This 200-901 practice question tests your understanding of network fundamentals. 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 are layers in the OSI model? (Select exactly three.)
Internet
Why wrong: 'Internet' is a layer in TCP/IP, not OSI.
Network Access
Why wrong: 'Network Access' is a TCP/IP layer, not OSI.
Transport
Layer 4 of the OSI model.
Presentation
Layer 6 of the OSI model.
Data Link
Layer 2 of the OSI model.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Transport
The Transport layer (Layer 4) of the OSI model is correct because it provides end-to-end communication, error recovery, and flow control between hosts. Protocols such as TCP and UDP operate at this layer, ensuring reliable or connectionless data delivery as required by applications.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Internet
Why it's wrong here
'Internet' is a layer in TCP/IP, not OSI.
Network Access
Why it's wrong here
'Network Access' is a TCP/IP layer, not OSI.
Transport
Why this is correct
Layer 4 of the OSI model.
Related concept
Read the scenario before looking for a memorised answer.
Presentation
Why this is correct
Layer 6 of the OSI model.
Related concept
Read the scenario before looking for a memorised answer.
Data Link
Why this is correct
Layer 2 of the OSI model.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Cisco often tests the distinction between the OSI and TCP/IP models, and the trap here is that candidates confuse the TCP/IP layers (Internet, Network Access) with OSI layers, leading them to select those incorrect options instead of the correct OSI layers like Data Link.
Detailed technical explanation
The OSI model's Transport layer segments data from the upper layers, adding a header with source and destination port numbers (e.g., TCP port 80 for HTTP). It manages reliability through sequence numbers, acknowledgments, and retransmissions in TCP, while UDP provides a lightweight, connectionless alternative. In real-world scenarios, firewalls often filter traffic based on Transport layer port numbers to enforce security policies.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A practitioner preparing for the 200-901 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
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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FAQ
Network Fundamentals — This question tests Network Fundamentals — Read the scenario before looking for a memorised answer..
The correct answer is: Transport — The Transport layer (Layer 4) of the OSI model is correct because it provides end-to-end communication, error recovery, and flow control between hosts. Protocols such as TCP and UDP operate at this layer, ensuring reliable or connectionless data delivery as required by applications.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 24, 2026
This 200-901 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 200-901 exam.
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