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Quick Answer
The correct answer is that a Layer 2 switch dynamically learns MAC addresses by examining the source MAC address of incoming frames on each port, forwards known unicasts only to the associated port, and floods broadcasts out all ports except the incoming port. This forwarding behavior relies on the switch building a MAC address table through source MAC inspection, which allows it to make precise forwarding decisions for known unicast traffic while using flooding for broadcasts and unknown unicasts. On the CCNA 200-301 v2 exam, this concept tests your understanding of how switches differ from hubs and routers, with a common trap being the assumption that unknown unicasts are dropped—they are actually flooded. A helpful memory tip is to remember that switches learn from the source, forward to the destination, and flood when they don’t know: “Learn the source, send to the known, flood the rest.”
CCNA Switching and Network Access Practice Question
This 200-301 practice question tests your understanding of switching and network access. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
Which three of the following correctly describe how a Layer 2 switch handles frames? (Choose three.)
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
If the destination MAC address is a known unicast, the switch forwards the frame only out of the port associated with that MAC address.
A Layer 2 switch forwards known unicasts only to the associated port (A), floods broadcasts out all ports except the incoming port (B), and dynamically learns MAC addresses from source MACs of frames (D). Unknown unicasts are flooded, not dropped (C is wrong). MAC address table learning relies on source MAC inspection, not CDP (E is wrong). If source and destination MAC are identical, the frame is not forwarded; it is typically dropped (F is wrong).
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that an unknown unicast is dropped, but the correct behavior is flooding; the trap is that candidates confuse 'unknown unicast' with 'unicast not in the table' and incorrectly assume it is treated like a loop-prevention drop.
Detailed technical explanation
How to think about this question
When a switch receives a frame with an unknown unicast destination MAC, it performs a 'flood' operation, sending the frame out all ports in the same VLAN except the ingress port. This behavior is defined in IEEE 802.1D and is essential for MAC address learning: the destination device will respond, allowing the switch to add its MAC address to the table. In a real-world scenario, if a switch dropped unknown unicasts, devices that have not yet communicated would never be reachable, breaking basic network functionality like ARP requests.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
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FAQ
Questions learners often ask
What does this 200-301 question test?
Switching and Network Access — This question tests Switching and Network Access — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: If the destination MAC address is a known unicast, the switch forwards the frame only out of the port associated with that MAC address. — A Layer 2 switch forwards known unicasts only to the associated port (A), floods broadcasts out all ports except the incoming port (B), and dynamically learns MAC addresses from source MACs of frames (D). Unknown unicasts are flooded, not dropped (C is wrong). MAC address table learning relies on source MAC inspection, not CDP (E is wrong). If source and destination MAC are identical, the frame is not forwarded; it is typically dropped (F is wrong).
What should I do if I get this 200-301 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 11, 2026
This 200-301 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 200-301 exam.
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