Reimaging an NSX node/host without first cleanly removing it from NSX resulted in the host being in a disconnected state.

Products

• VMware NSX

Issue/Introduction

• You are reimaging the host before following the recommended process, which is to first remove NSX from the host so NSX manager can properly decommission it. 
• It results in the host being in 'Host Disconnected' state for NSX configuration.
• 

Environment

VMware NSX 

Cause

The host was reimaged before the NSX manager could properly decommission it. This leaves the manager thinking the node is still part of the fabric, but without a valid management plane connection.

Resolution

• Follow resolution steps mentioned in KB Installing or Upgrading NSX on an ESXi host fails reporting the node already exists
• If your NSX version is one of the versions affected by the JDK bug(NSX is Impacted by JDK-8330017: ForkJoinPool Stops Executing Tasks Due to ctl Field Release Count (RC) Overflow), you might need to first perform rolling reboot of the managers before following above-mentioned steps.