DNS settings for DCs in remote sites

Question

I have our main DC here at the main site acting as the DNS server by itself, I have plans to put an additional one later. This is how its IP is configured

DC1
IP:  10.10.5.201/24
Preferred DNS:  10.10.5.201
Alternate DNS:  blank

I set up two additonal DCs at remote sites, connected through a VPN, and would like to have them all replicating. I wasn't sure on what the "Best Practice" is for setting DNS up on those remote DCs. Do I set the Primary as its own IP address? Or the IP of the DC at the main site? This is how I have it now

DC2
IP:  10.20.5.201/24
Preferred DNS:  10.20.5.201
Alternate DNS:  10.10.5.201

DC3
IP:  10.30.5.201/24
Preferred DNS:  10.30.5.201
Secondary DNS:  10.10.5.201

Is that correct? Or should I have the preferred DNS be DC1 for these two?

Answer 1

Not quite.

Every DC/DNS server hosting AD-integrated zones should contain '127.0.0.1' in its list of DNS servers, but only as the last entry.

Ideally, you want the "Preferred DNS" to be a different DC in the same site, followed by a different DC in a different site if possible, and then localhost at the end of the list. In your case where you only have 1 DC in one site, go ahead and make the Preferred DNS server one of the DCs in the other site.

Source: Microsoft Windows Server Best Practices Analyzer.

PS - Bonus reading: Search for "active directory island problem"