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Prerequisites for Deploying an RODC

Updated: April 26, 2012

Applies To: Windows Server 2008, Windows Server 2008 R2, Windows Server 2012

Complete the following prerequisites before you deploy a read-only domain controller (RODC):

  • Ensure that the forest functional level is Windows Server 2003 or higher, so that linked-value replication (LVR) is available. This provides a higher level of replication consistency. The domain functional level must be Windows Server 2003 or higher, so that Kerberos constrained delegation is available. If the forest functional level is Windows Server 2003, the domain functional level of all domains in the forest is Windows Server 2003 or higher.

    Constrained delegation supports security calls that must be impersonated under the context of the caller. Delegation makes it possible for applications and services to authenticate to a remote resource on behalf of a user. Because it provides powerful capabilities, typically only domain controllers are enabled for delegation. For RODCs, applications and services must be able to delegate, but only constrained delegation is allowed because it prevents the target from impersonating again and making another hop. The user or computer must be cacheable at the RODC for constrained delegation to work. This restriction places limits on how a rogue RODC may be able to abuse cached credentials.

  • Run Adprep.exe commands to prepare your existing forest and domains for domain controllers that run Windows Server 2008 or Windows Server 2008 R2. The adprep commands extend the Active Directory schema and update security descriptors so that you can add the new domain controllers. There are different versions of Adprep.exe for Windows Server 2008 and Windows Server 2008 R2. For more information, see Running Adprep.exe (http://go.microsoft.com/fwlink/?LinkID=142597).

    1. Prepare the forest and domains. There are three adprep commands to complete and have the changes replicate throughout the forest. Run the three commands as follows:

    2. Install Active Directory Domain Services (AD DS). You can install AD DS by using a wizard, the command line, or an answer file. For more information, see Installing an Additional Domain Controller (http://go.microsoft.com/fwlink/?LinkID=93254).

  • Deploy at least one writable domain controller running Windows Server 2008 or Windows Server 2008 R2 in the same domain as the RODC and ensure that the writable domain controller is also a DNS server that has registered a name server (NS) resource record for the relevant DNS zone. An RODC must replicate domain updates from a writable domain controller running Windows Server 2008 or Windows Server 2008 R2.

    An RODC that runs Windows Server 2008 R2 can replicate the domain partition from a writable domain controller that runs Windows Server 2008 or Windows Server 2008 R2. But if an RODC that runs Windows Server 2008 R2 is added to a domain that has only a writable domain controller that runs Windows Server 2008, the RODC logs Event ID 2916 in the Directory Services log. This error can be disregarded, and it will not appear if there is a writable domain controller that runs Windows Server 2008 R2 in the domain. For more information, see Known Issues for Deploying RODCs.

    For fault tolerance, deploy at least two writable domain controllers running Windows Server 2008 or Windows Server 2008 R2. An RODC can use the second domain controller for failover if the first domain controller is not available. The registration of the name server (NS) resource record is necessary to allow dynamic updates to replicate to the RODC by using a replicate-single-object (RSO) operation. For more information about how DNS updates are replicated to an RODC, see DNS updates for clients that are located in an RODC site.

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