vNIC disabled for VM in FT after sync - VM looses its primary IP

[antonellaandreoni]

Hi Ricardo,

First of all, I really appreciate the netbox-sync tool — I'm using it to synchronize our VMware datacenters.
My current setup is NetBox v3.7.3 and netbox-sync 1.6.0.

Sometimes, after running a sync, a VM loses its primary IP address.
In some cases, I’ve noticed that simply restarting VMware Tools resolves the issue, and the primary IP is correctly restored during the next sync.

Recently, however, I’ve encountered this issue with a few VMs that are configured with Fault Tolerance (FT), where both a primary and a secondary VM exist.
After enabling debug logging, I see that the sync process correctly finds the device by MAC address, finds the VM, the NIC, and the VLAN — but the IP is not detected as assigned to the vNIC, and it gets removed.

2025-05-08 16:14:37,938 - DEBUG2: Trying to match current object interfaces in NetBox with discovered interfaces
2025-05-08 16:14:37,949 - DEBUG2: Found '1' NICs in NetBox for 'TACP-BE-HDEM001'
2025-05-08 16:14:37,949 - DEBUG2: Found 1:1 name match for NIC 'vNIC 1 (VL501_HRZ-BE)'
2025-05-08 16:14:37,949 - DEBUG2: Parsing 'virtual machine interface' data structure: vNIC 1 (VL501_HRZ-BE) (TACP-BE-HDEM001)
2025-05-08 16:14:37,969 - INFO: IP address is no longer assigned to vNIC 1 (VL501_HRZ-BE) (TACP-BE-HDEM001) and therefore removed from this interface
2025-05-08 16:14:37,969 - INFO: Setting attribute 'primary_ip4' for 'TACP-BE-HDEM001' to None
2025-05-08 16:14:37,969 - INFO: Setting attribute 'assigned_object_id' for '10.5.101.10/24' to None
2025-05-08 16:14:37,969 - INFO: Setting attribute 'assigned_object_type' for '10.5.101.10/24' to None

Could the FT setup be causing this behavior?
Any insight on how netbox-sync handles FT configurations and IP assignments in such cases would be greatly appreciated.

Thanks again for your work on this tool!

Antonella

[bb-Ricardo]

Hi,

Would firstly recommend to upgrade to the latest 1.8.0 release.

On the other hand I don't know how the FT feature works in VMware.

May I suggest to test 1.8.0 and play around with the FT feature on said VM and report back on the findings. That would be highly appreciated.

Thank you.

[antonellaandreoni]

HI Ricardo,

I upgraded to latest 1.8.0 release and made some tests.
I made a test with FT enabled (primary and secondary VM exist) and the netbox-sync returns this message:

WARNING: Virtual machine 'TACP-BE-HDEM001' for cluster 'xxxxx' already parsed. Make sure to use unique VM names. Skipping

and on NetBox the vm has any primary IP assigned.

Then, I tested with FT disabled, so the VM is unique. In this case the netbox-sync script assigned correctly the primary IP to the VM.

With FT enabled, two virtual machine with the same name exist: primary vm and secondary vm. The secondary VM is ready to start
in the event that the host running the primary virtual machine fails.

As a workaround I will exclude FT virtual machines from syncing.

Maybe, to avoid this issue, it might be sufficient to test the FT status and if the role of the vm is secondary, skip that vm.

Thanks

Antonella

[bb-Ricardo]

Hi @antonellaandreoni,

a FT test could actually be added. I unfortunately don't have access anymore to an actual current vCenter and there I'm not able to check the API output to find the value if this VM is configured with FT and if this VM is the active or passive one.

[antonellaandreoni]

Hi,

if you can point me to where I should add this check, I can try to implement the FT (Fault Tolerance) detection myself.

thanks

Antonella

[bb-Ricardo]

would you be able to configure a VM with FT and then run the script in -l DEBUG3 mode. and capture the whole output. I Just need the VMware API output for both VMs (the active and the passive one)

[antonellaandreoni]

Hi,

these are the configuration I found for my vm TACP-BE-HDEM001:

Primary VM:

   ftInfo = (vim.vm.FaultTolerancePrimaryConfigInfo) {
       dynamicType = <unset>,
       dynamicProperty = (vmodl.DynamicProperty) [],
       **role = 1,**
       instanceUuids = (str) [
          '5006640e-2369-1346-b597-ba9bf89bcb46',
          '500617f6-f9d3-b256-e314-3cc9536e0704'
       ],
       configPaths = (str) [
          '[vsanDatastore] fc971f66-f2d8-7f25-9566-1423f2d96c90/TACP-BE-HDEM001.vmx',
          '[vsanDatastore] 05e12a68-10af-494f-cfde-1423f2d99510/TACP-BE-HDEM001.vmx'
       ],
       orphaned = false,
       secondaries = (vim.VirtualMachine) [
          'vim.VirtualMachine:vm-67159'
       ]
    },

Secondary VM:

   ftInfo = (vim.vm.FaultToleranceSecondaryConfigInfo) {
      dynamicType = <unset>,
      dynamicProperty = (vmodl.DynamicProperty) [],
      **role = 2**,
      instanceUuids = (str) [
         '5006640e-2369-1346-b597-ba9bf89bcb46',
         '500617f6-f9d3-b256-e314-3cc9536e0704'
      ],
      configPaths = (str) [
         '[vsanDatastore] fc971f66-f2d8-7f25-9566-1423f2d96c90/TACP-BE-HDEM001.vmx',
         '[vsanDatastore] 05e12a68-10af-494f-cfde-1423f2d99510/TACP-BE-HDEM001.vmx'
      ],
      orphaned = false,
      primaryVM = 'vim.VirtualMachine:vm-5438'
   },

Hope this helps.

Please, tell me if you need more info.

Thanks

Antonella