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AWS Prefix List

In AWS, a Prefix List is a set of one or more CIDR blocks that can be used as a reference in security groups, route tables, and network ACLs. It simplifies network management by allowing you to group multiple IP ranges under a single identifier instead of managing multiple individual CIDR blocks.

Types of Prefix Lists

  1. AWS-Managed Prefix Lists
    • Maintained by AWS and contain public CIDR blocks for AWS services like S3, DynamoDB, CloudFront, etc.
    • Examples:
      • pl-63a5400a → Amazon S3
      • pl-81a92ef7 → Amazon DynamoDB
    • Useful for allowing access to AWS services without manually adding IPs.
  2. Customer-Managed Prefix Lists
    • Created and managed by customers.
    • Useful for defining custom IP ranges that can be referenced in security rules.

Use Cases

  • Simplify security group and route table configurations.
  • Reduce the need for frequent updates when AWS services change their IPs.
  • Improve readability and manageability of network policies.

How to Use Prefix Lists

  • Route Tables: Add a prefix list as a destination to simplify routing rules.
  • Security Groups: Use a prefix list as a source/destination in inbound/outbound rules.
  • Network ACLs: Reference a prefix list in network ACL rules.