Network Implementation: Routing, Switching, and Wireless Protocols Practice Test

The aging timer for the CAM table controls how long a learned MAC address stays in the switch’s memory after its last seen frame. When a device sends a frame, the switch learns its source MAC and records the port in the CAM. If that MAC stops transmitting, the entry would sit in the CAM forever unless it’s aged out. The aging process periodically removes those inactive entries so memory can be reused for new devices and the switch can adapt to topology changes.

When MAC churn is high—many devices frequently appearing, disappearing, or moving across ports—the CAM can fill up quickly as new addresses are learned and old ones are removed. Once the CAM is full, the switch may have to flood frames for destinations it doesn’t know on a specific port, increasing broadcast or unknown-unicast flooding. This extra flooding consumes bandwidth, taxes processing, and can reduce overall forwarding performance and stability.

So the aging timer serves to prune inactive MAC entries, and high MAC churn can lead to CAM exhaustion, flooding, and degraded performance.