Your organization had asked to be cost-efficient in designing AWS solutions. You have created three VPCs(VPC A, VPC B, VPC C), peered VPC A to VPC B and VPC B to VPC
C. You have created a NAT gateway in VPC B and would like to use the same NAT Gateway for resources within VPC A and VPC
C. However, the resources within VPC A and VPC C cannot communicate to the internet through NAT Gateway, but resources in VPC B can communicate. What could be the reason?

Answer options:

A.Route tables in VPC A and VPC C are not configured to have VPC B’s NAT gateway.
B.Using another VPC`s NAT Gateway is not supported in AWS.
C.VPC B’s subnet which contains NAT gateway is not configured in VPC A and VPC C route tables.
D.NAT Gateway is not created inside VPC B’s public subnet.

Answer: B
In a VPC peering connection, using the NAT Gateway of another VPC becomes transitive routing and is not supported in AWS.
https://docs.aws.amazon.com/AmazonVPC/latest/UserGuide/vpc-nat-gateway.html#nat- gateway-basics
For
Option A, in VPC’s route table, only NAT Gateway of the belonging VPC can be configured. VPC A and VPC C cannot configure VPC B’s NAT Gateway in their respective route tables. This option is incorrect.
For Option B, as explained above, transitive routing is not supported. This option is correct.
For Option C, even if two VPCs have peered and configured route tables with their entire IP range, as explained above, transitive routing is not supported. This option is incorrect.
For Option D, the question says VPC B resources can communicate with the internet, for which NAT gateway should be on a public subnet. So this option is not valid.