- A
Verify that the network ACLs for both subnets allow the required traffic
Network ACLs are stateless and filter traffic at the subnet boundary.
- B
Enable VPC Flow Logs to analyze traffic
Why wrong: Flow logs help diagnose but are not a configuration check.
- C
Verify that the security groups of both instances allow inbound/outbound traffic on the required ports
Security groups act as instance-level firewalls.
- D
Verify that the NAT Gateway is configured correctly
Why wrong: NAT Gateway is for internet access, not internal communication.
- E
Verify that the route tables for both subnets have routes to each other's CIDR
Without proper routes, packets cannot be forwarded between subnets.
Question 719 of 1,546
SOA-C02 Network ACL (NACL) 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. A key principle to apply: network ACL (NACL). 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 needs to troubleshoot connectivity between two EC2 instances in the same VPC but different subnets. The instances cannot communicate. Which THREE checks should the administrator perform? (Choose three.)
Answer choices
Why each option matters
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 network ACLs for both subnets allow the required traffic
Correct answers: A, C, and E. Option A is correct because network ACLs (NACLs) at the subnet level can block traffic between subnets, so verifying both subnet NACLs is necessary. Option C is correct because security groups (SGs) at the instance level control inbound/outbound traffic; if SGs don't allow the required ports, instances cannot communicate. Option E is correct because route tables in each subnet must have routes to the other subnet's CIDR for traffic to be forwarded. Option B (flow logs) is a monitoring tool, not a cause. Option D (NAT Gateway) is used for outbound internet access, not internal VPC communication.
Key principle: Network ACL (NACL)
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Verify that the network ACLs for both subnets allow the required traffic
Why this is correct
Network ACLs are stateless and filter traffic at the subnet boundary.
Related concept
Network ACL (NACL)
- ✗
Enable VPC Flow Logs to analyze traffic
Why it's wrong here
Flow logs help diagnose but are not a configuration check.
- ✓
Verify that the security groups of both instances allow inbound/outbound traffic on the required ports
Why this is correct
Security groups act as instance-level firewalls.
Related concept
Network ACL (NACL)
- ✗
Verify that the NAT Gateway is configured correctly
- ✓
Verify that the route tables for both subnets have routes to each other's CIDR
Why this is correct
Without proper routes, packets cannot be forwarded between subnets.
Related concept
Network ACL (NACL)
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap is focusing on flow logs or NAT Gateway as connectivity checks, when the root causes are typically NACLs, SGs, and routing.
Detailed technical explanation
How to think about this question
Treat this as a scenario question. Identify the problem, the constraint, and the best action. Then compare each option against those facts.
KKey Concepts to Remember
- Network ACL (NACL)
- Security Group (SG)
- Route Table
- VPC Flow Logs
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Network ACL (NACL)
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.
Visual reference
What to study next
Got this wrong? Here's your next step.
Review network ACL (NACL), then practise related SOA-C02 questions on the same topic to reinforce the concept.
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FAQ
Questions learners often ask
What does this SOA-C02 question test?
Networking and Content Delivery — This question tests Networking and Content Delivery — Network ACL (NACL).
What is the correct answer to this question?
The correct answer is: Verify that the network ACLs for both subnets allow the required traffic — Correct answers: A, C, and E. Option A is correct because network ACLs (NACLs) at the subnet level can block traffic between subnets, so verifying both subnet NACLs is necessary. Option C is correct because security groups (SGs) at the instance level control inbound/outbound traffic; if SGs don't allow the required ports, instances cannot communicate. Option E is correct because route tables in each subnet must have routes to the other subnet's CIDR for traffic to be forwarded. Option B (flow logs) is a monitoring tool, not a cause. Option D (NAT Gateway) is used for outbound internet access, not internal VPC communication.
What should I do if I get this SOA-C02 question wrong?
Review network ACL (NACL), then practise related SOA-C02 questions on the same topic to reinforce the concept.
What is the key concept behind this question?
Network ACL (NACL)
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Last reviewed: Jun 20, 2026
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