CM1000 and xfinity gigabit

Disconnect the external router from the modem to isolate the issue. 

Be sure you don't have any coax cable line splitters in between the modem and ISP service box. 

Try testing with a different wired PC with the modem. Some older PCs can't handle speed testing near 900Mbps. You need a quad core PC to get good results. 

It's up to the ISP to ensure you have good signal and line quality up to the modem. 

Test with a wired PC directly connected to the modem. If you do experience same issues with this PC, try another modem out to see if same thing happens. IF it does, then ISP needs to send someone out and check the line up to the modem. If need be, get a modem from the ISP and let them prove to you that you can get near 900Mbps on your PC. If they can do that, then at some point try your own modem again. 

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Gavinwatson1984 wrote:
I know this has been posted a couple times but it is not letting me interact with the previous posts. Has the issue with "very" slow xfinity speeds on the CM1000 modem been resolved yet? The comcast guy said he cant help me trouble shoot because I have my own modem. I am pretty much always getting 350mbs down and 40 mbs up. The most I've seen directly on the modem was around 400mbs. With the router and modem I have in my set up I should beable to get fast speed everywhere in my house. Right? Please help!

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Agree with FURRYe38 is saying in regards to the modem. You should be able to get gigabit at the modem and hardwired into the router. In regards to your getting 350mbps.  You don't put how you're getting those speeds. Are they wired/wireless? Devices testing with? Website used for speedtesting?

If you're getting that over wireless, thats about what you can expect to get. Wireless isn't going to be able to hit gigabit speeds. The only real way to speedtest gigabit is over a hardwired connection with a computer that supports it. 

Another thing you say is you should be able to get fast speed everywhere in your house. How big is your house? Housing materials? These make a big difference as large houses usually need an additional access point. And if your house is made from concrete/brick/adobe/plaster lathe it can really interfere with wireless signals.