ANS-C01 Question 340
Single answerYour company has recently implemented an AWS Transit Gateway to connect multiple VPCs in different AWS Regions. You notice that some traffic between two VPCs in different regions is not flowing as expected. Upon investigation, you find that one of the VPCs is using a custom route table. What could be the potential issue and how can you resolve it?
- A
The route table associated with the VPC does not have a route pointing to the Transit Gateway attachment.
- B
The Transit Gateway is not configured for inter-region peering.
- C
The security group associated with the instances in the VPC is blocking the traffic.
- D
The Transit Gateway attachment in the VPC is not in an 'Available' state.
Show answer and explanation
Correct answer: A
Explanation
The issue is related to the custom route table in the VPC not being configured correctly. To ensure traffic flows between VPCs via the Transit Gateway, the route table associated with the VPC must have a route pointing to the Transit Gateway attachment as the target. This allows the VPC to route traffic to the Transit Gateway, which handles the inter-VPC connectivity.
- A. Correct.
If the route table associated with the VPC does not have a route pointing to the Transit Gateway attachment, traffic will not know how to reach the destination and will fail to flow correctly.
- B. Incorrect.
While inter-region peering is required for Transit Gateway to connect VPCs across regions, this is not the issue in this specific scenario because the problem is isolated to a single VPC route table.
- C. Incorrect.
Security groups control inbound and outbound traffic at the instance level, but the absence of a route for the Transit Gateway attachment in the VPC route table is the root cause here.
- D. Incorrect.
If the Transit Gateway attachment is not in an 'Available' state, it could cause issues, but the question indicates the issue is related specifically to the route table configuration.