How a Switch Performs Frame Switching

200-301 By islever Editorial Last updated

Describe switching concepts

Short answer

B On receiving a frame, the switch looks up the destination MAC in its MAC address table to find the outgoing interface.

Question

What is a characteristic of frame switching?
  1. rewrites the source and destination MAC address
  2. performs a lookup to learn the destination interface Correct Answer
  3. sends a retransmission request when a new frame is received
  4. inspects and drops frames from unknown destinations

Key Takeaways

Frame switching = destination-MAC lookup in the MAC table for the egress port. Rewriting MACs is router/L3 behavior; dropping unknown unicast is not how switches behave.

A Layer 2 switch forwards frames by looking up the destination MAC in the MAC address table (CAM table) to select the egress port. It does not rewrite MAC addresses, does not request retransmission (that is TCP), and floods—not drops—unknown destinations.

Common mistake: Picking A (switches don't rewrite MACs), C (retransmission is L4/TCP), or D (unknown destinations are flooded, never dropped).

Expert Analysis

Why the Answer Is Correct

B is correct. A switch performs a MAC address table lookup on the destination MAC to determine the outgoing interface, then forwards the frame only out that port (or floods if unknown).

Why the Other Options Are Wrong

A is wrong: a Layer 2 switch never rewrites source/destination MAC addresses (that is router/L3 behavior). C is wrong: retransmission requests are a transport-layer (TCP) function, not switching. D is wrong: unknown destinations are flooded, not dropped.

Community Comment Notes

The vote is B (100). Commenters confirm the switch looks up the destination MAC in the CAM/forwarding table to find the egress port, and that A/C/D describe router or TCP behavior instead.

Official Reference

https://learningnetwork.cisco.com/s/ccna-exam-topics

This link opens the official vendor documentation in a new tab.

Community Votes

B
100%

100% of anonymous learners picked answer B. Votes are pick records left by other test-takers — they are not the verified answer.

Discussion 5 contributions

Compiled from public community threads and reader submissions, lightly edited for clarity. Handles and vote tallies are shown as recorded, and comments reflect the views of individual contributors.

From public community threads 5

  1. Bahdguy001 👍 2 Answered B
    B. performs a lookup to learn the destination interface. Explanation: Frame switching involves forwarding Ethernet frames based on the destination MAC address. When a switch receives a frame, it looks up the destination MAC address in its MAC address table (also known as CAM table or forwarding table). The lookup process helps the switch determine the outgoing interface (port) through which the frame should be forwarded. This lookup is essential for efficient and accurate forwarding of frames within a local network segment.
  2. squagmire 👍 2 Answered B
    is CISCLOWN time!! try and guess which one is the least incorrect out of 4 awful questions!!!! .. B seems to be the least incorrect, i just don't care enough anymore A -> switches don't do that, thats a function of a router or layer3 switch C -> he just
  3. Starlord2535 👍 1 Answered B
    I guess the answer is B but I don’t like how it is worded. The device that performs a lookup to learn the destination interface in frame switching is a Layer 2 switch. Layer 2 switches do not change the MAC addresses of frames; instead, they filter, forward, or flood frames based on the information in the MAC address table[1]. When a frame is received by a Layer 2 switch, it checks the destination MAC address against its MAC address table to determine the appropriate outgoing interface for forwarding the frame. This lookup process allows the switch to efficiently direct frames to their intended destinations within the network without altering the source and destination MAC addresses[3].
  4. [Removed] 👍 1 Answered B
    B is correct In frame switching, when a frame is received, the switch examines its destination MAC address and performs a lookup in its MAC address table to determine the appropriate outgoing interface. This allows the switch to forward the frame directly to the destination device without flooding it to all ports, which enhances network efficiency.
  5. sy0_061 👍 1
    Learning the destination address has a different meaning than Determining the destination address. Learning implies the switch puts that address into the MAC table. It does this when it receives an unkown source mac on an interface. Determining a port to forward a packet is termed as looking up the address in its address book.

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