What happens when the source MAC address of a frame entering a switch appears in the MAC address table associated with a different port?

What happens when the source MAC address of a frame entering a switch appears in the MAC address table associated with a different port?

• A. The switch ignores the frame and drops it
• B. The switch replaces the old entry and uses the more current port
• C. The switch generates an alert for the network administrator
• D. The switch disables the port temporarily

Answer: (B)

When a frame enters a switch and its source MAC address is already in the MAC address table associated with a different port, the switch will replace the old entry and update it to reflect the more current port. This behavior is crucial for maintaining an accurate understanding of which devices are connected to which ports at any given time. This updating process occurs because switches rely on the MAC address table to forward frames efficiently. When a frame is received, the switch checks the source MAC address. If that address is already listed in the MAC address table but associated with a different port, the switch assumes that the device has moved to this new port, and it updates the table accordingly. This ensures that future frames destined for that MAC address are sent to the correct port, maintaining optimal network performance and ensuring communication continuity. The other choices do not align with how switches function in this scenario. Ignoring the frame would disrupt communications, generating an alert is typically not part of standard switch operations for such events, and disabling the port is an extreme measure that a switch generally does not take in these circumstances.

When a frame enters a switch and its source MAC address is already in the MAC address table associated with a different port, the switch will replace the old entry and update it to reflect the more current port. This behavior is crucial for maintaining an accurate understanding of which devices are connected to which ports at any given time.

This updating process occurs because switches rely on the MAC address table to forward frames efficiently. When a frame is received, the switch checks the source MAC address. If that address is already listed in the MAC address table but associated with a different port, the switch assumes that the device has moved to this new port, and it updates the table accordingly. This ensures that future frames destined for that MAC address are sent to the correct port, maintaining optimal network performance and ensuring communication continuity.

The other choices do not align with how switches function in this scenario. Ignoring the frame would disrupt communications, generating an alert is typically not part of standard switch operations for such events, and disabling the port is an extreme measure that a switch generally does not take in these circumstances.