- A
Check physical connectivity (cables, link lights)
This is correct because the bottom-up OSI approach starts at Layer 1 (Physical). Checking cables and link lights verifies the physical connection before moving to higher layers.
- B
Verify IP configuration (DHCP, subnet mask)
This is incorrect because IP configuration is Layer 3 (Network), which comes after Layer 2 in the bottom-up approach. Physical and data link layers should be verified first.
- C
Test DNS resolution (nslookup)
This is incorrect because DNS resolution is Layer 7 (Application), which is the last step in the bottom-up approach. It should only be tested after all lower layers are verified.
- D
Ping the default gateway
This is incorrect because pinging the default gateway is a Layer 3 test, which should be performed after verifying Layer 1 and Layer 2. It is not the first step.
CCNA Network Infrastructure and Connectivity Practice Question
This 200-301 practice question tests your understanding of network infrastructure and connectivity. 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.
Drag and drop the following troubleshooting steps into the correct order to diagnose a client connectivity issue using the OSI bottom-up method.
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
Check physical connectivity (cables, link lights)
The bottom-up approach starts at Layer 1 (physical connectivity), then moves to Layer 3 (IP configuration and gateway ping), and finally to Layer 7 (DNS resolution). No Layer 2 step is included in these steps. Verifying IP configuration, such as DHCP and subnet mask, is a Layer 3 activity, not Layer 2. This method ensures systematic isolation of the problem from the physical layer upward.
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.
- ✓
Check physical connectivity (cables, link lights)
Why this is correct
This is correct because the bottom-up OSI approach starts at Layer 1 (Physical). Checking cables and link lights verifies the physical connection before moving to higher layers.
Related concept
CIDR notation defines the prefix length.
- ✓
Verify IP configuration (DHCP, subnet mask)
Why this is correct
This is incorrect because IP configuration is Layer 3 (Network), which comes after Layer 2 in the bottom-up approach. Physical and data link layers should be verified first.
Related concept
CIDR notation defines the prefix length.
- ✓
Test DNS resolution (nslookup)
- ✓
Ping the default gateway
Why this is correct
This is incorrect because pinging the default gateway is a Layer 3 test, which should be performed after verifying Layer 1 and Layer 2. It is not the first step.
Related concept
CIDR notation defines the prefix length.
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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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 — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Check physical connectivity (cables, link lights) — The bottom-up approach starts at Layer 1 (physical connectivity), then moves to Layer 3 (IP configuration and gateway ping), and finally to Layer 7 (DNS resolution). No Layer 2 step is included in these steps. Verifying IP configuration, such as DHCP and subnet mask, is a Layer 3 activity, not Layer 2. This method ensures systematic isolation of the problem from the physical layer upward.
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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Last reviewed: Jun 6, 2026
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