Question 419 of 1,020

IP Addressing →easyMultiple ChoiceObjective-mapped

Why a Laptop Can't Connect When Its IP is on a Different Subnet

This 220-1201 practice question tests your understanding of ip addressing. 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 customer reports that their laptop can connect to the internet at home but not at a coffee shop. The coffee shop uses a /24 subnet with a gateway of 192.168.1.1. The laptop's IP is 192.168.2.10. What 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.

A
The DNS server address is incorrect.
Why wrong: DNS issues would affect name resolution, but the laptop cannot even reach the gateway, so this is not the primary cause.
B
The laptop's IP address is on a different subnet than the coffee shop's network.
The laptop's IP (192.168.2.10) is on the 192.168.2.0/24 subnet, while the coffee shop uses 192.168.1.0/24, preventing gateway communication.
C
The wireless card is faulty.
Why wrong: The laptop works at home, so the wireless card is functional; the issue is network configuration.
D
The subnet mask is set to 255.0.0.0.
Why wrong: A /24 subnet mask is 255.255.255.0; using 255.0.0.0 would make the laptop think it's on a larger network, but the specific mismatch here is the IP range.

Full breakdown with real-world context →

Quick Answer

The answer is that the laptop’s IP address is on a different subnet than the coffee shop’s gateway. This is because a device must be on the same logical subnet as its default gateway to send traffic outside the local network; here, the laptop’s IP of 192.168.2.10 falls in the 192.168.2.0/24 subnet, while the coffee shop’s gateway at 192.168.1.1 belongs to the 192.168.1.0/24 subnet, so the laptop cannot even reach the router. On the CompTIA A+ Core 1 220-1201 exam, this scenario tests your understanding of subnetting and how IP addressing directly affects connectivity—a common trap is assuming any 192.168.x.x address will work on any 192.168 network, but the third octet must match the gateway’s subnet. A quick memory tip: think of subnets like neighborhoods—if your house number is on a different street, you can’t reach the main road.

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 laptop's IP address is on a different subnet than the coffee shop's network.

The coffee shop's network uses a /24 subnet (255.255.255.0), which means all devices must have an IP address in the 192.168.1.0/24 range to communicate with the gateway at 192.168.1.1. The laptop's IP address of 192.168.2.10 falls in a different subnet (192.168.2.0/24), so the laptop cannot send frames to the gateway or receive a DHCP lease, preventing internet access despite a successful Wi-Fi association.

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 DNS server address is incorrect.
Why it's wrong here
DNS issues would affect name resolution, but the laptop cannot even reach the gateway, so this is not the primary cause.
✓
The laptop's IP address is on a different subnet than the coffee shop's network.
Why this is correct
The laptop's IP (192.168.2.10) is on the 192.168.2.0/24 subnet, while the coffee shop uses 192.168.1.0/24, preventing gateway communication.
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 wireless card is faulty.
Why it's wrong here
The laptop works at home, so the wireless card is functional; the issue is network configuration.
✗
The subnet mask is set to 255.0.0.0.
Why it's wrong here
A /24 subnet mask is 255.255.255.0; using 255.0.0.0 would make the laptop think it's on a larger network, but the specific mismatch here is the IP range.

Common exam traps

Common exam trap: answer the scenario, not the keyword

Cisco often tests the concept that a device can associate with a Wi-Fi network (Layer 2) but still fail to communicate at Layer 3 if its IP address is not in the same subnet as the gateway, leading candidates to incorrectly suspect DNS or hardware issues.

Detailed technical explanation

How to think about this question

When a client connects to a Wi-Fi network, it must perform a four-way handshake (802.11 authentication) and then obtain an IP via DHCP. If the client's IP is statically set or from a previous network, the ARP request for the gateway (192.168.1.1) will fail because the client's own IP is not in the same broadcast domain; the gateway will not respond to ARP requests from a different subnet. In real-world troubleshooting, using 'ipconfig /all' (Windows) or 'ifconfig' (Linux/macOS) reveals the subnet mask mismatch, and the fix is to set the client to obtain an IP automatically via DHCP.

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 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.

Visual reference

What to study next

Got this wrong? Here's your next step.

Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.

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FAQ

Questions learners often ask

What does this 220-1201 question test?

IP Addressing — This question tests IP Addressing — Read the scenario before looking for a memorised answer..

What is the correct answer to this question?

The correct answer is: The laptop's IP address is on a different subnet than the coffee shop's network. — The coffee shop's network uses a /24 subnet (255.255.255.0), which means all devices must have an IP address in the 192.168.1.0/24 range to communicate with the gateway at 192.168.1.1. The laptop's IP address of 192.168.2.10 falls in a different subnet (192.168.2.0/24), so the laptop cannot send frames to the gateway or receive a DHCP lease, preventing internet access despite a successful Wi-Fi association.

What should I do if I get this 220-1201 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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