Upon upgrading hosts using maintenance mode to NSX 4.1.2, the underlay gateway IP/MAC for VTEPs vanishes post-upgrade. This disruption leads to L2/L3 overlay traffic failures in customer setups where local and remote TEPs are situated in different underlay subnets. This problem manifests after the host exits maintenance mode during the upgrade.
The issue arises from the following upgrade workflows:
For systems already exhibiting this problem and missing gateway information, place the host into maintenance mode and then reboot. This action will restore the absent gateway IP/MAC.
To prevent encountering this issue, execute the NSX host upgrade using the in-place upgrade method.