Overview: How to Troubleshoot Active Directory Replication Issues

How To Generate all Domain Controllers in Active Directory

Here we describe how to generate all Domain Controllers in Active Directory Sites and Services tool.

Active directory Sites and Services can be seen as an administrative tool, used to manage sites and the related components on Microsoft server systems.

It contains is a list of all Domain Controller connected to the system, no matter of number.

In some situations, admins can notice more than one DC listed under NTDS settings.

What are this other DC ’s, and how can they be generated automatically?

KCC

Those DC’s are called KCC’s ( Knowledge Consistency Checker) nominated bridgehead server per site to handle replication between specific sites.

That bridgehead server is then responsible for replicating any changes to all remaining DCs in its site.

In simple words, KCC takes care of replication by generating DC which communicates with other DC’s KCC’S auto-generated domain controllers and takes care of replication.

How to create automatically generated Domain Controllers

There are situations like server moves or adding new organizational Domain Controller when you can get to the situation that Active Directory is not creating ‘Automatically Generated’ connections with root Domain Controller. So, the Domain Controller can be seen, but not on the “real” Domain Controller list.

There is more than one solution, to this problem, we will bring most used and tested ones.

Manually forcing auto generation

The first method, although it can get in “workaround” category, should be manually force of auto-generation. It can be done on a way to right click on the NTDS Settings option, then choose All Tasks and Check Replication Topology in the end. That should force trigger auto-generation of all Domain Controllers, and your Domain Controllers should be visible on the list.

Repadmin

Repadmin Is a command line tool, used for replication problems diagnostic and repair.

It can be used from an elevated command prompt by typing ntdsutil.

By entering command

repadmin / showrepl*

an output is replication state of all DC’s in the system.

By command

Repadmin/replicate

force replication is started, and, considering our article, this command could by forcing replication, generate all Domain Controllers on the Sites and Services list.

Conclusion

It is usually not necessary to create manual connections when the KCC is being used to generate automatic connections. If any conditions change, the KCC automatically reconfigures connections. Adding manual connections when the KCC is employed potentially increases replication traffic and that will conflict with optimal settings set by KCC.

If a connection is not working due to a failed domain controller, the KCC automatically builds temporary connections to other replication sites ( if the damage is not too big ), to ensure that replication occurs. If all the domain controllers in a site are unavailable, the KCC automatically creates replication connections between domain controllers from another site.”

It is not recommended to manually modify this – unless you have a very specific use case.  As long as these records are auto-generated, they can survive a Domain Controller failure as the KCC/ISTG will automatically create a new connection.  However, if you manually create a connection/specify a bridgehead server, if that server goes offline, KCC will not create a new connection and replication between the affected sites will stall.

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