ANS-C01 Network Design Practice Question
A company is setting up a new AWS environment for a project. The network architect decides to use a hub-and-spoke model with a central inspection VPC for east-west traffic inspection. The inspection VPC (VPC-Hub) contains a firewall appliance that inspects traffic between spoke VPCs. All VPCs are attached to an AWS Transit Gateway. The architect creates a route table in the Transit Gateway for the inspection VPC and another route table for the spoke VPCs. The inspection VPC route table has a default route (0.0.0.0/0) pointing to the firewall appliance. The spoke VPCs have route tables that point to the inspection VPC for traffic to other spoke VPCs. The firewall appliance is configured to forward traffic after inspection. However, traffic between spoke VPCs is not being routed through the inspection VPC. Which configuration change should the architect make to ensure traffic between spoke VPCs is inspected?
⚠ Common exam trap
The trap here is that candidates often focus on the spoke VPC route tables (thinking they need to remove the default route or add static routes) instead of recognizing that the inspection VPC route table must have routes to the spoke VPCs via route propagation to allow the firewall to forward inspected traffic back to the Transit Gateway.
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
✓
Enable route propagation on the inspection VPC attachment for the inspection route table
The inspection VPC route table needs to learn the spoke VPC CIDRs dynamically via route propagation from the Transit Gateway attachment. Without propagation, the inspection VPC route table only has a default route pointing to the firewall appliance, but no specific routes for the spoke VPCs. When the firewall appliance forwards traffic after inspection, it needs to know how to reach the destination spoke VPC; enabling route propagation on the inspection VPC attachment for the inspection route table allows the Transit Gateway to inject the spoke VPC routes into that route table, enabling proper return traffic flow.
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 VPC Peering between the spoke VPCs instead of Transit Gateway
Why it's wrong here
Incorrect; VPC Peering would bypass inspection.
- ✗
Create a static route in the inspection VPC route table for each spoke VPC CIDR
Why it's wrong here
Incorrect; this would be manual and not scalable; route propagation is better.
- ✗
Remove the default route from the spoke VPC route tables
Why it's wrong here
Incorrect; the default route is needed for other traffic.
- ✓
Enable route propagation on the inspection VPC attachment for the inspection route table
Why this is correct
Correct; propagation allows the inspection VPC to learn the spoke CIDRs.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.