The correct solution is to use AWS Transit Gateway inter-region peering with a VPN attachment between the transit gateways. This works because inter-region peering alone provides only route exchange and traffic forwarding, but does not inherently encrypt the data plane traffic; by attaching a VPN connection—typically using IPsec tunnels—between the two peered transit gateways, you force all cross-region traffic through encrypted tunnels over the AWS global network. On the AWS Certified Advanced Networking Specialty ANS-C01 exam, this question tests your understanding that Transit Gateway peering is a network-layer construct, not a security layer, and that encryption must be explicitly added via a VPN attachment. A common trap is assuming that inter-region peering is automatically encrypted, when in fact it only encrypts the control plane. Memory tip: think “Peering for paths, VPN for protection”—the peering handles routing, while the VPN attachment wraps the traffic in IPsec.
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 uses AWS Transit Gateway to connect multiple VPCs and on-premises networks. They need to ensure that traffic between VPCs in different regions is encrypted. Which solution should be used?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use AWS Transit Gateway inter-region peering with a VPN attachment between the transit gateways.
Option B is correct because AWS Transit Gateway inter-region peering provides encrypted transit between VPCs in different regions by establishing a VPN attachment between the transit gateways. This leverages IPsec VPN tunnels to encrypt traffic as it traverses the AWS global network, meeting the requirement for cross-region encryption without routing through on-premises infrastructure.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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 a Site-to-Site VPN from each VPC to the on-premises network and route traffic through the corporate network.
Why it's wrong here
This adds unnecessary latency and does not directly encrypt VPC-to-VPC traffic.
✓
Use AWS Transit Gateway inter-region peering with a VPN attachment between the transit gateways.
Why this is correct
VPN attachment provides encryption for inter-region transit gateway traffic.
Related concept
Read the scenario before looking for a memorised answer.
✗
Use VPC Peering connections between the VPCs, which encrypts traffic automatically.
Why it's wrong here
VPC Peering does not encrypt traffic by default.
✗
Use AWS PrivateLink to connect the VPCs across regions.
Why it's wrong here
PrivateLink does not support inter-region VPC-to-VPC connectivity.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume VPC Peering (Option C) provides encryption by default, but it does not; AWS only guarantees encryption for traffic within a single region via the AWS backbone, and cross-region VPC Peering traffic is not encrypted unless additional measures are taken.
Detailed technical explanation
How to think about this question
Transit Gateway inter-region peering uses the AWS global network backbone, but the VPN attachment adds IPsec encryption (IKEv2, AES-256) to ensure data confidentiality across regions. This is critical for compliance with regulations like PCI DSS or HIPAA, where encryption in transit is mandatory even within AWS infrastructure. The VPN attachment can be configured with multiple tunnels for high availability, and traffic is routed via Transit Gateway route tables to enforce encryption policies.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
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
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Network Design — This question tests Network Design — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Use AWS Transit Gateway inter-region peering with a VPN attachment between the transit gateways. — Option B is correct because AWS Transit Gateway inter-region peering provides encrypted transit between VPCs in different regions by establishing a VPN attachment between the transit gateways. This leverages IPsec VPN tunnels to encrypt traffic as it traverses the AWS global network, meeting the requirement for cross-region encryption without routing through on-premises infrastructure.
What should I do if I get this ANS-C01 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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