What is 'MAC address table aging' on a switch, and what is the default aging time on most enterprise switches?

• A.The MAC address table (CAM table) has a configurable aging timer (default 300 seconds on most Cisco switches); if no frame with a particular source MAC is seen for 300 seconds, the entry is removed; on the next frame for that MAC as a destination, the switch floods it as unknown unicast until the MAC is re-learned from a new source frame
• B.MAC aging is disabled by default and must be manually enabled with a CLI command, so a table on a fresh box instead grows without bound until an engineer turns the timer on and the entries from machines that have been moved to another closet linger in the list for weeks and take up room that a new station could otherwise use on that port
• C.MAC address aging permanently removes inactive MACs and requires manual re-entry