Active Directory & Office 365 Reporting Tool

Repadmin: Check Active Directory Replication / Health. In the dynamic realm of network administration, ensuring the seamless functioning of Active Directory (AD) is paramount for the stability and reliability of an organization’s IT infrastructure. The heartbeat of user authentication and data management, AD relies on robust replication mechanisms across domain controllers. This article delves into the critical task of monitoring AD replication health, exploring the significance of tools like Repadmin.

Repadmin: Check Active Directory Replication / Health

Repadmin is the Active Directory replication diagnostics tool installed on all domain controllers running Windows Server 2008 and newer. We may also install Repadmin on other computers using the Remote Server Administration Tools (RSAT). In the later sections of the article, we look at how to use Repadmin and what to look for in the diagnostics results, but before that, let’s have a brief refresher on what repadmin is.

Brief Overview of the Repadmin Tool

We primarily use the Repadmin tool to force replication between the domain controllers or to diagnose replication issues in our network. We also use the tool to configure our domain’s replication topology manually. However, there are minor caveats.

Manually changing the replication topology with Repadmin in Active Directory is discouraged due to the complexity and potential for errors, risking replication failures and downtime. Automated tools like the Active Directory Sites and Services console or PowerShell cmdlets are recommended for their user-friendly interfaces and adherence to best practices, ensuring a more reliable and efficient replication topology.

For now, we are going to focus on the most commonly used commands:

  • repadmin /replsummary : Summary of failing in- & outbound connections
  • repadmin /showrepl : Status per naming context between two domain controllers
  • repadmin /queue : Displays inbound replication queue
  • repadmin /syncall : Synchronizes a specified domain controller
  • repadmin /syncall /AdeP : Push changes outwards to all domain controllers
  • repadmin /replicate : Displays inbound replication queue

One of the primary functions of repadmin is monitoring the replication status between the domain controllers. There are two options: either view the status of the synchronization of all domain controllers by using the command repadmin /replsummary, or view the status with the direct neighbour of the domain controller with repadmin /showrepl.

					repadmin /replsummary

We see two tables with stats; the first is the Source DSA. These are the stats for the outgoing replications. The latter, Destination DSA, is the incoming replications.

The largest Delta is always an interesting one. It tells us the longest unused connection time between two domain controllers. Now, this goes up to 60 minutes, which is normal. 

Our domain replicates changes within seconds, like password resets. But others, like schema changes, only happen sometimes and are only checked once per hour. The domain controllers check at least every hour for changes, so that is why the time can get up to 60 minutes.

The field total shows the number of replication links the domain controller has. Fails tells us how many have a Failed status (should be zero, of course), and %% is the percentage of the failed links out of the total. We see the error code under the error field.

Detailed Information on Replications

In case of errors, we must zoom in on the replication to view what is going wrong. To do this, use the command repadmin /showrepl. It shows all inbound connections and their status and displays of replication status between domain controllers.

					repadmin /showrepl

When you run the repadmin /showrepl it holds key statistics :

  1. Source and Destination Domain Controllers: The command lists the domain controllers involved in replication, indicating the source and destination of replication.

  2. Naming Contexts: It displays the naming contexts being replicated, such as the default directory partition and any application directory partitions.

  3. Last Successful Replication Time: This timestamp indicates when the last successful replication occurred, providing insights into the freshness of replicated data.

  4. Failure Timestamps: If there are replication failures, the command highlights the timestamps of the last failed replication attempts, aiding in troubleshooting.

  5. Status of Replication: The status column shows whether replication is successful, in progress, or encountering errors, allowing administrators to identify any issues quickly.

  6. Consecutive Failures: It indicates the number of consecutive replication failures, measuring the severity and persistence of replication problems.

  7. Propagation Synchronization Objects: This section displays the replication status for specific objects, helping pinpoint issues at a more granular level.

Zoom in further by adding the parameter /all, which also adds the outbound connections and the KCC connection objects. If we have a lot of connections, which can happen when we have a lot of domain controllers, then I recommend adding the parameter /errorsonly. As the name implies, this shows only the connection in an error state. We are making it easier to troubleshoot any issues.

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Showing the Replication Queue

A small queue of replications is standard in large environments, but for smaller networks, the replication queue should always contain 0 items. If we have replication issues, monitoring the queue is an excellent way to check whether our domain is healthy.

					repadmin /queue

The repadmin /queue command in Active Directory is used to view the replication queue on a domain controller. A critical component that manages the replication requests waiting to be processed between domain controllers. Running repadmin /queue provides valuable insights into the pending replication operations.

The results of the repadmin /queue command includes information such as:

  1. Naming Contexts: It lists the naming contexts for which replication requests are queued, giving administrators visibility into specific partitions awaiting synchronization.

  2. Source and Destination Domain Controllers: Displays the domain controllers involved in the replication, indicating where the queued replication requests originated and where they are destined.

  3. Pending Operations: Details the types and number of pending replication operations, such as updates, deletes, or modifications, allowing administrators to assess the workload on the replication queue.

By examining the results of repadmin /queue, administrators identify potential bottlenecks, troubleshoot replication delays, and take corrective actions to ensure timely and efficient synchronization between domain controllers. Monitoring the replication queue is crucial for maintaining the health and performance of the Active Directory replication process.

Forcing Domain Synchronization

Sometimes, we need to force the synchronization between the domain controllers, for example, after creating a new user on one of our domain controllers and requiring that user in Microsoft 365. Then, we want the new users synced to Azure AD as fast as possible to the domain controller.

The most common way to force synchronization in a single-domain environment is to run the command below. This command  pushes all changes from the domain controller that we run the command on to all other domain controllers.

					repadmin /syncall /AdeP

Note that the switch can be rearranged in any way. The /AdeP switch has the following meanings:

  • A: This switch stands for “All partitions.” It instructs Repadmin to synchronize all directory partitions on the specified domain controller when used. This ensures replication occurs for every partition hosted on that domain controller.

  • d: The “d” switch is for “Domain.” It specifies that the synchronization should occur at the domain level, including the domain directory partition.

  • e: The “e” switch is for “Enterprise Configuration.” It includes the configuration directory partition, ensuring that any changes in the enterprise configuration are synchronized.

  • P: This switch stands for “Schema.” Including this switch ensures that the schema directory partition is synchronized, allowing for propagating any schema changes made within the Active Directory forest.

Instead of pushing the changes outwards to the other domain controllers, we can also pull the changes to the domain controller on which we run the command. For this, we only need to remove the flag P.

					repadmin /syncall /Ade

Other Synchronization Options

There are also other ways to force replication between domain controllers. We can, for example, force the replication of only a specific domain controller with the command repadmin /syncall followed by the domain controller name:

					repadmin /syncall dc01

The Repadmin utility offers a diverse set of commands, and among them, the /replicate command stands out as a critical instrument for administrators seeking precise control over Active Directory replication. When executed, the /replicate command enables administrators to trigger immediate replication between specified domain controllers. This targeted approach proves invaluable in scenarios such as:

  • Forcing Urgent Replication: In situations where timely dissemination of information is critical, the /replicate command allows administrators to force an urgent replication, ensuring constant propagation of updates throughout the network.
  • Resolving Lingering Object Issues: The command proves particularly useful in addressing lingering object issues, a common challenge in large and complex AD environments. Administrators resolve discrepancies and maintain data consistency by initiating replication with precision.
  • Isolating and Testing Replication Paths: Administrators use the /replicate command to selectively test replication paths, facilitating a granular approach to troubleshooting. This targeted testing ensures that administrators accurately identify and address replication issues.
					repadmin /replicate dc01 srvlab03 CN=Configuration,DC=contoso,DC=co

The repadmin /replicate command empowers administrators with a fine-grained control mechanism to orchestrate and validate replication processes with surgical precision. This level of control is instrumental in maintaining a  healthy and efficient Active Directory environment.

Repadmin Command and Monitoring the Health of AD Replication

Ensuring the seamless operation of Active Directory (AD) is crucial for our network infrastructure’s overall health and functionality. The Repadmin command emerges as a linchpin in this endeavor, offering administrators a powerful tool to inspect and manage AD replication.

Regular deployment of the Repadmin command provides real-time insights into the replication status across domain controllers, enabling administrators to identify and rectify issues promptly. For instance:

  • Immediate Detection of Replication Failures: Repadmin’s real-time monitoring allows administrators to swiftly identify replication failures, preventing potential data inconsistencies and ensuring data integrity.
  • Timely Troubleshooting: Administrators can troubleshoot issues promptly by actively using Repadmin to monitor the health of AD replication. This proactive approach reduces downtime and enhances the overall reliability of the network.
  • Efficient Resource Utilization: Monitoring AD replication with Repadmin aids in optimizing resource utilization by pinpointing and addressing inefficiencies. This process, in turn, ensures that network operations remain smooth and responsive.

The repadmin command is the vigilant guardian of AD replication, allowing administrators to proactively manage and maintain a robust and efficient Active Directory environment.

Repadmin: Check Active Directory Replication / Health Conclusion

In conclusion, vigilantly monitoring and maintaining the health of Active Directory replication is not merely an administrative task; it is a strategic imperative in the ever-evolving landscape of network management. As explored in this article, tools like Repadmin are pivotal in providing administrators with the insights and control needed to ensure the seamless operation of AD across domain controllers.


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Marion Mendoza

Marion Mendoza

Windows Server and VMware SME. Powershell Guru. Currently working with Fortune 500 companies responsible for participating in 3rd level systems support across the enterprise. Acting as a Windows Server engineer and VMware Specialist.

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