200-301 Question 153
Select 2A network administrator is troubleshooting a Layer 2 Ethernet switch. They observe that when a frame arrives at a switch port, the switch forwards it to a specific port rather than broadcasting it to all ports. Which of the following conditions must be true for the switch to forward the frame in this manner?
- A
The MAC address of the destination is already in the switch's MAC address table.
- B
The frame is tagged with a VLAN ID recognizable by the switch.
- C
The switch is operating in cut-through mode.
- D
The source MAC address of the frame is in the switch's MAC address table.
- E
The destination MAC address is a broadcast address.
Show answer and explanation
Correct answers: A, B
Explanation
In frame switching, a switch uses its MAC address table to forward frames to specific ports. If the destination MAC address is already in the MAC address table, the frame is forwarded to the corresponding port. Additionally, VLAN information ensures that the frame is forwarded within the correct VLAN, enabling proper segmentation and traffic management. Without these conditions, the frame may be flooded to all ports or dropped.
- A. Correct.
Correct. A switch uses its MAC address table to determine the specific port to which it should forward a frame. If the destination MAC address is in the table, the frame is sent to the associated port.
- B. Correct.
Correct. VLAN tagging ensures the frame is recognized by the switch and forwarded appropriately within the correct VLAN. Without VLAN identification, the frame may not be forwarded correctly.
- C. Incorrect.
Incorrect. The cut-through switching method determines when the switch begins forwarding a frame, but it does not affect whether the frame is forwarded to a specific port or broadcast to all ports.
- D. Incorrect.
Incorrect. The source MAC address being in the MAC address table allows the switch to learn the source port, but it does not determine which port the frame is forwarded to.
- E. Incorrect.
Incorrect. A broadcast address indicates the frame should be sent to all ports within the VLAN, not to a specific port.