Smarts does not generate a down notification for a device which is down. Provides details on criteria/conditions for a down notification.
Smarts 10.1.X / 2.X
The down notification generates if the following conditions are satisfied:
(IsUnresponsive && (HasNoPartition || !IsEveryNeighborUnresponsive))
So if IsUnresponsive = TRUE and HasNoPartition = TRUE or IsEveryNeighborUnresponsive = FALSE the down event is triggered.
Hence, at least one of a device's neighbors should be responsive, to get a down event in Smarts. If all connected devices are also down, no down notification is created.
Also if the device is part of a partition and all the devices in the partition group are down, the partition down event overrides the system down event.