Downloading MAC address table for a VLAN-backed NSX-T segment throws an error "CCP: null.. (Error code: 500255)"

Products

• VMware NSX

Issue/Introduction

• When trying to download MAC address table for a VLAN-backed NSX Segment (both in cases when the segment is empty and non-empty) from NSX UI over the 'Central Control Plane' component, an error similar to the following is generated:
  
  Error: Runtime API failed with error: Failed to fetch MAC or VTEP table of logical switch <UUID> from CCP: null... (Error code: 500255)
  
  
• The same observation can be seen when trying to perform the same operation via the API:
  
  

  GET https://<nsx-mngr>/policy/api/v1/infra/segments/VLAN-Test-Segment/mac-table?format=csv
  
  o/p:
  {
      "error_code": 500255,
      "module_name": "Policy",
      "error_message": "Runtime API failed with error: Failed to fetch MAC or VTEP table of logical switch 200330e7-####-####-####-651c7235f464 from CCP: null.."
  }

• A similar observation can be seen for an Overlay-backed NSX-T segment which is 'empty' (no VMs nor any gateway logical-switch-ports are connected on the segment).

 

Environment

VMware NSX 4.1.0
VMware NSX-T

Cause

• For VLAN-backed NSX segments, there are no MAC address table or VTEP table(only applicable for Overlay segments) that gets maintained on the transport nodes. This we can verify by running the below cmd in a host where we have VMs connected on a VLAN-backed NSX segment.
  ex:
  
  

  > get logical-switch 200330e7-####-####-####-651c7235f464 mac-table
  Fri Nov 03 2023 UTC 02:52:27.091
  % VLAN backed logical switch not supported

• When you try to download the MAC address table for such segment from CCP component of the NSX Managers, it tries to fetch the data from the transport nodes only. As the returned value is empty in this case the CCP returns the error.
• The same logic applies to a empty Overlay NSX segment as well.

Resolution

This issue is resolved in VMware NSX 4.2.0

Note: From NSX 4.1.1 onwards the error message has been modified to provide more context on why the error is thrown (i.e. "NOT_FOUND") instead of the generic error we can see in the "Issue/Introduction" section.

"error_message": "CCP replied with error NOT_FOUND, for MAC or VTEP table of logical switch 200330e7-####-####-####-651c7235f464."

Additional Information