I have a 2008 domain and I'm trying to add another DC to it, which is running Windows Server 2012r2
When I try to promote to a DC, it fails on prerequisite check with the following error:
Verification of prerequisites for Active Directory preparation failed. Unable to verify whether schema master has completed a replication cycle after last reboot.
Exception: Unavailable Critical Extension. Server extended error: 8366. Server extended message: 000020AE: SvcErr: DSID-03210384, problem 5010 (UNAVAIL_EXTENSION), data 8610
Adprep failed to verify whether schema master has completed a replication cycle after last reboot.
The schema is not upgraded.
Check the log file ADPrep.log in the C:\Windows\debug\adprep\logs\20151010161101-test directory for possible cause of failure.
I ran adprep manually on my 2008 DC and it said: Domain-wide information has already been updated.
Adprep did not attempt to rerun this operation.