Connectivity Issues with 3rd party modem (Netgear CM1150V) - Comcast Tech Request Please

Came down this morning to completely off-line 

Attached is the Modem Status and the Error log before I did anything 

https://www.dropbox.com/s/zbgz3w4o2o62flw/Event_Error_Log_12-27-20.pdf?dl=0

Then I Power Cycled the Modem and it immediately came back on line and reported Speed Test at Full Speed (the Modem Status and Speed Test for that condition are also reported in the file above) 

Then I went to revisit this page and refresh to report, no more than 2 minutes later - page would not load (nor any other); Speed test failed! 

I went through same 'trick' I found where I could repeatedly request Speed Test and it evntually kicked in *after about 10 sequential fails);

the other thing I found was while it was actually processing traffic it would (typically) stay alive - so I just launched a YouTube video in another tab to play in the background (which would also give me an instant indication of if/when the internet connection dropped) while composing this update; well after about 3 mins the video stalled and no other page would load; 

this time my repeated speed test request trick failed and after about 20 attempts forced to power cycle the modem again to complete this post. 

I should add that in that period where there is no internet (and Speed Test repeatedly fails with a 'No Internet' error) all the front panel status leds on the modem are normal - soild green, no apparent flickering 

Please Help! 

I have a very expensive paper weight on my hands 

I still have the XB7 here (waiting to be confident the problem was reolved before returning) so I can put that back on - but that leaves me in quasi state where the source of the problem is unknown. I may be forced to - the CM1150V is pretty unusable at present. (Again - this new unit worked perfectly for 12 days until it suddenly developed the exact same issue as the original. I should add this replacement appears to be a brand new factory package, not a refurbished unit. 

It still seems too much of coincidence that both CM1150V had been originally working perfectly then from one day to the next (and beyond) they fell off a cliff, again making me suspect some firmware change - a Comcast Tech can probably see this one way or the other I would expect? 

Can a COMCAST TECH maybe take a look at my logs and interpret what is going on? 

I'm sorry if seems impatient but my system is virtually unusable and my wife is back at work (from home) this week and really needs fast stable internet. It won't give me an internet connection for more thana few minutes without having to either power-cycle or other tricks to force connection 

As mentioned I'm reluctant to reconnect the XB7 as I lose any opportunity to then diagnose the issue 

Please help!!!!!

This is the log from just the last couple of hours 

This is Modem Status immediately after power cycle when it is connecting normally 

(but even after it loses connection, it does not change and all front panel LEDs remain constant green) 

Frequency start ValueThis field below allows you to modify the frequency the cable modem start with its scan during initialization and registration. Enter the new start frequency and restart the cable modem for it to take effect.

Startup Procedure

Downstream Bonded Channels

Upstream Bonded Channels

Downstream OFDM Channels

Upstream OFDMA Channels

Current System Time:Mon Dec 28 11:41:40 2020System Up Time:00:02:24

The upstream power is too high / almost out of spec, and it may be intermittently fluctuating even higher to out of spec levels. That can cause random disconnects, spontaneous re-booting of the modem, speed, packet loss, latency problems, and the un-bonding of channels.

In a self troubleshooting effort to try to obtain better connectivity / more wiggle room, check to see if there are there any excess/unneeded coax cable splitters in the line leading to the modem that can be eliminated/re-configured. Any splitters that remain should be high quality and cable rated for 5-1002 MHz, bi-directional, and no gold colored garbage types like GE, RadioShack, RCA, Philips, Leviton, Magnavox, and Rocketfish from big box stores like Home Depot, Lowes, Target, Wal-Mart etc. Splitters should be swapped with known to be good / new ones to test

If there aren't any unneeded splitters that can be eliminated and if your coax wiring setup can't be reconfigured so that there is a single two way splitter connected directly off of the drop from the street/pole with one port feeding the modem and the other port feeding the rest of the house/equipment with additional splits as needed, and you've checked all the wiring and fittings for integrity and tightness and refresh them by taking them apart then check for and clean off any corrosion / oxidation on the center wire and put them back together again, then perhaps it's best to book a tech visit to investigate and correct.

This is with NO Internet Connection - modem Status looks essentially the same 

Also again, all front panel LEDs are solid green 

Startup Procedure

Downstream Bonded Channels

Upstream Bonded Channels

Downstream OFDM Channels

Upstream OFDMA Channels

Current System Time:Mon Dec 28 13:32:55 2020System Up Time:01:53:39

---

@1113361 wrote:

This is with NO Internet Connection - modem Status looks essentially the same 

Also again, all front panel LEDs are solid green 

---

An upstream channel / return path impairment will cause that (communication lapses). It may not show up in the signal stats that can be read by the modem. There are other upstream receive signal stats that can't be read by the modem, but are equally important. The CMTS will have difficulties hearing your modem. It doesn't necessarily have to be losing complete sync with the system for those communication lapses to happen.

Does any of those troubleshooting tips apply ?

---

@1113361 wrote:

A 3-way unbalanced should be no different than a 2-way plus another 2-way for the TV's should it not? 

 

3.5 dB loss is 3.5 dB loss no matter how you slice it.

 

I removed the splitter for testing and installed a coupler - it certainly made a difference to the power levels 

The Upstream Power is now at about 47.5 - is that acceptable or still marginal? 

 

Below 50 dB is "acceptable". 40 to 45 dB is ideal !

---

It may be best to get the techs involved again to investigate / properly balance the line.

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.
Good luck !

@EG wrote:

The upstream power is too high / almost out of spec, and it may be intermittently fluctuating even higher to out of spec levels. 

 Any splitters that remain should be high quality and cable rated for 5-1002 MHz, bi-directional, 
If there aren't any unneeded splitters that can be eliminated and if your coax wiring setup can't be reconfigured so that there is a single two way splitter connected directly off of the drop from the street/pole with one port feeding the modem and the other port feeding the rest of the house/equipment with additional splits as needed

Thank you for your inputs - much appreciated. 

It has a Comm-Scope SV-3G  3-way Unbalanced splitter with the -3.5 db connected to the cable modem and the two -7db splits to the TV's 

Interestingly when it configured previously it was perfect for almost a year with no problems whatsoever and it actually had the cable modem connected to one of the -7 db splits !!!  - when the Xfinity tech was out it was still connected via  the -7db splite & he deemed the signal levels good at the modem input cable (he was unaware, did not inspect the splitter - I actually reconfigured it later when I thought to look at it, even though the XB7 was installed like this too and working properly on the -7db split; however at that time I swapped it over to the -3.5db split  regardless) 

A 3-way unbalanced should be no different than a 2-way plus another 2-way for the TV's should it not? 

I removed the splitter for testing and installed a coupler - it certainly made a difference to the power levels 

The Upstream Power is now at about 47.5 - is that acceptable or still marginal? 

However after a couple of minutes, even though my status is as reported below it has the same issue - internet has no connection - I had to play tricks again to get a connection to post this update 

(again it has a bizarre behaviour - all panel lights normal, the status is as shown below but the interent connection goes out - if I keep requesting a speed test, it will eventually make a connection, slowly at first but rising to full spec by the end of the download)  

Startup Procedure

Downstream Bonded Channels

Upstream Bonded Channels

Downstream OFDM Channels

Upstream OFDMA Channels

Current System Time:Mon Dec 28 14:04:11 2020System Up Time:00:09:58

Had already scheduled tech for today but prior to his arrival:

This morning

Completely unusable - nothing I could do could get the modem to synch (and therefor unable to get power levels) 

I bypassed the Splitter and used a coupler so signal ONLY connected to the Modem 

That got me a connection, with Power Levels at ~48 

However it would still drop out quite frequently throughout the morning, would reconnect after series of SpeedTest requests 

Tech visit today:

Tech checked the quality of signal at the 'street' box, at the House Connection and then at the Splitter; he replaced a few connectors on the cables.

He deemed signals at the house were good ~34 if I recall

Then at the input to the Splitter - here he found an issue - one channel was completely blank (he showed me on his tablet)

He went back to the box on side of house and replaced the Ground Block

Then re-tested at the Splitter (other end of the cable leaving the Ground Block) and signal was restored

Now - I'm not convinced necessarily that ground block connector was a real issue as the problem NOW is pretty much as it was before - however the data at that point indicated it may well have been

After replacing we went inside to the Modem

Initially he had connected the Modem to the -7dB terminal (he said that it was std practice to use the -3.5dB for the DVR if that was furthest away)

At this point the Modem would not synch up - it just kept retrying but would never synch

I asked him to swap to the -3.5 - now it synch'd but with the Upstream power levels at 51

Then we tried the XB7 and it to synched with Upstream only slightly lower at 49

Then we bypassed the Splitter and got about 47/48 on the Netgear Upstream (but of course we NEED the splitter for normal operation)

His Xfinity meter/modem showed 41 at this location

He acknowledged the numbers were high (on the modems) but said that the XB7 was still synching so not much he could do. 

I requested he leave ticket open and escalate to Networking 

Summary

Netgear ..... -7dB - modem would not synch (unable to read power level without synch)

Netgear ..... -3.5dB - synched up, Upstream power at ~51 (the 4 channels were low of 50.3, high 51)

Netgear when installed about 3 weeks ago ...... -3.5dB - ~47dBmV 

Xfinity Xb7* ....... -3.5dB - synched - Upstream Power at ~ 49

Xfinity Modem Tool .... -3.5dB - Upstream Power at ~ 41

* The XB7 was not activated - but hooked up, it synch'd (white LED on) and I read the Upstream Power levels connected via ethernet

OK - so the XB7 is marginally better (~2dB) than the Netgear, but still on the high side?

It was connecting to Internet before he left, but shortly after it started dropping again.

It just lost synch again and required a power cycle of the modem, after which it resynched with these metrics 

Startup Procedure

Downstream Bonded Channels

Upstream Bonded Channels

Downstream OFDM Channels

Upstream OFDMA Channels

Current System Time:Wed Dec 30 18:53:28 2020System Up Time:00:02:48

Still too high !!!

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.
Good luck With this !

I'm going to escalate your issue to the Comcast corporate employees that are available to these boards. 

You should get a reply here in your topic. Good luck !

---

@EG wrote:

Still too high !!!

---

Agreed! 

This morning I could not get the Modem to Lock with splitter in line. 

I bypassed the splitter - it locked - and got signal levels of 47.5 - and internet connection.  

Those numbers are consistent with when this modem was first installed a few weeks back WITH a 3.5db split

The Tech gave me his supervisors contact info and I sent him incredibly lengthy e-mail loaded with data but autoreply says he won't return until next week  

How do I get an Xfinity/Comcast agent to look at this thread? 

I've seen posts by Comcast techs saying to PM but when I click on a name I don't see a message option ........ 

@ComcastRob wrote:

 .... Please click on my handle (ComcastRob) and send a private message ...  

---

I do not appear to have Private Messaging enabled and cannot see where to do that?

In forum search I see suggestions to enable in Settings/Preferences but I do not even have a Private Messaging option and see other replies in forums where a Comcast Support person must first enable it 

Currently when I click on your name @ComcastRob it just takes me to your 'about' page and I don't see any link for messaging 

 

PLEASE help! 

This is INCREDIBLY frustrating - the only way I can connect at all is to completely disconnect the Splitter (so no TV available) and even then, it may 'lock' but Internet keeps dropping out (even though modem still shows locked); with splitter connected there is zero chance of it locking and unable to get beyond that. 

I even tried connecting directly at the Ground Block yesterday morning and could not get it to lock there at all let alone get Internet; so ALL the house wiring was eliminated completely with modem alone connected directly to the Ground Block. 

Yesterday I finally got connection at about 1pm (coincidentally this was about the same as the day before) and it worked reasonably well/consistently for the afternoon/early evening but then starting disconnecting again at about 7pm (also about the same time window as day before!) to where it was again not usable at all. 

Overnight (every morning) I come down to the Modem in endless boot loop trying to connect.

As I write this I have gone through MULTIPLE Power Cycles until I eventually got a lock - and then get Internet Briefly but in the course of writing this it's gone again. (again, nothing else connected, no splitters, just the modem) I just looked over at the modem and the Upstream Light is flashing and in the Cable Connection metrics it shows Upstream Channel 2 is not locked and zero power - which I now recall when the tech was here we saw one instance of an Upstream Channel completely at zero on his test modem/Tablet.

 

Upstream Bonded Channels (Partial Service)

Channel Lock Status US Channel Type Channel ID Symbol Rate Frequency Power 1 Locked ATDMA 1 5120 Ksym/sec 17300000 Hz 46.3 dBmV 2 Not Locked Unknown 2 0 Ksym/sec 17300000 Hz 0.0 dBmV 3 Locked ATDMA 3 5120 Ksym/sec 30300000 Hz 47 dBmV 4 Locked ATDMA 4 5120 Ksym/sec 36700000 Hz 46.8 dBmV 5 Not Locked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV 6 Not Locked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV 7 Not Locked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV 8 Not Locked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV

 

Subsequently it re-locked again (re-tried on its own) - but then I saw Upstream flashing AGAIN 

And this time TWO channels not locked 

 

Upstream Bonded Channels (Partial Service)

Channel Lock Status US Channel Type Channel ID Symbol Rate Frequency Power 1 Not Locked Unknown 1 0 Ksym/sec 30300000 Hz 0.0 dBmV 2 Not Locked Unknown 2 0 Ksym/sec 17300000 Hz 0.0 dBmV 3 Locked ATDMA 3 5120 Ksym/sec 30300000 Hz 42.5 dBmV 4 Locked ATDMA 4 5120 Ksym/sec 36700000 Hz 46.8 dBmV 5 Not Locked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV 6 Not Locked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV 7 Not Locked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV 8 Not Locked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV

 

I have to use my mobile hot spot just to post this message! 

(I just noticed I have no screen name - don't know why that is and/or whether related to the Private Messging thing) 

Edit - I now have screen name and my Private Messaging is enabled 

Bizarre situation now ............ 

Yesterday - could not get modem to lock virtually all day except for the briefest time with collectively only a few minutes of available internet over whole course of day - absolutely nothing, incredibly frustrating day of persistently trying it - power cycles, left off for period and returning, all with same result i.e. no result! 

Today - started it up this morning and it connected first time and has been perfect all day! 

Go figure!!!! 

I'm not counting chickens yet - the parameters are essentially unchanged, nothing stands out as being particularly different and there appears to be the finest marginality of it working - or not.

Nor have have I chanced disconnecting it to reconnect with the splitter - my suspicion is that will 'break' it again, but reluctant to prove that for now - will leave it alive for as long as it will stay on, and see how things look tomorrow 

But here's something else that is equally strange:

When I look on the Xfinity apps on my phone this is what they give - that my modem is offline (yet at time of image it is actually - surprisingly - working great!) 

Also related to that, if I try to request a modem reset from the App, it says it cannot access my modem.