As a follow-up to the Install ISC DHCP on macOS Catalina post, I wanted to create a quick how-to on setting up ISC DHCP failover…because having at least two DHCP servers is a good practice. It WILL save your behind…at some point you are going to fat-finger something in the DHCP configuration, or you will want to do maintenance/updates on the servers, and dhcpd will stop working. Having DHCP failover setup will keep things running, and your users blissfully unaware while you find and fix your typo, or performing maintenance/updates.

In late-2018, Apple stopped bundling a host of open-source software into macOS Server. Since then, I’ve seen a spike in hits on a post from 2011, Install ISC DHCP on Mac OS X Server. That post should still be relevant up to at least Mac OS X El Capitan (10.11), which is where the Mac mini hardware I have running ISC DHCP has remained, dutifully handing out IP addresses across our network.

While those Mac minis have been rock solid, they are aging. So when a pair of fairly new Mac minis decommissioned and no longer needed for their original purpose, I took the opportunity to install macOS Catalina on them, and revisit installing ISC DHCP. I have documented that process here, which hasn’t changed much.