Posted On: Aug 24, 2020

Earlier this year, we launched VPC Prefix List, a feature that allows you to group multiple CIDR blocks into a single object, and use it as a reference to simplify network configuration. Today, we are adding Prefix Lists support to AWS Transit Gateway, making it easier for you to manage Transit Gateway route tables.

A VPC Prefix List is a collection of CIDR blocks and can be shared with other AWS accounts using the Resource Access Manager (RAM). Prefix Lists allow you to group multiple CIDR blocks into a single object and reference it in AWS Transit Gateway route tables. This simplifies your audit process, and also make it easier to roll out changes to AWS Transit Gateways, and maintain consistent routing behavior across AWS environment. For example, when you peer with an AWS Transit Gateway in a different AWS region, you can create a Prefix List to represent your VPCs, and use that Prefix List to configure your AWS Transit Gateway route tables. When you add a new VPC, you can simply add its CIDR block to the Prefix List, and this will automatically establish connectivity to the new VPC.

To get started, use the AWS CLI, SDK, or AWS Management Console to create Prefix Lists. There is no additional charge to use Prefix Lists and are available in all public Regions — with support in China (Beijing) and China (Ningxia) coming soon. You can also find more information in Prefix Lists public documentation and Transit Gateway public documentation.