- A
Layer 2: Data Link - PDU: Frame - Responsibility: Provides node-to-node data transfer and handles error detection from the Physical layer.
This is correct because the Data Link layer (Layer 2) encapsulates packets into frames, adds MAC addresses, and handles error detection. It is responsible for node-to-node delivery.
- B
Layer 3: Network - PDU: Packet - Responsibility: Provides end-to-end delivery and logical addressing (IP addresses) for routing across networks.
Why wrong: This is incorrect because the Network layer (Layer 3) uses packets, but the question asks for the correct pairing of layer, PDU, and responsibility. While the description is accurate for Layer 3, it is not the correct answer for the given matching set.
- C
Layer 4: Transport - PDU: Segment - Responsibility: Provides reliable or unreliable delivery and error recovery between hosts.
Why wrong: This is incorrect because the Transport layer (Layer 4) uses segments, but the question asks for the correct pairing of layer, PDU, and responsibility. While the description is accurate for Layer 4, it is not the correct answer for the given matching set.
- D
Layer 1: Physical - PDU: Bits - Responsibility: Transmits raw bit stream over the physical medium.
Why wrong: This is incorrect because the Physical layer (Layer 1) uses bits, but the question asks for the correct pairing of layer, PDU, and responsibility. While the description is accurate for Layer 1, it is not the correct answer for the given matching set.
CCNA Network Infrastructure and Connectivity Practice Question
This 200-301 practice question tests your understanding of network infrastructure and connectivity. 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.
Drag and drop the OSI model layer names on the left to the correct PDU name and responsibility description on the right.
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
Layer 2: Data Link - PDU: Frame - Responsibility: Provides node-to-node data transfer and handles error detection from the Physical layer.
In the OSI model, data is encapsulated as it moves down the layers. At the Data Link layer (Layer 2), a header and trailer are added to form a frame, which enables node-to-node delivery and error detection via CRC. The Network layer (Layer 3) adds a header to create a packet (or datagram) that includes logical addressing (IP) and enables routing between different networks. The Transport layer (Layer 4) segments data and adds a header with port numbers to create a segment (TCP) or datagram (UDP), providing either reliable (connection-oriented) or unreliable (connectionless) end-to-end delivery. The Session, Presentation, and Application layers (Layers 5-7) generally use the generic PDU name 'Data', with Layer 5 managing sessions, dialog control, and synchronization, and Layer 7 providing network services to user applications. Matching any other PDU name or responsibility to these layers would violate this encapsulation hierarchy and functional separation.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Layer 2: Data Link - PDU: Frame - Responsibility: Provides node-to-node data transfer and handles error detection from the Physical layer.
Why this is correct
This is correct because the Data Link layer (Layer 2) encapsulates packets into frames, adds MAC addresses, and handles error detection. It is responsible for node-to-node delivery.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Layer 3: Network - PDU: Packet - Responsibility: Provides end-to-end delivery and logical addressing (IP addresses) for routing across networks.
Why it's wrong here
This is incorrect because the Network layer (Layer 3) uses packets, but the question asks for the correct pairing of layer, PDU, and responsibility. While the description is accurate for Layer 3, it is not the correct answer for the given matching set.
- ✗
Layer 4: Transport - PDU: Segment - Responsibility: Provides reliable or unreliable delivery and error recovery between hosts.
Why it's wrong here
This is incorrect because the Transport layer (Layer 4) uses segments, but the question asks for the correct pairing of layer, PDU, and responsibility. While the description is accurate for Layer 4, it is not the correct answer for the given matching set.
- ✗
Layer 1: Physical - PDU: Bits - Responsibility: Transmits raw bit stream over the physical medium.
Why it's wrong here
This is incorrect because the Physical layer (Layer 1) uses bits, but the question asks for the correct pairing of layer, PDU, and responsibility. While the description is accurate for Layer 1, it is not the correct answer for the given matching set.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The 200-301 exam frequently reuses these exact scenarios with slightly different constraints.
✓Layer 2: Data Link - PDU: Frame - Responsibility: Provides node-to-node data transfer and handles error detection from the Physical layer.Correct answer▾
Why this is correct
This is correct because the Data Link layer (Layer 2) encapsulates packets into frames, adds MAC addresses, and handles error detection. It is responsible for node-to-node delivery.
✗Layer 3: Network - PDU: Packet - Responsibility: Provides end-to-end delivery and logical addressing (IP addresses) for routing across networks.Wrong answer — click to see why▾
Why this is wrong here
The specific factual error is that this option correctly describes Layer 3, but the correct answer is Layer 2 for the given PDU and responsibility.
Why candidates choose this
Candidates might pick this because they know Layer 3 uses packets and IP addressing, but they fail to match it to the specific PDU and responsibility listed in the question.
✗Layer 4: Transport - PDU: Segment - Responsibility: Provides reliable or unreliable delivery and error recovery between hosts.Wrong answer — click to see why▾
Why this is wrong here
The specific factual error is that this option correctly describes Layer 4, but the correct answer is Layer 2 for the given PDU and responsibility.
Why candidates choose this
Candidates might pick this because they recall that Transport layer uses segments and provides reliability, but they do not match it to the specific PDU and responsibility in the question.
✗Layer 1: Physical - PDU: Bits - Responsibility: Transmits raw bit stream over the physical medium.Wrong answer — click to see why▾
Why this is wrong here
The specific factual error is that this option correctly describes Layer 1, but the correct answer is Layer 2 for the given PDU and responsibility.
Why candidates choose this
Candidates might pick this because they know Physical layer deals with bits, but they do not match it to the specific PDU and responsibility in the question.
Analysis generated from the official 200-301blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
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.
- Use explanations to understand the rule behind the answer.
TExam Day Tips
- Underline the problem statement mentally.
- 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 practitioner preparing for the 200-301 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
Got this wrong? Here's your next step.
Identify which 200-301 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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Network Infrastructure and Connectivity — study guide chapter
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FAQ
Questions learners often ask
What does this 200-301 question test?
Network Infrastructure and Connectivity — This question tests Network Infrastructure and Connectivity — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Layer 2: Data Link - PDU: Frame - Responsibility: Provides node-to-node data transfer and handles error detection from the Physical layer. — In the OSI model, data is encapsulated as it moves down the layers. At the Data Link layer (Layer 2), a header and trailer are added to form a frame, which enables node-to-node delivery and error detection via CRC. The Network layer (Layer 3) adds a header to create a packet (or datagram) that includes logical addressing (IP) and enables routing between different networks. The Transport layer (Layer 4) segments data and adds a header with port numbers to create a segment (TCP) or datagram (UDP), providing either reliable (connection-oriented) or unreliable (connectionless) end-to-end delivery. The Session, Presentation, and Application layers (Layers 5-7) generally use the generic PDU name 'Data', with Layer 5 managing sessions, dialog control, and synchronization, and Layer 7 providing network services to user applications. Matching any other PDU name or responsibility to these layers would violate this encapsulation hierarchy and functional separation.
What should I do if I get this 200-301 question wrong?
Identify which 200-301 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
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Last reviewed: Jun 6, 2026
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