- A
The printer is on a different VLAN
Why wrong: In a small office with a simple wireless router, VLANs are rarely configured. Even if VLANs were used, the router would need to route between them, and the printer's IP 192.168.1.50 suggests the same VLAN as the laptop (192.168.1.100).
- B
The subnet mask is incorrect
If the printer is configured with a static subnet mask that is not /24 (e.g., /28 or /25), it will calculate that the laptop's IP is outside its local subnet. It will then try to send traffic to the default gateway instead of directly to the laptop, and if the gateway does not forward it (or the printer's gateway is wrong), communication fails.
- C
The default gateway is misconfigured
Why wrong: For local subnet communication (same network), the default gateway is not used. Devices use ARP to find each other directly. A misconfigured gateway on the printer would only affect traffic to other subnets.
- D
The DHCP scope is exhausted
Why wrong: The laptop obtained an IP (192.168.1.100), so the DHCP scope is not exhausted. DHCP scope exhaustion would prevent new devices from getting IP addresses, but the printer has a static IP, so it is not affected by DHCP.
Quick Answer
The answer is an incorrect subnet mask on the printer. This is the most likely cause because the laptop, receiving its IP via DHCP, is assigned a standard subnet mask of 255.255.255.0, which defines a /24 network from 192.168.1.1 to 192.168.1.254. If the printer’s static IP of 192.168.1.50 is configured with a different subnet mask, such as 255.255.255.252, it calculates its network as 192.168.1.48 to 192.168.1.51, placing the laptop’s IP of 192.168.1.100 on a different subnet. This mismatch causes the printer to ignore ARP requests from the laptop or route traffic to its default gateway instead of responding directly, making it unreachable. On the CompTIA Network+ N10-009 exam, this scenario tests your understanding of subnetting and how static IP configuration errors break local communication—a common trap is assuming the IP address itself is wrong. Remember the memory tip: “Mask the mismatch” to check subnet masks first when a static device is unreachable on the same IP range.
N10-009 Network Implementation Practice Question
This N10-009 practice question tests your understanding of network implementation. 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 small office uses a wireless router that provides both wired and wireless connectivity. The router's LAN IP is 192.168.1.1. A new printer with a static IP of 192.168.1.50 cannot be reached from a laptop obtaining an IP via DHCP. The laptop's IP is 192.168.1.100. Which of the following is the most likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"most likely"Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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
The subnet mask is incorrect
The laptop obtains an IP address via DHCP, which typically assigns a subnet mask of 255.255.255.0 for a /24 network. If the printer has a static IP of 192.168.1.50 but is configured with an incorrect subnet mask (e.g., 255.255.255.252), the printer may believe it is on a different subnet than the laptop (192.168.1.100). This prevents the laptop from reaching the printer because the printer will not respond to ARP requests or will send traffic to its default gateway instead of directly to the laptop.
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.
- ✗
The printer is on a different VLAN
Why it's wrong here
In a small office with a simple wireless router, VLANs are rarely configured. Even if VLANs were used, the router would need to route between them, and the printer's IP 192.168.1.50 suggests the same VLAN as the laptop (192.168.1.100).
- ✓
The subnet mask is incorrect
Why this is correct
If the printer is configured with a static subnet mask that is not /24 (e.g., /28 or /25), it will calculate that the laptop's IP is outside its local subnet. It will then try to send traffic to the default gateway instead of directly to the laptop, and if the gateway does not forward it (or the printer's gateway is wrong), communication fails.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
The default gateway is misconfigured
Why it's wrong here
For local subnet communication (same network), the default gateway is not used. Devices use ARP to find each other directly. A misconfigured gateway on the printer would only affect traffic to other subnets.
- ✗
The DHCP scope is exhausted
Why it's wrong here
The laptop obtained an IP (192.168.1.100), so the DHCP scope is not exhausted. DHCP scope exhaustion would prevent new devices from getting IP addresses, but the printer has a static IP, so it is not affected by DHCP.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that a misconfigured default gateway is the cause of local subnet communication failures, but the trap here is that the default gateway is irrelevant for same-subnet traffic; the real issue is the subnet mask, which determines whether the destination is considered local or remote.
Detailed technical explanation
How to think about this question
When two hosts are on the same IP subnet, they communicate directly via ARP to resolve MAC addresses, bypassing the default gateway. An incorrect subnet mask on the printer (e.g., 255.255.255.252 instead of 255.255.255.0) would cause the printer to calculate that the laptop's IP (192.168.1.100) is on a different subnet, so the printer would attempt to send traffic to its configured default gateway rather than responding to ARP requests from the laptop. This is a common misconfiguration in static IP setups, especially when copying settings from a different network or using a /30 mask for point-to-point links.
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 help-desk technician troubleshoots why a newly connected PC cannot reach shared printers on the same floor. The cable is good, the switch port is active, but the PC is in VLAN 20 and the printers are in VLAN 10. The uplink trunk only allows VLAN 10. A trunk being up does not mean every VLAN crosses it.
What to study next
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FAQ
Questions learners often ask
What does this N10-009 question test?
Network Implementation — This question tests Network Implementation — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The subnet mask is incorrect — The laptop obtains an IP address via DHCP, which typically assigns a subnet mask of 255.255.255.0 for a /24 network. If the printer has a static IP of 192.168.1.50 but is configured with an incorrect subnet mask (e.g., 255.255.255.252), the printer may believe it is on a different subnet than the laptop (192.168.1.100). This prevents the laptop from reaching the printer because the printer will not respond to ARP requests or will send traffic to its default gateway instead of directly to the laptop.
What should I do if I get this N10-009 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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 N10-009 practice question is part of Courseiva's free CompTIA 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 N10-009 exam.
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