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DNS Resolution for Remote Sites

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)?
1 Solution
Yes it should. It will only use the secondary server if the primary server is offline.
hirenvmajithiyaManager (System Administration)Commented:
If you are running single domain, then all of your DNS will be having the same data.
So, you can use local DNS as far as it is available. In non-availability you can go to other(remote) servers.

If there are two DNS servers configured, by default the primary is used for DNS resolution. Since you are using the  local DNS server as primary, the traffic is confined locally

However, if the primary DNS server is down, the traffic will move to Secondary DNS

Another possibility is that if the primary DNS server is unable to resolve a particular record, it might contact the root hints/forwarders configured. In this case the traffic will move out of local.
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