The answer is that the network ACL for the subnet does not allow outbound traffic, which is the most likely cause of the SAP connectivity drop. This is because network ACLs are stateless, meaning they require explicit rules for both inbound and outbound traffic; even if the security group allows inbound HTTPS on port 443, the stateless ACL will block the return traffic if its outbound rule denies it. On the AWS Certified SAP on AWS Specialty PAS-C01 exam, this scenario tests your understanding of the critical difference between stateless network ACLs and stateful security groups—a common trap is assuming that allowing inbound traffic is sufficient. Remember that security groups automatically allow return traffic, but network ACLs do not, so you must check both directions. A useful memory tip: "Stateless means you must write the return path yourself."
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.
Network Topology
An operations engineer runs the AWS CLI command above to check the state of an EC2 instance. The output shows the instance is running. However, the SAP application cannot connect to the instance. The security group allows inbound traffic on port 443 from the application's IP. What is the most likely cause of the connectivity issue?
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 network ACL for the subnet does not allow outbound traffic
The instance is running, so the issue is likely network configuration. A network ACL is stateless and must allow both inbound and outbound traffic. If the outbound rule denies traffic, responses are blocked. Security groups are stateful. The instance state is running, so it is not stopped or terminated. The command only checks state, not health checks.
Key principle: Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
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 network ACL for the subnet does not allow outbound traffic
Why this is correct
Network ACLs are stateless; if outbound rules are missing, return traffic is blocked.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Status checks affect instance health but not basic network connectivity.
✗
The security group is not associated with the instance
Why it's wrong here
The engineer can verify association; if not associated, traffic would be blocked.
Common exam traps
Common exam trap: usable hosts are not the same as total addresses
Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.
Trap categories for this question
Command / output trap
The output shows the instance is running.
Detailed technical explanation
How to think about this question
Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.
KKey Concepts to Remember
CIDR notation defines the prefix length.
Block size helps identify subnet boundaries.
Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
The required host count determines the smallest suitable subnet.
TExam Day Tips
→Write the block size before choosing the subnet.
→Check whether the question asks for hosts, subnets or a specific address range.
→Do not confuse /24, /25, /26 and /27 host counts.
Key takeaway
Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Real-world example
How this comes up in practice
A company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
What to study next
Got this wrong? Here's your next step.
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related PAS-C01 subnetting questions on CIDR, address ranges, and subnet selection.
Operations and Maintenance — This question tests Operations and Maintenance — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: The network ACL for the subnet does not allow outbound traffic — The instance is running, so the issue is likely network configuration. A network ACL is stateless and must allow both inbound and outbound traffic. If the outbound rule denies traffic, responses are blocked. Security groups are stateful. The instance state is running, so it is not stopped or terminated. The command only checks state, not health checks.
What should I do if I get this PAS-C01 question wrong?
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related PAS-C01 subnetting questions on CIDR, address ranges, and subnet selection.
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?
CIDR notation defines the prefix length.
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Question Discussion
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