- A
At the application layer, the PDU is called a segment and includes a transport layer header.
Why wrong: The application layer PDU is simply called data; a segment is a transport layer PDU.
- B
At the transport layer, the PDU is called a segment (for TCP) and includes source and destination port numbers.
The transport layer encapsulates data with a header containing port numbers to identify the application.
- C
At the network layer, the PDU is called a frame and includes source and destination MAC addresses.
Why wrong: The network layer PDU is a packet, not a frame; frames are at the data link layer.
- D
At the network layer, the PDU is called a packet and includes source and destination IP addresses.
The network layer encapsulates the segment with an IP header containing source and destination IP addresses.
- E
At the data link layer, the PDU is called a packet and includes source and destination IP addresses.
Why wrong: The data link layer PDU is a frame, not a packet, and it uses MAC addresses, not IP addresses.
Quick Answer
The correct answer identifies that at the transport layer, the PDU is called a segment (for TCP) and includes source and destination port numbers, while at the network layer, the PDU is a packet containing source and destination IP addresses. This is because the TCP/IP encapsulation process layers follow a strict order: application data is handed down, the transport layer adds a header with port numbers to form a segment, the network layer wraps that segment with IP addresses to create a packet, and finally the data link layer adds MAC addresses to produce a frame. On the CCNA 200-301 v2 exam, this question tests your ability to map each PDU name to its correct layer and header fields, a common trap being confusion between frames and packets. Remember the mnemonic “Some People Fear Data” — Segment (Transport), Packet (Network), Frame (Data Link), Data (Application) — to keep the encapsulation order straight.
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.
Which TWO statements accurately describe the encapsulation process in the TCP/IP model as data moves from the application layer to the network access layer?
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
At the transport layer, the PDU is called a segment (for TCP) and includes source and destination port numbers.
At the transport layer, TCP creates segments that include source and destination port numbers (B correct). At the network layer, the PDU is a packet containing source and destination IP addresses (D correct). Option A is wrong because the application layer generates data, not segments, and transport headers are added later. Option C mislabels the network layer PDU; it is a packet, not a frame, and MAC addresses belong to frames. Option E is wrong because the data link layer PDU is a frame, not a packet, and it uses MAC addresses, not IP addresses.
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.
- ✗
At the application layer, the PDU is called a segment and includes a transport layer header.
Why it's wrong here
The application layer PDU is simply called data; a segment is a transport layer PDU.
- ✓
At the transport layer, the PDU is called a segment (for TCP) and includes source and destination port numbers.
Why this is correct
The transport layer encapsulates data with a header containing port numbers to identify the application.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
At the network layer, the PDU is called a frame and includes source and destination MAC addresses.
Why it's wrong here
The network layer PDU is a packet, not a frame; frames are at the data link layer.
- ✓
At the network layer, the PDU is called a packet and includes source and destination IP addresses.
Why this is correct
The network layer encapsulates the segment with an IP header containing source and destination IP addresses.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
At the data link layer, the PDU is called a packet and includes source and destination IP addresses.
Why it's wrong here
The data link layer PDU is a frame, not a packet, and it uses MAC addresses, not IP addresses.
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.
✓At the transport layer, the PDU is called a segment (for TCP) and includes source and destination port numbers.Correct answer▾
Why this is correct
The transport layer encapsulates data with a header containing port numbers to identify the application.
✗At the application layer, the PDU is called a segment and includes a transport layer header.Wrong answer — click to see why▾
Why this is wrong here
The application layer PDU is called data, not a segment. A segment is the transport layer PDU, and it includes a transport layer header, not an application layer header.
Why candidates choose this
Students often confuse the terms 'segment' and 'data' because they know that segmentation occurs at the transport layer, but they may incorrectly associate the term with the application layer.
✗At the network layer, the PDU is called a frame and includes source and destination MAC addresses.Wrong answer — click to see why▾
Why this is wrong here
The network layer PDU is called a packet, not a frame. Frames are at the data link layer and include MAC addresses, not IP addresses.
Why candidates choose this
Students may confuse the terms 'packet' and 'frame' because both are used in networking, and they might think that frames contain IP addresses since they are used in local delivery.
✗At the data link layer, the PDU is called a packet and includes source and destination IP addresses.Wrong answer — click to see why▾
Why this is wrong here
The data link layer PDU is called a frame, not a packet. Frames include source and destination MAC addresses, not IP addresses.
Why candidates choose this
Students often mix up the terms 'packet' and 'frame' because both are encapsulated units, and they may incorrectly associate IP addresses with the data link layer due to their role in end-to-end communication.
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
Cisco often tests the specific PDU naming conventions (segment, packet, frame) and the layer at which each header is added, causing candidates to confuse the network layer packet with the data link layer frame or to misidentify the transport layer PDU.
Detailed technical explanation
How to think about this question
In the TCP/IP model, encapsulation adds headers at each layer: the transport layer adds a TCP or UDP header (with port numbers), the network layer adds an IP header (with source/destination IP addresses), and the data link layer adds a frame header (with MAC addresses). The term 'segment' specifically applies to TCP, while UDP uses 'datagram'; both are transport layer PDUs. Understanding the exact PDU names and the layer where each header is added is critical for troubleshooting and protocol analysis.
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?
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: At the transport layer, the PDU is called a segment (for TCP) and includes source and destination port numbers. — At the transport layer, TCP creates segments that include source and destination port numbers (B correct). At the network layer, the PDU is a packet containing source and destination IP addresses (D correct). Option A is wrong because the application layer generates data, not segments, and transport headers are added later. Option C mislabels the network layer PDU; it is a packet, not a frame, and MAC addresses belong to frames. Option E is wrong because the data link layer PDU is a frame, not a packet, and it uses MAC addresses, not IP addresses.
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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