One of the first tools written for troubleshooting Windows 2000 Server was Replication Monitor (ReplMon), which soon became the lifeblood for debugging Active Directory replication problems.
Microsoft included ReplMon in the first set of Windows Support Tools and it survives in the latest version for Windows Server 2003. But with so many tools developed over the past seven years, it's easy to forget how powerful ReplMon still is. This article will take a close look at how ReplMon can help diagnose a host of AD replication issues.
Getting started with ReplMon
Replication Monitor is a Windows Support Tools component that can be initiated by simply entering ReplMon from Start-Run or the command window. Initially it's empty, so you have to add monitored servers. From the Edit menu on the tool bar, select "Add monitored server," then add the domain controllers you want to view. Figure 1 shows several DCs added and expanded.
Figure 1
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Under each server you'll see a list of naming contexts (configuration, schema, domain, forestdnszones, etc.) hosted on that DC, along with the name of the replication partner. Clicking on any of these partitions will display the replication details in the right pane. This is the information you'd get from the repadmin/showrepl command, except that you get a lot more information from other servers quickly.
To get the most out of ReplMon, you should enable additional logging. Go to View – Options to get the dialog shown in Figure 2. These options are pretty self explanatory, but I recommend enabling at least "Show Transitive Replication Partners and Extended Data." Then click the Status Logging tab (Figure 3) and check "Group Policy Objects" and "Display Changed Attributes when Replication Occurs." This will provide additional information in the left pane for monitored servers about GPO replication success or failure, and identifies the object tha
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t was replicated and the update sequence number (USN).
Figure 2
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Figure 3
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In terms of troubleshooting with ReplMon, here are my favorite selections:
Figure 4
[IMAGE]There are also some powerful server options. Right click a DC icon and a list of actions will be shown (Figure 5). Most are obvious and the results can be saved as text files.
Figure 5
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At the end of the list shown in Figure 5, there is a Properties option where there are some more cool features:
Figure 6
[IMAGE]Finally, to eliminate the need to manually connect to the domain controllers each time you use ReplMon, go to File-Save Monitored List As. You can save the list of DCs in the tool to a text file (*.ini). You can also edit the file to add additional DCs. Then you can select File-Open Script and select the .ini file you saved to load the DCs.
While all of these features are great, I've left the best for last -- the Status Report. Right click on the DC icon and select Generate Status Report. Keep the default options and provide a file name. This status report is a dump of all data related to replication. It evaluates DNS, replication objects, connections and so forth. You can then take the status report and construct the replication topology -- site names, DC names, site link information, as well as replication related errors and significant events. It serves as a very nice one-stop shopping list for troubleshooting Active Directory replication failure.
Yes, there are a lot of sophisticated tools out there, but don't forget ReplMon. It is still a very powerful tool for monitoring and troubleshooting all aspects of Active Directory replication.
Do you have an Active Directory issue or problem that you'd like Gary to write an article about? Email him at glo11749@yahoo.com. Note: Gary cannot answer each query personally or guarantee that all will be answered. However those queries that have widespread interest or involve common AD issues will be addressed.
Gary Olsen is a systems software engineer for Hewlett-Packard in Global Solutions Engineering. He authored Windows 2000: Active Directory Design and Deployment and co-authored Windows Server 2003 on HP ProLiant Servers. Gary is a Microsoft MVP for Directory Services and formerly for Windows File Systems.
