# Subnet total count should be retrievable

Subnet total count should be retrievable. A Maester check for Active Directory, Sites and subnets.

Source: https://maester.dev/docs/tests/AD-SUB-01

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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-01
```

## Overview

Subnets are the foundation of Active Directory site assignment:

- **Client location**: Subnets determine which site a client belongs to
- **Authentication routing**: Directs clients to the nearest domain controller
- **Service discovery**: Helps clients find local services
- **Network segmentation**: Reflects the physical network topology

Understanding the number and distribution of subnets helps ensure proper client site assignment across the organization.

#### Control Type

**Operational**

#### Security Recommendation

- Maintain accurate subnet definitions that reflect the physical network
- Review subnet assignments during network changes
- Remove obsolete subnets to prevent misconfiguration
- Ensure all IP ranges in use are properly defined

#### How the Test Works

This test retrieves all Active Directory subnets using `Get-ADReplicationSubnet` and counts the total number of subnets configured.

#### Related Tests

- `Test-MtAdSubnetSiteAssociationCount` - Counts sites with subnet associations
- `Test-MtAdSubnetWithoutSiteCount` - Identifies orphaned subnets
- `Test-MtAdSiteTotalCount` - Counts total sites in the domain

## Details

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

| Field | Value |
| --- | --- |
| Test ID | AD-SUB-01 |
| 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-MtAdSubnetTotalCount](https://github.com/maester365/maester/blob/main/tests/ad/site/Test.AD-SUB-01.ps1) |
| Services | ActiveDirectory |
| Permissions | ActiveDirectory:Ldap:subnet:ReadProperty |

</details>

## Source

- Test: [`tests/ad/site/Test.AD-SUB-01.ps1`](https://github.com/maester365/maester/blob/main/tests/ad/site/Test.AD-SUB-01.ps1)
- Documentation: [`tests/ad/site/Test.AD-SUB-01.md`](https://github.com/maester365/maester/blob/main/tests/ad/site/Test.AD-SUB-01.md)