To use dcdiag, you must run the dcdiag command from an elevated command prompt. Dcdiag is available if you have the Active Directory Domain Services (AD DS) or Active Directory Lightweight Directory Services (AD LDS) server role installed. It is also available if you install the AD DS Tools that are part of the Remote Server Administration Tools (RSAT).