I have a client that has a primary data center containing three domain controllers. They also have five buildings across town connected by a Metropolitan area network. Initially, they did not have domain controllers in all of the remote buildings and their WAN links were saturated with traffic making accessing files from the data center slow.
In an effort to reduce congestion across the WAN, we installed domain controllers in each remote building to keep logon traffic and DNS name resolution in the remote building. We configured DHCP to assign the local buildings DNS server as a primary DNS server and the secondary DNS servers located in the data center (across the wan link). We configured Sites and Services with the proper sites and subnet information and created sites links with a cost of 50 for the remote building and a cost of 100 for the remote data center.
My question is when a workstation in a remote building needs to query DNS for a resource on the domain, should that traffic stay local to the remote building (Site)?