are no longer supported by Comcast. Comcast refused to enable this "End of Life" modem for new accounts. I had to buy another DOCSIS3.0 modem. This is a list of their supported modems: http://mydeviceinfo.comcast.net/
πΆ Motorola SB6120 SURFboard DOCSIS 3.0 Advanced Broadband Cable Modem
5 Review
Verizon Jetpack 4620L Wireless Hotspot
4 Review
Enhance Efficiency with Command Communications Comswitch 5500 3-Port Phone/Fax Modem Line Sharing Device
5 Review
π Efficient High-Speed Internet Connectivity with Motorola Surfboard SB6121 Cable Modem
3 Review
UGREEN USB 3.0 Ethernet Adapter Hub with RJ45: Fast Gigabit Ethernet Converter, 3 Ports USB 3.0 Hub Compatible for MacBook, iMac, Surface Pro, Chromebook, Laptop, PC
11 Review
π USR-TCP232-410s: RS232/RS485 Serial to Ethernet Adapter/IP Device Server with DHCP/DNS Support
4 Review
π CERRXIAN RS232 to Ethernet Serial Device Server - TCP/IP Converter with 1Port DB9 RS232 Serial to Ethernet Connectivity
3 Review
π StarTech.com NETRS232 Serial to IP Ethernet Device Server - DIN Rail Mountable - Serial Device Server - Serial Over IP Device Server (Black)
4 Review