Terraform: How to create multiple aws subnets from one resource block?

Question

I\'m trying to create multiple subnets from one resource block and I get the following error

Error: aws_subnet.private: cidr_block must be a single v

Answer 1

private_subnet is a list, so you should pick a single element, e.g.

cidr_block = "${element(var.private_subnet,count.index)}"

Answer 2

You have to create multiple aws_subnet resources by utilitizing the count argument to create one resource for each entry in your var.private_subnet list:

resource "aws_subnet" "private" {
  count                   = "${length(var.private_subnet)}"
  vpc_id                  = "${aws_vpc.vpcname.id}"
  cidr_block              = "${var.private_subnet[count.index]}"
  availability_zone       = "${data.aws_availability_zones.available.names[count.index]}"
  map_public_ip_on_launch = false
}

This expands the single aws_subnet resource into two, each with slightly different values based on the enumeration of count when each resource block is evaluated by terraform.