Why HTTP (Port 80) is required between ClearPass cluster nodes?
ClearPass uses port 80 for Performance Monitoring.
Performance Monitoring can be enabled under Administration > Server Manager > Server Configuration > Select the Server:
Performance Monitoring uses an API call to fetch the Performance output.
If Port 80 disabled between ClearPass nodes, the Performance Monitor page will not show any records. It will display "No Activity" message in the output.
We can modify this port in Cluster-wide parameters if we don't want to use port 80: