VMware Virtual Machine Instances

[ctdemato]

In our environment, we have virtual desktops that are 1 time use only, then destroyed. Next log in, a new desktop is created with the same name but can be different IP and MAC addresses. It appears that vCenter discovery does not use the IRE. I had created a rule with advanced options, and found that it would not work. So, my question is what can I do to specify how those desktops are put into the CMDB.  The goal would be for any VMI with a client OS to simply match on name and update the record instead of creating hundreds of VM CIs which are just cluttering up the DB.

I am also open to alternative solutions to this issue if anyone has handled this differently. It would be great if we could just use the IRE for them.

[Cassandra Kittl]

I think all you need to do is NOT discover the vcenter and discover the IPs directly, making sure the identity is on the Name only (may need to update properties)

[AJ-TechTrek]

Hi @ctdemato ,

As per my understanding the Problem recap:

* Virtual desktops (VDIs) get created and destroyed frequently.
* Each new instance might have different IP/MAC but same name.
* vCenter discovery typically creates new VMs each time because by default it uses identifiers like instance UUID, BIOS serial, or MAC, not just name.
* This leads to hundreds of obsolete CIs in the CMDB.

Solution & Best Practices:

1. Use a custom Identification Rule:
* Go to CI Class Manager → Identification Rule.
* Create or adjust the rule for the class cmdb_ci_vm_instance (or the class used for virtual desktops).
* In Advanced mode, add Name (name field) as an identifier (primary or secondary).
* This forces IRE to match incoming records by name instead of unique hardware attributes.
Note: This only works if your desktop names are truly unique and stable.
If there’s a chance the same name might appear on two different active VMs, you risk collisions.

2. Use Discovery Conditions or Filters:
* Configure discovery schedule or patterns to exclude ephemeral VMs (by name pattern, folder, or tag).
* For example, exclude VMs whose name starts with TEMP- or are in a known folder.

3. Use Lifecycle Management:
* Use Data Manager or Staleness Policies to automatically set Install Status to Retired or Absent for VMs not seen for X days.
* Helps auto-clean old/unused VDI CIs.

4. For vCenter Discovery specifically:
* Confirm vCenter discovery does use IRE.
* By default, it sends payloads to IRE unless there’s a customization that bypasses it.
* Validate payload via Discovery Log → look for Payload sent to IRE.
If not, fix it:
* Check discovery patterns, make sure they use standard Identification Sections.* Ensure cmdb_ci_vm_instance has an identification rule and is active.

5. Consider tagging ephemeral VMs:
* In vCenter, tag such VMs (e.g., ephemeral=true) and filter them out.
* In discovery, use that tag to decide not to create/update them in CMDB.

Alternative solutions:
* Instead of adding them into CMDB, track ephemeral desktops separately in a non-CMDB table.
* Use Dynamic CI Groups to track them live if needed, without persisting all CIs.

Suggestion :
* Adjust Identification Rule to include name as key identifier.
* Validate vCenter discovery really calls IRE.
* Use Data Manager to auto-retire old CIs.
* Filter ephemeral VMs at discovery or tagging level.

Thank You
AJ - TechTrek with AJ - ITOM Trainer
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ServiceNow Community MVP 2025

[ctdemato]

Thank you for your detailed reply. The whole issue is that the vCenter discovery does NOT use the IRE. It is all self-contained probes, sensors and script includes. If it did use the IRE, I'd have no issue taking care of this. I have advanced rules configured for the server instances it creates, and it keeps it to only 1 CI. As a workaround, which I do not like so much, I have created data manager rules to delete the VMIs that are showing retired with an os starting with Windows 1 which takes care of Win 10, 11 and eventually 12. I think ServiceNow should move this to patterns and utilize the IRE, just like they do for most other CI discovery. 

[AJ-TechTrek]

Hi @ctdemato ,

I agreed on this with you.

Please appreciate the efforts of community contributors by marking appropriate response as Mark my Answer Helpful or Accept Solution this may help other community users to follow correct solution in future.
 

Thank You
AJ - TechTrek with AJ - ITOM Trainer
LinkedIn:- https://www.linkedin.com/in/ajay-kumar-66a91385/
YouTube:- https://www.youtube.com/@learnitomwithaj
Topmate:- https://topmate.io/aj_techtrekwithaj (Connect for 1-1 Session)
ServiceNow Community MVP 2025