SDDC manager upgrade pre-check fails with: "There are hosts in this NSX that are not known to SDDC Manager"

Products

• VMware SDDC Manager

Issue/Introduction

SDDC manager upgrade pre-check fails with: "There are hosts in this NSX that are not known to SDDC Manager". You see the error message similar to the image below:

 

Environment

VCF 5.x

Cause

Invalid/Inconsistent DNS/hostname configurations for ESXi hosts. 
When running the following command on ESXi hosts, some may return mixed case, shortname, or FQDN : hostname -f

 

Resolution

From the ESXi host UI directly (not through vCenter), adjust the ESXi host domain suffix and hostname to be consistent case across cluster. Refer: Changing the hostname of an ESXi host

Once corrected, restart SDDC manager services, or reboot SDDC manager.