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Question 334 of 1,052
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CCNA Practice Question: Is troubleshooting a connectivity issue between…
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 engineer is troubleshooting a connectivity issue between two hosts on different subnets. The sending host has constructed a packet with a destination IP address of 192.168.2.10. As the packet travels down the OSI model layers on the sending host, which Protocol Data Unit (PDU) name is assigned to the data at the Transport layer after TCP segments are created, and at which layer does the IP address get encapsulated?
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
✓
PDU is a segment; IP address is added at the Network layer.
At the Transport layer, the PDU is called a segment (when using TCP) or datagram (when using UDP). The IP address is added during encapsulation at the Network layer (Layer 3), where the packet is formed. Understanding PDU names and encapsulation order is fundamental to the OSI model.
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.
- ✗
PDU is a frame; IP address is added at the Data Link layer.
Why it's wrong here
A frame is the PDU at the Data Link layer (Layer 2), not the Transport layer. IP addresses are added at the Network layer, not Data Link.
- ✓
PDU is a segment; IP address is added at the Network layer.
- ✗
PDU is a packet; IP address is added at the Transport layer.
Why it's wrong here
A packet is the PDU at the Network layer, not Transport. The IP address is added at the Network layer, not Transport.
- ✗
PDU is a datagram; IP address is added at the Transport layer.
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.
✓PDU is a segment; IP address is added at the Network layer.Correct answer▾
Why this is correct
TCP segments are formed at the Transport layer, and the IP address is encapsulated at the Network layer when creating the packet.
✗PDU is a frame; IP address is added at the Data Link layer.Wrong answer — click to see why▾
Why this is wrong here
Confuses the PDU name and encapsulation layer for IP addressing.
✗PDU is a packet; IP address is added at the Transport layer.Wrong answer — click to see why▾
Why this is wrong here
Mixes up PDU names and layers; the packet is a Layer 3 PDU, and IP is a Layer 3 function.
✗PDU is a datagram; IP address is added at the Transport layer.Wrong answer — click to see why▾
Why this is wrong here
Assumes UDP datagram and incorrectly places IP addressing at Transport 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.
Trap categories for this question
Scenario analysis trap
A datagram is the PDU for UDP at the Transport layer, but the scenario does not specify TCP or UDP; however, the IP address is still added at the Network layer, not Transport.
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 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
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: PDU is a segment; IP address is added at the Network layer. — At the Transport layer, the PDU is called a segment (when using TCP) or datagram (when using UDP). The IP address is added during encapsulation at the Network layer (Layer 3), where the packet is formed. Understanding PDU names and encapsulation order is fundamental to the OSI model.
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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