Skip to main content

    Support

    Offers

M
michaelxb
1st Topic
1st Reply

Visitor

 • 

12 Messages

Thursday, March 9th, 2023 4:17 PM

Closed

NetGear CM1200 Errors & Connection Issues

My internet has about 90% reliability, but once a week or so the speeds drop drastically and/or (more rarely) the connection goes out completely for a few minutes. A modem reboot usually clears things and gets me back up.

I have one line in with a splitter running that line to a single cable box and modem. I've tried troubleshooting and I'm pretty sure I've eliminated the router and modem as the culprit. I've run a factory reset on the modem, hardwired into it via ethernet and can still get the slow speeds when the issue is happening. The modem logs show frequent errors in the log with event codes 16 and 24. The cable connection ranges mostly look good, but upstream power looks high. 

An Xfinity tech just came out and immediately diagnosed it as my splitter – not that the splitter itself was bad, but that it didn't have some other sort of adapter on it to "keep my information from going to the neighbor" whatever that means. It looks like a 3-4" metal adapter between the line in and the splitter input. He installed this adapter, added a new coax connector, then ran diagnostics on his box and said everything looked good and left. 

I'm back up and running, but still seeing ongoing errors in the modem logs, and the upstream power still seems high. I'm concerned that the root cause wasn't fixed and I'll continue having issues. Anybody have other ideas on what to try, or do I just wait and see if the connection drops again? I tried asking the tech to inspect the line outside to make sure things looked good, but since his box was giving him OKs across the board, he wouldn't do anything else. 

Here are my modem stats, and some logs below that: 

Downstream Bonded Channels
Channel Lock Status Modulation Channel ID Frequency Power SNR Correctables Uncorrectables
1 Locked QAM256 17 519000000 Hz 3.7 dBmV 44.2 dB 435 926
2 Locked QAM256 14 495000000 Hz 3.5 dBmV 44.2 dB 263 847
3 Locked QAM256 15 507000000 Hz 4 dBmV 44.3 dB 243 850
4 Locked QAM256 16 513000000 Hz 3.8 dBmV 44.2 dB 399 885
5 Locked QAM256 18 525000000 Hz 3.7 dBmV 44.2 dB 510 1022
6 Locked QAM256 19 531000000 Hz 3.9 dBmV 44.2 dB 777 1116
7 Locked QAM256 20 537000000 Hz 3.7 dBmV 44 dB 1242 1323
8 Locked QAM256 21 543000000 Hz 3.6 dBmV 44 dB 1440 1725
9 Locked QAM256 22 549000000 Hz 3.6 dBmV 44 dB 1080 2276
10 Locked QAM256 23 555000000 Hz 3.5 dBmV 43.9 dB 1241 2599
11 Locked QAM256 24 561000000 Hz 3.3 dBmV 43.8 dB 1467 2882
12 Locked QAM256 26 567000000 Hz 3.2 dBmV 43.8 dB 1598 3173
13 Locked QAM256 27 573000000 Hz 3.3 dBmV 43.8 dB 175 485
14 Locked QAM256 28 579000000 Hz 3.2 dBmV 43.8 dB 0 0
15 Locked QAM256 29 585000000 Hz 3.2 dBmV 43.7 dB 2684 4116
16 Locked QAM256 30 591000000 Hz 3.1 dBmV 43.5 dB 0 0
17 Locked QAM256 31 597000000 Hz 3.3 dBmV 43.7 dB 0 0
18 Locked QAM256 32 603000000 Hz 3.3 dBmV 43.7 dB 0 0
19 Locked QAM256 33 609000000 Hz 3.3 dBmV 43.7 dB 0 0
20 Locked QAM256 34 615000000 Hz 3.1 dBmV 43.5 dB 14807 5766
21 Locked QAM256 35 621000000 Hz 3 dBmV 43.5 dB 0 0
22 Locked QAM256 36 627000000 Hz 3.1 dBmV 43.4 dB 98 588
23 Locked QAM256 37 639000000 Hz 3.2 dBmV 43.5 dB 31959 16198
24 Locked QAM256 38 645000000 Hz 3.4 dBmV 43.6 dB 36970 17954
25 Locked QAM256 39 651000000 Hz 3.5 dBmV 43.6 dB 41797 18446
26 Locked QAM256 40 657000000 Hz 3.4 dBmV 43.6 dB 47419 19692
27 Locked QAM256 41 663000000 Hz 3.1 dBmV 43.4 dB 59943 22184
28 Locked QAM256 42 669000000 Hz 3.2 dBmV 43.4 dB 69096 22964
29 Locked QAM256 43 675000000 Hz 3.5 dBmV 42.8 dB 83211 24038
30 Locked QAM256 44 681000000 Hz 3.4 dBmV 43.5 dB 85283 24764
31 Locked QAM256 45 687000000 Hz 3.2 dBmV 43.3 dB 307 980
32 Not Locked Unknown 0 0 Hz 0.0 dBmV 0.0 dB 0 0
 
Upstream Bonded Channels
Channel Lock Status US Channel Type Channel ID Symbol Rate Frequency Power
1 Locked ATDMA 77 5120 Ksym/sec 16400000 Hz 49.8 dBmV
2 Locked ATDMA 78 5120 Ksym/sec 22800000 Hz 49.5 dBmV
3 Locked ATDMA 79 5120 Ksym/sec 29200000 Hz 48.8 dBmV
4 Locked ATDMA 80 5120 Ksym/sec 35600000 Hz 48.3 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
 
Downstream OFDM Channels
Channel Lock
Status		 Modulation /
Profile ID		 Channel
ID		 Frequency Power SNR /
MER		 Active Subcarrier
Number Range		 Unerrored
Codewords		 Correctable
Codewords		 Uncorrectable
Codewords
1 Locked 0 ,1 ,2 ,3 25 693000000 Hz 3.3 dBmV 42.7 dB 1108 ~ 2987 12772318 8027537 542185
2 Not Locked 0 0 0 Hz 0 dBmV 0.0 dB 0 ~ 4095 0 0 0
 
Upstream OFDMA Channels
Channel Lock Status Modulation / Profile ID Channel ID Frequency Power
1 Not Locked 0 0 0 Hz 0 dBmV
2 Not Locked 0 0 0 Hz 0 dBmV
 

ERROR LOGS with MAC Redacted

Time Priority Description
Thu Mar 09 11:03:25 2023 Notice (6) CM-STATUS message sent. Event Type Code: 16; Chan ID: 25; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: 1 2 3.;CM-MAC=[removed];CMTS-MAC=[removed];CM-QOS=1.1;CM-VER=3.1;
Thu Mar 09 10:58:18 2023 Notice (6) CM-STATUS message sent. Event Type Code: 24; Chan ID: 25; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: 1 2 3.;CM-MAC=[removed];CMTS-MAC=[removed];CM-QOS=1.1;CM-VER=3.1;
Thu Mar 09 10:57:50 2023 Notice (6) CM-STATUS message sent. Event Type Code: 16; Chan ID: 25; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: 3.;CM-MAC=[removed];CMTS-MAC=[removed];CM-QOS=1.1;CM-VER=3.1;
Thu Mar 09 10:56:17 2023 Notice (6) CM-STATUS message sent. Event Type Code: 24; Chan ID: 25; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: 1 2 3.;CM-MAC=[removed];CMTS-MAC=[removed];CM-QOS=1.1;CM-VER=3.1;
Thu Mar 09 10:56:00 2023 Notice (6) CM-STATUS message sent. Event Type Code: 24; Chan ID: 25; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: 1 3.;CM-MAC=[removed];CMTS-MAC=[removed];CM-QOS=1.1;CM-VER=3.1;
Thu Mar 09 10:55:08 2023 Notice (6) CM-STATUS message sent. Event Type Code: 16; Chan ID: 25; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: 1 2 3.;CM-MAC=[removed];CMTS-MAC=[removed];CM-QOS=1.1;CM-VER=3.1;
Thu Mar 09 10:55:05 2023 Notice (6) CM-STATUS message sent. Event Type Code: 16; Chan ID: 25; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: 2 3.;CM-MAC=[removed];CMTS-MAC=[removed];CM-QOS=1.1;CM-VER=3.1;

Question

 • 

Updated 

2 years ago

1.6K

4

0

Accepted Solution

EG

Expert

 • 

110K Messages

2 years ago

Yes it's high / marginal. There isn't any wiggle room. It will likely go even higher with the increased heat of the coming Summer season. It's a problem just waiting to happen. 

More work needs to be done. You should get the techs involved again until it gets fixed properly. 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 !

(edited)

1

michaelxb

Visitor

 • 

12 Messages

@EG​ Thanks for looking! The internet just dropped again within 20 minutes of the tech leaving. Now getting all sorts of new errors in the logs. I will contact Xfinity again to see if they can escalate. 

Time Priority Description
Thu Mar 09 11:28:01 2023 Critical (3) 16 consecutive T3 timeouts while trying to range on upstream channel 3;CM-MAC=​​[removed];CMTS-MAC=[removed];CM-QOS=1.1;CM-VER=3.1;
Thu Mar 09 11:28:01 2023 Critical (3) Unicast Maintenance Ranging attempted - No response - Retries exhausted;CM-MAC=[removed];CMTS-MAC=[removed];CM-QOS=1.1;CM-VER=3.1;
Thu Mar 09 11:28:01 2023 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=[removed];CMTS-MAC=[removed];CM-QOS=1.1;CM-VER=3.1;
Thu Mar 09 11:27:37 2023 Notice (6) CM-STATUS message sent. Event Type Code: 8; Chan ID: 77 78 79; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: N/A.;CM-MAC=[removed];CMTS-MAC=[removed];CM-QOS=1.1;CM-VER=3.1;
Thu Mar 09 11:27:26 2023 Critical (3) 16 consecutive T3 timeouts while trying to range on upstream channel 0;CM-MAC=[removed];CMTS-MAC=[removed];CM-QOS=1.1;CM-VER=3.1;
Thu Mar 09 11:27:26 2023 Critical (3) Unicast Maintenance Ranging attempted - No response - Retries exhausted;CM-MAC=[removed];CMTS-MAC=[removed];CM-QOS=1.1;CM-VER=3.1;
Thu Mar 09 11:27:26 2023 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=[removed];CMTS-MAC=[removed];CM-QOS=1.1;CM-VER=3.1;
Thu Mar 09 11:27:07 2023 Notice (6) CM-STATUS message sent. Event Type Code: 8; Chan ID: 78 79; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: N/A.;CM-MAC=[removed];CMTS-MAC=[removed];CM-QOS=1.1;CM-VER=3.1;
Thu Mar 09 11:27:06 2023 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=[removed];CMTS-MAC=[removed];CM-QOS=1.1;CM-VER=3.1;
Thu Mar 09 11:27:02 2023 Critical (3) 16 consecutive T3 timeouts while trying to range on upstream channel 1;CM-MAC=[removed];CMTS-MAC=[removed];CM-QOS=1.1;CM-VER=3.1;
Thu Mar 09 11:27:02 2023 Critical (3) Unicast Maintenance Ranging attempted - No response - Retries exhausted;CM-MAC=[removed];CMTS-MAC=[removed];CM-QOS=1.1;CM-VER=3.1;
Thu Mar 09 11:27:02 2023 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=[removed];CMTS-MAC=[removed];CM-QOS=1.1;CM-VER=3.1;

2 years ago

0

EG

Expert

 • 

110K Messages

2 years ago

Quite welcome ! Good luck ! Please post back with how things go.

10

0

michaelxb

Visitor

 • 

12 Messages

2 years ago

I'm at my wit's end with troubleshooting a recent internet issue. I posted about it at length here, but the Xfinity rep (@XfinityRobertA) in the replies never responded to me, and I also tried sending a private message, but never got a response. I have a brand new line into my house, brand new modem, and the same issues I had at the beginning are still happening. If Comcast can't fix this, I will unfortunately have to consider switching providers. I work from home and can't afford daily internet outages, not to mention the headache of constantly troubleshooting. 

Since the new line was run, I was told that if the issues persisted, the cause probably lies outside my home somewhere in the neighborhood lines. How do I escalate and get a crew to further inspect the lines?

Note: This comment was created from a merged conversation originally titled How do I Request Line Maintenance?

0

0

user_92678d

1 Message

2 years ago

@michaelxb are you around? Facing the same issues without any solutions in sight.

2

0

michaelxb

Visitor

 • 

12 Messages

@user_92678d​ Yep, I'm still around.

Fortunately, my outages have seemed to become less frequent and may have been resolved entirely (fingers crossed). Haven't had one in maybe 1-2 months, and they were happening weekly. I'm not sure if Comcast changed anything with the signal and/or lines in the neighborhood, so it's hard to pinpoint. I did install an Antronix Return Amplifier which immediately brought my upstream power within recommended range (it's consistently at around 38-40 dBmV, down from 49-50) so that may have also helped. But before that, all my equipment and lines were brand new, so it was either a Comcast fix and/or the return amp. My modem no longer shows dozens of daily errors in the logs. If your upstream power is out of range after a tech visit, it might be worth trying the amp, especially since you can return it for free.

2 years ago

0

XfinityWilliam

Official Employee

 • 

1.2K Messages

Hello @user_92678d. We would be more than happy to assist in any internet issues you may be experiencing. Can you tell me a little more about your issues?

I am an Official Xfinity Employee.
Official Employees are from multiple teams within Xfinity: CARE, Product, Leadership.
We ask that you post publicly so people with similar questions may benefit from the conversation.
Was your question answered? Please, mark a reply as the Accepted Answer.tick

2 years ago

0

forum icon

New to the Community?

Start Here