DVA-C02 Troubleshooting and Optimization Practice Question
This DVA-C02 practice question tests your understanding of troubleshooting and optimization. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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.
Network Topology
Refer to the exhibit. A developer runs the AWS CLI command for an EC2 instance. The instance is in the 'running' state, but the application hosted on it is not reachable. What should the developer check first?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "first"
Why it matters: Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Check the security group rules for inbound traffic.
The application is unreachable despite the EC2 instance being in the 'running' state, which indicates the OS and instance services are operational. The most common cause for this scenario is that the security group's inbound rules are not allowing traffic on the application's port (e.g., HTTP/HTTPS on port 80/443). Security groups act as a virtual firewall at the instance level, and unless an inbound rule explicitly permits the traffic, it will be silently dropped, making the application unreachable.
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.
✓
Check the security group rules for inbound traffic.
Why this is correct
Security groups control inbound traffic; missing rules can block access.
Clue confirmation
The clue word "first" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
Check the instance status checks in the EC2 console.
Why it's wrong here
Status checks are about the instance's health, not network accessibility.
✗
Verify the instance ID is correct.
Why it's wrong here
The instance ID is correct as the query returned data.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume a 'running' instance means the application should be reachable, overlooking that security groups control network access independently of the instance's operational state.
Detailed technical explanation
How to think about this question
Security groups are stateful — if you allow inbound traffic on a port, the outbound return traffic is automatically permitted regardless of outbound rules. However, if no inbound rule exists for the application's port (e.g., TCP 80), the packet is dropped at the hypervisor level before reaching the instance's network stack. The AWS CLI command `describe-instances` or `describe-security-groups` can be used to inspect the attached security groups and their rules, and tools like `telnet` or `nc` from an external host can confirm whether the port is reachable.
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.
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: Check the security group rules for inbound traffic. — The application is unreachable despite the EC2 instance being in the 'running' state, which indicates the OS and instance services are operational. The most common cause for this scenario is that the security group's inbound rules are not allowing traffic on the application's port (e.g., HTTP/HTTPS on port 80/443). Security groups act as a virtual firewall at the instance level, and unless an inbound rule explicitly permits the traffic, it will be silently dropped, making the application unreachable.
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: "first". Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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