ANS-C01 Network Implementation Practice Question
A company is deploying a multi-tier application across multiple VPCs connected via AWS Transit Gateway. The web tier must be able to initiate connections to the app tier, but the app tier must not be able to initiate connections to the web tier. How can this be achieved?
⚠ Common exam trap
Candidates often assume security groups or network ACLs can enforce unidirectional traffic across VPCs, but they are either stateless (NACLs) or stateful (security groups) and cannot prevent the app tier from initiating new connections when return traffic is allowed.
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 centralized firewall appliance in a shared VPC and use Transit Gateway to route all inter-VPC traffic through it.
Routing all inter-VPC traffic through a centralized firewall appliance in a shared VPC via Transit Gateway allows you to enforce stateful inspection and access control policies. The firewall can be configured to permit only outbound connections from the web tier to the app tier while blocking any inbound connections initiated by the app tier, thus meeting the requirement without relying on VPC-native constructs that cannot enforce unidirectional stateful filtering across VPCs.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Configure network ACLs on the web tier subnets to allow outbound traffic and deny inbound from app tier.
Why it's wrong here
NACLs are stateless; return traffic would be blocked.
- ✗
Establish VPC peering between the web and app VPCs and restrict routes.
Why it's wrong here
Peering is transitive only via Transit Gateway, and does not enforce unidirectional traffic.
- ✗
Use security groups across the VPCs by referencing each other's CIDR blocks.
Why it's wrong here
Security groups cannot reference other VPCs' groups without AWS PrivateLink.
- ✓
Deploy a centralized firewall appliance in a shared VPC and use Transit Gateway to route all inter-VPC traffic through it.
Why this is correct
Enables stateful inspection and unidirectional rules.
Visual reference
Go deeper
Related to this question
About these practice questions
Courseiva writes every ANS-C01 question from scratch — 1,621 in total, each with an explanation and a wrong-answer breakdown. None are copied from real exams or dumps. Learn why practice questions differ from exam dumps →
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.