PAS-C01 Operations and Maintenance Practice Question
This PAS-C01 practice question tests your understanding of operations and maintenance. 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 SAP on AWS and uses an Application Load Balancer (ALB) to distribute traffic to web dispatchers. The operations team notices that some requests are failing with 503 errors. 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.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The target instances are failing health checks.
Option C is correct because 503 errors from an ALB indicate that the target instances are unhealthy or not responding. Option A is wrong because 503 errors are not caused by SSL certificate issues. Option B is wrong because security groups would cause connection timeouts, not 503. Option D is wrong because ALB capacity is automatically scaled.
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.
✗
The SSL certificate on the ALB has expired.
Why it's wrong here
Expired SSL certificate would cause SSL handshake failures, not 503 errors.
✗
Security groups allow too much traffic.
Why it's wrong here
Security groups would cause connection timeouts, not 503 errors.
✓
The target instances are failing health checks.
Why this is correct
Unhealthy targets cause ALB to return 503 errors.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Static NAT maps one inside address to one outside address.
✗
The ALB is out of capacity.
Why it's wrong here
ALB automatically scales to handle traffic; out of capacity is rare.
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
An e-commerce site experiences heavy traffic on Black Friday and near-zero traffic during off-peak weeks. Rather than provisioning permanent large VMs, the team uses auto-scaling groups that add capacity automatically under load and reduce it overnight. Questions like this test whether you understand elasticity, availability zones, and cloud compute scaling patterns.
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 PAS-C01 NAT questions on configuration and troubleshooting.
Operations and Maintenance — This question tests Operations and Maintenance — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: The target instances are failing health checks. — Option C is correct because 503 errors from an ALB indicate that the target instances are unhealthy or not responding. Option A is wrong because 503 errors are not caused by SSL certificate issues. Option B is wrong because security groups would cause connection timeouts, not 503. Option D is wrong because ALB capacity is automatically scaled.
What should I do if I get this PAS-C01 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 PAS-C01 NAT questions on configuration and troubleshooting.
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?
Static NAT maps one inside address to one outside address.
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Question Discussion
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