The correct answer is to create separate transit gateway route tables for each VPC and only propagate the shared services VPC routes. This works because transit gateway route tables control which VPCs can communicate through transitive routing; by isolating each VPC into its own route table and selectively propagating only the shared services routes, you prevent any two non-shared VPCs from learning each other’s routes, while still granting all VPCs access to the shared services VPC. On the AWS Certified Solutions Architect Professional SAP-C02 exam, this scenario tests your understanding of transit gateway route tables for VPC segmentation, a common pattern for multi-account network isolation. A frequent trap is assuming a single route table with route propagation from all VPCs will work, but that would allow full mesh connectivity. Instead, remember the memory tip: “One table per VPC, only share the services.” This ensures strict isolation while preserving shared access.
SAP-C02 Practice Question: Design Solutions for Organizational Complexity
This SAP-C02 practice question tests your understanding of design solutions for organizational complexity. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 has a central networking account that hosts a transit gateway (TGW). Multiple VPCs from various accounts are attached to the TGW. The security team wants to ensure that only specific VPCs can communicate with each other, but all VPCs need access to a shared services VPC. Which configuration 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
✓
Create separate TGW route tables for each VPC and only propagate the shared services VPC routes.
Option D is correct because using separate TGW route tables for each VPC allows you to control which VPCs can communicate by selectively propagating only the shared services VPC routes into each VPC's route table. This ensures all VPCs can reach the shared services VPC, while VPCs that do not have each other's routes in their respective route tables cannot communicate directly. This approach leverages the transitive routing capability of the transit gateway while maintaining strict isolation between non-shared VPCs.
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.
✗
Create a VPC peering connection between each pair of VPCs that need to communicate.
Why it's wrong here
This does not leverage the TGW and is not scalable.
✗
Use AWS PrivateLink to connect VPCs to the shared services VPC.
Why it's wrong here
PrivateLink is for accessing services, not for routing between VPCs.
✗
Use a single TGW route table for all attachments and control traffic with security groups.
Why it's wrong here
A single route table would allow all VPCs to communicate by default.
✓
Create separate TGW route tables for each VPC and only propagate the shared services VPC routes.
Why this is correct
This isolates VPCs from each other while allowing all to reach shared services.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume a single TGW route table with security groups can control inter-VPC traffic, but security groups cannot be applied to transit gateway attachments—they only work at the instance or ENI level, and TGW route tables control routing, not filtering.
Detailed technical explanation
How to think about this question
Transit gateway route tables support both static routes and route propagation from VPC attachments. By creating separate route tables and only propagating the shared services VPC's CIDR into each VPC's route table, you effectively create isolated routing domains. For VPCs that need to communicate with each other, you can add a static route or propagate the relevant VPC CIDR into the appropriate route tables. This design follows the hub-and-spoke model where the shared services VPC acts as the hub, and all other VPCs are spokes that cannot communicate with each other unless explicitly configured.
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.
Design Solutions for Organizational Complexity — This question tests Design Solutions for Organizational Complexity — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Create separate TGW route tables for each VPC and only propagate the shared services VPC routes. — Option D is correct because using separate TGW route tables for each VPC allows you to control which VPCs can communicate by selectively propagating only the shared services VPC routes into each VPC's route table. This ensures all VPCs can reach the shared services VPC, while VPCs that do not have each other's routes in their respective route tables cannot communicate directly. This approach leverages the transitive routing capability of the transit gateway while maintaining strict isolation between non-shared VPCs.
What should I do if I get this SAP-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 →
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 AWS Organizations with a multi-account setup. The central IT team manages a shared services VPC in the network account, which hosts a NAT gateway, a VPN connection to the on-premises network, and a transit gateway. Several application accounts have VPCs attached to the transit gateway. Recently, the application teams report that they cannot reach the on-premises network through the VPN. The network team confirms that the VPN is up and routes are propagated in the transit gateway route tables. However, the application VPCs are not receiving the routes. What is the MOST likely cause?
hard
A.The application VPCs have route tables that override the transit gateway routes with local routes.
B.The VPN connection is not configured to advertise the on-premises CIDR to the transit gateway.
C.The application VPCs have security groups that block traffic to the on-premises network.
✓ D.The transit gateway route tables are not associated with the application VPC attachments.
Why D: The most likely cause is that the transit gateway route tables are not associated with the application VPC attachments. Even if the VPN routes are propagated into the transit gateway route tables, the application VPCs will not receive those routes unless their VPC attachments are explicitly associated with the correct transit gateway route table. Without this association, the transit gateway does not propagate routes to the attached VPCs, leaving them unable to reach the on-premises network.
Last reviewed: Jun 24, 2026
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This SAP-C02 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 SAP-C02 exam.
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