The answer is to confirm that the ALB health check path configuration matches the application's custom endpoint '/health'. This is correct because the Application Load Balancer evaluates instance health by sending HTTP requests to the specified path; if the path is misconfigured—pointing to a default route like '/' instead of '/health'—the ALB will receive a non-200 response and mark the instance unhealthy, even if the application itself is running fine. On the AWS Certified DevOps Engineer Professional DOP-C02 exam, this scenario tests your understanding of target group health check settings and common misconfigurations, often appearing as a distractor where security groups or timeouts are blamed first. A common trap is overlooking that the health check path is case-sensitive by default, so 'Health' would fail against '/health'. Memory tip: "Path must match app's path—case counts, default fails."
DOP-C02 Monitoring and Logging Practice Question
This DOP-C02 practice question tests your understanding of monitoring and logging. 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 company runs a web application on Amazon EC2 instances behind an Application Load Balancer (ALB). The application uses a custom health check endpoint '/health'. The DevOps team notices that the ALB is marking some instances as unhealthy even though the application is running fine. The team checks the security groups and network ACLs and confirms they allow traffic. What should the team check next?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Confirm that the health check path is correctly configured to '/health' on the target group.
Option D is correct. The health check path must match the application's endpoint. If the path is wrong, the ALB will receive a non-200 response. Option A is incorrect because the health check port is typically the same as the traffic port. Option B is incorrect because response timeout is a symptom, not a cause. Option C is incorrect because the path is case-sensitive by default.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Ensure the health check path is case-insensitive.
Why it's wrong here
Health checks are case-sensitive.
✗
Increase the health check interval and timeout values.
Why it's wrong here
This might mask the issue, not solve it.
✓
Confirm that the health check path is correctly configured to '/health' on the target group.
Why this is correct
Misconfigured path leads to non-200 responses.
Related concept
Static NAT maps one inside address to one outside address.
✗
Verify that the health check port matches the application port.
Why it's wrong here
If the port were wrong, the health check would fail entirely, not intermittently.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
→Identify inside and outside interfaces first.
→Check whether the scenario needs static NAT, dynamic NAT or PAT.
→Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
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.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related DOP-C02 NAT questions on configuration and troubleshooting.
Monitoring and Logging — This question tests Monitoring and Logging — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: Confirm that the health check path is correctly configured to '/health' on the target group. — Option D is correct. The health check path must match the application's endpoint. If the path is wrong, the ALB will receive a non-200 response. Option A is incorrect because the health check port is typically the same as the traffic port. Option B is incorrect because response timeout is a symptom, not a cause. Option C is incorrect because the path is case-sensitive by default.
What should I do if I get this DOP-C02 question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related DOP-C02 NAT questions on configuration and troubleshooting.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
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