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Question 621 of 1,052
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CCNA Practice Question: A network technician is troubleshooting a…
This 200-301 practice question tests your understanding of 200-301 exam topics. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.
A network technician is troubleshooting a connectivity issue between two hosts on different subnets. During the analysis, the technician captures packets and observes that the data link layer frames are being stripped and rebuilt at each router hop. Which layer of the OSI model is responsible for encapsulating the original data into segments before transmission from the source host?
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
✓
Transport layer
The correct answer is the Transport layer (Layer 4) because it is responsible for segmenting data from upper-layer applications and encapsulating it into segments (TCP) or datagrams (UDP). The scenario describes the process of encapsulation from the source host, where the original data is first broken into segments. The other options refer to different layers: the Network layer handles packets and routing, the Data Link layer handles frames and local delivery, and the Application layer provides the original data but does not segment it.
Key principle: Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Network layer
Why it's wrong here
The Network layer (Layer 3) encapsulates segments into packets and adds logical addressing (IP addresses) for routing across networks.
- ✓
Transport layer
- ✗
Data Link layer
Why it's wrong here
The Data Link layer (Layer 2) encapsulates packets into frames and adds physical addressing (MAC addresses) for delivery on a local network segment.
- ✗
Application layer
Why it's wrong here
The Application layer (Layer 7) provides the interface for applications to generate data, but it does not perform segmentation or encapsulation into segments.
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.
✓Transport layerCorrect answer▾
Why this is correct
The Transport layer (Layer 4) is responsible for segmenting upper-layer data and adding a header to create segments (TCP) or datagrams (UDP), enabling reliable or connectionless communication.
✗Network layerWrong answer — click to see why▾
Why this is wrong here
This layer does not perform the initial segmentation; it works with segments received from the Transport layer.
✗Data Link layerWrong answer — click to see why▾
Why this is wrong here
It operates on packets from the Network layer, not on the original application data directly.
✗Application layerWrong answer — click to see why▾
Why this is wrong here
Segmentation occurs at the Transport layer, not at the Application layer.
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: usable hosts are not the same as total addresses
Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.
Detailed technical explanation
How to think about this question
Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.
KKey Concepts to Remember
- CIDR notation defines the prefix length.
- Block size helps identify subnet boundaries.
- Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
- The required host count determines the smallest suitable subnet.
TExam Day Tips
- Write the block size before choosing the subnet.
- Check whether the question asks for hosts, subnets or a specific address range.
- Do not confuse /24, /25, /26 and /27 host counts.
Key takeaway
Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Real-world example
How this comes up in practice
A network engineer segments a warehouse floor into three subnets: 20 scanners, 5 printers, and 2 management hosts. Picking the wrong mask wastes addresses or leaves too few usable hosts. Exam questions test whether you can apply CIDR notation, calculate block size, and identify the correct usable-host range for a given prefix.
What to study next
Got this wrong? Here's your next step.
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related 200-301 subnetting questions on CIDR, address ranges, and subnet selection.
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FAQ
Questions learners often ask
What does this 200-301 question test?
CIDR notation defines the prefix length.
What is the correct answer to this question?
The correct answer is: Transport layer — The correct answer is the Transport layer (Layer 4) because it is responsible for segmenting data from upper-layer applications and encapsulating it into segments (TCP) or datagrams (UDP). The scenario describes the process of encapsulation from the source host, where the original data is first broken into segments. The other options refer to different layers: the Network layer handles packets and routing, the Data Link layer handles frames and local delivery, and the Application layer provides the original data but does not segment it.
What should I do if I get this 200-301 question wrong?
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related 200-301 subnetting questions on CIDR, address ranges, and subnet selection.
What is the key concept behind this question?
CIDR notation defines the prefix length.
About these practice questions
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