How Checkpoint Interface check??

Critical Device "Interface Active Check" on ClusterXL Member reports its state as "problem"

• Output of the "cphaprob state" command shows the state of the member as "Down" or "Active Attention" (instead of "Active" / "Standby").
  
• Output of the "cphaprob list" / "cphaprob -l list" command shows that Critical Device "Interface Active Check" reports its state as "problem".
  
• Output of the "cphaprob -a if" command shows one of the interfaces as "Inbound: DOWN" or as "Outbound: DOWN".
  
• Output of "grep interface /var/log/messages*" command shows that "Interface Active Check" is present.
  
• In SmartView Tracker, go to the "Network & Endpoint" tab - right-click on the "Information" column title - click on "Edit Filter..." - select "Specific" - in the "Field:", select "Contains" - in the text enter/paste the cluster_info - click on OK. There displayed logs with events for "Interface Active Check".
  
  
  
  To answer this question ,  we need to know how the Checkpoint check the interfaces?