Active Directory domain controllers changes

Question

I'm writing to ask for your opinion about this.

SCENARIO

I have domain.local (forest and domain tree root) with these domain controllers:

DC1 | SO: Windows Server 2008 R2 | Roles: Schema, DomainNaming, PDC, RID, Infrastructure, DNS Server

DC2 | SO: Windows Server 2008 R2 | Role: DNS Server

DC3 | SO: Windows Server 2012 R2 | Role: DNS Server, DHCP Failover Load Balance Mode

DC4 | SO: Windows Server 2012 R2 | Role: DNS Server, DHCP Failover Load Balance Mode

Notes:

They are all Global Catalog.
DHCP is configured to assign DC1-IP1 and DC2-IP1 as primary and secondary DNS respectively to clients.
DC1-IP1 and DC2-IP1 are used as primary and secondary DNS (static) on servers and related applications

Assign DC1-IP1 to DC3
Assign DC2-IP1 to DC4
DC3 and DC4 will have only one IP Address: 172.16.1.10 and 172.16.1.20 respectively.
Dismiss DC1 and DC2

These are steps I intend to follow:

Then apply the steps above (from 2 to 7) for DC2 and DC4.

What is your opinion ? Do you suggest to switch between steps ? Or do I forgot something ?

Thank you a lot.

Regards, Luca

I don't get why you're making it so complicated. Follow Removing a Domain Controller from a Domain to remove any DC you want. Just deploy a server that has the right configuration and add it as a DC to the domain instead of juggling all that junk. Is there a specific reason that it's not an option? — Seth, Apr 6, 2017 at 13:21
"Removing DC" is listed in my steps but set as last operation. "Just deploy a server": I already have it; it is DC03. So I think my steps are simply detailed but what you propose is pretty the same I wrote (I think) — CyberLuke365, Apr 7, 2017 at 15:13
Not entirely. Instead of having an establish DC that you try to coax into taking the role of DC1, I'd opt to decommission DC1 and setup a new DC in it's place that has the correct configuration from the get go. Change the static IP of a DC would make your plan valid. Still I feel like it's a bit complicated, though you probably have your reasons. — Seth, Apr 7, 2017 at 16:20

Jose Ortega · Accepted Answer · 2017-04-07 15:27:55Z

If you want to remove DC1, DC2 and DC4.

Move all AD Roles from DC1 to DC3.
Change DHCP to give just DC3 as DNS (check time for DHCP to lease IPs) and wait that time, so all the clients' computer get the new DNS).
Demote DC1, DC2 and DC4 (to check replication check, AD sites and services that should be all running ok. Since you will only have 1 DC in the domain.

For best practices Microsoft recommends to use 2 domain controllers at least on the same site.

UPDATED

Move all AD Roles from DC1 to DC3.
Change DHCP to give just DC3 as DNS (check time for DHCP to lease IPs) and wait that time, so all the clients' computer gets the new DNS).
Demote DC1 and DC2
Change IP from DC4 to the one that had DC2. (now you have DC4 with DC2 IP)
Change DHCP to give just the IP of DC2 as DNS (wait the time)
Change IP from DC3 to match old DC1 (now you have DC3 with DC1 IP)
Add DHCP to give IPs from DC3 and DC4 as DNS

I don't want to remove DC3. To simplify: I need to have DC3 and DC4 with IP addresses of DC1 and DC2 respectively. And remove DC1 and DC2 from infrastructure. I know how to do this, I'd like to know better steps order. — CyberLuke365, Apr 7, 2017 at 15:17
I have updated the answer (I thought you wanted to have just DC3, (not DC4). — Jose Ortega, Apr 7, 2017 at 15:23