NSX upgrade fails with error message 'Error migrating management interfaces to netplan.'

Products

• VMware NSX
• VMware Cloud Foundation

Issue/Introduction

• When upgrading an NSX Edge from a version earlier than 9.1 to version 9.1, the process fails during the migrate_edge_config step.
• This issue typically occurs when the Edge was originally installed using the ISO interactive method with a static IPv4 management interface.
• Retrying the upgrade does not resolve the failure.

• Below logs will be seen under /var/log/syslog for the error:
  
  2026-01-12T07:34:30.669Z <hostname> NSX 54603 SYSTEM [nsx@4413 comp="nsx-edge" subcomp="upgrade-bundle" level="INFO"] Script /image/VMware-NSX-edge-9.1.0.0.25318228/scripts/migrate_edge_config.py exited with return code 255
  
  
• Verify Interface Configuration : Inspect the /etc/network/interfaces file. Look for the management interface configuration using CIDR notation for the address:
  
  address #.#.#.#/25

Environment

VMware NSX 4.2.x

VMware NSX 9.1.0

VMware Cloud Foundation 9.1.0 

Cause

The failure is caused by a netplan configuration conversion error. Specifically, the upgrade scripts in affected versions do not correctly handle management interface IP configurations that use CIDR notation (e.g., #.#.#.#/25) in the /etc/network/interfaces file.

Resolution

This is a known issue and it is fixed in future NSX releases.

Workaround: 

To resolve this, modify the /etc/network/interfaces file to use standard netmask notation instead of CIDR. This can be done before starting the upgrade to prevent the failure or during the upgrade after a failure has occurred. No reboot or service restart is required.:

1. 1. Inspect with  cat /etc/network/interfaces.

   2. Change address #.#.#.#/# to address #.#.#.# netmask #.#.#.#.

   3. Retry the upgrade.