Whilst researching some of the finer points of Windows Server 2008 Read Only Domain Controller's (RODC's), I have been reading knowledge base article (KB944043) which details what happens if an RODC is in the environment and the legacy Windows infrastructure does not have the compatibility pack installed.
I found it quite interesting reading as I have heard in many presentations that apart from extending your schema and the introduction of a Windows Server 2008 DC - nothing else needs to be done to support an RODC. Issue 10 could cause hours of fun if you are not aware.
Issue 1
Symptom
If a client can access only read-only domain controllers, Windows Management Instrumentation (WMI) filters that are configured for Group Policy are not applied. Additionally, the Gpsvc.log file contains the following information:
GPSVC(410.8ec) 15:17:45:808 FilterCheck: Found WMI Filter id of: filter ID
GPSVC(410.8ec) 15:18:21:838 FilterCheck: Filter doesn't exist. Evaluating to false
GPSVC(410.8ec) 15:18:21:838 ProcessGPO:CheckFilterAcess failed for <cn=GUID,cn=policies,cn=system,DC=name,DC=name,DC=name,DC=com>. Filter not found
GPSVC(410.8ec) 15:18:21:838 CGPAdminEventInitFailure::Initialize(): FormatMessage failed to look up error code (0x80041002) due to error 317. Can not log error description.
GPSVC(410.8ec) 15:18:21:838 ProcessGPO: The GPO does not pass the filter check and so will not be applied.
Scenario and affected clients
This issue affects clients in a site that has only read-only domain controllers available.
Influence
The Group Policy object to which the WMI filters are linked may not be applied.
Workaround
No workaround is available for this issue if the compatibility pack is not installed
Issue 2
Symptom
Internet Protocol security (IPsec) policies cannot be applied and Win32 error code 8219 (ERROR_POLICY_OBJECT_NOT_FOUND) is returned when only Windows Server 2008 read-only domain controllers are available.
Scenario and affected clients
This issue affects clients in a site that has only read-only domain controllers available. Typically, this issue occurs in a branch office scenario.
Influence
Computers that are running Windows 2000, Windows XP, or Windows Server 2003 do not receive IPsec policies that are applied by a read-only domain controller.
Workaround
No workaround is available for this issue if the compatibility pack is not installed
Issue 3
Symptom
Windows Server 2003 member computers and Windows XP member computers do not synchronize Win32 time with Windows Server 2008 read-only domain controllers.
Scenario and affected clients
This issue affects clients in a site that has only read-only domain controllers available. Typically, this issue occurs in a branch office scenario or in a perimeter network scenario in which a writable domain controller cannot be contacted.
Note A perimeter network is also known as "DMZ," "demilitarized zone," and "screened subnet."
Influence
If the time of services is severely asynchronous, you may receive error messages when you try to access resources on the network.
Workaround
To work around this issue, configure the client computers to synchronize time from another domain controller that is available on the network.
Issue 4
Symptom
Computers in a perimeter network cannot join the domain.
Scenario and affected clients
This issue affects clients in a site that has only read-only domain controllers available. Typically, this issue occurs in a branch office scenario or in a perimeter network scenario.
Influence
Computers cannot join the domain even though the computer account and the password are pre-populated on the read-only domain controller.
Workaround
To work around this issue, create firewall rules to enable a writable domain controller to be contacted or bridge the perimeter network and intranet networks.
Do this only when your organization's policies allow for this operation.
Issue 5
Symptom
In a site that has only read-only domain controllers available, users try to change their passwords on computers that are running Windows 2000, Windows XP, or Windows Server 2003. When the users do this, the password change operation fails.
Scenario and affected clients
This issue affects clients in a site that has only read-only domain controllers available. Typically, this issue occurs in a perimeter network scenario.
Influence
Users cannot change their passwords.
Workaround
To work around this issue, create firewall rules to enable a writable domain controller to be contacted. Or, have the users change passwords by using a computer that is running Windows Vista or Windows Server 2008.
Issue 6
Symptom
Windows Server 2008 read-only domain controllers cannot retrieve or create the public key certificate by using the LsaRetrievePrivateData function or the LsaStorePrivateData function.
The call to the LsaRetrievePrivateData function finishes. However, a NULL value is returned for the private data.
The call to the LsaStorePrivateData function fails, and error code 0xc0000034 is returned.
Scenario and affected clients
This issue affects clients in a site that has only read-only domain controllers available. Typically, this issue occurs in a branch office scenario or in a perimeter network scenario.
Influence
The Data Protection API (DPAPI) on clients that can access only read-only domain controllers cannot decrypt master keys unless these clients previously contacted a writable domain controller and retrieved a public key certificate. Even though a writable domain controller is available, the DPAPI still cannot decrypt master keys if the nearest domain controller is a read-only domain controller.
Workaround
When the DPAPI tries to decrypt master keys, make sure that the client has access to only a writable domain controller.
Note Typically, the DPAPI tries to decrypt master keys during password changes.
Issue 7
Symptom
When you try to publish a printer, the published printer may not work correctly.
Scenario and affected clients
This issue affects clients in a site that has only read-only domain controllers available. Typically, this issue occurs in a branch office scenario.
Influence
If a read-only domain controller receives a request to publish a printer, the read-only domain controller forwards the request to a writable domain controller. The spooler tries to read from the read-only domain controller immediately after the write action is implemented. However, the spooler does this before the printer publish information is replicated to the read-only domain controller. Therefore, the publish operation fails.
Workaround
No workaround is available for this issue if the compatibility pack is not installed
Issue 8
Symptom
In a site that has only read-only domain controllers available, you use the Find Printer dialog box on a client computer that is running Windows 2000, Windows XP, or Windows Server 2003. When you do this, the Find Printer dialog box stops responding.
Scenario and affected clients
This issue affects clients in a site that has only read-only domain controllers available. Typically, this issue occurs in a branch office scenario.
Influence
Users cannot find printers that are published in Active Directory Domain Services.
Workaround
No workaround is available for this issue if the compatibility pack is not installed.
Issue 9
Symptom
Active Directory Service Interfaces (ADSI) API functions in Windows Server 2003 and in Windows XP always send requests to a remote writable domain controller instead of to a local read-only domain controller.
Scenario and affected clients
This issue affects clients in a site that has only read-only domain controllers available. Typically, this issue occurs in a branch office scenario.
Influence
This issue causes unnecessary network traffic and access latency.
Workaround
Make sure that all clients have connectivity to a writable domain controller when these clients call ADSI API functions. Do this even if the function calls make only read operations.
Issue 10
Symptom
Domain controllers that are running Windows Server 2003 perform automatic site coverage for sites that have read-only domain controllers.
Scenario and affected clients
This issue affects domain controllers that provide automatic site coverage for other branch office sites. Typically, this issue occurs in a branch office scenario.
Influence
A domain controller that is running Windows Server 2003 may register its DNS SRV resource records for a site that contains a read-only domain controller. Therefore, the clients may not authenticate as expected with the local read-only domain controller.
Workaround
To work around this issue, use one of the following methods:
Make sure that only domain controllers that are running Windows Server 2008 are present in the site that is closest to the read-only domain controller site.
Disable automatic site coverage on domain controllers that are running Windows Server 2003.
Configure the weight or the priority of the DNS SRV records so that clients are more likely to authenticate with the read-only domain controller than with a remote Windows Server 2003 domain controller.
Use Group Policy settings to configure domain controller locator DNS records.