Logic for DC selection for authentication within the same AD site

Question

Hello All, I am working on extending AD service from an existing data center to a new data center. As part of co-existence, I have created new DC's in the new data center but kept them as part of the AD site in the existing data center. Both the data centers
have a 1 GB connectivity.
What I would like to know is - would there be any internal logic in calculating which DC should a client authenticate against based on network latency or something like that ? I wanted to know if there was any way I can restrict the user workstations at
the existing data center location (which is also the HQ location) to authenticate against the DC's available locally instead of travelling to the new DC's at the new data center, within the same AD site. I cannot make the new data center a separate AD site
for now due to the migration challenges.
Any inputs would be highly appreciated. Thanks in advance.

Answer 1

Hi Goldy,
I will recommend you to create a separate AD site and configure sites and services accordingly, if you dont want clients to authenticate against the new DC.
DC locator is the service name which is responsible for assigning a logon DC to the client.
If the DC's are in different sites you can configure the sites and services to point the client to correct DC in a site. AD authentication always distributed based on the sites and services you configured.
You can configure ldapsrv records to authenticate against specific DC.
Domain Controller Locator : an overview
http://blogs.technet.com/b/arnaud_jumelet/archive/2010/07/05/domain-controller-locator-an-overview.aspx
How DNS Support for Active Directory Works
http://technet.microsoft.com/en-us/library/cc759550(WS.10).aspx
LdapSrvWeight & LdapSrvPriority
http://blogs.dirteam.com/blogs/carlos/archive/2006/05/10/How-to-lessen-your-PDC_1920_s-load.aspx 
http://technet.microsoft.com/en-us/library/cc816793%28WS.10%29.aspx 
How
Domain Controllers Are Located in Windows
http://support.microsoft.com/kb/247811
Regards,
Rafic
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