http://blogs.technet.com/b/askds/ar...indows-server-2012-r2-domain-controllers.aspx
We have been getting quite a few calls lately where Kerberos authentication fails intermittently and users are unable to log on...
Anyway, weve been getting more calls than normal about this lately, and that led us to take a closer look at what was going on. What we found is that theres a problem that can manifest when you have Windows Server 2003 and Windows Server 2012 R2 domain controllers serving the same domain.