# All domain controllers should have DFS-R subscriptions

DFS-R (Distributed File System Replication) is the modern, recommended technology for replicating SYSVOL content between domain controllers:

Source: https://maester.dev/docs/tests/AD-DFSR-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 · Replication · <a href="/docs/tests">All checks</a></p>

```powershell title="Run this check"
Invoke-Maester -TestId AD-DFSR-01
```

## Overview

DFS-R (Distributed File System Replication) is the modern, recommended technology for replicating SYSVOL content between domain controllers:

- **Reliability**: DFS-R is more reliable than the legacy FRS (File Replication Service)
- **Scalability**: Better handles large SYSVOL contents and many DCs
- **Conflict Resolution**: Superior handling of file conflicts
- **Migration Status**: Indicates whether the domain has migrated from FRS to DFS-R

Microsoft recommends migrating from FRS to DFS-R for all domains. A count of DFS-R subscriptions compared to DC count shows migration coverage.

#### Control Type

**Detective**

#### Security Recommendation

- Migrate all domains from FRS to DFS-R if not already done
- Ensure all domain controllers have DFS-R subscriptions
- Monitor DFS-R replication health regularly
- Document any DCs without DFS-R subscriptions
- Plan migration for any remaining FRS-based SYSVOL replication

#### How the Test Works

This test counts DFS-R subscription objects and reports:
- Total DFS-R subscription count
- Domain controller count
- Coverage percentage (subscriptions vs. DCs)
- Details of subscription objects

#### Related Tests

- `Test-MtAdDisabledReplicationConnectionCount` - Checks AD replication connection health

## Details

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

| Field | Value |
| --- | --- |
| Test ID | AD-DFSR-01 |
| Severity | Low |
| Suite | Active Directory |
| Product | Active Directory |
| Feature | Replication |
| Area | Infrastructure hardening |
| Resource type | DomainController |
| User impact | Low |
| Implementation cost | Medium |
| MITRE ATT&CK | None |
| PowerShell test | [Test-MtAdDfsrSubscriptionCount](https://github.com/maester365/maester/blob/main/tests/ad/replication/Test.AD-DFSR-01.ps1) |
| Services | ActiveDirectory |
| Permissions | ActiveDirectory:Ldap:nTDSDSA:ReadProperty |

</details>

## Source

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