ANS-C01 Network Security, Compliance and Governance Practice Question
This ANS-C01 practice question tests your understanding of network security, compliance and governance. 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 network engineer is troubleshooting connectivity between two VPCs connected via a VPC peering connection. Security groups and NACLs are configured correctly. The engineer verifies that the route tables have the necessary entries. However, traffic from an EC2 instance in VPC A to an RDS instance in VPC B fails. Which TWO additional checks should be performed? (Choose two.)
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Check that the security group attached to the RDS instance allows inbound traffic from the CIDR block of VPC A.
Option B is correct because a VPC peering connection must accept the request; if it's in 'pending-acceptance' or 'rejected' state, traffic will not flow. Option D is correct because security group rules must allow inbound traffic from the peer VPC's CIDR; misconfigured rules can block traffic. Option A is wrong because NACLs are stateless and if correctly configured should allow traffic; but the issue is likely elsewhere. Option C is wrong because IAM roles are not required for VPC peering. Option E is wrong because the issue is not about Internet Gateway; it's about VPC peering.
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.
✓
Check that the security group attached to the RDS instance allows inbound traffic from the CIDR block of VPC A.
Why this is correct
Correct: Security groups must allow traffic from peer VPC.
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.
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 ANS-C01 subnetting questions on CIDR, address ranges, and subnet selection.
Network Security, Compliance and Governance — This question tests Network Security, Compliance and Governance — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Check that the security group attached to the RDS instance allows inbound traffic from the CIDR block of VPC A. — Option B is correct because a VPC peering connection must accept the request; if it's in 'pending-acceptance' or 'rejected' state, traffic will not flow. Option D is correct because security group rules must allow inbound traffic from the peer VPC's CIDR; misconfigured rules can block traffic. Option A is wrong because NACLs are stateless and if correctly configured should allow traffic; but the issue is likely elsewhere. Option C is wrong because IAM roles are not required for VPC peering. Option E is wrong because the issue is not about Internet Gateway; it's about VPC peering.
What should I do if I get this ANS-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 ANS-C01 subnetting questions on CIDR, address ranges, and subnet selection.
What is the key concept behind this question?
CIDR notation defines the prefix length.
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Question Discussion
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