200-301 Question 149
Single answerA network administrator observes that devices in a switched network are unable to communicate with each other after a period of inactivity. Upon investigation, they notice that MAC addresses are no longer present in the switch's MAC address table. What could be the reason for this behavior, and how can it be addressed?
- A
The MAC address table entries aged out due to the inactivity timer expiring, and the administrator can adjust the aging timer.
- B
The switch's MAC address table is full, and it randomly purged entries to make space for new ones.
- C
The devices moved to a different VLAN, causing the MAC addresses to be removed from the table.
- D
The switch experienced a power cycle, clearing the MAC address table.
Show answer and explanation
Correct answer: A
Explanation
In switched networks, MAC address tables use an aging timer to manage entries. When a device stops sending traffic, its corresponding MAC address is removed from the table after the timer expires. This behavior is normal but can cause communication issues if the timer is set too low. Adjusting the aging timer can help maintain MAC address entries for longer periods of inactivity, avoiding such problems.
- A. Correct.
Correct: MAC address table entries are removed after the inactivity timer expires if no traffic is received from the associated MAC address. The aging timer can be adjusted to prevent premature clearing of entries.
- B. Incorrect.
Incorrect: While a full MAC address table could cause issues, it does not result in entries being randomly purged. Instead, new MAC addresses are typically not added until space is available.
- C. Incorrect.
Incorrect: Moving devices to a different VLAN will cause their MAC addresses to be learned in the new VLAN, but this does not align with the described issue of entries being removed after inactivity.
- D. Incorrect.
Incorrect: A power cycle would indeed clear the MAC address table, but the scenario does not mention any power-related events.