I have a simple setup with three sites, each with a Windows 2012 R2 and linked by VPN to the other sites. No domains are involved, the servers are set up using Workgroups and generally work independent of each other. Now I'd like users to be able to access PCs on the other sites by hostname. For this I'd like to setup the DNS server role on the servers. So far, that's easy and I've done that for single sites before.
The question is how do I set up the separate DNS installations so that I don't have to register the individual A-records manually on each of the three servers? As I don't trust that the VPN is always up, I'd like to keep a copy on each of the servers that is somehow replicated to the others. That "somehow" is the question. (Please note again that there are and will be no domain controllers.)
Thanks for your support,