I just got Xfinity installed yesterday and had the same problem. I worked around this issue as follows: Connected just my laptop to the router Under Connections -> Local IP Network Changed the address of the router to 192.168.1.1 Changed DHCP Beginning Address to 192.168.1.254 Changed DHCP Ending Address to 192.168.1.254 Set DHCP Lease Time to Forever Save Settings Router reboots and my laptop gets IP address 192.168.1.254 Go back to Connections -> Local IP Network Change DHCP Beginning Address to 192.168.1.253 Change DHCP Ending Address to 192.168.1.253 Save Settings Now, my laptop gets it's DHCP address assigned by my Linux box. Why did this work? Because the Comcast router stored my original IP/MAC address "forever" as 192.168.1.254. And now it can only give out 192.168.1.253. So, the Comcast router doesn't get out an IP for my laptop, and my Linux DHCP server takes care of the request. Now, one of my network devices will get the IP of 192.168.1.253 from the Comcast router "forever". So, i just connected my printer to get this IP, then configured it as a static IP in my Linux DHCP/DNS server. At this point, the Comcast router can no longer respond to DHCP requests since its DHCP IP range is depleted.
... View more