Currently we have a site-to-site VPN setup between our two locations A and B. Location A has the domain controller; all hosts in location B connect via the site to site VPN to the DC in A. I was wondering if this is not ideal because if either Internet connection goes down, or the VPN/firewall server gets messed up, ii) the hosts in B cannot connect to DC on A, and more importantly, ii) the primary/secondary DNS servers on the domain are both located in A. Please advise on the best practice to alleviate this potential issue.
Promote a DC in Site B, create two sites in AD, then assign each domain controller to its appropriate site. Also, install DNS on this server, and use it as the primary for all hosts in Site B.
Ideally, the hosts in site A would use the local DNS server as primary and the DNS server at the opposite site as secondary. Vice-versa for hosts in Site B.
While you could set up a DC/DNS server in site B, I have to ask: where are the resources that the users use located? If the resources are in site A then it really doen't add any value to set up a DC/DNS server in site B. If site A is unavailable and that's where email, file, database, etc. services are then the clients ability in site B to log on to the domain via a local DC doesn't do much good.