# Domain controller count should be retrievable

Understanding the number and distribution of domain controllers in your domain is critical for:

Source: https://maester.dev/docs/tests/AD-DOM-03

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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 · Domain controllers · <a href="/docs/tests">All checks</a></p>

```powershell title="Run this check"
Invoke-Maester -TestId AD-DOM-03
```

## Overview

Understanding the number and distribution of domain controllers in your domain is critical for:

 * **High Availability**: Ensuring sufficient DCs exist to handle authentication load and provide redundancy
 * **Disaster Recovery**: Knowing how many DCs need to be recovered in a disaster scenario
 * **Site Coverage**: Verifying that all sites have appropriate DC coverage for local authentication
 * **Capacity Planning**: Determining if additional DCs are needed based on user and computer growth

#### Control Type

**Operational**

#### Security Recommendation

 * **Minimum Redundancy**: Maintain at least 2 DCs per domain for fault tolerance
 * **Geographic Distribution**: Place DCs strategically across sites to ensure local authentication
 * **RODC Consideration**: Consider Read-Only Domain Controllers (RODC) for branch offices
 * **Regular Monitoring**: Track DC health and availability as part of your security monitoring

#### How the Test Works

This test retrieves all domain controllers from Active Directory and counts them. It also lists the names of all DCs for easy reference.

#### Related Tests

- `Test-MtAdDomainFunctionalLevel` - Retrieves the domain functional level
- `Test-MtAdForestDomainCount` - Counts domains in the forest

## Details

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

| Field | Value |
| --- | --- |
| Test ID | AD-DOM-03 |
| Severity | Info |
| Suite | Active Directory |
| Product | Active Directory |
| Feature | Domain controllers |
| Area | Infrastructure hardening |
| Resource type | DomainController |
| MITRE ATT&CK | None |
| PowerShell test | [Test-MtAdDomainControllerCount](https://github.com/maester365/maester/blob/main/tests/ad/domain/Test.AD-DOM-03.ps1) |
| Services | ActiveDirectory |
| Permissions | ActiveDirectory:Ldap:domainDNS.name:ReadProperty, ActiveDirectory:Ldap:nTDSDSA:ReadProperty |

</details>

## Source

- Test: [`tests/ad/domain/Test.AD-DOM-03.ps1`](https://github.com/maester365/maester/blob/main/tests/ad/domain/Test.AD-DOM-03.ps1)
- Documentation: [`tests/ad/domain/Test.AD-DOM-03.md`](https://github.com/maester365/maester/blob/main/tests/ad/domain/Test.AD-DOM-03.md)