SOA-C02 Networking and Content Delivery Practice Question
This SOA-C02 practice question tests your understanding of networking and content delivery. 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.
Network Topology
Refer to the exhibit. An EC2 instance is registered with an ALB target group. The health check returns 502. 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.
Network Topology
A
The instance is not reachable from the ALB due to a network ACL.
Why wrong: Incorrect because that would cause connection timeout, not 502.
B
The instance is not registered with the target group.
Why wrong: Incorrect because the output shows the instance is registered but unhealthy.
C
The web server on the instance is returning an HTTP 502 response.
Correct because the health check receives a 502 from the target application.
D
The health check path is configured for HTTPS but the instance only supports HTTP.
Why wrong: Incorrect because the health check port is 80, not 443.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The web server on the instance is returning an HTTP 502 response.
Option C is correct because a 502 Bad Gateway from the ALB indicates that the target responded with an invalid or empty HTTP response, which is usually caused by the web server on the instance returning an HTTP 502 error. Option A is wrong because a network ACL blocking traffic would result in a connection timeout (504) or unreachable error, not a 502. Option B is wrong: if the instance were not registered, the ALB would not perform health checks on it; the fact that a health check is failing shows the instance is registered. Option D is wrong: a mismatch between HealthCheck protocol (HTTPS) and instance support (HTTP) would cause the ALB to fail to establish a TLS connection, resulting in a 504 Gateway Timeout or a connection error, not a 502.
Key principle: ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
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 instance is not reachable from the ALB due to a network ACL.
Why it's wrong here
Incorrect because that would cause connection timeout, not 502.
✗
The instance is not registered with the target group.
Why it's wrong here
Incorrect because the output shows the instance is registered but unhealthy.
✓
The web server on the instance is returning an HTTP 502 response.
Why this is correct
Correct because the health check receives a 502 from the target application.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Standard ACLs match source addresses.
✗
The health check path is configured for HTTPS but the instance only supports HTTP.
Why it's wrong here
Incorrect because the health check port is 80, not 443.
Common exam traps
Common exam trap: ACLs stop at the first match
ACLs are processed top to bottom. The first matching entry wins, and an implicit deny usually exists at the end.
Trap categories for this question
Command / output trap
Incorrect because the output shows the instance is registered but unhealthy.
Detailed technical explanation
How to think about this question
ACL questions test precision: source, destination, protocol, port and direction. A generally correct ACL can still fail if it is applied on the wrong interface or in the wrong direction.
KKey Concepts to Remember
Standard ACLs match source addresses.
Extended ACLs can match source, destination, protocol and ports.
The first matching ACL entry is used.
There is usually an implicit deny at the end.
TExam Day Tips
→Check inbound versus outbound direction.
→Read the ACL from top to bottom.
→Look for a broader permit or deny above the intended line.
Key takeaway
ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
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.
Visual reference
What to study next
Got this wrong? Here's your next step.
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related SOA-C02 ACL questions on filtering logic and placement.
Networking and Content Delivery — This question tests Networking and Content Delivery — Standard ACLs match source addresses..
What is the correct answer to this question?
The correct answer is: The web server on the instance is returning an HTTP 502 response. — Option C is correct because a 502 Bad Gateway from the ALB indicates that the target responded with an invalid or empty HTTP response, which is usually caused by the web server on the instance returning an HTTP 502 error. Option A is wrong because a network ACL blocking traffic would result in a connection timeout (504) or unreachable error, not a 502. Option B is wrong: if the instance were not registered, the ALB would not perform health checks on it; the fact that a health check is failing shows the instance is registered. Option D is wrong: a mismatch between HealthCheck protocol (HTTPS) and instance support (HTTP) would cause the ALB to fail to establish a TLS connection, resulting in a 504 Gateway Timeout or a connection error, not a 502.
What should I do if I get this SOA-C02 question wrong?
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related SOA-C02 ACL questions on filtering logic and placement.
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?
Standard ACLs match source addresses.
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