An alarm of "BFD Down on External interface" is shown on standby N-S Network Introspection (Service Insertion) edge nodes in Manager UI.
This is a false alarm because the BFD sessions on standby N-S Network Introspection (Service Insertion) edge nodes should be down as expected. This alarm should not be shown.
VMware NSX 4.2.0.x. NS Network Introspection is deployed on an active-standby T0 or T1 logical routers.
Upgrade to NSX 4.2.1 or above