Troubleshooting duplication issues in BMC Discovery

When you observe duplication issues in BMC Discovery, use the troubleshooting steps described in this section to either resolve the problem or create a BMC Support case.

Issue symptoms

• More than one Host or Network Device with the same name is observed
• There is more than one Software Instance (SI) with the same name on a Host

Resolution

Perform the following steps to troubleshoot and resolve the duplication issue in BMC Discovery:

More than one Host (or Network Device) with the same name is observed

The most common cause for this issue is that an identity change has occurred. A Host that was previously discovered has changed sufficiently that BMC Discovery considers it to be a new Host. This change is determined by an internal weighting algorithm. For more information, see Host node.

When an identity change occurs, there is a new Host and an old Host with the same name:

• The new Host will have a different key value than the old Host, and will also have a positive age count. This age count is incremented by 1 with each subsequent and successful Discovery Access (DA).
• After the identity change, the old Host will have an age count of -1. This age count is decremented by 1 with each subsequent DA.

When the old Host reaches the aging thresholds set in Administration > Model Maintenance, the Host is destroyed. At this point, there will be only one Host with the same name in BMC Discovery. For more information, see Configuring model maintenance settings.

A Host that has undergone an identity change will show this information in the "Identity" section of the UI Host page.

• For a new Host:
  • Endpoint Used To Be Identified As: my-hostname
  • Compare with endpoint's previous Host
• For an old Host:
  • Endpoint Now Identified As:
  • The endpoint used to discover this Host now corresponds to a different Host.
  • The new Host is my-hostname
  • Compare with endpoint's new Host

Click the compare link for either of these messages to display a side-by-side comparison of the attributes in the old and new Hosts.

• To identify Hosts with a recent identity change:
  • In the UI go to Explore > Reports and run the Devices with Endpoint Identity Change report.

• To identify Hosts that have a negative age count (possibly because of an identity change), run this query:
  
  

  SEARCH Host WHERE age_count < 0 SHOW name, #InferredElement:Inference:Associate:DiscoveryAccess.endpoint 
  AS 'Scanned via', age_count AS 'Age Count', key AS 'Key', last_update_failure AS 'Last Update Failure', 
  last_update_success AS 'Last Update Success', serial AS 'Serial Number'

• To search on a particular Host that has a duplicate, run this query:
  
  

  SEARCH Host WHERE name MATCHES "redfish" show #InferredElement:Inference:Associate:DiscoveryAccess.endpoint 
  AS 'Scanned via', age_count AS 'Age Count', key AS 'Key'

If duplicate Hosts exist in BMC Discovery, they are also synchronized to the CMDB. This is expected behavior. Assuming that continuous CMDB synchronization is turned on, when a Host reaches its aging limit and is destroyed, the deletion is propagated to the CMDB. As a result, the old Host CI is marked as deleted.

To destroy all the old Hosts immediately:

1. Run the report Devices with Endpoint Identity Change. 
2. Select all in the report results and then select Actions > Destroy.
   A delete record is sent to the CMDB, and the old Host CIs are marked as deleted in CMDB.

Additional reference

See the following knowledge articles in BMC Communities:

• KA 000336097 -  Duplicate hosts (two hosts with the same name) are observed on the Discovery appliance   
• KA 000290114 -  How to find hosts whose identity has changed, and delete these in Discovery and CMDB
• KA 000304375 -  What happens in the CMDB when the identity of a host changes?
• KA 000271707 -  Duplicate hosts or network devices inferred when concurrently scanning multiple IPs of a target