When the PC is c onnected to the router with the same cable if the speed is normal. If speed is also slow, check if there is any driver update for the Ethernet adapter on the PC.

Google is the one responsible for technical support of the onhub router. Call or email them http://g.co/onsupport

For cable modem, you just simply power it off and on, wait a few minutes, firmware will be updated if any.

Will that affect your network performance? I know some TP-LINK DSL modem router supports Auto Reboot that can specify the time and interval for auto rebooting the router. I think this good feature...

Good to know. Thanks for sharing!

It just display the info of IGMP, does not affect anything. And your IGMP is disabled. just ignore it