CM400 slowed from 160 mbps to 5 mbps

[Omega553]

This randomly started happening where my internet speed has dropped from the usual expected 160 mbps down to 5 mbps. I know the issue is with the CM400 and not my router because I get those speeds even when plugged directly into the CM400.

When I reboot the modem my speeds return to normal but only for a short time (minutes) before it drops back down again.

I've attached a screen capture of the modem logs.

Does anybody have any idea what could be going on?

This happened once before maybe a year ago and it magically resolved itself after a few days (I was about to pull the trigger and buy a new modem)

[Omega553]

A very interesting and unusual development...

I am still getting slow speeds when testing at speedtest.net but when I download a game from Steam I'm getting about 140-150 mbps. Why is that download speed fast but everything else is so slow?

[Kitsap]

Sometimes capacity testing through a web browser can yield irregular results.

Have you tried the Ookla native applications from the Windows Store or Android Play Store?

[Omega553]

Yes. When performing the speed test via the app on my cell phone I get the same slow results as the web browser version on my PC.

[plemans]

Your logs are indicating a line issue. 

Do you have a screensnip of the cable connections page? 

Start with removing any amplifiers, signal attenuators, or splitters from the coax.
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, bad/old/cheap connectors, or corroded connections. Replace them if you do.
If you can, simply connect the modem right where the coax comes into the home. This prevents wiring in the home from being the issue. And some ISP’s charge if the wiring issue is in the home. So this helps prevent this.

Might also be time to watch out for any sales on modems as thats a pretty base model device and some ISP's aren't supporting it anymore. 

My NETGEAR CM400, C3000v1, or C3700v1 cable product is having Internet connectivity issues suddenly....

[Omega553]

Here are the screen caps of the cable connection page:

What part of the log makes you say there is a line issue? I'm curious to learn a bit more about how to read the logs.

The ISP tech came yesterday and hooked up his own equipment directly to the coax that is plugged into my modem and said there is no issue on the line. He was able to get speeds up to 1.2 Gbps so it may not be a physical issue with the line.

I ordered a new modem today from Amazon and will see how that works. Should tell me if the issue is with the CM400 or the line itself.

[plemans]

You've got errors in the line and multiple lines in the logs are indicating the issues. Not just one. 

How to Read Your Cable Modem’s Diagnostic Page When Something Goes Wrong (howtogeek.com)

[Omega553]

Thanks for the link. From a quick look it seems that the signal strength of the line is good at least based on what the article suggests. Maybe this CM400 is on its way out. Let's see if the new modem fares any better.

[plemans]

The strength is in range but you have errors. And that cm400 only uses a limited number of channels versus whats available. If the modem switches between channels, the others could have more errors. Its why the logs help in conjunction with the cable connections page. 

[Omega553]

Are these errors caused by the modem itself or the line? Because absolutely nothing changed (as far as I'm aware) in my home that would cause speeds to drop suddenly like this.

I'd want to be able to pull the log and send it to my ISP and say "Look here, these logs show that my slow speeds are due to these errors that are coming from you, not from my modem"

[plemans]

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@Omega553 wrote:

Are these errors caused by the modem itself or the line?---thats what the challenge is to find out. Its why we have you check the line/connections.  Because absolutely nothing changed (as far as I'm aware) in my home that would cause speeds to drop suddenly like this.

I'd want to be able to pull the log and send it to my ISP and say "Look here, these logs show that my slow speeds are due to these errors that are coming from you, not from my modem"----The log isn't going to show speed changes, just that there's errors/issues. 

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[Omega553]

I just swapped to a new modem I purchased and everything is working fine now. Thank you for the help!!