I have two redudant Windows Server 2012R2 domain controller. The DNS is active directory integrated. Which order of dns ip address should the two domain controller have and why? Are there experience of Microsoft? Thank you in advance!
They should be looking at one another first. 127.0.0.1 second.
No matter how many domain controllers you have, you should always configure your DCs to look at another DC in the same site first for DNS, then a DNS server in another site if applicable, and 127.0.0.1 should always be listed as the last DNS server.
Source: Microsoft Best Practices Analyzer.
Even though the "island" problem that would occur when a domain controller looked only at itself for DNS has been largely mitigated, there are still rare situations where it can occur.
Secondly, a domain controller needs to look to another domain controller for DNS first, because it will cause delays in boot up time and take services longer to start up on that domain controller if the DC starts up and doesn't have an already-online DNS server to make queries to.