I am totally new to the servers. In our company domain & other configurations was done by another guy who had left already. So in our environment there are 3 domains i.e. D1 ; D2 & DR. D1 is the primary domain. So all the users should login in from either D1 or D2. But here in most of the cases users are getting logged in from DR . If the users gets logged in from DR then most of the times i get policy issue i.e. DFS is disabled. If they login from D1 & D2 everything works fine.
1st 2 servers are Windows server 2012 & the DR is Windows Server 2008
Please suggest me what to do so that all the users should get logged in from the 1st two DC's.