I have installed a DC – Let’s call it as DC1

I have installed a Second DC using (Additional Domain Controller for an existing domain controller option) – Let’s call it as DC2

Can anyone tell me:

1) If DC1(PDC) goes down, will DC2 (ADC) take over automatically i.e fail over mechanism on Domain controller????

2)When DC1 Goes Down, DFS can not be Queried /Accessible.

3) Why We Use ADC i.e ADC provides which Network Services ?

4) I want to have the complete automation fail over mechanism of domain controllers.

please guide me how to set up ADC in such a way that complete automated.

thnx in advance


To answer these questions we will need some more information, but more on that in a minute.

The Background (skip if needed)..

Each DC in an Active Directory contains a writeable version of the database, and each DC can make changes to objects within the domain. Each change is then notified and replicated to other DC's in the domain (replication is a complicated beast and this is a very basic explanation). As such there aren't really Primary DC's (although there is a domain role called the PDC Emulator) and Backup DC's like there were in a Windows NT domain, and any DC that is functioning correctly is used to service authentication requests from members.

But back to your the questions.

  1. If we are talking about user authentication and access control, then yes. However if we are talking about the FSMO roles that were currently assigned to DC1 then no, these will be unavalible untill DC1 is back online.

  2. I would not expect this and it sounds like DC2 isn't configured properly. Try running DCDIAG from a cmd prompt to determine if the domain is 'healthy'.

  3. I am not sure I understand the questions, but AD does require and depend heavily on DNS and I would recommend that it is installed on each DC and that you configure DNS to store its database within AD.

  4. I think I have covered this in the breif background I gave, but AD is running on any DC all of the time. And failing over, typically called seizing, FSMO roles really isn't recommended unless the DC is going to be unavalilbe for an extended amount of time.


  • you might want to tag this post with active directory as well to get more hits – commandbreak Feb 8 '10 at 8:52

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