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Answer: Deploy three NAT gateways, each in a different public subnet, and assign the Elastic IP address to these gateways. Enable health checks for the NAT gateways; if a gateway fails a health check, recreate it and reassign the Elastic IP address to the new gateway.
The correct answer is A. Deploying three NAT gateways, one in each public subnet, and assigning the Elastic IP address to these NAT gateways ensures high availability and fault tolerance. If a NAT gateway fails, health checks can detect the issue, and the NAT gateway can be recreated and the Elastic IP reassigned, thus mitigating failures automatically. Options B, C, and D either involve less optimal setups that don't fully address the high availability requirement or involve unnecessary complexity in managing health check and failover processes manually.
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A company has migrated a legacy application to the AWS Cloud, deploying three Amazon EC2 instances across three Availability Zones, with one instance in each zone. These instances operate within three private subnets of a VPC and are configured as targets for an Application Load Balancer (ALB) associated with three public subnets. The application requires secure communication with on-premises systems, allowing only traffic from the company's specified IP address range. The security team has designated a single internal IP address for cloud use, which has been whitelisted in the company's firewall and assigned an Elastic IP address. The solutions architect must devise a strategy that enables the application to communicate with on-premises systems while ensuring automatic failure mitigation. Which solution meets these criteria?
A
Deploy three NAT gateways, each in a different public subnet, and assign the Elastic IP address to these gateways. Enable health checks for the NAT gateways; if a gateway fails a health check, recreate it and reassign the Elastic IP address to the new gateway.
B
Replace the ALB with a Network Load Balancer (NLB), assign the Elastic IP address to the NLB, and enable health checks. If the NLB fails a health check, redeploy it in different subnets.
C
Deploy a single NAT gateway in one of the public subnets, assign the Elastic IP address to it, and use Amazon CloudWatch with a custom metric to monitor its health. If the NAT gateway becomes unhealthy, invoke an AWS Lambda function to create a new NAT gateway in a different subnet and reassign the Elastic IP address to it.
D
Assign the Elastic IP address to the ALB, create an Amazon Route 53 simple record with the Elastic IP address as the value, and set up a Route 53 health check. If the health check fails, recreate the ALB in different subnets.