- A
Use Transit Gateway with appliance mode enabled on the attachments to the inspection VPC, and route inter-VPC traffic through the inspection VPC.
Appliance mode allows Transit Gateway to send traffic to the appliance even if the return traffic takes a different path.
- B
Use VPC Peering connections between all VPCs and route traffic through the inspection VPC.
Why wrong: VPC Peering does not support transitive routing; you would need full mesh.
- C
Place the network appliance in a public subnet of the inspection VPC and use internet gateways for routing.
Why wrong: This is insecure and inefficient; traffic should stay private.
- D
Use Transit Gateway with route tables that point to the network appliance's ENI for all inter-VPC traffic.
Why wrong: Transit Gateway does not support pointing to an ENI directly; you need to use appliance mode.
Transit Gateway Appliance Mode: Centralizing Traffic Inspection
This SCS-C02 practice question tests your understanding of infrastructure security. 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 using AWS Transit Gateway to connect multiple VPCs and on-premises networks. The Security Engineer needs to ensure that traffic between VPCs is inspected by a central network appliance. Which architecture should the Engineer implement?
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
Use Transit Gateway with appliance mode enabled on the attachments to the inspection VPC, and route inter-VPC traffic through the inspection VPC.
Option A is correct because enabling appliance mode on the Transit Gateway attachments to the inspection VPC forces the Transit Gateway to preserve the source and destination MAC addresses of packets, ensuring that asymmetric routing does not cause the network appliance to drop traffic. By routing inter-VPC traffic through the inspection VPC, the appliance can inspect all packets, and appliance mode ensures that return traffic is sent back through the same appliance, maintaining stateful inspection.
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 Transit Gateway with appliance mode enabled on the attachments to the inspection VPC, and route inter-VPC traffic through the inspection VPC.
Why this is correct
Appliance mode allows Transit Gateway to send traffic to the appliance even if the return traffic takes a different path.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Use VPC Peering connections between all VPCs and route traffic through the inspection VPC.
Why it's wrong here
VPC Peering does not support transitive routing; you would need full mesh.
- ✗
Place the network appliance in a public subnet of the inspection VPC and use internet gateways for routing.
Why it's wrong here
This is insecure and inefficient; traffic should stay private.
- ✗
Use Transit Gateway with route tables that point to the network appliance's ENI for all inter-VPC traffic.
Why it's wrong here
Transit Gateway does not support pointing to an ENI directly; you need to use appliance mode.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume that simply routing traffic through an inspection VPC via Transit Gateway is sufficient, without understanding that appliance mode is required to prevent asymmetric routing and ensure stateful inspection works correctly.
Detailed technical explanation
How to think about this question
Transit Gateway appliance mode works by disabling the MAC address translation that Transit Gateway normally performs, so that the network appliance sees the original source and destination MAC addresses of the traffic. This is critical for stateful appliances (e.g., firewalls, IDS/IPS) that rely on MAC addresses to maintain session state. In a real-world scenario, without appliance mode, if traffic from VPC A to VPC B goes through the appliance but return traffic takes a different path, the appliance would drop the packets as it does not recognize the session.
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.
Quick reference
Asymmetric Encryption Algorithm Comparison
| Algorithm | Key Exchange | Signatures | Equivalent Security Key | Notes |
|---|---|---|---|---|
| RSA-3072 | Yes | Yes | 128-bit | Widely deployed; slow for bulk data |
| ECDSA P-256 | No | Yes | 128-bit | Fast signatures; standard TLS certs |
| ECDH / ECDHE | Yes | No | 128-bit | Perfect forward secrecy in TLS 1.3 |
| DH / DHE | Yes | No | 128-bit (3072-bit key) | Replaced by ECDHE in modern TLS |
| Ed25519 | No | Yes | ~128-bit | SSH keys, modern PKI |
What to study next
Got this wrong? Here's your next step.
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FAQ
Questions learners often ask
What does this SCS-C02 question test?
Infrastructure Security — This question tests Infrastructure Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Use Transit Gateway with appliance mode enabled on the attachments to the inspection VPC, and route inter-VPC traffic through the inspection VPC. — Option A is correct because enabling appliance mode on the Transit Gateway attachments to the inspection VPC forces the Transit Gateway to preserve the source and destination MAC addresses of packets, ensuring that asymmetric routing does not cause the network appliance to drop traffic. By routing inter-VPC traffic through the inspection VPC, the appliance can inspect all packets, and appliance mode ensures that return traffic is sent back through the same appliance, maintaining stateful inspection.
What should I do if I get this SCS-C02 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.
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
4 more ways this is tested on SCS-C02
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 uses an AWS Transit Gateway to connect multiple VPCs and on-premises networks. A security engineer needs to ensure that traffic between VPCs is inspected by a third-party firewall appliance. Which architecture should be used?
hard- A.Configure security groups on the transit gateway to inspect traffic.
- B.Create VPC endpoints for each VPC to route traffic through the firewall.
- ✓ C.Attach the firewall appliance to a dedicated inspection VPC and route traffic from other VPCs through the inspection VPC using transit gateway route tables.
- D.Use network ACLs on the transit gateway to filter traffic.
Why C: Option C is correct because it uses a dedicated inspection VPC as a central point for traffic inspection. By attaching the third-party firewall appliance to this inspection VPC and manipulating transit gateway route tables, you can force all inter-VPC traffic to be routed through the firewall for inspection. This architecture leverages the transit gateway's ability to route traffic between attachments based on route table entries, enabling centralized security enforcement without modifying individual VPC routing.
Variation 2. A company uses AWS Transit Gateway to connect multiple VPCs and on-premises networks via AWS Site-to-Site VPN. Security engineers need to ensure that traffic between VPCs is inspected by a third-party firewall appliance deployed in a centralized inspection VPC. Which architecture should be used?
medium- A.Use security groups in each VPC to allow only traffic from the firewall appliance's IP.
- B.Establish VPC Peering connections between each VPC and the inspection VPC.
- C.Configure Network ACLs in each VPC to deny traffic that does not originate from the inspection VPC.
- ✓ D.Create a central inspection VPC with the firewall appliance. Configure Transit Gateway route tables to route traffic between VPCs through the inspection VPC.
Why D: Option D is correct because Transit Gateway route tables can force traffic between VPCs through the inspection VPC by attaching the firewall appliance and using specific routing entries. Option A is incorrect because security groups only control traffic at the instance level and cannot redirect traffic to an inspection appliance. Option B is incorrect because VPC Peering does not support transitive routing, so traffic between two VPCs cannot go through a third VPC. Option C is incorrect because Network ACLs are stateless and can only filter traffic based on IP/port, not route traffic through an inspection appliance.
Variation 3. A company uses AWS Transit Gateway to connect multiple VPCs and on-premises networks. The security team wants to inspect all traffic between VPCs using a third-party firewall appliance. Which architecture should be used?
hard- A.Set up AWS Direct Connect and route all traffic through the on-premises firewall.
- ✓ B.Use Transit Gateway with appliance mode and route tables to direct traffic through a firewall appliance in a central VPC.
- C.Create VPC peering connections between each VPC and the firewall VPC.
- D.Configure network ACLs in each VPC to block traffic unless it comes from the firewall.
Why B: Option B is correct because Transit Gateway with appliance mode enables the firewall appliance in a central VPC to receive traffic from all attached VPCs with symmetric routing, ensuring that both forward and return traffic flows through the same appliance. By configuring route tables to direct inter-VPC traffic to the firewall appliance's elastic network interface (ENI), the security team can inspect all traffic without requiring complex peering or on-premises backhauling.
Variation 4. A company is using AWS Transit Gateway to connect multiple VPCs and on-premises networks via VPN. The security team wants to inspect all traffic between VPCs before it reaches its destination. Which architecture should be used?
hard- A.Use a VPN CloudHub to connect VPCs and inspect traffic at the VPN endpoint.
- B.Use AWS Direct Connect to connect VPCs and inspect traffic on-premises.
- ✓ C.Use a Transit Gateway with a central inspection VPC that hosts security appliances and route all inter-VPC traffic through it.
- D.Use VPC Peering and configure security groups on each VPC to allow only necessary traffic.
Why C: Option C is correct because AWS Transit Gateway can route inter-VPC traffic through a central inspection VPC that hosts security appliances (e.g., firewalls, IDS/IPS). By attaching the Transit Gateway to the inspection VPC and configuring route tables to force all traffic between VPCs to pass through the inspection VPC, the security team can inspect all traffic before it reaches its destination. This architecture provides centralized, scalable traffic inspection without requiring traffic to leave the AWS network.
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Last reviewed: Jul 4, 2026
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