The answer is to use AWS Firewall Manager to centrally define and enforce security group rules across all VPCs. This service allows you to centrally manage security group rules across VPCs connected via a transit gateway, applying a common security policy to multiple accounts and VPCs from a single administrative point, which ensures compliance without manual per-VPC configuration. On the AWS Certified SysOps Administrator Associate SOA-C02 exam, this scenario tests your understanding of governance tools versus networking primitives; a common trap is confusing security groups (stateful, per-VPC) with network ACLs (stateless, per-subnet) or assuming CloudFormation can handle ongoing rule enforcement. Remember that while CloudFormation deploys resources, it does not centrally manage rule compliance over time. Memory tip: think of Firewall Manager as the "security group cop" that patrols all your VPCs, while security groups themselves are just the "local laws" for each VPC.
SOA-C02 Security and Compliance Practice Question
This SOA-C02 practice question tests your understanding of security and compliance. 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 has an AWS account with multiple VPCs connected via a transit gateway. The security team wants to centrally manage VPC security group rules and ensure compliance. Which approach is most effective?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use AWS Firewall Manager to centrally define and enforce security group rules across all VPCs.
Option C is correct because AWS Firewall Manager allows centralized management of security group rules across accounts and VPCs. Option A is wrong because security groups are per-VPC and cannot be applied across multiple VPCs. Option B is wrong because network ACLs are stateless and not a replacement for security groups; also, they are per-subnet. Option D is wrong because CloudFormation can deploy but not centrally manage ongoing rule enforcement.
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.
✓
Use AWS Firewall Manager to centrally define and enforce security group rules across all VPCs.
Why this is correct
Firewall Manager provides centralized security group management across accounts and VPCs.
Create a single security group and attach it to all VPCs.
Why it's wrong here
Security groups are scoped to a single VPC and cannot be shared across VPCs.
✗
Define security group rules in AWS CloudFormation templates and deploy them to each VPC.
Why it's wrong here
CloudFormation can deploy but does not provide ongoing centralized enforcement.
✗
Use network ACLs instead of security groups for centralized management.
Why it's wrong here
Network ACLs are per-subnet and stateless; not a substitute for security groups.
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.
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 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.
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 SOA-C02 subnetting questions on CIDR, address ranges, and subnet selection.
Security and Compliance — This question tests Security and Compliance — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Use AWS Firewall Manager to centrally define and enforce security group rules across all VPCs. — Option C is correct because AWS Firewall Manager allows centralized management of security group rules across accounts and VPCs. Option A is wrong because security groups are per-VPC and cannot be applied across multiple VPCs. Option B is wrong because network ACLs are stateless and not a replacement for security groups; also, they are per-subnet. Option D is wrong because CloudFormation can deploy but not centrally manage ongoing rule enforcement.
What should I do if I get this SOA-C02 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 SOA-C02 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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