This counter reports the total bytes of unknown-unicast traffic on this port that exceeded the configured flood/storm-control threshold and were therefore dropped rather than forwarded, during the entire operational life of the element, uncleared. Because this figure accumulates over the element's uncleared operational lifetime and, unlike its clearable Stats-bin counterpart, defines no clear-time field at all, a single step-change in an otherwise-flat trend is a permanent record that a unknown-unicast flood happened at some point on this port, caused by a wave of frames destined for a MAC address that aged out of the forwarding table, or a MAC-flooding probe against the switch's CAM table, even after the underlying cause is long gone and any Stats-bin clear has erased the interim view. For example, a total that jumps by several megabytes in one day because of a wave of frames destined for a MAC address that aged out of the forwarding table, or a MAC-flooding probe against the switch's CAM table, and then stays perfectly flat for months afterward even through a Stats-bin clear, tells you that particular unknown-unicast flood was a single past incident already resolved, rather than something still actively happening today.