I came across an odd situation recently whereby my AADConnect installation had decided to communicate with a Domain Controller which was in another site, across an Active Directory replication link with a 180 minute replication interval. This was no good for my customer as they made their AD changes on the site local to AADConnect, so I decided to remedy this by forcing AADConnect to communicate with a particular DC. This can be useful for many reasons, and you can actually set a list of ‘preferred Domain Controllers’ to allow for fault tolerance.
To do this, go into the Synchronisation Service, head on over to the Connectors tab and find your Active Directory Domain Services Connector. The below example is synchronising multiple AD Forests. Once you’ve selected your domain, you can see which Domain Controller is currently in use by checking the ‘Connection Status’ area (shown in the central area of the below screenshot).
To change the Domain Controller in use, go to the Properties tab for your domain (on the right hand ‘Actions’ pane). Go into the ‘Configure Directory Partitions’ tab and you will see a handy tick box entitled ‘Only use preferred domain controllers’.
Place a checkmark in this box, and a window will appear, allowing you to enter your shortlist of Domain Controllers.
Once you’ve entered your preferred DCs, OK your way out of these windows and hey presto, you are done! It’s a nice and easy task to perform, but not one I’ve seen documented online before.
Thanks for reading!