While doing some NAT/private IP experiments with my experimental Virtualmin installation, I found the following problem:
The Vmin VM was reconfigured from a public IP to a private 10.* one.
I changed the option "System Settings / Virtualmin Configuration / Networking Settings : Default IP address for DNS records" to reflect the public IP, which gets forwarded to the private one via 1:1 NAT in a router.
Virtualmin noticed the primary IP address change and ushered me to the "Addresses and Networking / Change IP Addresses" dialog. I used that dialog to fix the IP address.
Result: Not only the virtual servers in Apache were IP-changed to the 10.* one, but also the BIND A records, despite the "Default IP address" setting above. Fail. ;)
(Creating new servers works okay: Apache gets the 10.* IP and BIND the public one.)