My ISP won't allow me to configure my ONU (a FiberHome HG6245D) as a bridge device, so I resorted to setting up a DMZ and adding my OpenWrt'd Archer C7 v4 router to it.
On the router's config I set the WAN as described in https://openwrt.org/docs/guide-user/network/wan/dmz-based-bridge-mode and everything is sort of working, but any devices I connect to the router's LAN ports are assigned IPs by the DHCP running on the HG6245D instead of using the OpenWrt's.
Is there a way to block the upstream DHCP or any other way of disabling it's use by the devices attached to the router? As a workaround, I disabled the DHCP on the HG6245D, but that keeps me from using it's Wi-Fi.
My ONU is in the 192.168.2.0/24 range and the router is in the 192.168.1.0/24.