- A
Deploy a Transit Gateway and attach a central inspection VPC with a firewall appliance. Configure route tables to send inter-VPC traffic through the inspection VPC.
This architecture allows centralized inspection of all traffic between VPCs by routing it through the inspection VPC.
- B
Create VPC Peering connections between each pair of application VPCs and apply security groups to the peer connections.
Why wrong: VPC Peering does not support security groups on peer connections; traffic between peered VPCs is filtered by security groups of instances, not centrally.
- C
Use security groups in each application VPC to control traffic between VPCs.
Why wrong: Security groups are applied to individual instances and do not filter traffic at the VPC level.
- D
Use network ACLs in each application VPC to filter traffic between VPCs.
Why wrong: Network ACLs operate at the subnet level within a VPC and cannot filter traffic between VPCs.
Quick Answer
The correct solution is to deploy a Transit Gateway with a central inspection VPC that hosts a firewall appliance, such as AWS Network Firewall or a third-party solution like Palo Alto Networks, and configure route tables to force all inter-VPC traffic through that inspection VPC. This design works because the Transit Gateway acts as a central hub, and by manipulating its route tables—specifically using a blackhole route or a static route pointing to the inspection VPC attachment—you can steer traffic between application VPCs through the firewall for stateful filtering and logging. On the AWS Certified Advanced Networking Specialty ANS-C01 exam, this scenario tests your understanding of centralized egress and inspection patterns, often appearing as a multi-account, multi-VPC architecture question. A common trap is confusing this with VPC Peering, which lacks a central inspection point, or relying on security groups or NACLs, which are per-resource or per-subnet and cannot filter traffic between separate VPCs. Memory tip: think “Transit Gateway + Inspection VPC = the only way to route inter-VPC traffic through a single firewall.”
ANS-C01 Network Design Practice Question
This ANS-C01 practice question tests your understanding of network design. 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 is deploying a multi-tier web application across multiple AWS accounts. They want to centralize network security by using a shared services VPC with a Transit Gateway. All application VPCs will be attached to the Transit Gateway. The security team needs to inspect and filter traffic between application VPCs. Which solution should be used to meet this requirement?
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
Deploy a Transit Gateway and attach a central inspection VPC with a firewall appliance. Configure route tables to send inter-VPC traffic through the inspection VPC.
Option C is correct because a Transit Gateway with a central inspection VPC containing a firewall appliance (like Palo Alto Networks or AWS Network Firewall) allows traffic to be routed through the inspection point for filtering. Option A is wrong because Network ACLs are stateless and applied at the subnet level, not between VPCs. Option B is wrong because security groups are stateful and applied at the instance level, not for traffic between VPCs. Option D is wrong because VPC Peering does not support centralized inspection by default.
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.
- ✓
Deploy a Transit Gateway and attach a central inspection VPC with a firewall appliance. Configure route tables to send inter-VPC traffic through the inspection VPC.
Why this is correct
This architecture allows centralized inspection of all traffic between VPCs by routing it through the inspection VPC.
Related concept
CIDR notation defines the prefix length.
- ✗
Create VPC Peering connections between each pair of application VPCs and apply security groups to the peer connections.
Why it's wrong here
VPC Peering does not support security groups on peer connections; traffic between peered VPCs is filtered by security groups of instances, not centrally.
- ✗
Use security groups in each application VPC to control traffic between VPCs.
Why it's wrong here
Security groups are applied to individual instances and do not filter traffic at the VPC level.
- ✗
Use network ACLs in each application VPC to filter traffic between VPCs.
Why it's wrong here
Network ACLs operate at the subnet level within a VPC and cannot filter traffic between VPCs.
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 media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
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.
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FAQ
Questions learners often ask
What does this ANS-C01 question test?
Network Design — This question tests Network Design — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Deploy a Transit Gateway and attach a central inspection VPC with a firewall appliance. Configure route tables to send inter-VPC traffic through the inspection VPC. — Option C is correct because a Transit Gateway with a central inspection VPC containing a firewall appliance (like Palo Alto Networks or AWS Network Firewall) allows traffic to be routed through the inspection point for filtering. Option A is wrong because Network ACLs are stateless and applied at the subnet level, not between VPCs. Option B is wrong because security groups are stateful and applied at the instance level, not for traffic between VPCs. Option D is wrong because VPC Peering does not support centralized inspection by default.
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.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Same concept, more angles
1 more ways this is tested on ANS-C01
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A company is using AWS Organizations to manage multiple accounts. The network team needs to allow a centralized inspection VPC to inspect all traffic between VPCs in different accounts. Which AWS service should be used to route traffic through the inspection VPC?
medium- ✓ A.AWS Transit Gateway
- B.VPC peering connections
- C.AWS PrivateLink
- D.AWS Site-to-Site VPN
Why A: Option C is correct because a Transit Gateway with route tables can route traffic between VPCs and send it to a network appliance in the inspection VPC. Option A is wrong because VPC peering is a simple point-to-point connection and does not support transitive routing. Option B is wrong because a VPN is for hybrid connectivity, not inter-VPC routing. Option D is wrong because PrivateLink is for accessing services privately, not for routing traffic.
Last reviewed: Jun 20, 2026
This ANS-C01 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the ANS-C01 exam.
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