This read-only Counter64 counts queries discarded because the ingress port was down at the moment the query arrived. A nonzero count right after a known link flap is expected and benign, but a steady trickle on a port that monitoring shows as up points to a state-tracking mismatch worth investigating; because it is drawn from the most recently completed short-interval historical bin, it is a closed record of the interval right before the current one, useful for checking whether a problem seen right now had already started in the previous window. On an access port serving a multi-dwelling unit, a count of 3,051 over the last completed collection window is the kind of number an admin would trend against the join/leave rate on the same port to judge whether it's normal channel-surfing or an anomaly worth a closer look.