I know what I did wrong: I shut down a host in my cluster without first putting it in maintenance mode. All other hosts in the cluster complained with the same warnng:
vSphere HA agent on this host cannot reach some of the management network addresses
The host that I shut down was long gone ; I couldn't add it back to the cluster. I did as suggsted above:
I stopped HA for the cluster.
I started HA for the cluster.
My cluster configuration settings were maintained; there was no need for me to configure anything else.
All of the hosts in the cluster cleared the warning message.
