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user_ult770
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Wednesday, July 23rd, 2025

CM1000v2 Upload Slow for Service Plans

Equipment: Netgear CM1000v2

I was on the 300 mb/s service plan previously and  I was getting on average 450 mb/s dl and 45 mb/s upload. I upgraded to the 1 gig service plan with 1 gb/s up and 100 mb/s down. Since the upgrade I average 650 mb/s down and 5 mb/s up.  I downgraded the service plan back to the previous one; the problem with the upload is still there locked to 5 mb/s here below are the settings

Frequency start Value
This 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.
Starting Frequency
<tabindex=-1>Startup Procedure</tabindex=-1>
Procedure Status Comment
Acquire Downstream Channel 567000000 Hz Locked
Connectivity State OK Operational
Boot State OK Operational
Security Enable BPI+
IP Provisioning Mode Honor MDD IPv6 only
<tabindex=-1>Downstream Bonded Channels</tabindex=-1>
Channel Lock Status Modulation Channel ID Frequency Power SNR / MER Unerrored Codewords Correctable Codewords Uncorrectable Codewords
1 Locked QAM256 28 567000000 Hz 0.2 dBmV 44.9 dB 41799162 0 0
2 Locked QAM256 1 405000000 Hz -1.4 dBmV 43.2 dB 40812140 0 0
3 Locked QAM256 2 411000000 Hz -0.7 dBmV 43.5 dB 40816913 0 0
4 Locked QAM256 3 417000000 Hz 0.1 dBmV 44.4 dB 40820653 0 0
5 Locked QAM256 4 423000000 Hz -0.1 dBmV 44.3 dB 40825093 0 0
6 Locked QAM256 5 429000000 Hz -1.0 dBmV 43.7 dB 40828322 0 0
7 Locked QAM256 6 435000000 Hz -1.4 dBmV 43.4 dB 40832305 0 0
8 Locked QAM256 7 441000000 Hz -1.1 dBmV 43.8 dB 40836340 0 0
9 Locked QAM256 8 447000000 Hz -0.3 dBmV 44.6 dB 40839788 0 0
10 Locked QAM256 9 453000000 Hz -0.5 dBmV 44.3 dB 40843796 0 0
11 Locked QAM256 10 459000000 Hz -1.1 dBmV 44.0 dB 40847393 0 0
12 Locked QAM256 11 465000000 Hz -1.1 dBmV 43.8 dB 40851223 0 0
13 Locked QAM256 12 471000000 Hz -0.7 dBmV 44.3 dB 40854857 0 0
14 Locked QAM256 13 477000000 Hz -0.3 dBmV 44.6 dB 40858278 0 0
15 Locked QAM256 14 483000000 Hz -0.6 dBmV 44.5 dB 40862664 0 0
16 Locked QAM256 15 489000000 Hz -0.9 dBmV 44.3 dB 40866529 0 0
17 Locked QAM256 16 495000000 Hz -0.5 dBmV 44.5 dB 40869898 0 0
18 Locked QAM256 17 501000000 Hz 0.1 dBmV 44.7 dB 40873532 0 0
19 Locked QAM256 18 507000000 Hz 0.3 dBmV 44.8 dB 40877197 0 0
20 Locked QAM256 19 513000000 Hz -0.4 dBmV 44.6 dB 40881616 0 0
21 Locked QAM256 20 519000000 Hz -0.8 dBmV 44.5 dB 40885032 0 0
22 Locked QAM256 21 525000000 Hz -0.5 dBmV 44.6 dB 40888391 0 0
23 Locked QAM256 22 531000000 Hz 0.2 dBmV 45.0 dB 40892583 0 0
24 Locked QAM256 23 537000000 Hz -0.2 dBmV 44.8 dB 40895991 0 0
25 Locked QAM256 24 543000000 Hz -1.1 dBmV 44.2 dB 40900026 0 0
26 Locked QAM256 25 549000000 Hz -1.1 dBmV 44.2 dB 40903026 0 0
27 Locked QAM256 26 555000000 Hz -0.4 dBmV 44.7 dB 40908103 0 0
28 Locked QAM256 27 561000000 Hz 0.5 dBmV 45.0 dB 40911931 0 0
29 Locked QAM256 29 573000000 Hz -0.6 dBmV 44.3 dB 40915077 0 0
30 Locked QAM256 30 579000000 Hz -0.6 dBmV 44.6 dB 40913085 0 0
31 Locked QAM256 31 585000000 Hz 0.4 dBmV 44.9 dB 40914492 0 0
32 Locked QAM256 32 591000000 Hz 1.1 dBmV 45.1 dB 40914396 0 0
<tabindex=-1>Upstream Bonded Channels</tabindex=-1>
Channel Lock Status Modulation Channel ID Frequency Power
1 Locked ATDMA 17 16400000 Hz 48.5 dBmV
2 Locked ATDMA 18 22800000 Hz 47.8 dBmV
3 Locked ATDMA 19 29200000 Hz 48.5 dBmV
4 Locked ATDMA 20 35600000 Hz 48.5 dBmV
5 Not Locked Unknown 0 0 Hz 0.0 dBmV
6 Not Locked Unknown 0 0 Hz 0.0 dBmV
7 Not Locked Unknown 0 0 Hz 0.0 dBmV
8 Not Locked Unknown 0 0 Hz 0.0 dBmV
<tabindex=-1>Downstream OFDM Channels</tabindex=-1>
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, 3 193 690000000 Hz -1.7 dBmV 41.0 dB 628 ~ 3467 2957064 1700020 0
2 Locked 0, 1, 2, 3 194 957000000 Hz -5.7 dBmV 37.8 dB 148 ~ 3947 3002613 2246901 0
<tabindex=-1>Upstream OFDMA Channels</tabindex=-1>
Channel Lock Status Modulation / Profile ID Channel ID Frequency Power
1 Not Locked Unknown 0 0 Hz 0 dBmV
2 Not Locked Unknown 0 0 Hz 0 dBmV

The power for upstream seems a bit high to my layman's eyes. 


BELOW is the Event Logs


Time Priority Description
2025-07-23, 13:30:55 Critical (3) UCD invalid or channel unusable;CM-MAC=REDACTED;CMTS-MAC=EXCISED;CM-QOS=1.1;CM-VER=3.1;
2025-07-23, 13:30:55 Notice (6) DS profile assignment change. DS Chan ID: 33; Previous Profile: ; New Profile: 1 2 3.;CM-MAC=REDACTED;CMTS-MAC=EXCISED;CM-QOS=1.1;CM-VER=3.1;
2025-07-23, 13:30:53 Notice (6) DS profile assignment change. DS Chan ID: 32; Previous Profile: ; New Profile: 1 2 3.;CM-MAC=REDACTED;CMTS-MAC=EXCISED;CM-QOS=1.1;CM-VER=3.1;
2025-07-23, 13:30:39 Notice (6) Honoring MDD; IP provisioning mode = IPv6
2025-07-23, 13:30:34 Critical (3) UCD invalid or channel unusable;CM-MAC=REDACTED;CMTS-MAC=EXCISED;CM-QOS=1.1;CM-VER=3.1;
Time Not Established Notice (6) Honoring MDD; IP provisioning mode = IPv6
Time Not Established Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=REDACTED;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;
2025-07-23, 12:52:35 Critical (3) UCD invalid or channel unusable;CM-MAC=REDACTED;CMTS-MAC=EXCISED;CM-QOS=1.1;CM-VER=3.1;
2025-07-23, 12:52:35 Critical (3) SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=REDACTED;CMTS-MAC=EXCISED;CM-QOS=1.1;CM-VER=3.1;
2025-07-23, 12:52:14 Critical (3) UCD invalid or channel unusable;CM-MAC=REDACTED;CMTS-MAC=EXCISED;CM-QOS=1.1;CM-VER=3.1;
Time Not Established Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=REDACTED;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;
2025-07-23, 08:05:21 Critical (3) UCD invalid or channel unusable;CM-MAC=REDACTED;CMTS-MAC=EXCISED;CM-QOS=1.1;CM-VER=3.1;
2025-07-23, 08:05:01 Critical (3) UCD invalid or channel unusable;CM-MAC=REDACTED;CMTS-MAC=EXCISED;CM-QOS=1.1;CM-VER=3.1;
Time Not Established Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=REDACTED;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;
2025-07-23, 07:48:12 Critical (3) UCD invalid or channel unusable;CM-MAC=REDACTED;CMTS-MAC=EXCISED;CM-QOS=1.1;CM-VER=3.1;
2025-07-23, 07:47:51 Critical (3) UCD invalid or channel unusable;CM-MAC=REDACTED;CMTS-MAC=EXCISED;CM-QOS=1.1;CM-VER=3.1;
Time Not Established Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=REDACTED;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;
2025-07-23, 07:42:11 Critical (3) UCD invalid or channel unusable;CM-MAC=REDACTED;CMTS-MAC=EXCISED;CM-QOS=1.1;CM-VER=3.1;
2025-07-23, 07:41:52 Critical (3) UCD invalid or channel unusable;CM-MAC=REDACTED;CMTS-MAC=EXCISED;CM-QOS=1.1;CM-VER=3.1;
Time Not Established Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=REDACTED;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;
2025-07-23, 07:32:04 Critical (3) UCD invalid or channel unusable;CM-MAC=REDACTED;CMTS-MAC=EXCISED;CM-QOS=1.1;CM-VER=3.1;
2025-07-23, 07:31:43 Critical (3) UCD invalid or channel unusable;CM-MAC=REDACTED;CMTS-MAC=EXCISED;CM-QOS=1.1;CM-VER=3.1;
Time Not Established Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=REDACTED;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;
2025-07-23, 06:02:50 Critical (3) UCD invalid or channel unusable;CM-MAC=REDACTED;CMTS-MAC=EXCISED;CM-QOS=1.1;CM-VER=3.1;
2025-07-23, 06:02:31 Critical (3) UCD invalid or channel unusable;CM-MAC=REDACTED;CMTS-MAC=EXCISED;CM-QOS=1.1;CM-VER=3.1;
Time Not Established Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=REDACTED;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;
2025-07-23, 00:07:06 Critical (3) UCD invalid or channel unusable;CM-MAC=REDACTED;CMTS-MAC=EXCISED;CM-QOS=1.1;CM-VER=3.1;
2025-07-23, 00:06:46 Critical (3) UCD invalid or channel unusable;CM-MAC=REDACTED;CMTS-MAC=EXCISED;CM-QOS=1.1;CM-VER=3.1;
Time Not Established Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=REDACTED;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;
2025-07-22, 19:43:04 Critical (3) UCD invalid or channel unusable;CM-MAC=REDACTED;CMTS-MAC=EXCISED;CM-QOS=1.1;CM-VER=3.1;
2025-07-22, 19:42:46 Critical (3) UCD invalid or channel unusable;CM-MAC=REDACTED;CMTS-MAC=EXCISED;CM-QOS=1.1;CM-VER=3.1;
Time Not Established Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=REDACTED;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;
2025-07-22, 19:39:14 Critical (3) UCD invalid or channel unusable;CM-MAC=REDACTED;CMTS-MAC=EXCISED;CM-QOS=1.1;CM-VER=3.1;
2025-07-22, 19:38:53 Critical (3) UCD invalid or channel unusable;CM-MAC=REDACTED;CMTS-MAC=EXCISED;CM-QOS=1.1;CM-VER=3.1;
Time Not Established Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=REDACTED;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;
2025-07-22, 19:37:51 Critical (3) Resetting the cable modem due to docsDevResetNow
2025-07-22, 19:21:54 Critical (3) UCD invalid or channel unusable;CM-MAC=REDACTED;CMTS-MAC=EXCISED;CM-QOS=1.1;CM-VER=3.1;
2025-07-22, 19:21:33 Critical (3) UCD invalid or channel unusable;CM-MAC=REDACTED;CMTS-MAC=EXCISED;CM-QOS=1.1;CM-VER=3.1;
Time Not Established Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=REDACTED;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;
2025-07-22, 19:17:23 Critical (3) UCD invalid or channel unusable;CM-MAC=REDACTED;CMTS-MAC=EXCISED;CM-QOS=1.1;CM-VER=3.1;

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1 month ago

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EG

Expert

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112.8K Messages

1 month ago

The CM1000 is not compatible with their new Next Gen / mid-split /enhanced upload speeds.

Check for third-party / retail purchased devices that are currently compatible here;

https://www.xfinity.com/support/internet/customerowned ". Scroll down to "See all Modems". Then scroll down to "Compatible Modems For Enhanced Speeds".

Their XB6, XB7, and XB8 rented gateway devices are also compatible.

(edited)

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BruceW

Gold Problem Solver

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26.6K Messages

1 month ago

... Netgear CM1000v2 ... 1 gig service ... 650 mb/s down and 5 mb/s up ...

The modem is not compatible with Gigabit service either. Comcast rates the CM1000v2 for use with plan speeds "Up to 950 Mbps". Follow the "See all modems" link near the bottom of https://www.xfinity.com/support/internet/customerowned and then under the "Compatible Modems" heading see the Netgear list.

Using devices on speed tiers for which they are not approved tends to produce unexpected results, often speeds below plan speed. Consider picking up one of the devices that is approved for Gigabit service, or dropping back to a speed tier for which the modem is approved. AFAIK Comcast has never said how they provision devices operating on speed tiers they're not approved for, but many customers who have tried it reported that they don't get the speeds they are paying for.

Please be aware that there are 2 kinds of responses in this Forum: Replies and Comments. When you Comment on a post by scrolling down to "Comment on this post here...", I am notified of your response. But if you select Reply, I am NOT notified and may not be aware of your response.

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EG

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112.8K Messages

1 month ago

@BruceW 

Thanks for expanding !

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user_ult770

Visitor

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8 Messages

1 month ago

I dropped back down to the low tiered plan of 300 mb/s and the upload still is still limited to 5 mb/s

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user_ult770

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8 Messages

I have attached some pictures that shows performance on the same tier 2 weeks ago and compared to now.

Nothing physically changed. Could the wrong policy be attached to my profile. Or is there traffic shaping being erroneously applied?

Several techs have been out to my place already. I really need a tier 3 engineer to investigate this as a logical issue before we revert back to physical fixes which have not worked

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1 month ago

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user_ult770

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8 Messages

1 month ago

These are the results of the new speedtest from the 300 mb/s service plan you can see the upload limit is locked at 5 mb/s in the same test two weeks ago it was at ~41 mb/s

new speed test results

(edited)

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XfinityFrank

Official Employee

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1.6K Messages

1 month ago

Hi there, @user_ult770! Thanks for reaching out to us here on the Community Forum. We can run diagnostics on our end to see if there is an issue with our system or signal that may be causing an issue with your upload. Please send a direct message to us by clicking the chat icon in the upper right corner of the page, click on the pen and paper icon, then enter “Xfinity Support” in the “To” section. Please include your full name and complete street address to get started.

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