ANS-C01 Network Management and Operations Practice Question
A company is using AWS Transit Gateway to connect multiple VPCs and on-premises networks. The network team notices that some VPCs cannot communicate with each other even though they are attached to the same transit gateway. What is the most likely cause?
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
✓
The transit gateway route tables are missing routes to the other VPCs.
Transit Gateway uses route tables to control inter-VPC traffic. If the route tables do not have routes to the other VPCs, or if the VPCs are in different route tables that are not associated or propagated correctly, communication fails. The most common issue is that the transit gateway route tables are not properly configured with routes to the other VPC attachments.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The security groups on the instances are not allowing inbound traffic from the other VPCs.
Why it's wrong here
Security groups can block, but the route table issue is more likely the cause of no communication.
- ✓
The transit gateway route tables are missing routes to the other VPCs.
Why this is correct
Proper routing configuration is essential for inter-VPC communication.
- ✗
The VPC attachments are not in the 'available' state.
Why it's wrong here
If they were not available, they wouldn't be able to send traffic at all.
- ✗
The VPCs' network ACLs are blocking traffic.
Why it's wrong here
This could be a secondary issue, but the transit gateway routing is more fundamental.
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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.