With the new Virtualcenter 2.5 Update 2 comes some tighter restrictions on HA network configurations. This error message commonly occurs when the nodes in a cluster contain incompatible networks. An attempt to reconfigure clusters might fail now if they do not have identical networks.
Some customer are reporting the message:
HA agent on <esxhostname> in cluster <clustername> in <datacenter> has an error Incompatible HA Network:
Consider using the Advanced Cluster Settings das.allowNetwork to control network usage.
I am also told VMware is working to have this included in the Update 2’s release notes.