The answer is to create a dedicated inspection VPC with firewall instances deployed across multiple Availability Zones. This design is correct because it establishes a centralized, scalable inspection point where all inter-VPC traffic is routed through the Transit Gateway to the inspection VPC, and the firewall appliances process traffic using elastic network interfaces in each subnet. By placing instances in different AZs, the solution achieves high availability, ensuring that if one AZ fails, traffic can still be inspected by the remaining firewall. On the AWS Certified Solutions Architect Professional SAP-C02 exam, this scenario tests your understanding of Transit Gateway route tables and the need to separate inspection from production traffic; a common trap is assuming a single route table or a single AZ is sufficient, which would create a single point of failure. Remember the key mnemonic: “Inspect across AZs, not across a single path” — always pair centralized inspection with multi-AZ deployment for true high availability.
SAP-C02 Continuous Improvement for Existing Solutions Practice Question
This SAP-C02 practice question tests your understanding of continuous improvement for existing solutions. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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 a production AWS account with multiple VPCs connected via a Transit Gateway. The security team wants to centrally inspect all traffic between VPCs using a third-party firewall appliance. The firewall must be able to process traffic, and the solution must be highly available. Which THREE steps should the company take?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Attach Elastic Network Interfaces (ENIs) of the firewall instances to the inspection VPC subnets.
Options A, B, and D are correct: A creates an inspection VPC, B places instances across AZs for HA, and D uses ENIs in each subnet. Option C is wrong because a single route table limits HA. Option E is wrong because it bypasses inspection.
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.
✓
Attach Elastic Network Interfaces (ENIs) of the firewall instances to the inspection VPC subnets.
Why this is correct
ENIs are required for traffic to pass through the firewall.
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
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 block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related SAP-C02 subnetting questions on CIDR, address ranges, and subnet selection.
Continuous Improvement for Existing Solutions — This question tests Continuous Improvement for Existing Solutions — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Attach Elastic Network Interfaces (ENIs) of the firewall instances to the inspection VPC subnets. — Options A, B, and D are correct: A creates an inspection VPC, B places instances across AZs for HA, and D uses ENIs in each subnet. Option C is wrong because a single route table limits HA. Option E is wrong because it bypasses inspection.
What should I do if I get this SAP-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 SAP-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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