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CM1000 comcast gigabit not surpassing 400mbps download

DRpeppZ
Tutor

CM1000 comcast gigabit not surpassing 400mbps download

I have recently upgraded my internet service through comcast from 500mbps down to gigabit internet. Before the upgrade i was consistently getting around 250-400 mbps and thought this was normal (quite obviously it isnt). After upgrading I'm not getting anywehre near the speeds im supposed to be getting. Upload itncreased by about 100%, from 20mbps to 40mbps, while download ranges between 250-400 like it used to. I have contacted xfinity support and after updating the boot file of the cm1000 they are assuring me that this is a problem on the netgear side of things. I have attached an image of the parameters on the router, can anyone provide me with some insight on this problem? 

 

Thank you.

Model: CM1000|Ultra-High Speed Cable Modem—DOCSIS® 3.1 Ready
Message 1 of 8
plemans
Guru

Re: CM1000 comcast gigabit not surpassing 400mbps download

Youre coming in a bit hot on your power but it shouldn't necessarily slow your speed down.

What website are you testing with? kind of key as many websites can't saturate gigabit

Are you testing over a hardwired connection?

Are you connecting directly to the modem from your pc?

What pc is it? (specs)

Message 2 of 8
DRpeppZ
Tutor

Re: CM1000 comcast gigabit not surpassing 400mbps download

Im using speedtest.net, my pc is more than capable of handling gigabit ethernet, and as of testing im hardwired to the modem. What could cause the power to be as high as it is? 

Message 3 of 8
plemans
Guru

Re: CM1000 comcast gigabit not surpassing 400mbps download

You could be close to the hub. which could cause that. 

Not a huge issue. I've ran up to 13dbmv without issue. Started getting sketchy after that.
what pc is it (specs)?

speedtest.net doesn't always saturate gigabit depending on what server its using. Try dslreports.com or speedtest.xfinity.com

 

Message 4 of 8
DRpeppZ
Tutor

Re: CM1000 comcast gigabit not surpassing 400mbps download

AMD 3900x cpu

16gb 3600mhz memory

2 500gb SSD, 1 2TB HDD

EVGA RTX 2070 Super XC gaming ultra

ASUS TUF Gaming X570-Plus motherboard 

 

I just tried both of those and was getting around 600, which is defnitely better than when using speedtest.net but still not within the range im expecting. Didn't know that about speedtest.net though, I'm expecting somwhere around 900mbps from seeing what others using the same service are capable of. 

Message 5 of 8
plemans
Guru

Re: CM1000 comcast gigabit not surpassing 400mbps download

want to cheat a little? try putting a 2x or 3x splitter in line and cap off the open ends. (if you've got it). it'll reduce signal strength similar to an attenuator. the key for gigabit is the docsis 3.1 connection and its a bit high. 

If it doesn't impact the speeds by doing that, then I'd have your isp both check the line and check the modem provisioning. 

Message 6 of 8
DRpeppZ
Tutor

Re: CM1000 comcast gigabit not surpassing 400mbps download

Don't have any splitters, and im not normally hard wired to the modem, just doing this right now for testing purposes. Would a splitter really be a solution to this problem or just a bandaid?  

Message 7 of 8
plemans
Guru

Re: CM1000 comcast gigabit not surpassing 400mbps download


@DRpeppZ wrote:

Don't have any splitters, and im not normally hard wired to the modem, just doing this right now for testing purposes. Would a splitter really be a solution to this problem or just a bandaid?  


both? 

Its kind of a bandaid as an attenuator is the "fix" but doing it with a splitter is effectively the same (provided you cap off the end not used on a splitter). 

Message 8 of 8
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