This read-write INTEGER, though its source description is empty, sits in the spanning tree group right after the topology-change fields and controls the aging time used to expire learned forwarding-database entries. An administrator tunes it to control how quickly stale learned MAC entries are flushed after a topology change reroutes traffic. For example, the admin shortens stAgeTime after a topology change so forwarding entries pointing at the old path are flushed faster, reducing temporarily black-holed traffic.