An auto ancillary manufacturing firm has started a factory unit in the US-west-1 region. For application servers deployed in the AWS cloud, they have created VPC with private & public subnets in each VPC. Multiple VPCs are created. Application servers placed in private need to have internet for downloading data from database servers deployed in the us-east-1 region. This Internet access should be a fully redundant & managed solution as the client does not have the competency to manage this internet access. Which of the following solution will meet this requirement?

Answer options:

A.Create a NAT Instance in the Public subnet of any one AZ in the region. Add a default route in the private subnet pointing to NAT Instance.
B.Create a NAT Gateway in the Public subnet of each AZ in the region. Add a default route in the private subnet pointing to NAT Gateway.
C.Create a NAT Gateway in the Public subnet of any one AZ in the region. Add a default route in the private subnet pointing to NAT Gateway.
D.Create a NAT Instance in the Public subnet of each AZ in the region. Add a default route in the private subnet pointing to NAT Instance.

Correct Answer – B
NAT Gateway is AWS Managed solution for internet to private subnets. This NAT Gateway is deployed in the public subnet. NAT Gateway is redundant in a specific AZ on which it is deployed. For Multi-AZ redundancy, NAT Gateway needs to be deployed in each AZ with a default route from the private subnet.
Options A & D are incorrect as the client is looking for a fully managed solution. NAT instance needs to be managed by the client.
Option C is incorrect as NAT Gateway is redundant in an AZ. For multi-AZ redundancy, add a NAT Gateway in each AZ.
For more information on the use case for NAT instance & NAT Gateway, refer to the following URL
https://docs.aws.amazon.com/vpc/latest/userguide/vpc-nat-comparison.html