As of Server 2012 it’s really easy to setup DHCP failover and should be done whenever possible. The last thing you’ll want is a bunch of computers not on the network because your DHCP server crashed, right? Let’s get to it.
I’ll be presuming you have a Server 2016 system with a static IP that has been already added to the domain. This will be basically the same in 2012 and 2012 R2 though.
If you’ve added your soon-to-be failover DHCP server to Server Manager, doing all this remotely will be a breeze. You can go All Servers on the left pane and right click there to go Add Roles and Features instead of going to the server itself.
Setting up DHCP Failover
First up, lets install the DHCP Services on our Server. Open Server Manager and go Add Roles and Features. In Server Roles, tick DHCP and click Next through to Install. Close it when done.
Go back to your current DHCP Server and expand it down to your DHCP Scope. Right Click and go Configure Failover….
In the wizard that pops up pick your scope if needed. Select all. will be automatically checked. Click Next.
Type in the name of the new DHCP Failover Server and click next.
You can change the Client Lead Time to suit your needs. It’s the time one of the servers would need to be down for before the other will take the full scope. Load balance will determine what part of your scope goes to what DHCP server. It uses MAC hashing to split clients pseudo-randomly based on these percentages. Type in a Shared Secret and click next.
Click Finish and you should be presented with screen saying how successful you are.
We have one more thing to do, we need to authorize the new DHCP Server. Go to the new DHCP server and open the DHCP MMC. Right click on Authorize it. You may need to Restart the service to see it change. Right click again and go All Tasks > Restart. After you’ve done this it should have a little green marker.
To make sure it’s working as intended you can right click on your Scope and go Properties > Failover tab. You can view the information on failover settings here.
