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Question 182 of 1,616

Troubleshooting and Optimization →easyMultiple ChoiceObjective-mapped

DVA-C02 Troubleshooting and Optimization Practice Question

This DVA-C02 practice question tests your understanding of troubleshooting and optimization. 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 developer receives an alert that an EC2 instance's status check fails. The instance is running, but the developer cannot SSH into it. 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 security group inbound rules are incorrect.
Correct. Incorrect security group inbound rules will prevent SSH access while the instance remains running, and a status check failure (instance status check) could be due to OS-level issues unrelated to SSH.
B
The instance has been terminated.
Why wrong: Incorrect. If the instance had been terminated, it would not be running.
C
There is a problem with the underlying host.
Why wrong: Incorrect. A problem with the underlying host (system status check failure) would typically cause a complete loss of connectivity and often trigger a system status check failure, but the instance would not be reachable at all, and the alert would be for a system status check.
D
The key pair is missing.
Why wrong: Incorrect. A missing key pair would prevent SSH authentication but would not cause a status check failure.

Full breakdown with real-world context →

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 security group inbound rules are incorrect.

The instance is running but cannot be SSH'd into, which typically points to a network configuration issue such as incorrect security group inbound rules. The status check failure is a separate alert indicating that the instance has a problem (often OS-level), but the inability to SSH is most likely caused by security group rules blocking SSH traffic (port 22). Option C is incorrect because a problem with the underlying host (system status check failure) would likely render the instance unreachable entirely, not just via SSH, and the instance would often appear as impaired or stopped.

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 security group inbound rules are incorrect.
Why this is correct
Correct. Incorrect security group inbound rules will prevent SSH access while the instance remains running, and a status check failure (instance status check) could be due to OS-level issues unrelated to SSH.
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 instance has been terminated.
Why it's wrong here
Incorrect. If the instance had been terminated, it would not be running.
✗
There is a problem with the underlying host.
Why it's wrong here
Incorrect. A problem with the underlying host (system status check failure) would typically cause a complete loss of connectivity and often trigger a system status check failure, but the instance would not be reachable at all, and the alert would be for a system status check.
✗
The key pair is missing.
Why it's wrong here
Incorrect. A missing key pair would prevent SSH authentication but would not cause a status check failure.

Common exam traps

Common exam trap: answer the scenario, not the keyword

The trap here is that candidates confuse a status check failure with a network configuration issue (security group) or authentication problem (key pair), but status checks are internal health probes that do not depend on security group rules or SSH keys.

Detailed technical explanation

How to think about this question

EC2 status checks are performed by the AWS hypervisor every minute: the system status check monitors the physical host (e.g., power, network, hardware), while the instance status check monitors the guest OS (e.g., IP reception, file system integrity). A failed instance status check with a running instance often points to a degraded underlying host, which can be resolved by stopping and starting the instance (which migrates it to a new host) or by enabling an AWS-managed recovery action via CloudWatch alarms.

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 healthcare organisation deploys an application with a public-facing web tier and a private database tier. The database subnet has no public IP and only accepts connections from the web tier's security group. Questions like this test whether you can design cloud network isolation using VNets/VPCs, subnets, and security group rules.

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 DVA-C02 question test?

Troubleshooting and Optimization — This question tests Troubleshooting and Optimization — Read the scenario before looking for a memorised answer..

What is the correct answer to this question?

The correct answer is: The security group inbound rules are incorrect. — The instance is running but cannot be SSH'd into, which typically points to a network configuration issue such as incorrect security group inbound rules. The status check failure is a separate alert indicating that the instance has a problem (often OS-level), but the inability to SSH is most likely caused by security group rules blocking SSH traffic (port 22). Option C is incorrect because a problem with the underlying host (system status check failure) would likely render the instance unreachable entirely, not just via SSH, and the instance would often appear as impaired or stopped.

What should I do if I get this DVA-C02 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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