This error most commonly occurs when replication topology in a DC that is initiating replication differs from the replication topology defined in the destination DCs copy of Active Directory.
The error naturally occurs when the replication topology in an Active Directory forest is being modified by:
- new partitions being added or removed from the forest (i.e. the promotion or demotion of the first / last DC in a domain, or the addition / removal of an application partition including default DNS application partitions)
- The addition or removal of directory partitions on existing DCs (i.e. the promotion / demotion of global catalog or addition / removal of an application partition).
- Changes in replication topology or settings (i.e. the promotion of new DCs, the demotion of existing DCs , changes to preferred / nominated bridgeheads, the building of alternate replication paths in response to replication failures or offline DCs, as well as site and sitelink changes).
The error can be transient in a forest undergoing the changes above until the set of source DCs and partitions that each destination DC replicates from has inbound replicated by triggering replication operations.
The error can be persistent when replication failures prevent the end-to-end replication of topology changes in the forest.
The error is most commonly seen in replication scenarios triggered by REPADMIN.EXE remotely (especially /SYNCALL) or the "replicate now command" in DSSITE.MSC where the copy of Active Directory on the DC triggering replication has a different list of source DCs that a destination DC replicates from partitions than what the destination DC has defined in its copy of Active Directory.
Windows 2000 domain controllers are particularly prone to this error during GC demotion as they are slow to remove objects from read-only partitions. Object removal during GC demotion improved dramatically on Windows Server 2003 and later OS versions.
The NTDS Replication event 1586 is caused when the PDC FSMO role for the domain has been seized or transferred to a domain controller that was not a direct replication partner of the previous role holder.
In rare conditions, the error can be caused by corruption in attributes like hasMasterNCs like msds-hasMasterNCs
The "More Information" section of this article contains explanations as to why the diagnostic and administrative tools listed in the Symptoms section of this article generate the 8452 error.
In summary, Error 8452 happens if anyone of the following is true:
- When DC1 <- DC2 replication is initiated for a NC, on DC1 there is no replica link for the NC from DC2
- When DC1 <- DC2 replication in initiated for a NC, the NC is in the process of being removed on DC2
- In mixed domain environment, PDC FSMO role is transferred from DC2 to DC1, but on DC1 there is no replica link from DC2
The REPADMIN /syncall operation will cause a DC to initiate replication from all of its source replication partners and make the source replication partners initiate replication from all of their source replication partners, and so on.
For example, suppose we have a replication topology DC1 <- DC2 <- DC3. “repadmin /syncall” on DC1 will initiate the following replication: DC2 <- DC3, and DC1 <- DC2.
There are two cases where error 8452 might be observed in this scenario:
Case 1: Change the replication topology to make DC2 inbound replicate from DC4 so that the current topology becomes DC1 <- DC2 <- DC4.
If we call “repadmin /syncall” on DC1 before knowledge of the DC2 <- DC4 topology change inbound replicates to DC1, the syncall operation will initiate DC2 <- DC3 replications because DC1 still has the old replication topology stored locally. Because on DC2 at this moment KCC has created a replica link from DC4 and has deleted the replica link from DC3, the replication from DC2 <- DC3 cannot be executed and the operation logs error 8452.
Case 2: Suppose a NC on DC3 is being removing while we call “repadmin /syncall <the NC>” on DC1. DC2 <- DC3 replication will be initiated as before. Because the NC on DC3 is in the process of being removed, it is not a valid replication source, the error 8452 will be observed.
Active Directory Sites and Services (DSSITE.MSC) -> Replicate Now
The Active Directory Sites and Services snap-in, DSSITE.MSC uses the topology information stored in its local copy of AD.
Given the replication topology DC1 <- DC2 <- DC3, a connection object exists under DC2’s NTDS Settings object. This connection object represents the route for DC2 to inbound replicate a NC (or multiple NCs) from DC3. If we right click on this connection object and select “replicate now”, we will initiate a DC2 <- DC3 replication on DC2.
As in the REPAMIN /SYNCALL example, there are also two cases where we might observe error 8452
Case 1: Suppose we change the replication topology on DC2 to make it inbound replicate from DC4. The new replication topology is DC1 <- DC2 <- DC4. Until knowledge of this this topology change outbound replicates to DC1, the topology on DC1 is still the old topology of DC1 <- DC2 <- DC3.
Starting the Active Directory Sites and Services UI focused on DC1s copy of Active Directory still shows that DC2 has an inbound connection object from source DC3. Right clicking on DCs inbound connection object from DC2 and choosing “replicate now” will initiate a DC2 <- DC3 replication on DC2. However, the KCC on DC2 already removed the replica link inbound replicating to DC2 from DC3 and created a replica link to DC2. Because the replication attempt DC2 <-> DC2 cannot be executed, the request fails error 8452.
Case2: Suppose we are removing a NC on DC3 when we right-click the connection object and select “replicate now” on DC1 to initiate DC2 <- DC3 replication for this NC. Because the NC on DC3 is in the process of being removed, DC3 is not a valid replication source. So we will see error 8452
REPADMIN /REPLICATE or REPADMIN /SYNC
The replicate (or sync) command of repadmin triggers immediate replication of a naming context (directory partition) to a destination DC from a source DC. Its (simplified) syntax is: repadmin /replicate <dest DC> <src DC> <replicated NC>
There are two cases that we will trigger error 8452 when the repadmin /replicate (or sync) command is used to initiate a replication:
Case 1: the <src DC> parameter is not a replication partner of <dest DC> for <replicated NC>. For example, we have to replication topology DC1 <- DC2 <- DC3 in which DC2 syncs a NC from DC3. If we call repadmin /replicate DC2 DC1 the NC, a replication DC2 <- DC1 will be initiated. Because on DC2 we do not have a replica link from DC1 for the NC, this replication cannot be executed, and we will get error 8452.
Case 2: the NC is being removed on src DC when we call repadmin /replicate <dest DC> <src DC> <the NC>, so <src DC> is not a valid replication source. So we will see error 8452.
The showrepl (or showreps) command of repadmin reports the replication status for each source DC from which the destination DC has an inbound connection object. The replications test of dcdiag checks for timely replication between DCs. If error 8452 in repadmin /showrepl report or dcdiag /test:replications report, the reason is that the replicated NC is being removed on the source DC when the last replication happened.
NTDS Replication Event 1586
NTDS replication event 1586 is generated in a mixed domain environment which contains both Windows NT 4.0 and Active Directory DCs. In this mixed domain environment, Active Directory domain controllers replicate amongst themselves using the DS replication protocol, while the Active Directory PDC replicates to NT4 BDCs using the legacy netlogon replication protocol. In this case the Active Directory PDC FSMO role holder is the single point for replication to NT4 BDCs in a common domain. The PDC maintains a checkpoint for each BDC representing the most recent replicated change. If the PDC FSMO role is transferred to another Active Directory DC in the domain, the information about each individual BDC’s checkpoint must be replicated to the new PDC FSMO role. Hence the new PDC FSMO role holder must have a direct replication relationship with the old PDC FSMO role holder. If the new PDC does not replicate directly with the old PDC (ie, on the new PDC there is no replica link from old PDC) , then we will see error 8452 in event 1586.
There is another scenario that DRAERR_NoReplica error will be returned. When we demote a DC, it will use DC locator to find a DC to replicate local changes to. If the found DC does not replicate directly with the being-deleted DC, DRAERR_NoReplica will be returned and DC locator will be called to find a destination DC. In this scenario, the error is not logged hence it is not observed.
How the Active Directory Replication Model Works
Reps From protocol documentation
for other considerations.
Article ID: 2023704 - Last Review: June 18, 2012 - Revision: 15.0
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