Move a Domain Controller to an Orphan Site.

If I demote one of the servers, it will disturb the communication among the other DC's as well

What is meant here?

I want to move one of DC's from one of the sites to an orphan site to cut off the traffic coming into that DC

If this will be permanent the you can perform cleanup to remove the DC from active directory.
https://video2.skills-academy.com/en-us/windows-server/identity/ad-ds/deploy/ad-ds-metadata-cleanup

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Hi,
Welcome to post here!
To know the questions more clearly, would you please tell more information following, if i misunderstand you ,please feel free to let me know:
All the DCs from one site(India) can communicate with DCs from the other site (China),right?
All the DCs within the same sites can communicates with each other, right?
When you said "move one of DC's from one of the sites to an orphan site to cut off the traffic coming into that DC", do you mean you want to create a new site ,and move one of the DCs into it?Or you just want to cut off the traffic coming into that DC?

Best Regards,

Hi,
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://video2.skills-academy.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

Now the question is, If I do so, then will it cut off the traffic coming in to that DC?

This is more a networking question. As long as there's no route between the two there will be no communications.

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