AWS now supports cross-subnet communication between EFA Interfaces for Amazon EC2 instances in the same Availability Zone. This enhancement allows you to communicate across subnets using EFA, which accelerates high-performance computing and machine learning applications. Previously, EFA traffic was limited to the same subnet, but now you can send traffic across subnets for new and existing instances. To utilize this feature, you must configure your security group rules to allow traffic between instances in different subnets and adjust your application configuration and orchestration logic accordingly. This capability is available in all AWS commercial Regions, the AWS GovCloud (US) Regions, and the Amazon Web Services China Regions. Visit the EFA Documentation Page for more information.
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https://aws.amazon.com/about-aws/whats-new/2024/07/elastic-fabric-adapter-cross-subnet-communication/
AWS now offers Elastic Fabric Adapter (EFA) with support for cross-subnet communication
