Recently had a problem where DNS Entries for a server were disappearing in active directory. We set the records manually after multiple ipconfig /registerdns still would not hold the entry in active directory.

We removed the device from the domain and rejoined still to no avail (to check domain trust was not the problem)

In the end we had to set the DNS entry statically in some of the servers util we found out what was causing it to be removed.

Cause

‘Turns out the someone had configured the RAS server to assign DHCP address’ on the same range statically assigned where. This wouldn’t of caused an IP conflict due to clever RAS routing , however it would of caused the DNS issue we saw randomly ( whenever someone logged into RAS to assign themself an address! )