Host Hyper-V server is getting it's Authentication/DNS from a DC that I need to remove. How do I proceed

Active Directory is a multi-master topology, so as long as your DC is healthy, advertising, and working properly (use dcdiag to check this) machines will seamlessly move among available DCs. They won't lock onto and authenticate against only one. So you can remove a DC easily and transparently without extra steps.

You will however want to ensure that the DC you are rebuilding does not hold the FSMO roles, and if it does transfer them to the DC that will remain active during this period.

So lets say the physical DC is off.  If I reboot the Host Hyper-V server, it will authenticate to the VM on itself that is the DC?

All FSMO roles have been moved to the VM DC.

That's what I thought.  Does it need to be a DNS server?

Thanks

got it.  It will using the existing scope that exists on AD, correct?

Scope?

Sorry, was thinking DHCP.  I just checked it has the proper "Zones"

So I am not sure there was a question there, but the rule is the same as it is for a domain controller. You want to make sure a DNS server is always available. If that means making a temp DC also be a DNS server then do that.

got it.  All is good.

Thanks

Final question.  I have the DHCP scope split over two DC.  If the DC that I'm shutting down is one DHCP and the other is the VM, is that a problem?

Thanks for all the help