How to change the logon DC to a new DC?

Question

Hi all,

We have several servers running on AWS, and our domain controller (DC) is located in an on-premises environment. Recently, we installed a new on-premises DC. However, we discovered that these servers cannot log in when we disable the network card on the old DC, as they are unable to locate the new DC server.

Could you please advise on where I should begin troubleshooting this issue? All FSMO roles are assigned to another Active Directory server at a different site, so I believe the problem is unrelated to the roles. Additionally, DNS is functioning correctly with the new DC, we need to ensure the new DC server is working before demoting the old one.

Thank you for your assistance.

Old DC: Server 2012R2

New DC: Server 2016

Answer 1

Hello KA CHEUNG TSE,

Thank you for posting in Q&A forum.

If there are multiple DCs at the same site, the machines at the site will randomly find a domain controller at the site for authentication.

Based on the description, I understand you have site and DCs as below.

Site one

Old DC: Server 2012R2 (also DNS server)

New DC: Server 2016 (also DNS server, it is RWDC instead of RODC)

Site two

DC with FSMO roles (also DNS server)

other DCs

Maybe other sites with other Domain Controllers.

Please check:

1.Domain client machines set IP of the new DC (DNS server).

2.Please run DCdiag /v on new DC to check health of new DC.

3.Please check AD replication between all DCs. Run commands below on PDC to check.

repadmin /showrepl >C:\rep1.txt

repadmin /replsum >C:\rep2.txt

repadmin /showrepl * /csv >c:\repsum.csv

4.Please check AD ports.

Active Directory and Active Directory Domain Services Port Requirements https://docs.microsoft.com/en-us/previous-versions/windows/it-pro/windows-server-2008-R2-and-2008/dd772723(v=ws.10)?redirectedfrom=MSDN

Active Directory Replication over Firewalls

https://docs.microsoft.com/en-us/previous-versions/windows/it-pro/windows-2000-server/bb727063(v=technet.10)?redirectedfrom=MSDN

I hope the information above is helpful.

If you have any questions or concerns, please feel free to let us know.

Best Regards,

Daisy Zhou

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