# Distinct first octets count should be retrievable

Distinct first octets count should be retrievable. A Maester check for Active Directory, Sites and subnets.

Source: https://maester.dev/docs/tests/AD-SUB-08

<!-- This file is generated by website/scripts/generate-test-docs.mjs. Do not edit manually. -->

<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-08
```

## Overview

Analyzing subnet distribution by first octet provides:

- **Addressing scheme visibility**: Understanding IP allocation patterns
- **Network segmentation insight**: How the network is logically divided
- **Capacity planning**: Identifying available address space
- **Documentation**: Supporting network topology documentation

Common patterns include using 10.x for corporate, 172.x for datacenters, etc.

#### Control Type

**Operational**

#### Security Recommendation

- Document the IP addressing scheme and first octet allocation
- Plan address space to avoid conflicts during acquisitions
- Reserve address space for future growth
- Review addressing scheme during network architecture changes

#### How the Test Works

This test extracts the first octet from all IPv4 subnets and counts the distinct values.

#### Related Tests

- `Test-MtAdSubnetFirstTwoOctetsCount` - Analyzes /16 networks
- `Test-MtAdSubnetFirstThreeOctetsCount` - Analyzes /24 networks
- `Test-MtAdSubnetTotalCount` - Counts total subnets

## Details

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

| Field | Value |
| --- | --- |
| Test ID | AD-SUB-08 |
| 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-MtAdSubnetFirstOctetCount](https://github.com/maester365/maester/blob/main/tests/ad/site/Test.AD-SUB-08.ps1) |
| Services | ActiveDirectory |
| Permissions | ActiveDirectory:Ldap:subnet:ReadProperty |

</details>

## Source

- Test: [`tests/ad/site/Test.AD-SUB-08.ps1`](https://github.com/maester365/maester/blob/main/tests/ad/site/Test.AD-SUB-08.ps1)
- Documentation: [`tests/ad/site/Test.AD-SUB-08.md`](https://github.com/maester365/maester/blob/main/tests/ad/site/Test.AD-SUB-08.md)