This is excerpted from my latest book Training Guide: Installing and Configuring Windows Server 2012 from Microsoft Press:
The Dsquery.exe command-line tool can be used to verify whether Adprep has extended your forest's schema. For example, let's say your existing forest has domain controllers running Windows Server 2008 R2. To determine the current schema level of your forest, open a command prompt on one of your domain controllers and run the following command:
dsquery * cn=schema,cn=configuration,dc=fabrikam,dc=com -scope base -attr objectVersion
The output from this command looks like this:
Now take a server running Windows Server 2012, join it to a domain in your forest, and use Server Manager to promote the server to a domain controller. After you finish introducing the new domain controller into your forest, re-run the preceding dsquery command on the domain controller you previously ran it on. The output from the command looks like this:
The version number 56 indicates that the schema of your forest has been extended to include domain controllers running Windows Server 2012.
Mitch Tulloch is an eleven-time recipient of the Microsoft Most Valuable Professional (MVP) award and a widely recognized expert on Windows Server and cloud computing technologies. Mitch is also Senior Editor of WServerNews. For more information about him see http://www.mtit.com.