CM3000 painfully slow speeds via Comcast

[mykchicken]

Hello folks - anyone else using a CM3000 and experiencing painfully slow speeds? 
I've ran through the typical troubleshooting (reboot, factory reset), confirmed the Modem is all green for Up/downstream, I've had comcast/Xfinity tech come out and confirmed they're getting gig speeds at the coaxial line in my home & confirm voltage/run other tests.

Yet when I hookup the CM3000 and directly connect to it via Cat5e or Cat6...I'm getting about 20-30Mbps down.

Pulling my hair out on this one.

[mykchicken · Accepted solution]

Wanted to follow up on this - 

I stopped by xfinity store and picked up an XB8 from them.

Plugged it in at home & within minutes I'm seeing the advertised speeds... pretty much nail in the coffin - it's the Modem that's the problem.

Going the RMA route to return it. 

Truly appreciate the ideas & support of all you fine folks.

Cheers

[plemans]

Got a screensnip of the cable connections page and event logs? 

One thing to try is have Comcast re-provision it. 

If that doesn't help, I'd try exchanging it. there's a pretty low failure rate but it could still be bad. 

And comcast isn't great at rechecking lines without charging you unless you've tried something drastic (like replace the modem)

[FURRYe38]

Is this with a directly connected PC or is there a external wifi router in the mix? Brand and model of this router please. 

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@mykchicken wrote:

Hello folks - anyone else using a CM3000 and experiencing painfully slow speeds? 
I've ran through the typical troubleshooting (reboot, factory reset), confirmed the Modem is all green for Up/downstream, I've had comcast/Xfinity tech come out and confirmed they're getting gig speeds at the coaxial line in my home & confirm voltage/run other tests.

Yet when I hookup the CM3000 and directly connect to it via Cat5e or Cat6...I'm getting about 20-30Mbps down.

Pulling my hair out on this one.

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[mykchicken]

This is with a direct connection to the Modem. I've removed the router from the equation in my troubleshooting.

[mykchicken]

I've had their techs remove it from my account and reprovision it 3 times over the last week with no improvements, but good call out. 

Attaching the cable connection screen. It's a long page 😄

The only thing that jumps out is that some of the power values are a bit high...but that shouldn't cause this kind of issue, and the modem internal time is 1 hour behind but...there's no way that's an issue..right? 

Good call on the exchange...at this point it's been several hours spent and it's definitely a $ net loss overall. 

[FURRYe38]

Powers a bit too high:

https://kb.netgear.com/24311/Power-level-guidelines-for-a-NETGEAR-cable-modem-router

Lets see the Events logs please.

[mykchicken]

Attaching the logs w/my CM3000 MAC redacted. 

[FURRYe38]

Seeing some criticals there. A T3 entry and those time entries need to be resolved by the ISP.

Any Criticals, Errors or Warnings seen in the event logs needs to be reviewed and resolved by the ISP. Indicates a signal issue on the ISP line up to the modem.

I'd ask for a -3 or -6Db attenuator to help bring down the power some. 

Have the ISP check the signal and line quality UP to the modem. Be sure the ISP provisions the modem correctly.
Be sure there are no coax cable line splitters in the between the modem and ISP service box. 
Be sure your using good quality RG6 coax cable up to the modem. 
From there check the line for kinks, damage, moisture in the line.
Check the connectors for improperly made ends, foil touching the copper coax line, loose connections, bad/old/cheap connectors, or corroded connections. Replace them if you do.
Be sure to power OFF the modem for 1 minute then back ON.
https://community.netgear.com/t5/Cable-Modems-Routers/General-info-and-Troubleshooting-for-Cable-Mod...
https://www.duckware.com/tech/solving-intermittent-cable-modem-issues.html
https://highspeed.tips/docsis-events/

[Kitsap]

Based on your cable connection values, you are definitely not in an area that has been upgraded to the enhanced speed network.  No upstream OFDMA channels to lock on to.  However your throughput values are definitely low.  What throughput plan (up and down) are you paying Xfinity for?

Are you certain the device you are directly connecting to the modem is working properly?  Such as operating system and driver updates are current.  What exactly is this device?

[mykchicken]

According to xfinity (they sent a confirmation email & techs confirmed via chat) that we are in the area with an enhanced network but I 100% agree the config says otherwise.

I'm paying for the 1gig plan so supposedly 1gb down, 35Mbps up.

I've used 2 separate Windows 11 devices, a desktop with a 2.5gb nic, and a laptop with a 1gig nic. Both updated & functioning without issue with other connections. 

[mykchicken · Accepted solution]

Wanted to follow up on this - 

I stopped by xfinity store and picked up an XB8 from them.

Plugged it in at home & within minutes I'm seeing the advertised speeds... pretty much nail in the coffin - it's the Modem that's the problem.

Going the RMA route to return it. 

Truly appreciate the ideas & support of all you fine folks.

Cheers

[plemans]

@mykchicken Not sure where you bought it but sometimes its faster to go through the site/building you bought it from. I've done exchanges on amazon that are faster than you'd even get an RMA started through netgear

[mykchicken]

@plemans Agreed. I wish it was available on Amazon - I went directly through Netgear to purchase it as that was the only place I could actually find the CM3000 for sale at the time. 

Time will tell how the actual process goes. 

[Kitsap]

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@mykchicken wrote:

Wanted to follow up on this - 

I stopped by xfinity store and picked up an XB8 from them.

Plugged it in at home & within minutes I'm seeing the advertised speeds... pretty much nail in the coffin - it's the Modem that's the problem.

Going the RMA route to return it. 

Truly appreciate the ideas & support of all you fine folks.

Cheers

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Thanks for the feedback and update.  Please keep us posted when you get your replacement modem installed.