inspec/docs/resources/aws_subnets.md.erb
Clinton Wolfe 2de06bdeb5 Clean injection of Availability section (#3206)
Signed-off-by: Clinton Wolfe <clintoncwolfe@gmail.com>
2018-08-09 08:34:49 -04:00

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---
title: About the aws_subnets Resource
platform: aws
---
# aws\_subnets
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.
<br>
## Availability
### Installation
This resource is distributed along with InSpec itself. You can use it automatically.
### Version
This resource first became available in v2.0.16 of InSpec.
## Syntax
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' }
end
<br>
## Examples
The following examples show how to use this InSpec audit resource.
As this is the initial release of `aws_subnets`, its limited functionality precludes examples.
<br>
## Filter Criteria
* `vpc_id`, `subnet_id`
## Filter Examples
### vpc\_id
A string identifying the VPC which may or may not contain subnets.
# 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' }
end
### subnet\_id
A string identifying a specific subnet.
# Examine a specific subnet
describe aws_subnets.where(subnet_id: 'subnet-12345678') do
its('cidr_blocks') { should eq ['10.0.1.0/24'] }
end
<br>
## Properties
* `cidr_blocks`, `states`, `subnet_ids`,`vpc_ids`
<br>
## Property Examples
### cidr\_blocks
Provides a string that contains the cidr block of ip addresses that can be given in the subnet.
# Examine a specific subnets cidr_blocks
describe aws_subnets.where( subnet_id: 'subnet-12345678') do
its('cidr_blocks') { should eq ['10.0.1.0/24'] }
end
### states
Provides an array of strings including if the subnets are available.
# Examine a specific vpcs Subnet IDs
describe aws_subnets.where( vpc_id: 'vpc-12345678') do
its('states') { should_not include 'pending' }
end
### subnet\_ids
Provides an array of strings containing the subnet IDs associated with a vpc.
# Examine a specific vpcs Subnet IDs
describe aws_subnets.where( vpc_id: 'vpc-12345678') do
its('subnet_ids') { should include 'subnet-12345678' }
its('subnet_ids') { should include 'subnet-98765432' }
end
### vpc\_ids
Provides an array containing a string of the vpc_id associated with a subnet.
# Examine a specific subnets VPC IDS
describe aws_subnets.where( subnet_id: 'subnet-12345678') do
its('vpc_ids') { should include 'vpc-12345678' }
end
<br>
## Matchers
For a full list of available matchers, please visit our [matchers page](https://www.inspec.io/docs/reference/matchers/).
### exists
The control will pass if the filter returns at least one result. Use `should_not` if you expect zero matches.
# You dont always have subnets, so you can test if there are any.
describe aws_subnets
it { should exist }
end
# Test that there are subnets in a vpc
describe aws_subnets.where(vpc_id: 'vpc-12345678')
it { should exist }
end
## AWS Permissions
Your [Principal](https://docs.aws.amazon.com/IAM/latest/UserGuide/intro-structure.html#intro-structure-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](https://docs.aws.amazon.com/IAM/latest/UserGuide/list_amazonec2.html).