Quick Answer
The answer is a problem with the underlying physical host. This is correct because AWS EC2 status checks are divided into two types: system status checks monitor the underlying host hardware and software, while instance status checks monitor the instance’s OS, file system, and network configuration. When an instance is running but you cannot SSH into it, the instance status check has failed, which typically points to issues like host hardware degradation, hypervisor-level network loss, or power failure—not a problem within the instance itself. On the AWS Certified Developer Associate DVA-C02 exam, this scenario tests your understanding of the separation between AWS responsibility (the host) and your responsibility (the guest OS). A common trap is assuming the instance is misconfigured or that a security group is blocking SSH, but since the instance is running and the system status check passes, the underlying host is the culprit. Memory tip: “Running but unreachable? Check the host, not the guest.”
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.
The security group inbound rules are incorrect.
Why wrong: Would not cause a status check failure.
The instance has been terminated.
Why wrong: The instance is running.
There is a problem with the underlying host.
Instance status check failure indicates host issues.
The key pair is missing.
Why wrong: Key pair is not related to status checks.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
There is a problem with the underlying host.
A status check failure on a running EC2 instance indicates that the instance is passing the system status check (i.e., the underlying host is operational) but failing the instance status check, which tests network connectivity, OS responsiveness, and file system integrity. Since the instance is running but SSH is unavailable, the most likely cause is a problem with the underlying physical host (e.g., hardware degradation, network connectivity loss at the hypervisor level) that prevents the instance from responding to network traffic, even though the instance state shows as 'running'.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
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 it's wrong here
Would not cause a status check failure.
The instance has been terminated.
Why it's wrong here
The instance is running.
There is a problem with the underlying host.
Why this is correct
Instance status check failure indicates host issues.
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 key pair is missing.
Why it's wrong here
Key pair is not related to status checks.
Common exam traps
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
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.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
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
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Troubleshooting and Optimization — study guide chapter
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FAQ
Troubleshooting and Optimization — This question tests Troubleshooting and Optimization — Read the scenario before looking for a memorised answer..
The correct answer is: There is a problem with the underlying host. — A status check failure on a running EC2 instance indicates that the instance is passing the system status check (i.e., the underlying host is operational) but failing the instance status check, which tests network connectivity, OS responsiveness, and file system integrity. Since the instance is running but SSH is unavailable, the most likely cause is a problem with the underlying physical host (e.g., hardware degradation, network connectivity loss at the hypervisor level) that prevents the instance from responding to network traffic, even though the instance state shows as 'running'.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 24, 2026
This DVA-C02 practice question is part of Courseiva's free Amazon Web Services 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 DVA-C02 exam.
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