This counter tracks the total number of forwarding database entries that were or would have been learned but were discarded due to lack of space in the forwarding database; an increasing counter indicates the database is regularly filling up, which hurts subnetwork performance, while a nonzero but flat counter shows the problem occurred but isn't ongoing. Admins monitor this to detect when the switch's MAC address table is undersized for the number of hosts on the network. For example, a steadily climbing count suggests the switch needs a larger forwarding table or the network has an unusually high number of active MAC addresses, such as from a MAC-flooding attack.