For Moving a Domain Controller to a Different Site
You can refer to the following procedures in order:
Chane the static IP address of a domain controller
Create a delegation for a domain controller
If the parent DNS zone of any zone that is hosted by this DNS server contains a delegation to this DNS server, use this procedure to update the IP address in all such delegations.
If your forest root domain has a parent DNS domain, perform this procedure on a DNS server in the parent domain. If you just added a new domain controller to a child domain, perform this procedure on a DNS server in the DNS parent domain. By following recommended practices, the parent domain is the forest root domain.
Verify that an IP address maps to a subnet and determine the site association
Determine whether the server is a preferred bridgehead server
Configure the server to not be a preferred bridgehead server
Move the Server object to the new site.
For more details you can refer to :https://learn.microsoft.com/en-us/previous-versions/windows/it-pro/windows-server-2003/cc739015(v=ws.10)?redirectedfrom=MSDN
Then when moved the DC successfully, you can cut down the traffic between from the new sites to other sites.(Make sure that the DC was acted as a DNS server also, or if you but down the traffic, the name resolution will not work.)
Active Directory Replication over Firewalls