I'm hoping someone here can assist or guide me in the right direction. We've recently completed a long-planned migration, but now we're running into problems. Here's what happened:
We set up a Server 2019 VM and went through several steps, including checking AD with dcdiag (no errors found), promoting the 2019 server as a domain controller, moving FSMO roles, and upgrading our domain and forest levels to 2016 before promoting our new Server 2025. We also demoted the SBS2011 and the Server 2019.
To maintain access, I added an A record in DNS to allow users to reach shared resources using the old server's hostname. The old hostname is 'grmserver,' and the new one is 'gmserver.' Despite the A record resolving correctly, we are now experiencing errors in dcdiag and nobody can access shares using the old hostname. The error states: '_Target principal name is incorrect_.' Any suggestions on what to check or fix next would be greatly appreciated!
3 Answers
Were you able to confirm that sysvol replicated properly before demoting the SBS? It’s also worth checking if the login speed issues mean your computers are still trying to connect to the old DC. If you ended up reusing the IP address for 'gmserver,' that could add complexity, but as long as everyone’s getting a new DHCP lease, you should be fine.
It sounds like the A record you added isn’t enough. Unfortunately, since you're using Kerberos for authentication, just changing the DNS isn't going to cut it. You might need to create a Service Principal Name (SPN) for the old hostname to avoid the '_Target principal name is incorrect_' error. You can use the netdom tool to help automate this setup. Good luck!
Just to echo the previous point, a simple A record can break Kerberos authentication. You may want to check that your clients are pointing to the new DC for DNS. It’s essential for everything to work smoothly. Also, did you happen to make a system state backup of the SBS2011 before you started making changes? That could help if you need to roll back or troubleshoot further.
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