# Non-RFC1918 (public IP) subnets count should be retrievable

Non-RFC1918 (public IP) subnets count should be retrievable. A Maester check for Active Directory, Sites and subnets.

Source: https://maester.dev/docs/tests/AD-SUB-06

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<div class="test-byline"><div class="test-byline-avatars"><a class="test-byline-avatar test-byline-avatar--author" href="/contributors/soulemike" title="Michael Soule · Original author"><img src="https://github.com/soulemike.png" alt="Michael Soule" width="28" height="28" loading="lazy" decoding="async" /></a></div><div class="test-byline-meta"><span class="test-byline-text">Contributed by <a href="/contributors/soulemike">Michael Soule</a></span><a class="test-byline-link" href="/contributors">All contributors →</a></div></div>

<p class="test-part">Part of <a href="/docs/tests/ad">Active Directory</a> · Active Directory · Sites and subnets · <a href="/docs/tests">All checks</a></p>

```powershell title="Run this check"
Invoke-Maester -TestId AD-SUB-06
```

## Overview

Using public IP addresses internally can cause:

- **Routing conflicts**: If public IPs are also used on the internet
- **Security risks**: Internal resources may be exposed
- **Compliance issues**: Violation of IP address allocation standards
- **Connectivity problems**: NAT and firewall complications

RFC1918 private ranges (10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16) should be used for internal networks.

#### Control Type

**Detective**

#### Security Recommendation

- Use RFC1918 private IP ranges for internal networks
- If public IPs are required internally, ensure proper isolation
- Document any exceptions with business justification
- Review subnet assignments for compliance

#### How the Test Works

This test identifies subnets that use public IP address ranges outside of RFC1918 private ranges.

#### Related Tests

- `Test-MtAdSubnetNonInternalDetails` - Lists public IP subnets
- `Test-MtAdSubnetTotalCount` - Counts total subnets
- `Test-MtAdSubnetCatchAllCount` - Identifies overly broad subnets

## Details

<details>
<summary>Every attribute of this check</summary>

| Field | Value |
| --- | --- |
| Test ID | AD-SUB-06 |
| Severity | Info |
| Suite | Active Directory |
| Product | Active Directory |
| Feature | Sites and subnets |
| Area | Infrastructure hardening |
| Resource type | AdSite |
| MITRE ATT&CK | None |
| PowerShell test | [Test-MtAdSubnetNonInternalCount](https://github.com/maester365/maester/blob/main/tests/ad/site/Test.AD-SUB-06.ps1) |
| Services | ActiveDirectory |
| Permissions | ActiveDirectory:Ldap:subnet:ReadProperty |

</details>

## Source

- Test: [`tests/ad/site/Test.AD-SUB-06.ps1`](https://github.com/maester365/maester/blob/main/tests/ad/site/Test.AD-SUB-06.ps1)
- Documentation: [`tests/ad/site/Test.AD-SUB-06.md`](https://github.com/maester365/maester/blob/main/tests/ad/site/Test.AD-SUB-06.md)