Exam AWS Certified Advanced Networking - Specialty ANS-C01 topic 1 question 194 discussion

It is asking a solution at network layer rather than application layer. Therefore it is A in my opinion. A managed prefix list is a set of one or more CIDR blocks. You can use prefix lists to make it easier to configure and maintain your security groups and route tables.

AWS Managed Prefix List for CloudFront: AWS provides a managed prefix list that includes the IP ranges for CloudFront edge locations. By using this list in the ALB's security group, the network engineer can restrict access to only traffic originating from CloudFront without manually managing IP ranges. Operational Efficiency: This approach is operationally efficient because: The managed prefix list is automatically updated by AWS whenever CloudFront's IP ranges change. Security groups are simple to configure and maintain compared to other options like network ACLs or AWS WAF.

C - This defines the solution https://docs.aws.amazon.com/AmazonCloudFront/latest/DeveloperGuide/restrict-access-to-load-balancer.html

Question explicitly ask for changes at network layer.

Option A is the most operationally efficient solution as it leverages AWS managed prefix lists, ensuring up-to-date and secure traffic management to the ALB from CloudFront. Security groups provide a straightforward way to enforce network layer restrictions without additional administrative overhead or application changes. This aligns well with the requirement to implement a solution strictly at the network layer.

A because is saying at network layer. https://aws.amazon.com/about-aws/whats-new/2022/02/amazon-cloudfront-managed-prefix-list/

cloudfront header and alb condition

Voting for C.