What action occurs when the source MAC address of a frame entering a switch is already in the MAC address table?

What action occurs when the source MAC address of a frame entering a switch is already in the MAC address table?

• A. The switch removes the entry from the table
• B. The switch updates the refresh times for the entry
• C. The switch ignores the incoming frame
• D. The switch sends a notification to the network administrator

Answer: (B)

When a frame enters a switch and the source MAC address is already present in the MAC address table, the switch updates the refresh times for that entry. This means that the entry's timer is reset, preventing it from being aged out of the table prematurely. Each entry in the MAC address table has a timer associated with it, which allows the switch to manage the memory effectively by removing entries that are no longer in use after a certain period. By updating the refresh times when the same source MAC address is detected again, the switch maintains an accurate and current table, ensuring that frames are forwarded correctly to the appropriate ports based on the most recent activity. The other actions mentioned in the choices would disrupt normal switch operations, such as unnecessarily removing entries or ignoring frames, which would hinder communication across the network. Notifying network administrators is also not a typical function of a switch when handling MAC addresses. Hence, updating the refresh times is the most logical and accurate action that the switch would take in this scenario.

When a frame enters a switch and the source MAC address is already present in the MAC address table, the switch updates the refresh times for that entry. This means that the entry's timer is reset, preventing it from being aged out of the table prematurely.

Each entry in the MAC address table has a timer associated with it, which allows the switch to manage the memory effectively by removing entries that are no longer in use after a certain period. By updating the refresh times when the same source MAC address is detected again, the switch maintains an accurate and current table, ensuring that frames are forwarded correctly to the appropriate ports based on the most recent activity.

The other actions mentioned in the choices would disrupt normal switch operations, such as unnecessarily removing entries or ignoring frames, which would hinder communication across the network. Notifying network administrators is also not a typical function of a switch when handling MAC addresses. Hence, updating the refresh times is the most logical and accurate action that the switch would take in this scenario.