ELB classic load balancers should span multiple availability zones¶

This control checks whether a Classic Load Balancer has been configured to span multiple Availability Zones. The control fails if the Classic Load Balancer does not span multiple Availability Zones.

How to fix¶

Attribute availability_zones of aws_elb must be non-empty.

Implementation options¶

Choose the option that matches how you manage Terraform. All options satisfy this control.

Option 1: Compliance.tf module (recommended)¶

Use the compliance.tf registry module to get this control enforced by default. This control is mapped to the frameworks shown in the tabs above. To begin, see get started with compliance.tf.

module "elb" {
  source  = "nistcsfv11.compliance.tf/terraform-aws-modules/elb/aws"
  version = ">=4.0.0,<5.0.0"

  health_check = {
    healthy_threshold   = 2
    interval            = 30
    target              = "HTTP:80/"
    timeout             = 5
    unhealthy_threshold = 2
  }
  listener = [
    {
      instance_port     = 80
      instance_protocol = "HTTP"
      lb_port           = 80
      lb_protocol       = "HTTP"
    }
  ]
  name            = "my-elb"
  security_groups = ["sg-12345678"]
  subnets         = ["subnet-12345678"]
}

module "elb" {
  source  = "rbiitfnbfc.compliance.tf/terraform-aws-modules/elb/aws"
  version = ">=4.0.0,<5.0.0"

  health_check = {
    healthy_threshold   = 2
    interval            = 30
    target              = "HTTP:80/"
    timeout             = 5
    unhealthy_threshold = 2
  }
  listener = [
    {
      instance_port     = 80
      instance_protocol = "HTTP"
      lb_port           = 80
      lb_protocol       = "HTTP"
    }
  ]
  name            = "my-elb"
  security_groups = ["sg-12345678"]
  subnets         = ["subnet-12345678"]
}

Option 2: Open source module (terraform-aws-modules)¶

If you use terraform-aws-modules/elb/aws, configure the required module inputs to satisfy this control. You can later migrate to the compliance.tf module with minimal changes because it is compatible by design.

module "elb" {
  source  = "terraform-aws-modules/elb/aws"
  version = ">=4.0.0,<5.0.0"

  health_check = {
    healthy_threshold   = 2
    interval            = 30
    target              = "HTTP:80/"
    timeout             = 5
    unhealthy_threshold = 2
  }
  listener = [
    {
      instance_port     = 80
      instance_protocol = "HTTP"
      lb_port           = 80
      lb_protocol       = "HTTP"
    }
  ]
  name            = "my-elb"
  security_groups = ["sg-12345678"]
  subnets         = ["subnet-12345678"]
}

Option 3: Terraform AWS provider resources¶

If you manage resources directly, configure the relevant Terraform AWS provider resources to meet this control. See docs for the resources involved: aws_elb.

resource "aws_elb" "this" {
  availability_zones = ["us-east-1a", "us-east-1b"]

  listener {
    instance_port     = 80
    instance_protocol = "http"
    lb_port           = 80
    lb_protocol       = "http"
  }
}

Tool mappings¶

Use these identifiers to cross-reference this control across tools, reports, and evidence.

• Compliance.tf (CTF) Control: elb_classic_lb_multiple_az_configured

• Powerpipe Control: aws_compliance.control.elb_classic_lb_multiple_az_configured