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Forum Discussion
CM1150V bandwidth intermittentently drops to below 1 mbps with Xfinity
When I first got this modem, everything was awesome, fast, stable, low latency, and no Intel Puma chipset issues. But now I'm intermittently rebooting the modem up to 12 times a day when speed of my 500/20 Comcast service drops to below 0.3 mbps up and down. When we experience this issue, the modem never goes offline and the LEDs are all solid as if service is having no issues, but with less than 1mbps of service, it's impossible to do any work from home. The only workaround is power cycle, which may last from minutes to hours, before the next powercycle is required.
I called Xfinity support and they've put a 7 day watch on my account but insist that there are problems with all 3rd party modems and only using their rented modem will resolve the problem. It seems that Comcast has taken the totalitarian approach of forcing more rentals by denying support for BYOD modems.
I'm on firmware version 4.02.02 which doesn't seem to be current, but again Comcast says they can't update the firmware of personal equipment.
If needed, I can publish the log, removing the MAC address of my cable modem, but any ideas on how this can be resolved. By the high number of issues in both Netgear and Xfinity forums, my issue doens't seem to be isolated.
6 Replies
What wireless router brand and model do you have connected to the CM modem?
How are you speed testing? WIred or wireless?
Please post a copy and paste of the modems connection status page.
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.
https://community.netgear.com/t5/Cable-Modems-Routers/General-info-and-Troubleshooting-for-Cable-Modems/m-p/1530376#M12853- I'm using Google WiFi at the moment. Speed testing wired with a desktop.
Here's a the status after a power cycle this morning that I needed to do to restore bandwidth.
Startup Procedure
Procedure Status Comment
Acquire Downstream Channel 507000000 Hz Locked
Connectivity State OK Operational
Boot State OK Operational
Security Enabled BPI+
IP Provisioning Mode Honor MDD honorMdd(4)
Downstream Bonded Channels
Channel Lock Status Modulation Channel ID Frequency Power SNR Correctables Uncorrectables
1 Locked QAM256 20 507000000 Hz 2.7 dBmV 39.8 dB 0 0
2 Locked QAM256 4 405000000 Hz 4.5 dBmV 41.2 dB 0 0
3 Locked QAM256 5 411000000 Hz 4.1 dBmV 41.1 dB 0 0
4 Locked QAM256 6 417000000 Hz 4.7 dBmV 41.2 dB 0 0
5 Locked QAM256 7 423000000 Hz 4.3 dBmV 41 dB 0 0
6 Locked QAM256 8 429000000 Hz 4.6 dBmV 41.2 dB 0 0
7 Locked QAM256 9 435000000 Hz 5.1 dBmV 41.1 dB 0 0
8 Locked QAM256 10 441000000 Hz 4.3 dBmV 40.8 dB 0 0
9 Locked QAM256 11 447000000 Hz 4.5 dBmV 40.8 dB 0 0
10 Locked QAM256 12 453000000 Hz 4.6 dBmV 40.7 dB 0 0
11 Locked QAM256 13 459000000 Hz 3.6 dBmV 40.3 dB 0 0
12 Locked QAM256 14 465000000 Hz 4.1 dBmV 40.4 dB 0 0
13 Locked QAM256 15 471000000 Hz 3.8 dBmV 40.3 dB 0 0
14 Locked QAM256 16 477000000 Hz 3.1 dBmV 40.1 dB 0 0
15 Locked QAM256 17 483000000 Hz 3.9 dBmV 40.3 dB 0 0
16 Locked QAM256 18 489000000 Hz 3.1 dBmV 40 dB 0 0
17 Locked QAM256 19 495000000 Hz 2.9 dBmV 40 dB 0 0
18 Locked QAM256 21 513000000 Hz 3 dBmV 39.9 dB 0 0
19 Locked QAM256 22 519000000 Hz 3.3 dBmV 39.9 dB 0 0
20 Locked QAM256 23 525000000 Hz 2.5 dBmV 39.7 dB 0 0
21 Locked QAM256 24 531000000 Hz 3.3 dBmV 39.9 dB 0 0
22 Locked QAM256 25 537000000 Hz 3 dBmV 39.8 dB 0 0
23 Locked QAM256 26 543000000 Hz 2.6 dBmV 39.7 dB 0 0
24 Locked QAM256 27 549000000 Hz 3.5 dBmV 39.9 dB 0 0
25 Locked QAM256 28 555000000 Hz 2.6 dBmV 39.6 dB 0 0
26 Locked QAM256 29 561000000 Hz 2.5 dBmV 39.5 dB 1 0
27 Locked QAM256 30 567000000 Hz 2.8 dBmV 39.5 dB 3 0
28 Locked QAM256 31 573000000 Hz 1.8 dBmV 39.1 dB 2 0
29 Locked QAM256 32 579000000 Hz 2.3 dBmV 39.3 dB 3 0
30 Locked QAM256 33 585000000 Hz 2.5 dBmV 39.4 dB 1 0
31 Locked QAM256 34 591000000 Hz 1.7 dBmV 39.2 dB 2 0
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 5 5120 Ksym/sec 17300000 Hz 45 dBmV
2 Locked ATDMA 6 5120 Ksym/sec 23700000 Hz 46.5 dBmV
3 Locked ATDMA 7 5120 Ksym/sec 30300000 Hz 47.5 dBmV
4 Locked ATDMA 8 5120 Ksym/sec 36700000 Hz 47.5 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 48 850000000 Hz 4.1 dBmV 40.0 dB 1108 ~ 2987 7026860 6786467 0
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
Current System Time:Sat Mar 06 04:36:59 2021
System Up Time:00:29:49- Here's the status of when bandwidth was near zero and speed test failed to load
Startup Procedure
Procedure Status Comment
Acquire Downstream Channel 507000000 Hz Locked
Connectivity State OK Operational
Boot State OK Operational
Security Enabled BPI+
IP Provisioning Mode Honor MDD honorMdd(4)
Downstream Bonded Channels
Channel Lock Status Modulation Channel ID Frequency Power SNR Correctables Uncorrectables
1 Locked QAM256 20 507000000 Hz 3 dBmV 39.9 dB 0 0
2 Locked QAM256 4 405000000 Hz 5.1 dBmV 41.2 dB 0 0
3 Locked QAM256 5 411000000 Hz 4.6 dBmV 41.1 dB 0 0
4 Locked QAM256 6 417000000 Hz 5.1 dBmV 41.3 dB 0 0
5 Locked QAM256 7 423000000 Hz 4.8 dBmV 41.1 dB 0 0
6 Locked QAM256 8 429000000 Hz 4.9 dBmV 41.2 dB 0 0
7 Locked QAM256 9 435000000 Hz 5.4 dBmV 41.2 dB 0 0
8 Locked QAM256 10 441000000 Hz 4.7 dBmV 40.9 dB 0 0
9 Locked QAM256 11 447000000 Hz 4.9 dBmV 40.9 dB 0 0
10 Locked QAM256 12 453000000 Hz 5 dBmV 40.7 dB 0 0
11 Locked QAM256 13 459000000 Hz 4 dBmV 40.4 dB 0 0
12 Locked QAM256 14 465000000 Hz 4.5 dBmV 40.5 dB 0 0
13 Locked QAM256 15 471000000 Hz 4.2 dBmV 40.3 dB 0 0
14 Locked QAM256 16 477000000 Hz 3.5 dBmV 40.2 dB 0 0
15 Locked QAM256 17 483000000 Hz 4.3 dBmV 40.4 dB 0 0
16 Locked QAM256 18 489000000 Hz 3.5 dBmV 40.1 dB 0 0
17 Locked QAM256 19 495000000 Hz 3.2 dBmV 40 dB 0 0
18 Locked QAM256 21 513000000 Hz 3.3 dBmV 40 dB 0 0
19 Locked QAM256 22 519000000 Hz 3.7 dBmV 40 dB 0 0
20 Locked QAM256 23 525000000 Hz 2.8 dBmV 39.8 dB 0 0
21 Locked QAM256 24 531000000 Hz 3.5 dBmV 40 dB 1 0
22 Locked QAM256 25 537000000 Hz 3.4 dBmV 40 dB 1 0
23 Locked QAM256 26 543000000 Hz 2.9 dBmV 39.8 dB 0 0
24 Locked QAM256 27 549000000 Hz 3.8 dBmV 39.9 dB 1 0
25 Locked QAM256 28 555000000 Hz 3 dBmV 39.2 dB 0 0
26 Locked QAM256 29 561000000 Hz 2.9 dBmV 39 dB 4 0
27 Locked QAM256 30 567000000 Hz 3.1 dBmV 39.6 dB 6 0
28 Locked QAM256 31 573000000 Hz 2.2 dBmV 39 dB 9 0
29 Locked QAM256 32 579000000 Hz 2.6 dBmV 39.3 dB 12 0
30 Locked QAM256 33 585000000 Hz 2.9 dBmV 39.6 dB 8 0
31 Locked QAM256 34 591000000 Hz 2.1 dBmV 38.9 dB 10 0
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 5 5120 Ksym/sec 17300000 Hz 55.3 dBmV
2 Locked ATDMA 6 5120 Ksym/sec 23700000 Hz 54.8 dBmV
3 Locked ATDMA 7 5120 Ksym/sec 30300000 Hz 54 dBmV
4 Locked ATDMA 8 5120 Ksym/sec 36700000 Hz 53.5 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 48 850000000 Hz 4.2 dBmV 39.9 dB 1108 ~ 2987 60633272 56983669 0
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
Current System Time:Sat Mar 06 08:01:50 2021
System Up Time:03:54:40
I'm also cross posting on an xfinity forum
What wireless router brand and model do you have connected to the CM modem?
How are you speed testing? WIred or wireless?
Over in one of the Xfinity forum posts, someone pointed out that there might be an upload signal threshold of 48 dBmV on this modem that is perhaps looser with Xfinity branded modems. Does such a limitation exist?
https://forums.xfinity.com/t5/Your-Home-Network/Netgear-CM1150V-Internet-Connectivity/m-p/3376884
This is what my modem looks like when the connection is normal:
Upstream Bonded Channels Channel Lock Status US Channel Type Channel ID Symbol Rate Frequency Power 1 Locked ATDMA 5 5120 Ksym/sec 17300000 Hz 45 dBmV 2 Locked ATDMA 6 5120 Ksym/sec 23700000 Hz 46.5 dBmV 3 Locked ATDMA 7 5120 Ksym/sec 30300000 Hz 47.5 dBmV 4 Locked ATDMA 8 5120 Ksym/sec 36700000 Hz 47.5 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 Then when bandwith is nil
Upstream Bonded Channels Channel Lock Status US Channel Type Channel ID Symbol Rate Frequency Power 1 Locked ATDMA 5 5120 Ksym/sec 17300000 Hz 55.3 dBmV 2 Locked ATDMA 6 5120 Ksym/sec 23700000 Hz 54.8 dBmV 3 Locked ATDMA 7 5120 Ksym/sec 30300000 Hz 54 dBmV 4 Locked ATDMA 8 5120 Ksym/sec 36700000 Hz 53.5 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 Here is my CM1200 on the UP:
Upstream Bonded Channels Channel Lock Status US Channel Type Channel ID Symbol Rate Frequency Power 1 Locked ATDMA 1 5120 Ksym/sec 36000000 Hz 39.3 dBmV 2 Locked ATDMA 2 5120 Ksym/sec 29000000 Hz 38 dBmV 3 Locked ATDMA 5 5120 Ksym/sec 22000000 Hz 38.5 dBmV 4 Locked ATDMA 6 2560 Ksym/sec 16000000 Hz 37.5 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 Though not same model# there similar in nature. The 1200 has 4 WAN ports. Mine also has a attenuator on the back of the coax connector. Tech said there line was running a bit hot so he added it a while back when I upgraded to the 1G service.
I would have the ISP check the line and ask if the power levels are good for this modem.
