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aws_subnets resource

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Use the aws_subnets InSpec audit resource to test properties of some or all subnets.

Subnets are networks within a VPC that can have their own block of IP address’s and ACL’s. VPCs span across all availability zones in AWS, while a subnet in a VPC can only span a single availability zone. Separating IP addresses allows for protection if there is a failure in one availability zone.


An aws_subnets resource block uses an optional filter to select a group of subnets and then tests that group.

# Test all subnets within a single vpc
describe aws_subnets.where(vpc_id: 'vpc-12345678') do
  its('subnet_ids') { should include 'subnet-12345678' }
  its('subnet_ids') { should include 'subnet-98765432' }


This resource does not expect any parameters.

See also the AWS documentation on Subnets.


subnet_idsThe name of the auto scaling launch configuration associated with the auto scaling group
vpc_idsAn integer indicating the maximum number of instances in the auto scaling group
cidr_blocksAn integer indicating the minimum number of instances in the auto scaling group
availability_zoneThe availability zone this subnet is part of.
map_public_ip_on_launchA boolean indicating if a public IP is automatically mapped to instances launched in this subnet.
statesAn array of strings corresponding to the subnet IDs associated with the auto scaling group
entriesProvides access to the raw results of the query, which can be treated as an array of hashes.


Look for all subnets within a vpc

describe aws_subnets.where( vpc_id: 'vpc-12345678') do
  its('subnet_ids') { should include 'subnet-12345678' }
  its('subnet_ids') { should include 'subnet-98765432' }

Examine a specific subnet

describe aws_subnets.where(subnet_id: 'subnet-12345678') do
  its('cidr_blocks') { should eq [''] }

Examine a specific vpcs Subnet IDs

describe aws_subnets.where( vpc_id: 'vpc-12345678') do
  its('states') { should_not include 'pending' }

Examine a specific subnets VPC IDS

describe aws_subnets.where( subnet_id: 'subnet-12345678') do
  its('vpc_ids') { should include 'vpc-12345678' }


For a full list of available matchers, please visit our matchers page.


The control will pass if the describe returns at least one result.

Use should_not to test the entity should not exist.

describe aws_subnets.where( <property>: <value>) do
  it { should exist }

describe aws_subnets.where( <property>: <value>) do
  it { should_not exist }

AWS Permissions

Your Principal will need the ec2:DescribeSubnets action with Effect set to Allow.

You can find detailed documentation at Actions, Resources, and Condition Keys for Amazon EC2.

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