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Connectivity instability, low speed, Power and SNR look out of spec

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Connectivity instability, low speed, Power and SNR look out of spec

Hi there,


First, I have had reliable fast internet for years from xfinity. Prior to 2-3 weeks ago I was consistently able to get ~900Mb down and ~41Mb up on most speed tests.  It was awesome!


The last few weeks I am running into issues with dropped connections at the WAN, and much slower bandwidth.


Equipment / config:

Netgear CM1150v (Firmware v04.02.02)

Coax connection, 1 splitter as the line enters the house. 2-way, -3.5dB

CAT 6e on all wired connections on equipment. Cable Modem to Router to Wired devices.

802.11ax on PC/iPad wireless connections



Wired Speedtest down: ~250Mb

Wired Speedtest up: ~39Mb


Ping / Packet Loss (looks ok)

Ping statistics for (
Packets: Sent = 114, Received = 114, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 9ms, Maximum = 44ms, Average = 16ms


Here are the cable modem details after factory reset and 1 hour of uptime. This is where I believe the issues are.

Downstream Power / SNR not great.

Upstream Power is low.


Startup Procedure
Acquire Downstream Channel627000000 HzLocked
Connectivity StateOKOperational
Boot StateOKOperational
IP Provisioning ModeHonor MDDhonorMdd(4)
Downstream Bonded Channels
ChannelLock StatusModulationChannel IDFrequencyPowerSNRCorrectablesUncorrectables
1LockedQAM25633627000000 Hz11.3 dBmV35.8 dB22400
2LockedQAM25613495000000 Hz13.5 dBmV37.2 dB630
3LockedQAM25614507000000 Hz13.4 dBmV37.1 dB1160
4LockedQAM25615513000000 Hz13.3 dBmV36.9 dB1680
5LockedQAM25616519000000 Hz13.1 dBmV37 dB1390
6LockedQAM25617525000000 Hz13 dBmV36.9 dB1790
7LockedQAM25618531000000 Hz12.8 dBmV36.8 dB2770
8LockedQAM25619543000000 Hz12.6 dBmV36.7 dB3050
9LockedQAM25620549000000 Hz12.4 dBmV36.6 dB3680
10LockedQAM25621555000000 Hz12.6 dBmV36.6 dB4640
11LockedQAM25622561000000 Hz12.7 dBmV36.7 dB5000
12LockedQAM25623567000000 Hz12.4 dBmV36.6 dB6110
13LockedQAM25624573000000 Hz12.4 dBmV36.6 dB778437
14LockedQAM25625579000000 Hz12.5 dBmV36.6 dB796445
15LockedQAM25626585000000 Hz12.2 dBmV36.4 dB1013464
16LockedQAM25627591000000 Hz11.8 dBmV36.3 dB1193196
17LockedQAM25628597000000 Hz11.9 dBmV36.3 dB1268467
18LockedQAM25629603000000 Hz12.1 dBmV36.3 dB1320448
19LockedQAM25630609000000 Hz11.7 dBmV36.2 dB1547447
20LockedQAM25631615000000 Hz11.5 dBmV36.1 dB1467462
21LockedQAM25632621000000 Hz11.4 dBmV35.9 dB1853468
22LockedQAM25634633000000 Hz10.9 dBmV35.6 dB3180480
23LockedQAM25635639000000 Hz10.6 dBmV35.6 dB3180486
24LockedQAM25636645000000 Hz10.6 dBmV35.6 dB2931485
25LockedQAM25637651000000 Hz10.7 dBmV35.5 dB3274493
26LockedQAM25638657000000 Hz10.5 dBmV35.4 dB43271157
27LockedQAM25639663000000 Hz10.5 dBmV35.4 dB39821139
28LockedQAM25640669000000 Hz10.4 dBmV35.3 dB45421140
29LockedQAM25641675000000 Hz10.4 dBmV35.1 dB39191147
30LockedQAM25642681000000 Hz10.2 dBmV35.3 dB46421219
31LockedQAM25643687000000 Hz10.4 dBmV35.3 dB44841104
32LockedQAM25644693000000 Hz10.3 dBmV35.2 dB43381097
Upstream Bonded Channels
ChannelLock StatusUS Channel TypeChannel IDSymbol RateFrequencyPower
1LockedATDMA15120 Ksym/sec17300000 Hz26.3 dBmV
2LockedATDMA25120 Ksym/sec23700000 Hz27.3 dBmV
3LockedATDMA35120 Ksym/sec30100000 Hz27.3 dBmV
4LockedATDMA45120 Ksym/sec36500000 Hz27.8 dBmV
5Not LockedUnknown00 Ksym/sec0 Hz0.0 dBmV
6Not LockedUnknown00 Ksym/sec0 Hz0.0 dBmV
7Not LockedUnknown00 Ksym/sec0 Hz0.0 dBmV
8Not LockedUnknown00 Ksym/sec0 Hz0.0 dBmV
Downstream OFDM Channels
Modulation /
Profile ID
FrequencyPowerSNR /
Active Subcarrier
Number Range
1Locked0 ,1159722000000 Hz9.6 dBmV35.2 dB1246 ~ 2849146581876378644532285
2Not Locked000 Hz0 dBmV0.0 dB0 ~ 4095000
Upstream OFDMA Channels
ChannelLock StatusModulation / Profile IDChannel IDFrequencyPower
1Not Locked000 Hz0 dBmV
2Not Locked000 Hz0 dBmV


Thu Nov 12 07:33:23 2020Notice (6)CM-STATUS message sent. Event Type Code: 5; Chan ID: 159; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: N/A.;CM-MAC=28:80:88:d1:6d:60;CMTS-MAC=00:42:5a:1d:8f:24;CM-QOS=1.1;CM-VER=3.1;
Thu Nov 12 07:33:15 2020Warning (5)REG-RSP-MP Mismatch Between Calculated Value for P1.6hi Compared to CCAP Provided Value;CM-MAC=28:80:88:d1:6d:60;CMTS-MAC=00:42:5a:1d:8f:24;CM-QOS=1.1;CM-VER=3.1;
Thu Nov 12 07:33:11 2020Notice (6)DS profile assignment change. DS Chan ID: 32; Previous Profile: ; New Profile: 1.;CM-MAC=28:80:88:d1:6d:60;CMTS-MAC=00:42:5a:1d:8f:24;CM-QOS=1.1;CM-VER=3.1;
Thu Nov 12 07:33:10 2020Notice (6)TLV-11 - unrecognized OID;CM-MAC=28:80:88:d1:6d:60;CMTS-MAC=00:42:5a:1d:8f:24;CM-QOS=1.1;CM-VER=3.1;
Thu Nov 12 07:32:59 2020Notice (6)Honoring MDD; IP provisioning mode = IPv6
Thu Nov 12 07:32:43 2020Warning (5)DBC-REQ Mismatch Between Calculated Value for P1.6hi Compared to CCAP Provided Value;CM-MAC=28:80:88:d1:6d:60;CMTS-MAC=00:42:5a:1d:8f:24;CM-QOS=1.1;CM-VER=3.1;
Thu Nov 12 07:32:33 2020Critical (3)SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=28:80:88:d1:6d:60;CMTS-MAC=00:42:5a:1d:8f:24;CM-QOS=1.1;CM-VER=3.1;
Thu Nov 12 07:32:06 2020Warning (5)MDD message timeout;CM-MAC=28:80:88:d1:6d:60;CMTS-MAC=00:42:5a:1d:8f:24;CM-QOS=1.1;CM-VER=3.1;


All help and advice appreciated. Thx!