Amazon Elastic Container Service (ECS) now supports native Internet Protocol version 6 (IPv6) for Amazon ECS tasks using task networking (awsvpc networking mode). Previously, IPv6 was only supported in host networking mode. With this capability, tasks using awsvpc networking mode can communicate with other endpoints in Amazon Virtual Private Cloud (Amazon VPC) and internet in dual-stack mode via either IPv4 or IPv6. This will allow customers to communicate with on-premises resources that support only IPv6 addresses and meet IPv6 compliance requirements.
Source:: Amazon AWS