OSPF adjacency goes down when OSFP interface is configured as passive. Even in such a case, NPM OSPF discovers OSPF adjacency between two OSPF interfaces. As there is no a way to identify OSPF passive interface through SNMP mib, NPM uses certain heuristics to prevent alarming on OSPF adjacency down caused by passive OSPF interface.
For non-passive interfaces, NPM assumes down alarms to be associated with either network failure, device physical failure, or OSPF configuration failure.
For passive interfaces, down status of the adjacency between two OSPF interfaces is assumed to be caused by passive interface if any of the following conditions are fulfilled:
One of the routers is a designated router and this OSPF adjacency has a neighbor state 1 which is down, that is, OSPFNeighborStateEnum::DOWN.
There is no physical failure, for example, router down, interface down, network failure, cable failure or other similar failures.
There is no OSPF configuration failure, for example, HelloOrDeadIntervalMismatch, AuthTypeMismatch, AuthKeyMismatch, AreaIDMismatch, AreaTypeMismatch and other similar failures.