AWS Certified Advanced Networking – Specialty (ANS-C01) — Question 156

A company recently experienced an IP address exhaustion event in its VPCs. The event affected service capacity. The VPCs hold two or more subnets in different Availability Zones.

A network engineer needs to develop a solution that monitors IP address usage across resources in the VPCs. The company needs to receive notification about possible issues so that the company can act before an incident happens.

Which solution will meet these requirements with the LEAST operational overhead?

Answer options

• A. Set up Amazon VPC IP Address Manager (IPAM) with a new top-level pool. In the top-level pool, create a pool for each VPC. In each VPC pool, create a pool for each subnet in that VPC. Turn on the auto-import option for the VPC pools and the subnet pools. Configure an Amazon CloudWatch alarm to send an Amazon Simple Notification Service (Amazon SNS) notification if the availability limit threshold is reached.
• B. Set up a log group in Amazon CloudWatch Logs for each subnet. Create an AWS Lambda function that reads each subnet's IP address usage and publishes metrics to the log group. Configure an Amazon CloudWatch alarm to send an Amazon Simple Notification Service (Amazon SNS) notification if the availability limit threshold is reached.
• C. Set up a custom Amazon CloudWatch metric for IP address usage for each subnet. Create an AWS Lambda function that reads each subnet's IP address usage and publishes a CloudWatch metric dimension. Schedule the Lambda function to run every 5 minutes. Configure a CloudWatch alarm to send an Amazon Simple Notification Service (Amazon SNS) notification if the availability limit threshold is reached.
• D. Set up Amazon VPC IP Address Manager (IPAM) with a new top-level pool. In the top-level pool, create a pool for each VPC. In each VPC pool, create a pool for each subnet in that VPC. Turn on the auto-import option for the VPC pools and the subnet pools. Configure an Amazon EventBridge rule that monitors each pool availability limit threshold and sends an Amazon Simple Notification Service (Amazon SNS) notification if the limit threshold is reached.

Correct answer: A

Explanation

Option A is the best choice as it leverages Amazon VPC IP Address Manager (IPAM) to automate IP address management with minimal manual intervention and directly integrates with CloudWatch for alerts. Other options, while functional, require more complex setups and continuous monitoring through Lambda functions or custom metrics, resulting in higher operational overhead.