200-301 Question 155
Select 3A network administrator is troubleshooting an issue where frames are not reaching their intended destination within the local network. Upon reviewing the switch configuration, it is found that the MAC address table is not populated correctly. Which of the following describes how frame switching works and could help resolve the issue?
- A
Switches use the destination MAC address to forward frames based on the MAC address table.
- B
If a destination MAC address is not found in the MAC address table, the switch will drop the frame.
- C
Switches use the source MAC address of incoming frames to build the MAC address table.
- D
If a destination MAC address is not found in the MAC address table, the switch floods the frame out of all ports except the source port.
- E
Switches forward frames based on IP address information stored in their routing table.
Show answer and explanation
Correct answers: A, C, D
Explanation
Frame switching is a Layer 2 operation where switches forward frames based on MAC address information. The switch consults its MAC address table to determine the port associated with the destination MAC address. If the MAC address is not in the table, the switch floods the frame to all ports except the source port. Additionally, switches learn the source MAC address of incoming frames to populate the MAC address table dynamically. Understanding these principles is crucial for troubleshooting issues like incomplete MAC address tables.
- A. Correct.
Correct. Switches rely on the destination MAC address in the frame header to decide where to forward the frame based on the MAC address table.
- B. Incorrect.
Incorrect. If a destination MAC address is not found in the MAC address table, the switch does not drop the frame; instead, it floods the frame out of all ports except the one it was received on.
- C. Correct.
Correct. A switch learns the source MAC address of incoming frames and associates it with the port on which the frame was received, populating the MAC address table.
- D. Correct.
Correct. When the switch cannot find the destination MAC address in its table, it floods the frame out of all ports except the one it was received on to ensure it reaches its destination.
- E. Incorrect.
Incorrect. Frame switching is based on Layer 2 (MAC address) information, not Layer 3 (IP address) routing.