EC2 instances should not use multiple ENIs¶

This control checks whether an EC2 instance uses multiple Elastic Network Interfaces (ENIs) or Elastic Fabric Adapters (EFAs). This control passes if a single network adapter is used. The control includes an optional parameter list to identify the allowed ENIs.

How to fix¶

Attribute network_interface of aws_instance must satisfy condition: exists.

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.

NIST Cybersecurity Framework v1.1

module "ec2_instance" {
  source  = "nistcsfv11.compliance.tf/terraform-aws-modules/ec2-instance/aws"
  version = ">=6.0.0"

  instance_type = "t3.nano"
  subnet_id     = "subnet-abc123"
}

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

If you use terraform-aws-modules/ec2-instance/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 "ec2_instance" {
  source  = "terraform-aws-modules/ec2-instance/aws"
  version = ">=6.0.0"

  instance_type = "t3.nano"
  subnet_id     = "subnet-abc123"
}

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_instance.

resource "aws_instance" "this" {
  ami                    = "ami-abc12345"
  instance_type          = "t4g.nano"
  subnet_id              = element(["subnet-abc123", "subnet-def456"], 0)
  vpc_security_group_ids = ["sg-abc12345"]
}

Which option should I choose?

Compliance.tf module (recommended): controls enforced by default and mapped to frameworks.
Open source module (terraform-aws-modules): compatible by design with compliance.tf. Same variable names for an easy, low-change migration path when you are ready.
Terraform AWS provider resources: manage Terraform resources directly.

Tool mappings¶

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

Compliance.tf (CTF) Control: ec2_instance_not_use_multiple_enis
AWS Config Managed Rule: EC2_INSTANCE_MULTIPLE_ENI_CHECK
Powerpipe Control: aws_compliance.control.ec2_instance_not_use_multiple_enis