All Ethernet connections to my combo modem/router (Arris SBG10) are not working. I have tried multiple computers with multiple cables. The Wi-Fi works fine. Resetting the modem/router through my ISP (Xfinity) didn't help nor did factory resetting the modem/router. All computers I connect with an Ethernet cable have a 169.254.x.x IPv4 address, suggesting the DHCP server is not working. When diagnosing the connection on a Windows 11 device, there is a "No DHCP server was found" error. However, when I login to my modem settings (192.168.0.1), the modem has DHCP enabled on both WAN and LAN.
How can I fix my Ethernet? Is the problem the SBG10? Or is the problem Xfinity?