Layer 2 Switch Forwarding: Explained | Cisco CCNA Exam 200-125

Layer 2 Switch Forwarding

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What does a Layer 2 switch use to decide where to forward a received frame?



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A. B. C. D. E. F.


The switch looks at the destination MAC address in the frame. It consults its switching table. If that MAC address is in the table, the switch sends the frame out the corresponding port which is associated with that MAC address in the table. Otherwise, the switch floods the frame out all ports except the one on which the frame arrived.

A Layer 2 switch is responsible for forwarding Ethernet frames within a local area network (LAN). When a switch receives an Ethernet frame, it examines the frame header to determine where to forward the frame. The frame header contains several fields, including the source and destination MAC addresses, the source and destination switch ports, and the Ethernet type.

Out of the given options, a Layer 2 switch uses the source MAC address and the destination MAC address to decide where to forward a received frame. Specifically, the switch consults its MAC address table, which maps MAC addresses to switch ports. The switch uses the source MAC address to learn the location of the sending device, and it uses the destination MAC address to determine which switch port to forward the frame to.

When the switch receives a frame with a destination MAC address that is not in its MAC address table, it will flood the frame out all of its ports (except the port that received the frame), in an attempt to reach the correct destination device. When the correct destination device responds to the flooded frame, the switch will update its MAC address table with the correct mapping.

Therefore, the correct answer to the question is F. destination MAC address, as it is the primary factor used by Layer 2 switches to determine where to forward a received frame.