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Background:

Currently we are managing around 300 sites each hosting one 2012 R2 machine having the DNS server role installed.

All site-local clients are pointing to their respective site-local DNS servers. This servers, in turn, are configured as forwarders pointing to 2 out of 10 DCs (2012 R2 machines as well), which are hosted in a datacenter. We have only one single domain.

Problem:

DNS utilization is not equally distributed/load balanced across DNS servers in the datacenter.

Question:

If I configure each site-local DNS forwarder to contain all DCs IP addresses (and not only two of them), will the site-local DNS forwarder load balance (in a round robin fassion) the queries towards the DCs? What other recommendations can you give to optimize DNS queries/WAN traffic in this situation? I hope you get my question.

  • I have to be honest, this question doesn't make a lot of sense to me. This servers, in turn, are configured as forwarders pointing to 2 out of 10 DCs - What do you mean by that exactly? If you're talking about DNS queries for DNS zones that these servers are authoritative for then they'll answer the queries directly. You can't forward DNS queries for authoritative zones to other DNS servers. You must mean queries for zones that these servers are not authoritative for, correct? – joeqwerty Nov 2 '15 at 18:31
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No, it is like the network adapter DNS servers. It uses the first entry, and will only use the other entries if the preceding entry times out.

If you aren't configuring forwarders globally (per-domain/per-forest), you can configure a different order for the forwarders for each DNS server.

Using Forwarders
https://technet.microsoft.com/en-us/library/cc754931.aspx

"The order of the IP addresses that are listed as forwarders on a DNS server determines the sequence in which the IP addresses are used."

Configure a DNS Server to Use Forwarders
https://technet.microsoft.com/en-us/library/cc754941.aspx

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