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
- AWS-Managed Prefix Lists
- Maintained by AWS and contain public CIDR blocks for AWS services like S3, DynamoDB, CloudFront, etc.
- Examples:
pl-63a5400a → Amazon S3pl-81a92ef7 → Amazon DynamoDB
- Useful for allowing access to AWS services without manually adding IPs.
- 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.