This read-write Integer32 (10 to 1,000,000 seconds) sets how long a dynamically learned MAC address entry stays in the switch's table before aging out if no traffic is seen from it. An admin tunes this value to balance MAC table freshness against churn: a short aging time reacts quickly to moved devices but increases relearning overhead, while a long one reduces flooding at the cost of stale entries. For example, setting this to 300 would age out inactive dynamic MAC entries after five minutes of silence.