DHCP.
If you know what you're doing, it's perfectly acceptable to have two DHCP servers on a network. I do. (I have my Freesco linux router 192.168.10.x and my WiFi router/switch combo. 192.168.2.x. The WiFi router has a port that gets an IP assigned by the Freesco router, and then assigns IPs to computers connected to it that use the freesco router port as a gateway. Sounds complicated, but it's not.)