Why ECS Exec Fails on ECS Managed Instance and How to Fix It

I hit an issue while testing ECS Managed Instance, so here's a quick note for future reference. ECS Exec Fails on a Task Container Running on ECS Managed Instance in a Public Subnet If you deploy this setup in a public subnet without any special network configuration and run the Exec command, you'll get the following error: An error occurred ( TargetNotConnectedException ) when calling the ExecuteCommand operation: The execute command failed. TargetNotConnected: ecs:ecs-task_xxxxxxxxxxxxxxxx is