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KMS 2025 Additional Install for Fail-over with Existing KMS Server

How To


Summary

KMS 2025 additional Install for Fail-over with Existing KMS Server

Objective

Setting up and installing KMS 2025 additional server for Fail-over with Existing KMS Server and ensuring prerequisites are met.

Prerequisites

  • A dedicated Windows Server 2025 instance, joined to the domain.
  • Administrative credentials for both the new server and your DNS environment.
  • A Windows Server 2025 KMS Host key (CSVLK), obtained from the Microsoft Volume Licensing Service Center (VLSC). This key can activate all earlier supported Windows Server and client versions. 

Environment

Windows Server 2025

Steps

1. Prepare the Windows Server 2025

  • Install Windows Server 2025 and ensure all the latest security patches and updates are installed.
  • Verify the server has a static IP address and correct network connectivity to your clients and Active Directory.
  • Ensure that TCP port 1688 is allowed through the Windows Firewall on the new server to accept incoming KMS client activation requests. 

2. Install the Volume Activation Services Role 

  • Open Server Manager on the new Windows Server 2025.
  • From the Manage menu, select Add Roles and Features.
  • Follow the wizard, selecting Role-based or feature-based installation, and choose your server from the server pool.
  • On the Select server roles page, check the box for Volume Activation Services, then continue through the wizard and install the role. 

3. Configure the KMS Host and Activate the Key 

  • After the role installation, open the Volume Activation Tools wizard by running vmw.exe from PowerShell or Command Prompt (Admin).
  • On the introduction page, select Next.
  • For the activation type, select Key Management Service (KMS) and enter localhost as the server’s name.
  • Select Install your KMS host key, enter the Windows Server 2025 KMS host key you obtained from the VLSC, and select Commit.
  • When prompted to activate the product, choose Activate online and select Commit. 

4. Verify DNS Records and Client Configuration 

 

KMS clients use DNS SRV records (_vlmcs._tcp) to automatically discover available KMS hosts. The Volume Activation Tools wizard typically creates this record automatically. 

  • Verify DNS: From any client machine, open an elevated command prompt and run nslookup -type=all _vlmcs._tcp. The output should list both your primary (Server 2022) and secondary (Server 2025) KMS server hostnames and their IP addresses.
  • Client Failover: KMS clients are designed to attempt activation against the first available KMS host in the DNS list. If the primary server is down, they will automatically try the secondary. No manual configuration is typically needed on the clients for failover if DNS is correctly configured.
  • Manual Testing (Optional): To test the new server's functionality immediately, you can manually point a test client to the new KMS server using the slmgr.vbs command:

 

bash

cscript slmgr.vbs -skms <Server2025_Hostname>

cscript slmgr.vbs -ato

Document Location

Worldwide

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Document Information

Modified date:
06 February 2026

UID

ibm17259970

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