Resolving Multiple 'Unknown Computers' in Configuration Manager: A Comprehensive Guide

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Microsoft System Center 2012 Configuration Manager (ConfigMgr 2012) is a powerful tool for managing devices within an enterprise environment. It provides comprehensive capabilities for operating system deployment, software distribution, patch management, and more. A fundamental aspect of OS deployment, particularly for bare-metal scenarios or reimaging devices, involves targeting the “Unknown computers” collection. These collections represent devices that ConfigMgr has discovered but for which it does not have a client installed or sufficient information to identify them as a known resource.

The “Unknown computers” collection is typically split into two sub-collections: “All Unknown Computers” and “x64 Unknown Computers” (or similar architecture-specific variants). These collections are dynamic and automatically populated by ConfigMgr based on discovery methods and information gathered during processes like PXE boot. When a device starts via PXE, ConfigMgr checks its database. If no record exists for the device based on its MAC address or SMBIOS GUID, it is considered an unknown computer and temporarily associated with an entry in the database, often represented within these collections. This allows administrators to target task sequences, primarily for OS deployment, to devices that are not yet fully managed clients.

Understanding the Scenario Leading to Multiple Unknown Collections¶

A specific issue can arise in ConfigMgr 2012 environments, leading to the appearance of multiple instances of the “Unknown computers” collection within the Configuration Manager console. This can cause confusion and potentially disrupt automated deployment processes targeting these collections. The scenario typically involves a series of site management actions that leave behind remnants or create conflicting entries in the database.

Consider a deployment hierarchy involving a central administration site (CAS) and one or more primary sites. The described issue is frequently observed in environments where a primary site was initially installed, subsequently uninstalled, and then reinstalled using the exact same server name and site code. While ConfigMgr attempts to clean up database entries during an uninstall, certain objects or references related to site-specific roles, such as the Distribution Point with PXE responder, might not be completely removed or might leave behind orphaned data that conflicts with the newly installed site components.

The reinstallation process creates new database entries for the site and its roles. However, if remnants from the previous installation exist, particularly those tied to device discovery or PXE services, ConfigMgr may interpret these old entries alongside the new ones. This can lead to the console displaying duplicate “Unknown computers” collections, each potentially linked to different, possibly inactive or conflicting, database records representing the unknown state of devices interacting with the site’s PXE service over time. This state of multiple collections makes it unclear which collection is the definitive target for current bare-metal or unknown machine deployments.

Symptoms of Duplicate Unknown Computer Collections¶

The most obvious symptom of this issue is seeing more than the standard one or two (All Unknown Computers, x64 Unknown Computers) sets of “Unknown computers” collections listed in the Device Collections node of the ConfigMgr console. You might see collections with identical names, or perhaps slight variations depending on how the database records are interpreted.

Navigating through the console and examining these collections might reveal that some contain active unknown computer entries (devices currently PXE booting), while others might appear empty or contain entries that correspond to older, inactive PXE boot attempts from the previously installed site. The presence of these duplicates complicates the selection of the correct target collection for deploying task sequences. If deployments are targeted to an incorrect or inactive duplicate collection, devices attempting to PXE boot and receive a task sequence may fail to find an advertised deployment, halting the OS installation process. This directly impacts the ability to perform bare-metal deployments or reimage machines efficiently using ConfigMgr.

Beyond the console clutter, the primary impact is on the reliability of Task Sequence deployments targeted at unknown machines. If a deployment is advertised to a collection that does not include the specific database object representing the currently PXE booting unknown device (perhaps because that object is associated with one of the ‘inactive’ duplicate collections), the device will not receive the policy and the task sequence will not run. This necessitates a clear and reliable method to target all potential unknown computer objects, regardless of which underlying database entry or ‘duplicate’ collection they might be associated with due to the site reinstallation scenario.

Workaround: Consolidating Unknown Objects into a Single Collection¶

The most effective workaround for this problem involves creating a new, consolidated device collection that includes all computer objects that ConfigMgr identifies as “Unknown”, regardless of which default “Unknown computers” collection they might currently appear in or which underlying database record represents them. By targeting deployments to this single, comprehensive collection, you ensure that any device presenting itself as unknown via PXE will be evaluated for applicable task sequence deployments, irrespective of the database anomaly causing the duplicate collections.

This approach circumvents the issue of relying on potentially problematic default collections by creating a new collection based on a query that captures the defining characteristics of all unknown systems within the ConfigMgr database. Once this collection is created and verified to contain the desired objects (both active and potentially inactive but still relevant ‘unknown’ entries), you can then retarget your OS deployment task sequence advertisements to this new, reliable collection. This guarantees that any unknown device contacting the site’s PXE service will receive the deployment policy, assuming all other prerequisites (like boundaries and task sequence content) are correctly configured.

The core of this workaround lies in defining a WQL (WMI Query Language) query for the new collection that selects all relevant unknown computer objects from the Configuration Manager database. The query needs to be broad enough to capture devices that are being presented as unknown via PXE. A common characteristic of these objects in the ConfigMgr database is their name representation or specific properties indicating a lack of client or assignment combined with a temporary discovery record.

Implementing the Workaround: Step-by-Step Guide¶

Follow these steps to implement the workaround:

1. Open the Configuration Manager Console: Launch the ConfigMgr 2012 console and navigate to the “Assets and Compliance” workspace.
2. Navigate to Device Collections: Expand “Device Collections”.
3. Create a New Device Collection: Right-click on “Device Collections” and select “Create Device Collection”.
4. Specify Collection Details:
   • Name: Give your collection a descriptive name, such as “All Unknown Computers Consolidated” or “PXE Deployment Target Collection”.
   • Comment: Add a comment explaining the purpose of the collection (e.g., “Consolidated collection for all unknown computers, workaround for multiple unknown collections issue”).
   • Limiting Collection: Choose a suitable limiting collection. For targeting all potential unknown devices within the hierarchy or specific sites, “All Systems” is often appropriate, but be mindful of scope. For a specific primary site experiencing the issue, limiting it to “All Systems” within that primary site’s scope might be preferable. Select the limiting collection and click “Next”.
5. Add Membership Rules: On the “Membership Rules” page, click “Add Rule” and select “Query Rule”.

6. Configure the Query Rule:

   • Name: Give the query rule a name (e.g., “Select All Unknowns”).
   • Click the “Edit Query Statement…” button.
   • In the Query Statement properties, go to the “Criteria” tab.
   • Click the “Show Query Language” button. This allows you to paste or type the WQL query directly.

   • Enter the following WQL query (or a similar query that targets objects known as ‘Unknown Computer’ in your environment):

     select
         SMS_R_System.ResourceId,
         SMS_R_System.ResourceType,
         SMS_R_System.Name,
         SMS_R_System.SMSUniqueIdentifier,
         SMS_R_System.ResourceDomainORWorkgroup,
         SMS_R_System.Client
     from
         SMS_R_System
     where
         SMS_R_System.Name = 'Unknown Computer'
     

     
     Explanation of the Query: This query selects resources from the SMS_R_System class (which represents discovered systems) where the Name property is exactly ‘Unknown Computer’. This targets the specific naming convention ConfigMgr uses for unknown systems appearing in the console, effectively consolidating all such entries regardless of which underlying system record or original unknown collection they might be associated with due to the reinstallation issue.

   • Click “OK” in the Query Statement properties.

   • Click “OK” in the Query Rule properties.
     7. Complete Collection Creation: Click “Next” through the summary pages and then “Close” to create the collection.
     8. Update Collection Membership: The new collection will appear in the Device Collections list. Right-click the new collection and select “Update Membership”. This triggers the evaluation of the query. Wait a few minutes for the membership to update.
     9. Verify Collection Members: Right-click the collection and select “Show Members” to verify that it populates with the expected unknown computer objects. You should see entries corresponding to the ‘Unknown Computer’ name.
     10. Retarget Task Sequence Advertisements: Navigate to “Software Library” > “Operating Systems” > “Task Sequences”. Find the OS deployment task sequence(s) you use for unknown or bare-metal machines. Right-click the deployment(s) and select “Properties”. Go to the “General” tab and update the “Collection” field to point to your newly created consolidated collection. You might need to delete the old advertisement and create a new one targeting the new collection, depending on your process. Ensure your task sequence deployments are now targeting this new collection instead of the potentially problematic default “Unknown computers” collections.

By following these steps, you establish a single, reliable target collection for your unknown computer deployments, effectively bypassing the issues caused by the duplicate default collections.

Why This Workaround is Effective¶

The success of this workaround stems from how ConfigMgr processes deployments and unknown devices. When a device PXE boots and contacts a Distribution Point configured for PXE, the DP sends a request to the management point to identify the device and check for available deployments. The management point queries the ConfigMgr database using the device’s MAC address and SMBIOS GUID.

In the scenario causing duplicate unknown collections, the database might contain multiple, potentially conflicting or orphaned records associated with the same physical device (identified by MAC/GUID over time or across site re installations), or simply multiple abstract ‘unknown’ placeholders. The default “Unknown computers” collections are dynamically built based on internal rules that might get confused by these database inconsistencies, leading to the display of duplicates.

By creating a new collection with a query based on the visible characteristic (Name = 'Unknown Computer'), you create a collection that should pull in all records that ConfigMgr designates with this name, regardless of the underlying duplicate issue. When a device PXE boots, the management point’s lookup process will find the record representing that device (even if it’s one of the ‘problematic’ ones) and check its collection memberships. Since your new collection is based on a query that encompasses all such records, the device will be correctly identified as a member of your new collection, and the task sequence deployment targeted to that collection will become available to it.

This method ensures that the deployment policy reaches the device by consolidating all possible ‘unknown’ database representations into a single, reliable collection target.

Considerations and Further Troubleshooting¶

While the workaround addresses the immediate issue of targeting deployments, the underlying database inconsistency causing the duplicate collections may persist. In most cases, this console clutter is harmless once deployments are redirected to the new collection. However, in rare instances or if other related issues arise, a deeper database analysis and cleanup might be necessary. Such database modifications should only be performed by experienced ConfigMgr administrators and ideally under the guidance of Microsoft Support, as incorrect changes can severely damage the ConfigMgr environment.

It’s also important to ensure that your PXE-enabled Distribution Points are healthy and communicating correctly with the site. Issues with WDS, the PXE responder service, or communication channels between the DP and Management Point can also prevent unknown computers from booting correctly or finding deployments, even with the consolidated collection in place. Always check the relevant log files on the client (smsts.log if the task sequence starts, PXESetup.log, PXEControl.log on the DP) and site server for clues.

The lifecycle of unknown computer objects in ConfigMgr involves temporary records created during discovery or PXE boot. These records are often replaced or associated with a full system record once the ConfigMgr client is installed. The issue of duplicates in this scenario highlights how site infrastructure changes can sometimes interfere with the clean management of these temporary or initial discovery records.

For further learning on Configuration Manager OS Deployment, PXE, and collection management, you can find numerous resources online. Searching platforms like YouTube for tutorials on “SCCM 2012 OS Deployment Unknown Computers” or “ConfigMgr PXE Boot Troubleshooting” can provide valuable visual guides and additional tips. For example, videos demonstrating the process of creating collections or deploying task sequences to unknown machines in ConfigMgr 2012 can be helpful supplementary material when implementing this workaround.

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Addressing the appearance of multiple ‘Unknown computers’ collections in Configuration Manager 2012, particularly after a site reinstallation scenario, is crucial for maintaining a reliable OS deployment process via PXE. By implementing the described workaround of creating a consolidated collection based on a WQL query targeting all objects named ‘Unknown Computer’, administrators can ensure that task sequence deployments consistently reach any device presenting itself as unknown, effectively mitigating the confusion and deployment failures caused by the duplicate default collections. While the visual clutter in the console may remain, the operational impact on OS deployment is resolved by redirecting deployment targets to this reliable, custom-built collection.

What other challenges have you encountered with ConfigMgr Unknown Computers or PXE deployments, and how did you resolve them? Share your experiences in the comments below!