Very Slow CM500 connection speed

[Hapa]

Brand new Netgear CM500 16x4 modem, Linksys AC1000 dual band wifi 5 router, and 600mbps Xfinity plan.
I am only getting about 30mbps DL speed and about 10mbps upload speed.
Xfinity says they are seeing full speed entering my address and that it must be an issue with the modem. Does anyone have troubleshooting steps or see an issue with this combination?
Thanks.

[plemans]

Do you have a screen snip of the cable connections page and the modem logs? 
That's helps check your signal. 

When you're speedtesting, are you directly connected to the modem? That's the first thing I'd try. That ensures the router isn't causing the slowdown. 

Something to also keep in mind, xifnity only rates the CM500 for up to 372mpbs. so its a bit pointless to be paying for 600mbps if you're modem can't get those speeds with the way xfinity provisions. A cheaper plan or upgrading the modem might be worth looking into. 

[Hapa]

Thanks for the response. I just speed tested with direct connection to modem and got about 400mbps but connected to wifi I get about 25mbps. Does this confirm that the router is what is causing the slow speeds? That's an enormous difference. This Linksys AC1000 is supposedly able to handle 1000mbps.

[plemans]

it means the modem's putting out full speed. Its related to the router. 

Which router is it? (hint, AC1000 is a speed, not a model)

might want to start with the linksys support site. 

https://www.linksys.com/us/support/

[raj_bodanki]

Hi,

   Pls check your wifi - you would see 2 Wifi access points - one saying 5G in the end - that's the one you should use to achieve the higher speeds.

Rgds

Raj

[decosse]

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@Hapa wrote:
Thanks for the response. I just speed tested with direct connection to modem and got about 400mbps but connected to wifi I get about 25mbps. Does this confirm that the router is what is causing the slow speeds? That's an enormous difference. This Linksys AC1000 is supposedly able to handle 1000mbps.

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Yes, if your direct connection to modem gets 400, it is definitely the Router - do you have good Ethenet Cable (Cat 6) between the devices? 

You mention 25Mbps on wifi however - the CM500 has no Wifi, so if direct connected to the modem (i.e. Router not connected to the Modem), not sure how/where you are getting any wifi connection to measure. 

If doing speed tests, be sure you are using a good testing service - Xfinity tester will always pick a local server; I like the Ookla Speed Test app also - and be sure that for WiFi speed tests you are using a 5G connection.