The answer is to inspect the application logs on the EC2 instances, check the security group rules, and verify the health check path and interval settings. These three steps directly address the most common root causes of ALB health check failures: application-level errors blocking the response, network access control lists or security groups blocking traffic from the ALB, and misconfigured health check parameters like a wrong path or timeout. On the AWS Certified SysOps Administrator Associate SOA-C02 exam, this scenario tests your ability to differentiate between infrastructure misconfigurations and application-layer issues, a frequent trap where candidates mistakenly blame DNS or scaling policies. Remember that health checks are a layer 4/7 probe—they don’t care about DNS resolution or instance count. A useful memory tip: “Logs, Rules, Path”—always check the application logs first, then the security group rules, and finally the health check path configuration.
SOA-C02 Reliability and Business Continuity Practice Question
This SOA-C02 practice question tests your understanding of reliability and business continuity. 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 SysOps administrator is troubleshooting a high error rate on an Application Load Balancer (ALB). The ALB is configured with two target groups: one for EC2 instances and one for Lambda functions. The administrator notices that the EC2 target group is unhealthy. Which THREE steps should the administrator take to resolve the issue?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Verify that the EC2 instances' security groups allow traffic from the ALB.
Options A, B, and D are correct. Checking security groups ensures traffic from ALB is allowed, health check configuration ensures correct path and interval, and instance logs help identify application errors. Option C is wrong because DNS issues are not related to health checks. Option E is wrong because scaling does not fix health check failures.
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.
✗
Review the ALB's DNS resolution for the target instances.
Why it's wrong here
DNS is not used for internal ALB-to-instance communication.
✓
Verify that the EC2 instances' security groups allow traffic from the ALB.
Why this is correct
Security group misconfiguration can block health checks.
Related concept
Static NAT maps one inside address to one outside address.
✗
Increase the size of the Auto Scaling group to distribute load.
Why it's wrong here
Scaling does not fix health check issues.
✓
Check the health check settings on the target group for correct path and interval.
Why this is correct
Incorrect health check settings cause false failures.
Related concept
Static NAT maps one inside address to one outside address.
✓
Inspect the application logs on the EC2 instances for errors.
Why this is correct
Application errors can cause health check failures.
Related concept
Static NAT maps one inside address to one outside address.
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 SOA-C02 NAT questions on configuration and troubleshooting.
Reliability and Business Continuity — This question tests Reliability and Business Continuity — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: Verify that the EC2 instances' security groups allow traffic from the ALB. — Options A, B, and D are correct. Checking security groups ensures traffic from ALB is allowed, health check configuration ensures correct path and interval, and instance logs help identify application errors. Option C is wrong because DNS issues are not related to health checks. Option E is wrong because scaling does not fix health check failures.
What should I do if I get this SOA-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 SOA-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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Question Discussion
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