DHCP Server Authorization Failure: Troubleshooting Error Code 20079

Table of Contents

• Resolving Error Code 20079: Step-by-Step Solutions¶
• Frequently Asked Questions (FAQ)¶

Encountering the error message “The authorization of DHCP server failed with Error Code 20079” during the setup of a DHCP server on Windows Server environments can be a frustrating roadblock. This issue is known to occur across various Windows Server versions, including 2025, 2022, 2019, and 2016, potentially disrupting network configuration and client IP address assignment.

The complete error notification typically presents as follows:

Authorizing DHCP server…… Failed

The authorization of DHCP server failed with Error Code: 20079. The specified servers are already present in the directory service.

If the DHCP server is not authorized by AD DS, it cannot respond to DHCP requests.

This error commonly arises after installing the DHCP server role, specifically when the post-installation wizard attempts to configure the server. The root cause often lies in the failure of Active Directory Domain Services (AD DS) to authorize the newly installed DHCP server. Without proper authorization from AD DS, the DHCP server is rendered incapable of fulfilling DHCP requests, leading to network connectivity problems for client machines.

This article provides a structured approach to resolving the “Error Code 20079” DHCP server authorization failure in Windows Server. We will explore a series of troubleshooting steps, ranging from simple service restarts to more comprehensive solutions like manual server deletion and reinstallation.

Resolving Error Code 20079: Step-by-Step Solutions¶

To effectively address the “The authorization of DHCP server failed with Error Code 20079” error within your Windows Server environment, consider implementing the following solutions sequentially. These methods are designed to progressively tackle the issue, starting with the least disruptive and most common fixes.

1. Restart the DHCP Server Service¶

The initial and often simplest step in troubleshooting this error involves restarting the DHCP Server service. Temporary glitches or internal service disruptions can sometimes lead to authorization failures. A service restart can effectively clear these transient issues and re-establish proper functionality.

To restart the DHCP Server service, follow these steps:

1. Access the Services Manager: Begin by opening the Services application. The quickest way is to type “services” directly into the Taskbar search bar and select the “Services” application from the search results.

2. Locate the DHCP Server Service: In the Services window, scroll down the list of services until you find “DHCP Server”. The services are typically listed alphabetically, making it easier to locate.

3. Open Service Properties: Double-click on the “DHCP Server” service entry to open its Properties window.

4. Stop the Service: In the Properties window, under the “Service status” section, if the service is running, click the “Stop” button. Allow a few moments for the service to completely stop.

5. Configure Startup Type: In the “Startup type” dropdown menu, ensure that “Automatic” is selected. This setting ensures that the DHCP Server service starts automatically whenever the server is booted.

6. Start the Service: Click the “Start” button to restart the DHCP Server service. Wait for the service status to change to “Running.”

7. Confirm and Close: Click the “OK” button to save the changes and close the DHCP Server service Properties window.

After restarting the DHCP Server service, attempt to authorize the DHCP server again through the DHCP Manager console. Check if the error code 20079 is resolved. If the issue persists, proceed to the next solution.

2. Restart the Active Directory Domain Services (AD DS) Service¶

Since Active Directory Domain Services (AD DS) plays a crucial role in DHCP server authorization, restarting the AD DS service is a logical next step. Issues within the AD DS service itself can prevent proper authorization processes from completing. Restarting AD DS can resolve underlying problems that are hindering DHCP server authorization.

To restart the Active Directory Domain Services service:

1. Open Services Manager: Access the Services application again, as described in the previous solution, by searching for “services” in the Taskbar search.

2. Locate Active Directory Domain Services: In the Services window, find the “Active Directory Domain Services” service in the list.

3. Open Service Properties: Double-click on “Active Directory Domain Services” to open its Properties window.

4. Stop the Service: If the service is running, click the “Stop” button. Stopping AD DS is a more impactful action than stopping DHCP Server, so allow sufficient time for the service to shut down completely. This might take slightly longer as other services may depend on AD DS.

5. Start the Service: Once the service is stopped, click the “Start” button to restart Active Directory Domain Services. Allow the service to initialize fully.

6. Confirm and Close: Click “OK” to save the changes and close the Properties window.

After restarting the AD DS service, re-attempt the DHCP server authorization process. Verify if error code 20079 is still present. If the error remains, it indicates a potentially deeper configuration issue requiring further intervention.

3. Manually Delete the DHCP Server from Active Directory Sites and Services¶

Error code 20079 can also occur if there are remnants of a previous DHCP server configuration within Active Directory Domain Services. This scenario is common if a DHCP server with the same name was previously configured and then removed without properly deleting its entry from AD DS. In such cases, the system may perceive a conflict, preventing the authorization of the current DHCP server. Manually deleting the old server entry can resolve this conflict.

To manually delete the DHCP server entry from Active Directory Sites and Services:

1. Open Server Manager: Launch Server Manager on your Windows Server.

2. Access Active Directory Sites and Services: In Server Manager, click on “Tools” in the top right corner, and then select “Active Directory Sites and Services” from the dropdown menu.

3. Show Services Node: In the Active Directory Sites and Services console, right-click on the root “Active Directory Sites and Services” in the left pane. Navigate to “View” and click “Show Services Node”. This action will expose the “Services” node in the console tree.

4. Navigate to NetServices: Expand the “Services” node, and then select “NetServices”.

5. Locate and Delete the Server: In the right pane, you will see a list of registered network services. Find the entry corresponding to the DHCP server you are trying to authorize. The server name should be identifiable. Right-click on the server entry you wish to delete.

6. Confirm Deletion: Select “Delete” from the context menu. A confirmation dialog box will appear asking if you are sure you want to delete the object. Click “Yes” to confirm the deletion.

After deleting the server entry, proceed with the DHCP Server setup wizard again to attempt authorization. If the issue was due to a duplicate server entry, this step should resolve error code 20079.

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4. Reinstall the DHCP Server Role¶

If none of the preceding solutions successfully resolve the DHCP server authorization failure, a more drastic measure is to uninstall and then reinstall the DHCP Server role. This process ensures a clean slate, eliminating any potential corruption or misconfiguration within the DHCP Server role installation itself.

To uninstall and reinstall the DHCP Server role:

1. Open Server Manager: Launch Server Manager on your Windows Server.

2. Remove Roles and Features Wizard: Click on “Manage” in the top right corner, and then select “Remove Roles and Features”. This will open the Remove Roles and Features Wizard.

3. Before You Begin: Click “Next” on the “Before you begin” page.

4. Server Selection: Ensure the correct server is selected in the “Select server(s) from server pool” page and click “Next”.

5. Remove Server Roles: On the “Remove server roles” page, uncheck the box next to “DHCP Server”.

6. Remove Features Confirmation: A dialog box may appear asking if you want to remove features that depend on DHCP Server. Click “Remove Features” to proceed.

7. Confirmation and Removal: Click “Next” on the “Remove server roles” page and then click “Remove” on the “Confirmation” page to begin the uninstallation process.

8. Complete Uninstallation: Allow the wizard to complete the uninstallation of the DHCP Server role. Click “Close” once the process is finished.

9. Install DHCP Server Role: After uninstalling, you need to reinstall the DHCP Server role. Refer to instructions on how to install the DHCP Server role in Windows Server. The process is typically done through the “Add Roles and Features Wizard” in Server Manager, selecting the “DHCP Server” role, and following the on-screen prompts.

After reinstalling the DHCP Server role, run the DHCP Server post-installation configuration wizard again to authorize the server. This fresh installation should resolve any underlying software issues that were causing error code 20079.

Frequently Asked Questions (FAQ)¶

How do I authorize DHCP server if authorization failed with error 20079?

The primary method to authorize a DHCP server after encountering error 20079 involves addressing the underlying cause of the failure. As detailed in the solutions above, this often entails restarting relevant services (DHCP Server and AD DS), manually removing conflicting server entries from Active Directory Sites and Services, or, as a last resort, reinstalling the DHCP Server role. After implementing these solutions, re-run the DHCP Server configuration wizard to attempt authorization again. In many cases, simply restarting the DHCP server service or AD DS service after encountering the error can resolve the issue during a subsequent authorization attempt.

What is error code 20070 related to DHCP authorization?

Error code 20070, similar to 20079, indicates a DHCP authorization failure. Both errors suggest that the DHCP server is not being authorized by Active Directory Domain Services (AD DS). While 20079 specifically points to potential duplicate server entries in AD DS, error 20070 often signifies a broader issue related to permissions or communication problems between the DHCP server and AD DS. Troubleshooting steps for error 20070 are largely similar to those for 20079, focusing on service restarts, permission checks within AD DS, and ensuring proper network connectivity between the DHCP server and domain controllers. It is crucial to verify that the user account used for DHCP server setup has sufficient domain administrator privileges to authorize the server within AD DS.

By systematically applying these troubleshooting steps, you should be able to effectively resolve the “DHCP Server Authorization Failure: Error Code 20079” and ensure your DHCP server is properly authorized and functioning within your Windows Server environment.

If you continue to experience issues or have further questions, please feel free to leave a comment below. Your experiences and questions can help others facing similar challenges.