Exam AWS Certified Advanced Networking - Specialty ANS-C01 topic 1 question 43 discussion

https://docs.aws.amazon.com/vpc/latest/tgw/transit-gateway-appliance-scenario.html Option B)

B - Transit gateway Appliance mode should be enabled for the appliance VPC attachment to avoid dropping of the cross AZ traffics.

B - Should be enabled under VPC which the appliance is located.

B is the correct answer. Appliance mode needs to be enabled on the shared VPC where the stateful inspection appliance resides.

I think that it's correcty answer is B.

For sure B.

B. Appliance mode needs to be enabled in the appliance VPC

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A - correct. Option D suggests that the issue is caused by Appliance Mode not being enabled on the transit gateway attachment to the application VPCs. However, this is unlikely to be the cause of the problem described in the scenario, because Appliance Mode is used to forward all traffic to the next hop, without performing routing table lookups or IP address translations. In this case, the issue is related to inter-VPC traffic between different Availability Zones, and the fact that the stateful security appliances in the shared services VPC are dropping the traffic. Therefore, the root cause of the problem is related to the deployment of the stateful security appliances and the transit gateway attachments in the shared services VPC, as well as the fact that they are not able to handle the inter-Availability Zone traffic from the application VPCs. This is why the correct answer is option A, which suggests that the stateful appliances and the transit gateway attachments are deployed in a separate subnet in the shared services VPC.