Netgear CM500 T3 or T4 Timeouts

Hi,

Is someone able to offer feedback regarding these timeout issues I’m having? Thanks!

Since nobody else picked this up, that stats at that time after a fresh reboot looked OK to me.  Towards the high signal power side, but that can be OK.  That might not be true after it's up for a while.  When you want to look at it is when you are having issues. 

You older DOCSIS 3.0 CM500 might not be supported anymore in your market.  It might not matter, but some say it can be unpredictable.  You can see if it is by looking for approved 3rd party gateways/modems here:  https://www.xfinity.com/support/articles/list-of-approved-cable-modems At one location I have a slightly newer Netgear 3.0 that is still 'approved' -- for now -- and throws errors too from time to time.  You will probably see uncorrectable errors increment when that happens too.  Some errors are just cable distribution and they happen.  Frequent errors are a problem and can be caused by a lot of reasons.

https://forums.xfinity.com/conversations/your-home-network/internet-troubleshooting-tips/602dae4ac5375f08cde52ea0

docsDevResetNow -> I don't know if that was you, or Xfinity trying to push something and a remote reboot.  They can reset from their side regardless of if you can or can't do it from the website.

You hit a spontaneous reboot out of the blue sometime after 2023-1-27, 17:33:59.  That's when the date reverted back to 1970.  That might have been upstream or downstream power drifting too high.  Some other internal failure or power supply glitch.  Hard to say without more info.  Keep an eye on it over time and see if you can get more information or catch the signal power drifting out of range.  Mine will reboot it it drifts up around 15dBmV on downstream, maybe 50+dBmV on upstream, but it will start flaking out before then.

App not working?  Well, it's a 3rd party device so I wouldn't hold out hope there (It's actually good that it can't).  Administer it locally.

@dub1_1dub 

The signal status values at that snapshot in time were OK but the error log entries indicate that something is going on. Perhaps there is noise ingress into the line(s) /  an upstream channel / return path impairment somewhere.

There are other signal stat values that can't be read by the modem. They are the "Upstream Rx Power" (Upstream Receive Power Level), the "Upstream SNR Ch." (Upstream Signal To Noise Ratio), and the "Upstream ICFR" (In Channel Frequency Response). These are as equally important in diagnosing connectivity issues as are the modem's stats.

I'm going to escalate your issue to the Comcast corporate employees that are available to these boards. They will be able to poll the CMTS (Cable Modem Termination System) to check for any real-time degradation and / or error reports, see your node / cable plant, and modem health, and see whether or not everything is in the green zone. They can also see a history plot for the modem and poll the CMTS for those upstream receive signal stats.

You should get a reply here in your topic.

Also bear in mind that if the premises-facing techs can not find or fix a problem at your home, it is they who are responsible for escalating it to their line / network / maintenance dept. techs. The problem may lie beyond your home in the local neighborhood infrastructure somewhere but it is their S.O.P. to start at the home. And if the problem is found to be on their side of the demarcation point, there will not be any charge. Good luck!

Thanks for the responses thus far. Here's the latest stats pulled today 2/4/23 @ 10:28 AM (EST).

Since nobody else picked this up, that stats at that time after a fresh reboot looked OK to me.  Towards the high signal power side, but that can be OK.  That might not be true after it's up for a while.

@flatlander3 Yes, I noticed that the high signal power readings too, as compared to others who have/had this specific model and shared their results in previous threads. I'm not sure what's the cause or how to remedy that. 

You older DOCSIS 3.0 CM500 might not be supported anymore in your market.  It might not matter, but some say it can be unpredictable.  You can see if it is by looking for approved 3rd party gateways/modems here: https://www.xfinity.com/support/articles/list-of-approved-cable-modemsAt one location I have a slightly newer Netgear 3.0 that is still 'approved' -- for now -- and throws errors too from time to time.  You will probably see uncorrectable errors increment when that happens too.  Some errors are just cable distribution and they happen.  Frequent errors are a problem and can be caused by a lot of reasons.

https://forums.xfinity.com/conversations/your-home-network/internet-troubleshooting-tips/602dae4ac5375f08cde52ea0

I checked and it shows it's compatible with the 200 Mbps and lower tiers; it's incompatible with the 400 Mbps and above tiers. For the record, I had this modem for over 2 years now. 

docsDevResetNow -> I don't know if that was you, or Xfinity trying to push something and a remote reboot.  They can reset from their side regardless of if you can or can't do it from the website.

You hit a spontaneous reboot out of the blue sometime after 2023-1-27, 17:33:59.  That's when the date reverted back to 1970.  That might have been upstream or downstream power drifting too high.  Some other internal failure or power supply glitch.  Hard to say without more info.  Keep an eye on it over time and see if you can get more information or catch the signal power drifting out of range.  Mine will reboot it it drifts up around 15dBmV on downstream, maybe 50+dBmV on upstream, but it will start flaking out before then.

I'm not sure about the docsDevResetNow incident. It could have been when I attempted to reboot it through the app. I think the connection failed and I was troubleshooting through the app. I use the Xfinity My Account app for iOS and not the newer Xfinity app (purple icon). Not sure if it makes much of a difference. As for the spontaneous reboot, I remember doing a physical reboot as stated in my initial post. I physically disconnected everything, reconnected, and powered it back up.

The signal status values at that snapshot in time were OK but the error log entries indicate that something is going on. Perhaps there is noise ingress into the line(s) /  an upstream channel / return path impairment somewhere.

There are other signal stat values that can't be read by the modem. They are the "Upstream Rx Power" (Upstream Receive Power Level), the "Upstream SNR Ch." (Upstream Signal To Noise Ratio), and the "Upstream ICFR" (In Channel Frequency Response). These are as equally important in diagnosing connectivity issues as are the modem's stats.

I'm going to escalate your issue to the Comcast corporate employees that are available to these boards. They will be able to poll the CMTS (Cable Modem Termination System) to check for any real-time degradation and / or error reports, see your node / cable plant, and modem health, and see whether or not everything is in the green zone. They can also see a history plot for the modem and poll the CMTS for those upstream receive signal stats.

@EG So far, there's been only one more error entry on the log dated 2023-1-28, 13:21:52. However, as you can see, the power levels are now slightly higher and there are some "correctables" and "uncorrectables" on quite a few channels as compared to my initial post. Thank you for escalating the issue, btw. I was contacted by @XfinityShan and will send a DM as requested. 

Also bear in mind that if the premises-facing techs can not find or fix a problem at your home, it is they who are responsible for escalating it to their line / network / maintenance dept. techs. The problem may lie beyond your home in the local neighborhood infrastructure somewhere but it is their S.O.P. to start at the home. And if the problem is found to be on their side of the demarcation point, there will not be any charge. Good luck!

Thanks, I'll be sure to make note of that. Hopefully, the problem(s) can be found and rectified without cost.

Best of luck with it !

Quick update: The Xfinity techs arrived earlier today and confirmed that there were indeed issues going on. They traced and isolated it to a bad "tap" in the junction box outside of my apartment. Said they placed a service request to have it repaired. I'll see if that resolves the issues once it's corrected.