As per the design, IP unmanages certain AAL5|ATM subinterfaces interfaces in ic-post-port-manager.asl file. This is done to produce proper Root Cause Analysis. In this case, these unmanaged interfaces were managed explicitly by the user script. This resulted in an incorrect RCA of Interface::Down for the AAL5 interface that was explicitly managed by the user but the actual problem was Router DOWN. When the underlying AAL5/ATMSUBINTERFACE interfaces are managed, IP Manager has an additional symptom set to deduce the AAL5/ATMSUBINTERFACE as DOWN instead of arriving to Router DOWN.