OpenWrt Forum Archive
https://forum.archive.openwrt.org/viewtopic.php?id=2968722.04.2011 · I want to use a Windows DHCP server which resides on my main LAN subnet (vlan 1) to assign IP addresses for all subnets in my 8 vlans, using different scopes off course. I don't want to use the DHCP server of OpenWrt to assign IP adresses so i want to use a DHCP Relay in OpenWrt to forward DHCP requests to my main Windows DHCP server.
OpenWrt Forum Archive
https://forum.archive.openwrt.org/viewtopic.php?id=7054511.04.2017 · DHCP relay is a function which adds a tag to the DHCP request (option 82, circuit ID). This allows your DHCP server to respond with the correct subnet address to the request. You would need to configure DHCP relay on DNSMasq on the OpenWRT router, and configure your DHCP server to interpret the circuit ID. Here's the DNSMasq sample config: