WAN interface failure with B20? Or?

[TK_Liew]

@Rick-DC, do you think forum below help?

SB6121 Cable Modem

Community, This is currently a popular cable modem in use today and it has a very picky Ethernet negotiation characteristic. The fix is simple, just lock down the Ethernet WAN port speed to 1000Mbps Full Duplex and uncheck the “Advertise Speed”. Save and apply and then reboot the cable modem, you are good to go. You may not see this issue on all of our devices but it definitely applies to the Surf SOHO. Thanks.