CM1000 - Xfinity Gigabit tier - slow download speed

[fiscap]

I've recently noticed slow download speeds on my Xfinity Gigabit Internet tier and I've been unable to determine what is causing the issue - I think it's on the Comcast end, but haven't ruled out that it may be an issue with my Netgear CM1000 cable modem.

First, a little history - I've had the CM1000 since October 2017 and have been running the Gigabit tier since that time. I've got everything behind a fairly beefy pfsense firewall and have consistently sustained 850-950 Mbps download speeds since installing the setup last year.

I don't usually keep a close eye on download speeds, but recently my wife started complaining about uploading/downloading large photography sets for her business. I thought she was just imagining it until I checked and sure enough, our download speeds for the past week or so of checking have been hovering right around 50 Mbps at most. I've tried several bandwidth tools, but the http://speedtest.xfinity.com has always been the go to test, however even directly to Comcast it'll throttle up around 90-100 Mbps for a split second and then drop back to 50 Mbps for the remainder of the test.

I've tried a couple different computers with gigabit ports patched directly to the CM1000 LAN side to rule out anything funky that may be going on inside the network, but I still get the same results. Upload speeds appear to be unaffected by whatever is going on as I consistently obtain about 40+ Mbps during these test, which is right where it should be for the Gigabit tier.

I spoke with Comcast earlier today to make sure that everything looks 'okay' on their end - provisioning, modem model information, correct tier, no bandwidth cap, etc. From what they told me, everything seems to be okay on their end. I also checked the source file for the config that Comcast is pushing in 192.168.100.1/DocsisStatus.asp and it indicates 'd11_m_cm1000_gigabit_c01.cm' - which is what I believe the latest is for the CM1000.

Below are the status table for the CM1000 and the event log  (CM-MAC is scrubbed) as well - I'd appreciate any further troubleshooting suggestions

[fiscap]

[billq]

Wow, not a single response to this since 01/02...

I have the same setup - CM1000 + Xfinity Gigabit tier.  I see from your screenshot that you have unlocked downstream channels.  I suspect this might be the cause of your poor download speed, though sad to say I have no idea how to fix it.  I have a similar issue, though the only downstream bonded channel that is unlocked in my case is channel 32.  I believe that channel is needed for Gigabit speed, as I am only able to get ~400 Mb/s.

Does anyone at Netgear read these?  I read through their docs, and can find zero info on how to fix this issue.  Their link to "how to fix slow download speeds" is just a link to what firmware the modem should be running.  I think I may go back to Arris or Motorola.

[Lesnla]

I have the same problem - 4 unlocked upstream channels, and capping at around 415 downstream with 41 up.

is anyone going to respond to this message from Netgear? 

Thank you

[MMERIDETH]

same issue with two different netgear routers.  help has been helpless

[jrowlands]

I have the CM1150V which adds telephony to the CM1000. I too am having issues with erratic download speeds. Channels 1-31 downstream are locked with frequency range from 477Mhz to 675Mhz. Channel 32 is not locked. Speeds range from 647mbps to 25mbps using a macbook pro via thunderbolt to cat8. Xfinity techs measured 947mbps via cat6 to their rasberry pi. I was told the Docsis 3.1 frequencuies are above 675Mhz, none of my channels are using these frequencies.

The upstream has channels 1-4 locked on, while 5-8 are not locked. Xfinity says they only have 4 upstream channels. Speeds are consistent around 32mbps to 41mbps. 

There is only one firmware available for this model and it is only available for xfinity. 

[MMERIDETH]

I ended up just bridge moding the comcast router and that solved all my problems at least for download speeds.

[sniper_tim]

I don't have GB service from comcast, however as soon as I swapped out my comcast provided router with the CM1100, my download speeds dropped in half.  I have the 200MB tier service from comcast and consistently obtained 180Mbps (speakeasy) download speeds via wireless or directly connected.  Now I consistently get only 85Mbps.  This has been going on since January and originally I thought I'd give it some time to obtain updates etc, however now I'm quite disapointed.  What do you mean "bridge moding", do you think this would help for my situation?  From what I initially read, it was primarily for gigabit service, which I don't have and ignored the instructions.  Is this required to set up a local SAN/external HD for making my media available to my network?  Any advice would be helpful, thanks in advance.

Cheers,

Tim

[MMERIDETH]

without bridge mode I was getting the comcast router and my router interfering with each others IP address assignments. i would recommend if you have a router from comcast, either use their router or put it in bridge mode and use your router.

Marcus