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Hello. I ended up replacing my apparently defective, several years old, SB8200 modem with a new SB8200. I have Xfinity cable internet and am paying for 500 Mbps speed. The past few weeks my speed had dropped to around 40 Mbps or dropped off completely. An Xfinity technician came out and checked my outside cable and measured the signal coming into the. It measured at around 1,700 Mbps and only about 40 Mbps coming out of the old SB8200. While the old SB8200 was working, the download light was always blue, indicating that it was operating in DOCSIS 3.1 mode. I have installed the new SB8200 and am measuring download speeds of around 550 Mbps. However, the download light on the modem is staying green, indicating DOCSIS 3.0 mode. Is there something wrong with the new modem that is keeping it in DOCSIS 3.0 mode? Or did Xfinity set up the connection incorrectly with the new SB8200?

Thanks for any feedback.

Basically,  slow speed, intermittent connection or no internet access occurs usually out of cable signal level, out of acceptable range and it will be resolved after the power level are adjusted by the service provider.  So for this we need to check the cable signal level to confirm what causing this issue to proceed further. 

Please follow the steps mentioned on the below link to check the cable signal level on direct connection.

http://arris.force.com/consumers/articles/General_FAQs/SB8200-Cable-Signal-Levels

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