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Guide to Domain Controllers in Windows Server 2025: Setup, Requirements

Windows Server
DomainController-BG

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Reading time: 3 min.

Table of Contents

  1. Introduction to Active Directory Domain Services (AD DS)
  2. Key Services in a Windows Server 2025 Domain Controller
  3. Prerequisites for Setting Up a Domain Controller
  4. Step-by-Step Domain Controller Installation
  5. Understanding Domain Synchronization (Replication)
  6. Authentication & Authorization in AD DS
  7. Best Practices for Domain Controller Management
  8. Troubleshooting Common Issues
  9. Conclusion & Future Enhancements

1. Introduction to Active Directory Domain Services (AD DS)

Active Directory Domain Services (AD DS) is Microsoft’s directory service that provides centralized identity and access management (IAM) in a Windows domain environment. A Domain Controller (DC) is a server that runs AD DS and manages authentication, authorization, and directory services for users, computers, and other network resources.

In Windows Server 2025, Microsoft has introduced several enhancements:

  • Cloud-integrated AD DS for hybrid environments
  • Enhanced security with Zero Trust policies
  • Faster replication and improved Kerberos authentication
  • AI-driven monitoring for AD health

2. Key Services in a Windows Server 2025 Domain Controller

A Domain Controller provides multiple critical services:

ServiceFunction
Active Directory Domain Services (AD DS)Manages user logins, security policies, and resource access.
DNS ServerResolves domain names to IP addresses (required for AD).
Kerberos AuthenticationProvides secure ticket-based authentication.
LDAP (Lightweight Directory Access Protocol)Allows directory queries (e.g., user/group lookups).
SYSVOL ReplicationEnsures Group Policy Objects (GPOs) and scripts are synced across DCs.
DFS Replication (DFSR)Replicates AD database (ntds.dit) and SYSVOL.
NetLogonHandles secure channel communications between DCs and clients.
Global Catalog (GC)Provides forest-wide search capabilities.

3. Prerequisites for Setting Up a Domain Controller

Before installing a DC, ensure:

  • Windows Server 2025 Standard/Datacenter Edition is installed.
  • Static IP Address (No DHCP for DCs).
  • DNS Server Role (AD DS requires DNS).
  • NTFS File System (for SYSVOL and AD database).
  • Administrative Privileges (Local admin rights).
  • Minimum Hardware Requirements:
  • CPU: 2+ cores (4+ recommended)
  • RAM: 8GB (16GB+ for production)
  • Storage: 50GB+ (SSD recommended for ntds.dit)

4. Step-by-Step Domain Controller Installation

Step 1: Install AD DS Role

  1. Open Server Manager → Add Roles and Features.
  2. Select Active Directory Domain Services.
  3. Complete the installation and promote the server to a DC.

Step 2: Promote Server to Domain Controller

  1. Run dcpromo or use Server Manager → Promote this server to a domain controller.
  2. Choose Add a new forest (for first DC) and enter a domain name (e.g., corp.contoso.com).
  3. Set Forest & Domain Functional Levels (Windows Server 2025).
  4. Configure DNS Delegation (if applicable).
  5. Define Directory Services Restore Mode (DSRM) Password.
  6. Complete the installation and reboot.

Step 3: Verify AD DS Installation

  • Open Active Directory Users and Computers (ADUC) to confirm domain structure.
  • Run dcdiag /v to check for errors.
  • Verify DNS records with nslookup.

5. Understanding Domain Synchronization (Replication)

AD DS uses multi-master replication to sync changes between DCs.

Replication Types

TypeDescription
Intra-site ReplicationFast sync within the same site (15 sec default).
Inter-site ReplicationSlower sync between different sites (configurable).
Urgent ReplicationImmediate sync for critical changes (e.g., password updates).

Monitoring Replication

  • Use repadmin /showrepl to check replication status.
  • DFS Replication (DFSR) logs can be checked in Event Viewer.

6. Authentication & Authorization in AD DS

Authentication Methods

1- Kerberos v5 (Default for domain-joined machines)

  • Uses Ticket-Granting Tickets (TGTs) and Service Tickets.

2- NTLM (Legacy)

  • Used when Kerberos fails (deprecated in Server 2025).

3- LDAP Bind

  • For application authentication (secure with LDAPS).

Authorization (Access Control)

  • Security Identifiers (SIDs) uniquely identify users/groups.
  • Access Control Lists (ACLs) define permissions on objects.
  • Group Policy Objects (GPOs) enforce security policies.

7. Best Practices for Domain Controller Management

  • Deploy at least two DCs for redundancy.
  • Enable Active Directory Recycle Bin for object recovery.
  • Backup ntds.dit regularly using Windows Server Backup.
  • Monitor with Azure AD Connect for hybrid environments.
  • Harden DCs with LAPS (Local Administrator Password Solution).

8. Troubleshooting Common Issues

IssueSolution
Replication FailsRun repadmin /syncall and check firewall rules.
DNS Resolution ErrorsVerify _msdcs zone and SRV records.
Kerberos Authentication FailuresCheck system time sync (w32tm /query /status).
SYSVOL Not ReplicatingUse dfsrmig.exe to migrate to DFSR.

9. Conclusion & Future Enhancements

Windows Server 2025 brings AI-driven security enhancements, faster replication, and better hybrid AD integration. Properly configuring DCs ensures a secure and efficient identity management system.

Next Steps:

  • Implement Azure AD Hybrid Join for cloud integration.
  • Explore Windows Admin Center for modern DC management.
  • Consider Just-In-Time (JIT) Administration for Zero Trust.

Final Thoughts

Setting up a Domain Controller requires careful planning, but with this guide, you can deploy AD DS efficiently in Windows Server 2025. Need help? Ask in the comments! 🚀

Abdelhaleem Ali
Abdelhaleem Alihttps://cupsdeeps.com

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