N10-009 Network Implementation Practice Question
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?
⚠ Common exam trap
The N10-009 exam 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.
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.
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).
When this WOULD be correct
A question where devices on the same physical network but with different VLAN assignments cannot communicate, e.g., a printer on VLAN 10 and a laptop on VLAN 20 with no inter-VLAN routing configured.
- ✓
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.
- ✗
The default gateway is misconfigured
Why it's wrong here
A misconfigured default gateway on the printer would not prevent communication with the laptop if both devices are intended to be on the same local subnet. Devices communicate directly within their local subnet using Address Resolution Protocol (ARP) to map IP addresses to MAC addresses, bypassing the gateway. The default gateway is only utilized when a device needs to send traffic to an IP address located on a different subnet, so its misconfiguration would not impact local peer-to-peer communication.
When this WOULD be correct
A question where devices are on different subnets and need to communicate through a router. For example: 'A workstation with IP 192.168.1.10 cannot reach a server at 10.0.0.5. The workstation can ping its own gateway. Which is the most likely cause?'
- ✗
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.
When this WOULD be correct
A question where clients cannot obtain IP addresses and receive APIPA addresses (169.254.x.x) or fail to get an IP, with the DHCP server showing no available leases, would make DHCP scope exhaustion the correct answer.
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 N10-009 exam frequently reuses these exact scenarios with slightly different constraints.
✓The subnet mask is incorrectCorrect answer▾
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.
✗The printer is on a different VLANWrong answer — click to see why▾
Why this is wrong here
The question states the router's LAN IP is 192.168.1.1 and the laptop and printer are on the same subnet (192.168.1.0/24). There is no mention of VLANs or a managed switch that would separate them into different VLANs, so VLAN misconfiguration is unlikely.
★ When this WOULD be the correct answer
A question where devices on the same physical network but with different VLAN assignments cannot communicate, e.g., a printer on VLAN 10 and a laptop on VLAN 20 with no inter-VLAN routing configured.
Why candidates choose this
Candidates may think that any connectivity issue between devices on the same router could be due to VLAN segmentation, especially if they have experience with managed networks where VLANs are common.
✗The default gateway is misconfiguredWrong answer — click to see why▾
Why this is wrong here
The default gateway is used for traffic destined outside the local subnet. Since both the laptop (192.168.1.100) and printer (192.168.1.50) are on the same subnet (assuming a /24 mask), the laptop does not need a gateway to reach the printer. A misconfigured gateway would not prevent local communication.
★ When this WOULD be the correct answer
A question where devices are on different subnets and need to communicate through a router. For example: 'A workstation with IP 192.168.1.10 cannot reach a server at 10.0.0.5. The workstation can ping its own gateway. Which is the most likely cause?'
Why candidates choose this
Candidates often associate connectivity issues with gateway misconfiguration, not realizing that local subnet communication does not require a gateway. They may overlook that the problem is within the same subnet.
✗The DHCP scope is exhaustedWrong answer — click to see why▾
Why this is wrong here
The DHCP scope is exhausted would prevent the laptop from obtaining an IP address, but the laptop already has IP 192.168.1.100, indicating DHCP is working. The issue is connectivity to a static IP printer, not IP address availability.
★ When this WOULD be the correct answer
A question where clients cannot obtain IP addresses and receive APIPA addresses (169.254.x.x) or fail to get an IP, with the DHCP server showing no available leases, would make DHCP scope exhaustion the correct answer.
Why candidates choose this
Candidates may confuse IP assignment issues with connectivity problems, assuming that if a device cannot be reached, it must be due to DHCP exhaustion, especially when DHCP is involved in the scenario.
Analysis generated from the official N10-009blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Visual reference
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Related to this question
Learn chapter
Wireless Standards and Configuration
Key term
Subnet mask
A subnet mask is a 32-bit number that helps a computer or network device determine which part of an IP address identifies the network and which part identifies the host device on that network.
Key term
LAN
Local Area Network — a network confined to a single physical location such as an office, building, or campus.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.