I have a network with:
1 x 2012R2 DC
1 x 2008 DC
1 x 2003 DC
The 2003 DC is working fine and is in the process of being retired and will be correctly DCPromo soon.
I am having issues with the 2008 DC though.
The group policy managements is showing that this DC is not in sync and is inaccessbile.
I can browse to the SYSVOL folder of that server from the other DC's.
I have checked the metadata cleanup to make sure there are no old servers lying around and all looks ok.
DCDIAG is fine on both the other servers.
If i run it on the 2008 server i just get FRS events.