Cannot get 500 Mbps on CM600

[Alf_12]

I have a CM600 and cable service with Cox.  Cox was to up the speed to 500 Mbps, but they say the CM600 can't handle that speed.  The specs say the modem can handle up to 960 Mbps.  Has anyone else had this issue?

[plemans]

Its a cox certification issue. 
it looks like just recently cox changed their requirements. For speeds 500mbps and higher, they're requiring docsis 3.1 devices. 

https://community.netgear.com/t5/General-WiFi-Routers-Non/C6300v2-not-support-cox-service/m-p/196298...