I have two Windows server 2012 VMs that are DC and DNS servers. I set up DHCP on one with scope and configured fail over to the other VM that is also a DC and DNS server on another HYPER-V host.
After 3 weeks or so, they stopped leasing IP address. There where no errors and warning in either event Logs. Reboots etc.. made to difference.
In the end I had to put DHCP on a 2003 Server and have that leasing out the IPs.
I removed the role on both 2012 servers and rebooted. I then added the role on DHCP01 and saw that the scope database was still intact with exclusion, reservations etc.. I did not set back up the failover. I unauthorised the 2003 and authorised the 2012. All was fine for two hours or so and again no IPs. Back to 2003. In event logs there was database backup issues for DHCP. Forums stated AV and to exclude the DHCP folder. that was there already but stopped AV anyway. Switched back off 2003 and back on 2012, but the same after a while with no event logs.
I then 'moved' the role from DHCP01 to the other 2012 server, DHCP02, but the same would happen after a few hours with no errors.
The DHCP01 VM and DHCP02 VM are on different Hyper-V Hosts.
What can cause this to happen? I have other customers with server 2012 DHCP server with no issues.?