After the upgrade from OES11 SP2 to OES2015 I am trying to make use of
the new features for AD integration. Joining the server to an AD domain
with YaST went through without obvious errors. The CIFS server is up and
running allowing eDirectory users to access the NSS volumes.
However, an AD user logged in on a Windows domain member will not be
able to access the data. Also trying to define a trustee for such a user
with the rights command gives the following error message:

Error in adding the trustee: Error: -9016. NITERR_AD_NOT_REACHABLE.

So clearly something is still wrong. As I am not very much experienced
with Microsoft AD I am asking for suggestions on how to troubleshoot this.