How can a CAM table become stale or fail and how to mitigate?

• A. CAM entries never age and are permanent once learned.
• B. CAM aging occurs only when the device is rebooted.
• C. CAM tables are static and never reflect changes in topology.
• D. CAM entries age out with inactivity; spoofing or heavy churn can cause mislearning; mitigations include port security and appropriate aging settings.

Answer: (D)

CAM tables are dynamic mappings that link every observed source MAC address to the switch port on which it was seen. To keep this directory useful as devices connect, move, or stop talking, entries are allowed to age out after a period of inactivity. If a device changes its port, or if an attacker introduces spoofed MACs or there’s a lot of rapid MAC/port changes, the switch can learn incorrect locations or keep stale mappings longer than needed, leading to misforwarding or unnecessary flooding. That’s why aging is essential: it refreshes the table so it reflects the current topology and device activity.

Mitigation centers on controlling how long entries stay and who can contribute to the table. Tuning the aging timer to a sensible value helps balance stability with accuracy. Port security can restrict or fix the MAC addresses learned on a port, preventing spoofing and limiting the impact of mislearning. For critical devices, using static or sticky MAC entries provides guaranteed, known mappings. Together, these practices reduce the window during which spoofing or heavy churn can cause the CAM table to mislearn and misforward traffic.