The answer is to create a separate Transit Gateway route table for VPC-C and not propagate VPC-A and VPC-B routes into it, then associate that route table with the Direct Connect gateway attachment. This works because Transit Gateway route tables control the flow of traffic between attachments; by isolating VPC-C’s route table and only propagating the on-premises routes, you effectively block VPC-to-VPC communication while allowing the hybrid connection. On the AWS Certified Advanced Networking Specialty ANS-C01 exam, this scenario tests your understanding of Transit Gateway route table isolation as a security boundary—a common trap is assuming that simply attaching VPCs to the same Transit Gateway automatically isolates them, but without separate route tables, all attachments can communicate by default. A key memory tip is “separate table, separate fate”: if you want to restrict VPC-to-VPC traffic while preserving on-premises access, always give the isolated VPC its own route table and only propagate the routes it needs.
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 designing a hybrid network using AWS Transit Gateway. The company has three VPCs (VPC-A, VPC-B, VPC-C) all attached to the same Transit Gateway. The on-premises network connects to the Transit Gateway via a Direct Connect gateway. The company needs to ensure that VPC-C can communicate with the on-premises network but not with VPC-A or VPC-B. Which TWO actions should the network engineer take?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Associate the VPC-C route table with the Direct Connect gateway attachment.
Option B is correct because associating the VPC-C route table with the Direct Connect gateway attachment allows VPC-C to exchange routes with the on-premises network via the Transit Gateway, enabling communication. Option D is correct because creating a separate Transit Gateway route table for VPC-C and not propagating VPC-A and VPC-B routes ensures that VPC-C has no routes to those VPCs, effectively isolating it from them at the network layer.
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 security groups on VPC-C to deny traffic from VPC-A and VPC-B.
Why it's wrong here
Security groups are stateful and do not control routing.
✓
Associate the VPC-C route table with the Direct Connect gateway attachment.
Why this is correct
This enables VPC-C to communicate with on-premises via Direct Connect.
Related concept
Read the scenario before looking for a memorised answer.
✗
Establish VPC peering connections between VPC-C and VPC-A, and VPC-C and VPC-B.
Why it's wrong here
Peering is not needed and adds complexity.
✓
Create a separate Transit Gateway route table for VPC-C and do not propagate VPC-A and VPC-B routes.
Why this is correct
This isolates VPC-C from VPC-A and VPC-B.
Related concept
Read the scenario before looking for a memorised answer.
✗
Apply a network ACL on VPC-C subnets to block traffic from VPC-A and VPC-B.
Why it's wrong here
Network ACLs are stateless and not the best approach for routing isolation.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse security groups or network ACLs as mechanisms to control inter-VPC traffic across a Transit Gateway, when in fact route table isolation is the correct method to enforce such network segmentation at the transit layer.
Detailed technical explanation
How to think about this question
Transit Gateway route tables control the propagation and association of routes for attachments; by creating a separate route table for VPC-C and associating only the Direct Connect gateway attachment, you ensure that VPC-C learns only on-premises routes and not routes from VPC-A or VPC-B. This leverages the transitive routing capability of Transit Gateway while enforcing isolation through route table segmentation, a common pattern in hub-and-spoke designs where specific spokes need selective connectivity.
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 company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
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: Associate the VPC-C route table with the Direct Connect gateway attachment. — Option B is correct because associating the VPC-C route table with the Direct Connect gateway attachment allows VPC-C to exchange routes with the on-premises network via the Transit Gateway, enabling communication. Option D is correct because creating a separate Transit Gateway route table for VPC-C and not propagating VPC-A and VPC-B routes ensures that VPC-C has no routes to those VPCs, effectively isolating it from them at the network layer.
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.
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 →
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
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.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.