Cannot create secondary ip on aws_instance self created ENI

Terraform Providers AWS
1

We need to be able to have a secondary ip on an aws_instance and are able to do this using aws_network_interface, but that adds and creates it on a second ENI. We need it to be on the primary ENI that is created with the aws_instance. I cant find anywhere how I can do that.

I can do this via console, but would like to have this part scripted. Is this possible?

2

Yes, looks like you can create the interface yourself first, and then refer to it as eth0: https://www.terraform.io/docs/providers/aws/r/instance.html#network-interfaces

If you retrieve the ENI id with a data source for the instance then the ENI itself is not a resource managed by Terraform and thus you won’t be able to change it.

This comes from the descriptive nature of Terraform.

3

Ahh, thanks for nudging me in the right direction. I thought it was possible to create the ENI, then reference its id, in the aws_instance, but I was trying to assign it like

network_interface_id = “${aws_network_interface.myinterface.id}”

as a root variable of aws_instance, where it needs to be part of network_interface block in aws_instance like:

network_interface {
    device_index = 0
    network_interface_id = "${aws_network_interface.myinterface.id}"
}

I also had to comment subnet_id, vpc_security_group_ids, and associate_public_ip_address, since the aws_network_interface takes care of that.

Again, many thanks!

4

Hi @phoeniixdotcom on this query about adding secondary interface in terraform script, I would like to know how you achieved this,
your help is greatly appreciated.