vSphere HA Configuration Fails with “Insufficient resources to satisfy vSphere HA failover level” due to missing firewall rules on HA master host

Products

• VMware vSphere ESXi
• VMware vCenter Server

Issue/Introduction

• Configuring vSphere HA fails with HA Agent Unreachable error
• Cluster summary shows warning "Insufficient resources to satisfy vSphere HA failover level"

Cause

This issue can be caused due to vSphere HA firewall rules getting disabled on the master host agent, hence the communication between the master and slave HA agent host breaks.

Resolution

Re-create the firewall rules by following below steps :

• Put the vSphere HA master agent host in maintenance mode.
• Reboot the host to restore all the default firewall rules.
• Reconfigure vSphere HA