ECS cluster network changes

The below might help you.

https://stackoverflow.com/questions/57827251/change-aws-ecs-services-security-groups

To specify a security group for the EC2 instances in your ECS cluster, you can use the launch template or launch configuration that you used to create your EC2 instances. You can specify a security group in the launch template or launch configuration, and any EC2 instances launched with that template or configuration will have the specified security group.

To add additional security groups to your ECS cluster after it has been created, you can modify the launch template or launch configuration to include the additional security group(s), and then update your EC2 instances using the updated template or configuration.

Alternatively, you can add the additional security group(s) directly to the EC2 instances in your cluster using the EC2 console or AWS CLI. To do this, locate the EC2 instances in your cluster and modify their security group settings to include the additional group(s).

Keep in mind that when you modify the security groups associated with your EC2 instances, you may also need to update the security group settings for any load balancers or other resources that communicate with the instances.