Active Directory Replication Diagnostics

Have you ever found yourself in a sea of event log errors for Active Directory replication? How do you begin to diagnose Active Directory replication? Below are basic steps that I have come up with for my own use. Undoubtedly, you can get more detailed but this is a good starting point.

With Windows Server 2008 you have several powerful utilities at your disposal. But, what is missing? Replmon is now discontinued with Windows Server 2008. So where do you start?

First, you need to see the structure of replication and view the Active Directory replication status. All of the following commands can be accessed via the command prompt. Use the following to view the current replication partners against Active Directory partitions:

repadmin /showrepl

Now that you have a good idea of your replication partners you need to know if there are any items in queue to be replicated. Use the following to view the queue for Active Directory partitions:

Repadmin /queue

Now you have a good idea where there might be an issue. The next command will give you a basic health summary of replication status.

repadmin /replsummary

To view how up-to-date a server is with replication use the showutdvec command. This displays the highest Update Sequence Number (USN):

repadmin /showutdvec localhost dc=domain,dc=local

With Active Directory, DNS is vital. To verify that the Domain Controller has valid DNS entries necessary for Active Directory use the following command:

dcdiag /test:connectivity

After you troubleshoot any errors that you may have encountered you nwo want to test replication. To test replication you can use the following command:

dcdiag /test:replications

If everything is looking good or you want to force a replication to view possible errors in the event log, use the following command:

repadmin /syncall

Finally, you can verify the Active Directory replication topology, use the following command:

repadmin /kcc

This of course is a starting point to help with diagnosing Active Directory replication and there are many more useful repadmin and dcdiag commands.