vSphere HA issue

Today i was involved in a problem with HA configuration of my datacenter.
I’ve added a new host in my cluster and then i’ve made an update of vCenter. After that, when i enabled the HA on the cluster the result was:
Host 1 OK
Host 2 OK
Host 3 : Cannot complete the configuration of the HA agent on the host. Other HA configuration error.
After waiting for 3-4 minutes on 88%/91%

In detail HA agent on Host 2 in cluster XX in XX has an error:
cmd addnode failed for primary node: Internal AAM Error – agent could not start.: Unknown HA error

I’ve tried the following countermeasures:
+ Reconfigure Host for HA(not working)
+ Disable HA for the Cluster(not working)

I’ve found different documentation about this problem, the most complete is this

In my case the solution was a misconfiguration of dns, so the hosts cannot resolve the name of Host3 and then cannot add him to the HA cluster.
I’ve enabled Tech Support SSH from Configuration->Secuirty Profile and i checked this. After that i added a dns entry directly in my DNS Server.
After that all rise up normally.

Here some References:
Enable Tech Support: One
Resolve DNS problems: Two

~ di diegotech su maggio 20, 2011.