DHCP Failover and Recovery

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I recently had an issue with a Domain Controller that was unresponsive at a remote site. Since it was just a virtual machine with no special settings, I punted and rebuilt the server. After I did all the recommended steps for removing a DC from Active Directory and was already configuring the new server, I remembered that I had setup DHCP Failover for this site. I would be lying if I did not say a twinge of panic set in at that moment. I had setup DHCP Failover in hot standby mode almost five years ago and had not not given it a second thought. Fortunately, the process was so simple that I did not even need to use PowerShell. I deleted the old Failover Relationship and then recreated it. The detailed steps are below.

Delete Old Failover Relationship

First on the active DHCP server, open DHCP Manager. Right click on IPv4 and choose Properties

On the Failover tab, select the failover relationship and click Delete.

Click OK to confirm the deletion.

The Failover Relationship is deleted. Note that you will see failure messages if the partner server cannot be reached. Click Close.

Create New Failover Relationship

Now that the old failover relationship is removed, we can recreate it. Obviously, you will need to repair or rebuild the DCHP failover partner server first. Once the partner server is ready, open the DHCP Manager on the active server. Right click on the scope and choose Configure Failover.

Select the Scopes and click Next.

Click Add Server.

Type the server name or select it from the list of authorized DHCP servers. Click OK.

Click Next.

Configure Failover Options for your environment. You may need to choose a new Relationship Name if the previous DHCP Failover was not successfully deleted. Click Next.

Confirm the settings and click Finish.

Once the DHCP Failover is created click Close.

DHCP Failover is easy to configure and easy to recover. I was surprised at how smoothly I was able to add and delete the partnerships using Windows Server 2016 and 2019. I repeated the process several times as I wrote this article. I would suggest creating a DHCP failover partner especially if you have a remote site with little or no IT support staff. I was fortunate that I had setup DHCP Failover at this site several years ago. Of course, in my case better monitoring software would have helped alert me to the server failure sooner. Hopefully, I will be writing about installing and configuring monitoring software soon.

You may need to rely on PowerShell to remove a Failover Relationship. The commend Remove–DhcpServerv4Failover will delete the specified partnership. A complete list of PowerShell commands can be found here:

https://blogs.technet.microsoft.com/teamdhcp/2012/12/18/dhcp-failover-using-powershell/

 

Ben Dumke

@BenDumke

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