Generally the recommendation would be to monitor the clustered services against the Cluster IP or VIP. This way, your application monitor is more reflective of the actual user experience.
Cluster VIP - Added as an ICMP-only node to Orion and all application monitors are assigned here
Server A/B - Added as WMI/SNMP nodes to Orion for local statistics and availability of the node, no application monitoring at this level.
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