AWS Certified Advanced Networking – Specialty (ANS-C01) — Question 88

A company has several production applications across different accounts in the AWS Cloud. The company operates from the us-east-1 Region only. Only certain partner companies can access the applications. The applications are running on Amazon EC2 instances that are in an Auto Scaling group behind an Application Load Balancer (ALB). The EC2 instances are in private subnets and allow traffic only from the ALB. The ALB is in a public subnet and allows inbound traffic only from partner network IP address ranges over port 80.

When the company adds a new partner, the company must allow the IP address range of the partner network in the security group that is associated with the ALB in each account. A network engineer must implement a solution to centrally manage the partner network IP address ranges.

Which solution will meet these requirements in the MOST operationally efficient manner?

Answer options

• A. Create an Amazon DynamoDB table to maintain all IP address ranges and security groups that need to be updated. Update the DynamoDB table with the new IP address range when the company adds a new partner. Invoke an AWS Lambda function to read new IP address ranges and security groups from the DynamoDB table to update the security groups. Deploy this solution in all accounts.
• B. Create a new prefix list. Add all allowed IP address ranges to the prefix list. Use Amazon EventBridge (Amazon CloudWatch Events) rules to invoke an AWS Lambda function to update security groups whenever a new IP address range is added to the prefix list. Deploy this solution in all accounts.
• C. Create a new prefix list. Add all allowed IP address ranges to the prefix list. Share the prefix list across different accounts by using AWS Resource Access Manager (AWS RAM). Update security groups to use the prefix list instead of the partner IP address range. Update the prefix list with the new IP address range when the company adds a new partner.
• D. Create an Amazon S3 bucket to maintain all IP address ranges and security groups that need to be updated. Update the S3 bucket with the new IP address range when the company adds a new partner. Invoke an AWS Lambda function to read new IP address ranges and security groups from the S3 bucket to update the security groups. Deploy this solution in all accounts.

Correct answer: C

Explanation

Option C is the most efficient solution because it utilizes a shared prefix list across accounts, simplifying the management of IP address ranges without needing to update multiple security groups individually. Options A and D involve additional complexity and operational overhead, as they require maintaining separate tables or buckets and invoking Lambda functions for updates. Option B, while effective, does not offer the centralized management benefits that come from sharing a prefix list across accounts.