It definetly feels good to manually verify my hardware working with my custom Ethernet Firmware to isolate the issue to LwIP. I could definetly capture some nice wireshark screenshots of "invalid" DHCP packages being sent with a checksum of 0 for my bachelor thesis. I now know, that isc-dhcp-server(on pfsense) accepts these DHCP requests, unbound-DHCP(on OPNsense) doesn't and whatever a generic GLinet router uses also doesn't accept it. #microcontroller #electronics