This article describes how to troubleshoot a problem in which Active Directory replication fails and generates error 8453: "Replication access was denied."
This error has the following primary causes:
- The destination domain controller does not have the required permissions to replicate the naming context / partition.
- The administrator who manually initiated replication does not have permissions to do this.
Note This condition does not affect periodic or scheduled replication.
For period or scheduled replication, if the destination domain controller is a Read-Only Domain Controller (RODC):
The Enterprise Read-Only Domain Controllers security group does not have “Replicating Directory Changes” permissions on the root of the naming context (NC) for the partition that doesn't replicate and returns error 8453.
On each NC that RODCs don't replicate and that return error 8453: Grant "Replicating Directory Changes" permissions to the forest-root domain's Enterprise Read-only Domain Controllers security group.
An RODC childdc2.child.contoso.com doesn't replicate the contoso.com partition and returns error 8453. To troubleshoot this situation, follow these steps:
- Open ADSIEDIT.msc on a contoso.com domain controller.
- Open a connection to the contoso.com domain NC (default naming context).
- Open the properties of the dc=contoso,dc=com NC, and select the Security tab.
- Click Add, and enter the following in the text box:
Contoso\Enterprise Read-Only Domain Controllers
Note This group exists only in the forest-root domain.
- Select Check Names, and then select OK.
- In the Permissions for Enterprise Read-Only Domain Controllers dialog box, clear the Allow check boxes that are automatically selected:
- Read domain password & lockout policies
- Read Other domain parameters
- Select the Allow box next to Replicating Directory Changes, and then select OK.
If these steps do not resolve the problem, see the rest of this article.
When this problem occurs, you experience one or more of the following symptoms:
- The DCDIAG Replication test (DCDIAG /TEST:NCSecDesc) reports that the tested domain controller "failed test replications" and has a status of "8453: Replication access was denied":
Starting test: Replications
[Replications Check,<destination domain controller] A recent replication attempt failed:
From <source DC> to <Destination DC
Naming Context: <DN path of failing directory partition>
The replication generated an error (8453):
Replication access was denied.
The failure occurred at <date> <time>.
The last success occurred at <date> <time>.
%#% failures have occurred since the last success.
The machine account for the destination <destination DC>.
is not configured properly.
Check the userAccountControl field.
The machine account is not present, or does not match on the.
destination, source or KDC servers.
Verify domain partition of KDC is in sync with rest of enterprise.
The tool repadmin/syncall can be used for this purpose.
......................... <DC tested by DCDIAG> failed test Replications
- The DCDIAG NCSecDesc test (DCDIAG /TEST:NCSecDes) reports that the domain controller that was tested by DCDIAG "failed test NCSecDec" and that one or more permissions are missing on the NC head of one or more directory partitions on the tested domain controller that was tested by DCDIAG:
Starting test: NCSecDesc
Error NT AUTHORITY\ENTERPRISE DOMAIN CONTROLLERS doesn't have
Replicating Directory Changes <- List of missing access
Replication Synchronization <- rights required for each Manage Replication Topology <- security group could vary
Replicating Directory Changes In Filtered Set <- depending in missing
access rights for the naming context: <- right in your environment
Error CONTOSO\Domain Controllers doesn't have
Replicating Directory Changes All
access rights for the naming context:
Error CONTOSO\Enterprise Read-Only Domain Controllers doesn't have
Replicating Directory Changes
access rights for the naming context:
......................... CONTOSO-DC2 failed test NCSecDesc
- The DCDIAG MachineAccount test (DCDIAG /TEST:MachineAccount) reports that the comain controller that was tested by DCDIAG "failed test MachineAccount" because the UserAccountControl attribute on the DCs computer account is missing the SERVER_TRUST_ACCOUNT" OR "TRUSTED_FOR_DELEGATION" flags:
Starting test: MachineAccount
The account CONTOSO-DC2 is not trusted for delegation. It cannot
The account CONTOSO-DC2 is not a DC account. It cannot replicate.
Warning: Attribute userAccountControl of CONTOSO-DC2 is:
0x288 = ( HOMEDIR_REQUIRED | ENCRYPTED_TEXT_PASSWORD_ALLOWED | NORMAL_ACCOUNT )
Typical setting for a DC is
0x82000 = ( SERVER_TRUST_ACCOUNT | TRUSTED_FOR_DELEGATION )
This may be affecting replication?
......................... CONTOSO-DC2 failed test MachineAccount
- The DCDIAG KCC event log test indicates the hexadecimal equivalent of Microsoft-Windows-ActiveDirectory_DomainService event 2896:
B50 hex = 2896 decimal. This error may be logged every 60 seconds on the infrastructure master domain controller.
Starting test: KccEvent
* The KCC Event log test
An error event occurred. EventID: 0xC0000B50
Time Generated: 06/25/2010 07:45:07
A client made a DirSync LDAP request for a directory partition. Access was denied due to the following error.
<DN path of directory partition>
8453 Replication access was denied.
The client may not have access for this request. If the client requires it, they should be assigned the control access right "Replicating
Directory Changes" on the directory partition in question.
- REPADMIN.EXE reports that a replication attempt failed and returned an 8453 status.
REPADMIN commands that commonly indicate the 8453 status include but are not limited to the following.
· REPADMIN /KCC
· REPADMIN /REHOST
· REPADMIN /REPLICATE
· REPADMIN /REPLSUM
· REPADMIN /SHOWREPL
· REPADMIN /SHOWREPS
· REPADMIN /SHOWUTDVEC
· REPADMIN /SYNCALL
Sample output from "REPADMIN /SHOWREPS" showing inbound replication from CONTOSO-DC2 to CONTOSO-DC1 that fail and return the "replication access was denied" error is as follows:
DSA Options: IS_GC
Site Options: (none)
DSA object GUID: b6dc8589-7e00-4a5d-b688-045aef63ec01
DSA invocationID: b6dc8589-7e00-4a5d-b688-045aef63ec01
==== INBOUND NEIGHBORS ======================================
Default-First-Site-Name\CONTOSO-DC2 via RPC
DSA object GUID: 74fbe06c-932c-46b5-831b-af9e31f496b2
Last attempt @ <date> <time> failed, result 8453 (0x2105):
Replication access was denied.
<#> consecutive failure(s).
Last success @ <date> <time>.
- The "replicate now" command in Active Directory Sites and Services returns a "replication access was denied" error.
Right-clicking the connection object from a source domain controller and then selecting "replicate now" fails and returns a "replication access was denied" error. The following error message is displayed:
Dialog title text: Replicate Now
Dialog message text: The following error occurred during the attempt to synchronize naming context <%directory partition name%> from Domain Controller <Source DC> to Domain Controller <Destination DC>:
Replication access was denied
The operation will not continue
Buttons in Dialog: OK
- NTDS KCC, NTDS General or Microsoft-Windows-ActiveDirectory_DomainService events that have the 8453 status are logged in the Active Directory Directive Services (AD DS) event log.
Active Directory events that commonly indicate the 8453 status include but are not limited to the following:
1699 This directory service failed to retrieve the changes requested for the following directory partition. As a result, it was unable to send change requests to the directory service at the following network address.
Microsoft-Windows-ActiveDirectory_DomainService 2896 A client made a DirSync LDAP request for a directory partition. Access was denied due to the following error.
Active Directory attempted to communicate with the following global catalog and the attempts were unsuccessful.
NTDS KCC 1265 The attempt to establish a replication link with parameters
Partition: <partition DN path>
Source DSA DN: <DN of source DC NTDS Settings object>
Source DSA Address: <source DCs fully qualified CNAME>
Inter-site Transport (if any): <dn path>
failed with the following status:
The attempt to establish a replication link for the following writable directory partition failed.
Error 8453: "Replication Access was denied" has multiple root causes, including the following:
- The UserAccountControl attribute on the destination domain controller computer account is missing either the SERVER_TRUST_ACCOUNT or TRUSTED_FOR_DELEGATION flag.
- The default permissions do not exist on the one or more directory partitions to allow scheduled replication to occur in the operating system's security context.
- The default or custom permissions do not exist on one or more directory partitions to allow users to trigger ad-hoc or immediate replication by using DSSITE.MSC -> "replicate now," "repadmin /replicate," "repadmin /syncall," or similar commands.
- The permissions that are required to trigger ad-hoc replication are correctly defined on the relevant directory partitions. However, the user is not a member of any security groups that have been granted the replication directory changes permission.
- The user who triggers ad-hoc replication is a member of the required security groups, and those security groups have been granted the "replicating directory changes" permission. However, membership in the group that's granting the "replicating directory changes" permission is removed from the user's security token by the "User Account Control" (split user access token) feature that was introduced in Windows Vista and Windows Server 2008.
Note Do not confuse the "User Account Control" split token security feature that was introduced in Vista and Windows Server 2008 with the UserAccountControl attribute that is defined on domain controller role computer accounts that are stored by the Active Directory service.
- If the destination domain controller is an RODC, RODCPREP has not been run in domains that are currently hosting read-only domain controllers, or the Enterprise Read-Only Domain Controllers group does not have Replicate Directory Changes permissions for the partition that is not replicating.
- DCs that are running new operating system versions was added to an existing forest where Office Communication Server has been installed.
- You have LDS instances, and the NTDS Settings object for the affected instances are missing from the LDS configuration container. For example, you see the following entry:
Active Directory errors and events such as those that are mentioned in the "Symptoms" section may also occur and generate an error 5: "Access is denied" message.
Applying the steps for either error 5 or error 8453 that are mentioned in the "Resolution" section will not resolve replication failures on computers that are currently failing replication and that are generating the other error message.
Common root causes for failing Active Directory operations failing that are generating error 5 messages include the following:
- Excessive Time Skew
- The fragmentation of UDP-formatted Kerberos packets by intermediate devices on the network
- Missing "access this computer from network" rights
- Broken secure channels or intra-domain trusts
- CrashOnAuditFail = 2 entry in the registry
To resolve this problem, use the following methods.
Run a health-check by using DCDIAG + DCDIAG /test:CheckSecurityError
- Run DCDIAG on the destination DC that's reporting the 8453 error or event.
- Run DCDIAG on the source domain controller on which the destination domain controller is reporting that the 8453 error or event is occurring.
- Run DCDIAG /test:CheckSecurityError on the destination domain controller.
- Run DCDIAG /test:CheckSecurityError on the source DC.
Fix invalid UserAccountControl
The UserAccountControl attribute includes a bitmask that defines the capabilities and state of a user or computer account. For more information about UserAccountControl flags, see the following Knowledge Base article and MSDN topic:
305144 How to use the UserAccountControl flags to manipulate user account properties
The typical UserAccountControl attribute value for a writeable ("full") DC computer account is 532480 decimal or 82000 hex. UserAccountControl values for a DC computer account can vary, but must contain the SERVER_TRUST_ACCOUNT and TRUSTED_FOR_DELEGATION flags, as shown in the following table.
The typical UserAccountControl attribute value for a read-only domain controller computer account is 83890176 decimal or 5001000 hex.
Typical UserAccountControl Value for RODC
- The UserAccountControl attribute on the destination domain controller is missing the SERVER_TRUST_ACCOUNT flag
If the DCDIAG MachineAccount test fails and returns a "failed test MachineAcccount" error message, and the UserAccountControl attribute on the tested domain controller is missing the SERVER_TRUST_ACCOUNT flag, add the missing flag in the tested domain controller's copy of Active Directory.
- Start ADSIEDIT.MSC on the console of the domain controller that's missing the SERVER_TRUST_ACCOUNT as reported by DCDIAG.
- Right-click "ADSIEDIT" in the top-left pane of ADSIEDIT.MSC, and then select connect to.
- In the Connection Settings dialog box, click Select a well known naming context, and then select Default naming context (the computer account domain partition).
- Click "Select or type a domain or server," and select the name of the domain controller that's failing in DCDIAG.
- Click OK.
- In the domain naming context, locate and right-click on the domain controller computer account, and select Properties.
- Double-click the UserAccountControl attribute, and then record its decimal value.
- Start Windows Calculator in scientific mode (Windows 2000 or Windows Server 2003) or programmer mode (Windows Server 2008 and later versions).
- Enter the decimal value for UserAccountControl. Convert the decimal value to its hexadecimal equivalent, add 0x80000 to the existing value, and then press the equals sign (=).
- Convert the newly calculated UserAccountContorl value to its decimal equivalent.
- Enter the new decimal value from Windows Calculator to the UserAccountControl attribute in ADSIEDIT.MSC.
- Click OK two times to save.
- The UserAccountControl attribute on the destination domain controller is missing the TRUSTED_FOR_DELEGATION flag
If the DCDIAG MachineAccount test returns a "failed test MachineAcccount" error message, and the UserAccountControl attribute on the tested domain controller is missing the TRUSTED _FOR_DELEGATION flag, add the missing flag in the tested domain controller's copy of Active Directory.
- Start Active Directory Users and Computers (DSA.MSC) on the console of the domain controller that was tested by DCDIAG.
- Right-click the domain controller computer account.
- Click the Delegation tab.
- On the domain controller machine account, select the "Trusted this computer for delegation to any service (Kerberos only)" option.
Fix invalid default security descriptors
Active Directory operations take place in the security context of the account that initiated the operation. Default permissions on Active Directory partitions allow the following operations:
- Members of the Enterprise Administrators group can initiate ad-hoc replication between any domain controller in any domain in the same forest.
- Members of the Built-in Administrators group can initiate ad-hoc replication between domain controllers in the same domain.
- Domain Controllers in the same forest can initiate replication by using either change notification or replication schedule.
Default permissions on Active Directory partitions do not allow the following operations by default:
- Members of the Built-in Administrators group in one domain cannot initiate ad-hoc replication to domain controllers in that domain from domain controllers in different domains.
- Users that are not members of the Built-in Administrators group cannot initiate ad-hoc replication from any other domain controller in the same domain or forest.
By design, these operations fail until default permissions or group memberships are modified.
Permissions are defined at the top of each directory partition ("NC head") and are inherited throughout the partition tree. Verify that explicit (groups that the user is directly a member of) and implicit groups (groups that explicit groups have nested membership of) have the required permissions. Also verify that "Deny" permissions that are assigned to implicit or explicit groups do not take precedence over the required permissions.
For more information about default directory partitions, see the following TechNet topic:
- Verify that default permissions exist in the "top" of each directory partition that is failing and returning "replication access was denied"
If ad-hoc replication is failing between domain controllers in different domains, or between domain controllers in the same domain for non-domain administrators, see the "Grant non-domain admins permissions" section.
If ad-hoc replication is failing for members of the Enterprise Administrators group, focus on NC head permissions that are granted to the Enterprise Administrators group.
If ad-hoc replication is failing for members of a Domain Administrators group, focus on the permissions that are granted to the built-in Administrators Security group.
If a scheduled replication that is initiated by domain controllers in a forest are failing and returning error 8453, focus on permissions for the Enterprise Domain Controllers and Enterprise Read-Only Domain Controllers security groups.
If a scheduled replication is initiated by domain controllers on a read-only domain controller (RODC) is failing and returning error 8453, verify that the Enterprise Read-Only Domain Controllers security group is granted the required access on the NC head of each directory partition.
The followiong table shows the default permission that are defined on the schema, configuration, domain, and DNS applications by various Windows versions.
DACL required on each directory partition
Windows Server 2003 and 2003 R2
Windows Server 2008 and later
Manage Replication Topology
Replicating Directory Changes
Replicating Directory Changes All
Replicating Changes in Filter Set
Note The DCDIAG NcSecDesc test may report false positive errors when it's run in environments that have mixed system versions, as documented in the following Knowledge Base article:
829306 "Replicating Directory Changes All" error message when you run the Dcdiag.exe utility
The DSACLS command can be used to dump the permissions on a given directory partition by using the following syntax:
DSACLS <DN path of directory partition>
For example, use the following command:
The command can be targeted to a remote domain controller by using the syntax
Be wary of "DENY" permission on NC heads removing the permissions for groups that the failing user is a direct or nested member of.
Use the Active Directory ACL editor in ADSIEDIT.MSC to add the missing DACLS.
Grant non-domain admins permissions to replicate between domain controllers in the same domain or non-enterprise administrators to replicate between domain controllers in different domains
Default permissions on Active Directory partitions do not allow the following operations:
- Members of the Built-in Administrators group in one domain cannot initiate ad-hoc replication from domain controllers in different domains.
- Users that are NOT members of the built-in domain admins group to initiate ad-hoc replication between domain controllers in the same domain or different domain.
Thesew operations fail until permissions on directory partitions are modified.
To resolve this problem, use either of the following methods.
- Add users to existing groups that have already been the granted the required permissions to replicate directory partitions. (Add the Domain administrators for replication in the same domain, or the Enterprise Administrators group to trigger ad-hoc replication between different domains.)
- Create your own group, grant that group the required permissions on directory partitions throughout the forest, and then add users to those groups.
Knowledge Base article 303972 describes how to create a security group, add the required members to those groups, and grant the group the required DACLS on Active Directory partitions. Grant the security group in question the same permissions that are listed in the table in the "Fix Invalid Default Security Descriptors" section in this article.
For more information, see the following Knowledge Base article and TechNet white paper:
303305: "Access Denied" error message when you use the Active Directory Sites and Services tool
Verify group membership in the required security groups
After the correct security groups have been granted the required permissions on directory partitions, the last remaining task is to verify that users who initiate replication have effective membership in direct or nested security groups that are granted replication permissions. To do this, follow these steps:
- Log on by using the user account in which ad-hoc replication is failing and returning "replication access was denied."
- At a command prompt, run the following command:
- Verify membership in the security groups that have been granted the "replicating directory changes" permissions on the relevant directory partitions.
If the user was added to the permissioned group that was changed after the last user logon, log on a second time, and then run
WHOAMI /ALLstill does not show membership in the expected security groups, open an elevated Command Prompt window, on the local computer, and run
WHOAMI /ALLat the command prompt.
If the group membership differs between the
WHOAMI /ALLoutput that is generated by elevated and non-elevated command prompts, see Knowkledge Base article 976063.
- Verify that the expected nested group memberships exist.
If a user is getting permissions to run ad-hoc replication as a member of nested group that is a member of group that has been directly granted replication permissions, verify the nested group membership chain. For example, Microsoft CSS has seen ad-hoc Active Directory replication fail because the Domain Administrators and Enterprise Administrators groups were removed from the built-in Administrators groups.
If computer-initiated replication is failing on RODCs, verify that you have run
ADPREP /RODCPREP as specified in Knowledge Base aricle 967482 and that the Enterprise Read-Only Domain Controller group is granted the "replicate directory changes" right on each NC head.
Office Communication Server
If you notice that AD operations fail and return the 8453 "replication access was denied" error in an existing forest that's running either Microsoft Office Communications Serv 2005 or Microsoft Office Communications Server 2007, and if this occurs immediately after the promotion of or upgrade to Windows Server 2008 or Windows Server 2008 R2 domain controllers, see the following Knowledge Base articles:
982020: Office Communications Server 2007 R2, OCS 2007 or LCS 2005 does not work correctly after you upgrade to Windows Server 2008 R2
982021: Supportability is available for Office Communications Server 2007 R2 member server role on a Windows Server 2008 R2 operating system
Missing NTDS Settings object for LDS server
In Active Directory Lightweight Directory Services (LDS), it's possible to simply delete the object (without a metadata cleanup in DBDSUTIL). Therefore, this is likely the cause of this problem. In order to restore the instance to the configuration set, you have to uninstall the LDS instance on the affected servers, and then run the ADAM configuration wizard.
Note If you have added LDAPS support for the instance, you have to configure the certificate in the service store again because the uninstallation of the instance also removes the service instance.