Create AWS target groups with IPs

Hi all,
I am pretty new to terraform and AWS. I am trying to deploy all the infra for this platform and need some instances in a aws_lb_target_group. These instances will be created by a different system later but I do know what the IP addresses will be.
From the docs it seems I can use the IP type but not sure how to define those IPs and whether they need to exist or not during terraform deployment.
I have a similar script for Azure and got this working just fine but need help with this one please. Thanks in advance!

Hi @larreaj ,

you can create a target group for specific IPs using Target Group Attachments:
Not sure how you plan to create the instances behind the load balancer but usually it is preferred to register instances instead of the IP addresses.

I see, thank you. So I will use terraform for the initial infrastructure but once Bosh is deployed, it will deploy and manage the other components including the instances that will be the LB backend. I can specify which IP to use but won’t know the instance ID until after.
Do you know if for target_id I can use multiple comma separated IPs or a range?