VCF Import Precheck fails with "Exception in elm_ring_topology_check"

Products

• VMware vCenter Server
• VMware SDDC Manager
• VMware Cloud Foundation

Issue/Introduction

• When running the vcf_brownfield.py script to perform a precheck for a VCF import, the process fails with the following error: "vc_precheck: Exception in elm_ring_topology_check ELM ring topology check.. INTERNAL_ERROR". 
• In vCenter the output/vcf_precheck.log file does not contain specific details regarding this failure and shows data size is 0. 
• In vCenter output/vcf_brownfield.log file you see entries as below: 
  

  [YYYY-MM-DD HH:MM:SS] [INFO] vc_precheck:649: ESC[91mPre-checks failed!ESC[INTERNAL_ERROR]
  [YYYY-MM-DD HH:MM:SS] [INFO] vc_precheck:650: ESC[93m9. ELM ring topology check -> An internal error has occured. Please check the script logs in '/tmp/vcfimport/vcf-brownfield-import-5.2.#.#-buildversion/vcf-brownfield-toolset/output/vcf_precheck.log'

Environment

• VMware vCenter Server 8.x
• VMware Cloud Foundation 5.2 and above. 
• VMware SDDC Manager 5.2.x 

Cause

This issue occurs when the brownfield precheck script attempts to validate the vCenter topology and if the API call to the vCenter is not answered, times out, or returns a null/unexpected response, the script raises an internal error exception. 

Resolution

The script expects the vCenter to respond with the node type VCSA_EMBEDDED. 

Workaround:

• To troubleshoot this issue, verify the topology check via the vSphere Client to determine if the vCenter is reporting its status correctly. Follow the below steps.
  • Log in to the vSphere Web Client for the affected vCenter.
  • Navigate to Menu > Developer Center.
  • Select the API Explorer tab.
  • In the search bar, type topology/nodes to filter the API calls.
  • Locate and expand the GET /api/vcenter/topology/nodes endpoint.
  • Click Execute. (Note: Ensure you select the parameter type as VCSA_EMBEDDED if prompted, or simply execute to view the default node list.)

Validating the Response:

• Compare the output in the API Explorer with the expected JSON structure below. A healthy response should list the node with the type VCSA_EMBEDDED.
  [
    {
        "node": "vCenter_Address",
        "replication_partners": [],
        "type": "VCSA_EMBEDDED"
    }
]

Next Steps:

• If the node type is VCSA_EMBEDDED, this pre-check failure is safe to ignore. 
• If the API response is different from the expected output (e.g., the list is empty, the type is incorrect, or the API fails to execute), please open a support request with the Broadcom Support team for further investigation into the vCenter topology state.

Additional Information

Run a Precheck on the Target vCenter Before Conversion