CM1000 intermittent connection loss on XFinity cable

G0atHax0r · ‎2020-05-14

Hi All,

I'm troubleshooting what seems to be intermittent drops throughout the day on XFinity cable... and the culprit is either the CM1000 going bad, or some kind of line quality/hardware issues on the XFinity side. Before you ask, no there aren't any splitters between the modem and the XFinity cable box. I have worked with XFinity support, who is reporting that all is fine on their end, and is pointing the finger at the modem. They ran line quality tests, and I'm getting excellent speedtests when things are working. Here's the order of events when I catch it happening:

1.) Internet service is lost

2.) The green "internet" icon light on the CM1000 starts flashing, and will eventually reconnect and go solid. (2nd light from the bottom, above the network icon)

3.) Internet service returns

4.) Total time occurred during outage is usually a minute or 2, while minimal, is disruptive enough to anger those in the household as it interrupts streaming, browsing, you name it.

I have pulled some logs from the CM1000 to get some feedback on what these might indicate? Is it truly an XFinity issue, or is this just normal with the modem going bad?

Here are some events from 5/11:

2020-05-11, 12:01:46	Notice (6)	CM-STATUS message sent. Event Type Code: 24; Chan ID: 37; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: 1.;CM-MAC=a0:04:60:fc:37:50;CMTS-MAC=00:01:5c:a2:6a:51;CM-QOS=1.1;CM-VER=3.1;
2020-05-11, 12:00:51	Notice (6)	CM-STATUS message sent. Event Type Code: 16; Chan ID: 37; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: 1 2 3.;CM-MAC=a0:04:60:fc:37:50;CMTS-MAC=00:01:5c:a2:6a:51;CM-QOS=1.1;CM-VER=3.1;
2020-05-11, 12:00:30	Notice (6)	CM-STATUS message sent. Event Type Code: 16; Chan ID: 37; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: 2 3.;CM-MAC=a0:04:60:fc:37:50;CMTS-MAC=00:01:5c:a2:6a:51;CM-QOS=1.1;CM-VER=3.1;
2020-05-11, 12:00:16	Notice (6)	DS profile assignment change. DS Chan ID: 32; Previous Profile: ; New Profile: 1 2 3.;CM-MAC=a0:04:60:fc:37:50;CMTS-MAC=00:01:5c:a2:6a:51;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=a0:04:60:fc:37:50;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;
2020-05-11, 11:54:16	Critical (3)	Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=a0:04:60:fc:37:50;CMTS-MAC=00:01:5c:a2:6a:51;CM-QOS=1.1;CM-VER=3.1;
2020-05-11, 11:43:53	Critical (3)	SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=a0:04:60:fc:37:50;CMTS-MAC=00:01:5c:a2:6a:51;CM-QOS=1.1;CM-VER=3.1;
2020-05-11, 11:43:50	Critical (3)	No Ranging Response received - T3 time-out;CM-MAC=a0:04:60:fc:37:50;CMTS-MAC=00:01:5c:a2:6a:51;CM-QOS=1.1;CM-VER=3.1;
2020-05-11, 11:43:38	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=a0:04:60:fc:37:50;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;
2020-05-11, 11:43:36	Critical (3)	SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=a0:04:60:fc:37:50;CMTS-MAC=00:01:5c:a2:6a:51;CM-QOS=1.1;CM-VER=3.1;
2020-05-11, 11:43:34	Critical (3)	No Ranging Response received - T3 time-out;CM-MAC=a0:04:60:fc:37:50;CMTS-MAC=00:01:5c:a2:6a:51;CM-QOS=1.1;CM-VER=3.1;
2020-05-11, 11:43:07	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=a0:04:60:fc:37:50;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;
2020-05-11, 11:42:50	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=a0:04:60:fc:37:50;CMTS-MAC=00:01:5c:a2:6a:51;CM-QOS=1.1;CM-VER=3.1;
2020-05-11, 11:42:49	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=a0:04:60:fc:37:50;CMTS-MAC=00:01:5c:a2:6a:51;CM-QOS=1.1;CM-VER=3.1;

Here are some events from 5/14:

2020-05-14, 10:42:54	Notice (6)	DS profile assignment change. DS Chan ID: 32; Previous Profile: ; New Profile: 1 2 3.;CM-MAC=a0:04:60:fc:37:50;CMTS-MAC=00:01:5c:a2:6a:51;CM-QOS=1.1;CM-VER=3.1;
2020-05-14, 10:42:46	Notice (6)	Honoring MDD; IP provisioning mode = IPv6
2020-05-14, 10:41:35	Critical (3)	No Ranging Response received - T3 time-out;CM-MAC=a0:04:60:fc:37:50;CMTS-MAC=00:01:5c:a2:6a:51;CM-QOS=1.1;CM-VER=3.1;
2020-05-14, 10:41:29	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=a0:04:60:fc:37:50;CMTS-MAC=00:01:5c:a2:6a:51;CM-QOS=1.1;CM-VER=3.1;
2020-05-14, 10:41:28	Critical (3)	Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=a0:04:60:fc:37:50;CMTS-MAC=00:01:5c:a2:6a:51;CM-QOS=1.1;CM-VER=3.1;
2020-05-14, 10:41:12	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=a0:04:60:fc:37:50;CMTS-MAC=00:01:5c:a2:6a:51;CM-QOS=1.1;CM-VER=3.1;
2020-05-14, 10:41:11	Warning (5)	MDD message timeout;CM-MAC=a0:04:60:fc:37:50;CMTS-MAC=00:01:5c:a2:6a:51;CM-QOS=1.1;CM-VER=3.1;
2020-05-14, 10:40:47	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=a0:04:60:fc:37:50;CMTS-MAC=00:01:5c:a2:6a:51;CM-QOS=1.1;CM-VER=3.1;
2020-05-14, 10:40:47	Warning (5)	MDD message timeout;CM-MAC=a0:04:60:fc:37:50;CMTS-MAC=00:01:5c:a2:6a:51;CM-QOS=1.1;CM-VER=3.1;
2020-05-14, 10:40:35	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=a0:04:60:fc:37:50;CMTS-MAC=00:01:5c:a2:6a:51;CM-QOS=1.1;CM-VER=3.1;
2020-05-14, 10:40:34	Warning (5)	MDD message timeout;CM-MAC=a0:04:60:fc:37:50;CMTS-MAC=00:01:5c:a2:6a:51;CM-QOS=1.1;CM-VER=3.1;
2020-05-14, 10:40:22	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=a0:04:60:fc:37:50;CMTS-MAC=00:01:5c:a2:6a:51;CM-QOS=1.1;CM-VER=3.1;
2020-05-14, 10:40:22	Warning (5)	MDD message timeout;CM-MAC=a0:04:60:fc:37:50;CMTS-MAC=00:01:5c:a2:6a:51;CM-QOS=1.1;CM-VER=3.1;
2020-05-14, 10:40:11	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=a0:04:60:fc:37:50;CMTS-MAC=00:01:5c:a2:6a:51;CM-QOS=1.1;CM-VER=3.1;
2020-05-14, 10:40:10	Warning (5)	MDD message timeout;CM-MAC=a0:04:60:fc:37:50;CMTS-MAC=00:01:5c:a2:6a:51;CM-QOS=1.1;CM-VER=3.1;
2020-05-14, 10:39:52	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=a0:04:60:fc:37:50;CMTS-MAC=00:01:5c:a2:6a:51;CM-QOS=1.1;CM-VER=3.1;
2020-05-14, 10:39:51	Warning (5)	MDD message timeout;CM-MAC=a0:04:60:fc:37:50;CMTS-MAC=00:01:5c:a2:6a:51;CM-QOS=1.1;CM-VER=3.1;
2020-05-14, 10:39:03	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=a0:04:60:fc:37:50;CMTS-MAC=00:01:5c:a2:6a:51;CM-QOS=1.1;CM-VER=3.1;
2020-05-14, 10:39:02	Warning (5)	MDD message timeout;CM-MAC=a0:04:60:fc:37:50;CMTS-MAC=00:01:5c:a2:6a:51;CM-QOS=1.1;CM-VER=3.1;
2020-05-14, 10:38:39	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=a0:04:60:fc:37:50;CMTS-MAC=00:01:5c:a2:6a:51;CM-QOS=1.1;CM-VER=3.1;
2020-05-14, 10:38:38	Warning (5)	MDD message timeout;CM-MAC=a0:04:60:fc:37:50;CMTS-MAC=00:01:5c:a2:6a:51;CM-QOS=1.1;CM-VER=3.1;
2020-05-14, 10:38:32	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=a0:04:60:fc:37:50;CMTS-MAC=00:01:5c:a2:6a:51;CM-QOS=1.1;CM-VER=3.1;
2020-05-14, 10:38:32	Warning (5)	MDD message timeout;CM-MAC=a0:04:60:fc:37:50;CMTS-MAC=00:01:5c:a2:6a:51;CM-QOS=1.1;CM-VER=3.1;
2020-05-14, 10:38:30	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=a0:04:60:fc:37:50;CMTS-MAC=00:01:5c:a2:6a:51;CM-QOS=1.1;CM-VER=3.1;
2020-05-14, 10:38:25	Notice (6)	CM-STATUS message sent. Event Type Code: 21; Chan ID: 37; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: N/A.;CM-MAC=a0:04:60:fc:37:50;CMTS-MAC=00:01:5c:a2:6a:51;CM-QOS=1.1;CM-VER=3.1;
2020-05-14, 10:38:24	Notice (6)	CM-STATUS message sent. Event Type Code: 20; Chan ID: 37; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: N/A.;CM-MAC=a0:04:60:fc:37:50;CMTS-MAC=00:01:5c:a2:6a:51;CM-QOS=1.1;CM-VER=3.1;
2020-05-14, 10:38:24	Notice (6)	CM-STATUS message sent. Event Type Code: 16; Chan ID: 37; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: 0 1 2 3.;CM-MAC=a0:04:60:fc:37:50;CMTS-MAC=00:01:5c:a2:6a:51;CM-QOS=1.1;CM-VER=3.1;
2020-05-14, 10:37:05	Notice (6)	CM-STATUS message sent. Event Type Code: 4; Chan ID: 5 11 12 13 14 15 16 17 18 19 20 21 22 23 37; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: N/A.;CM-MAC=a0:04:60:fc:37:50;CMTS-MAC=00:01:5c:a2:6a:51;CM-QOS=1.1;CM-VER=3.1;
2020-05-14, 10:37:05	Notice (6)	CM-STATUS message sent. Event Type Code: 24; Chan ID: 37; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: 0.;CM-MAC=a0:04:60:fc:37:50;CMTS-MAC=00:01:5c:a2:6a:51;CM-QOS=1.1;CM-VER=3.1;
2020-05-14, 10:37:04	Notice (6)	CM-STATUS message sent. Event Type Code: 16; Chan ID: 37; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: 1 2 3.;CM-MAC=a0:04:60:fc:37:50;CMTS-MAC=00:01:5c:a2:6a:51;CM-QOS=1.1;CM-VER=3.1;
2020-05-14, 10:37:02	Notice (6)	CM-STATUS message sent. Event Type Code: 16; Chan ID: 37; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: 2 3.;CM-MAC=a0:04:60:fc:37:50;CMTS-MAC=00:01:5c:a2:6a:51;CM-QOS=1.1;CM-VER=3.1;
2020-05-14, 10:37:01	Notice (6)	CM-STATUS message sent. Event Type Code: 16; Chan ID: 37; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: 3.;CM-MAC=a0:04:60:fc:37:50;CMTS-MAC=00:01:5c:a2:6a:51;CM-QOS=1.1;CM-VER=3.1;
2020-05-14, 10:37:01	Notice (6)	CM-STATUS message sent. Event Type Code: 22; Chan ID: 37; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: N/A.;CM-MAC=a0:04:60:fc:37:50;CMTS-MAC=00:01:5c:a2:6a:51;CM-QOS=1.1;CM-VER=3.1;
2020-05-14, 10:36:58	Warning (5)	MDD message timeout;CM-MAC=a0:04:60:fc:37:50;CMTS-MAC=00:01:5c:a2:6a:51;CM-QOS=1.1;CM-VER=3.1;
2020-05-14, 10:36:57	Notice (6)	CM-STATUS message sent. Event Type Code: 16; Chan ID: 37; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: 0 1 2 3.;CM-MAC=a0:04:60:fc:37:50;CMTS-MAC=00:01:5c:a2:6a:51;CM-QOS=1.1;CM-VER=3.1;
2020-05-14, 10:36:45	Notice (6)	CM-STATUS message sent. Event Type Code: 16; Chan ID: 37; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: 1 2 3.;CM-MAC=a0:04:60:fc:37:50;CMTS-MAC=00:01:5c:a2:6a:51;CM-QOS=1.1;CM-VER=3.1;
2020-05-14, 10:36:35	Notice (6)	CM-STATUS message sent. Event Type Code: 4; Chan ID: 5 11 12 13 14 15 16 17 18 19 20 21 22 23 37; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: N/A.;CM-MAC=a0:04:60:fc:37:50;CMTS-MAC=00:01:5c:a2:6a:51;CM-QOS=1.1;CM-VER=3.1;
2020-05-14, 10:36:20	Notice (6)	CM-STATUS message sent. Event Type Code: 24; Chan ID: 37; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: 0 1.;CM-MAC=a0:04:60:fc:37:50;CMTS-MAC=00:01:5c:a2:6a:51;CM-QOS=1.1;CM-VER=3.1;
2020-05-14, 10:36:20	Notice (6)	CM-STATUS message sent. Event Type Code: 16; Chan ID: 37; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: 2 3.;CM-MAC=a0:04:60:fc:37:50;CMTS-MAC=00:01:5c:a2:6a:51;CM-QOS=1.1;CM-VER=3.1;
2020-05-14, 10:36:15	Notice (6)	CM-STATUS message sent. Event Type Code: 16; Chan ID: 37; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: 3.;CM-MAC=a0:04:60:fc:37:50;CMTS-MAC=00:01:5c:a2:6a:51;CM-QOS=1.1;CM-VER=3.1;

Thank you very much for your support, ideas and feedback!

G0atHax0r · ‎2020-05-29

So here's an update to my situation... it seems that @Googalabosh was experiencing similar issues, so I'll write down my findings/experience here...

1.) XFinity tech came out and ran tests from the entry point to my CM1000 cable modem - no problems (and no, there are no splitters... it's a straigh run)

2.) XFinity tech ran a test from the entry point to the junction box at the street - no problem.

3.) XFinity tech ran a test from the junction box at the street, to the nearest node - again, no problems...

He said everything according to his readings were within parameters and nothing looked abnormal. This was frustrating both to me and him, since we couldn't pinpoint anything weird. I asked him if he could put a network monitor on our account, which he was happy to do -- and I would *recommend* you asking for this same thing. This will give them detailed reports of when things misbehave, which is what I suspect happened in my case.

After the tech left, my device continued to drop for the next few days off and on throughout the day... then, things stabilized. My connection has not dropped for almost 4 days straight now., which is unheard of. 🙂 The tech said he or someone else would call back and give an update, but I have not heard anything yet. I will definitely find out what the problem was, but I suspect it had to do with some changes at the upstream node.

I started keeping careful track of what my modem stats were looking like throughout the day, and found that if the downstream channels power dropped below -4.5 or -5 dBmV, which also seems to drop the SNR/MER to below 36dB, then I would start accumulating more and more uncorrectable codewords, including drops. Since they did something on their end, my power has remained around -2 or -3dBmV and the SNR/MER remains at 40dB on average...

I would focus on ensuring that these values are in the middle of the range (Power should ideally be at 0dBmV and SNR/MER should ideally be at 40dB), but it fluctuates up or down... which typically is still OK, but I guess certain modems/connections are more finicky than others. Hope this helps!

View solution in original post

plemans · ‎2020-05-17

do you also have the Cable connection page to go with the logs?

G0atHax0r · ‎2020-05-17

@plemans wrote:
do you also have the Cable connection page to go with the logs?

Unfortunately I don't have a snapshot of these connection logs when the issue is occurring, but I'll try for next time. Here's what they look like when things are working:

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	579000000 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	17	579000000 Hz	-2.7 dBmV	39.6 dB	46209713	14779	14713
2	Locked	QAM256	1	483000000 Hz	-3.1 dBmV	39.1 dB	45233431	370	70
3	Locked	QAM256	2	489000000 Hz	-2.9 dBmV	39.2 dB	64685880	5903	28809
4	Locked	QAM256	3	495000000 Hz	-2.8 dBmV	39.6 dB	64692870	5652	27540
5	Locked	QAM256	4	501000000 Hz	-3.0 dBmV	39.3 dB	64697151	5531	26572
6	Locked	QAM256	5	507000000 Hz	-2.8 dBmV	39.4 dB	64700840	3120	14280
7	Locked	QAM256	6	513000000 Hz	-2.6 dBmV	39.6 dB	64706758	5173	24780
8	Locked	QAM256	7	519000000 Hz	-2.9 dBmV	39.3 dB	64711093	1930	7965
9	Locked	QAM256	8	525000000 Hz	-3.3 dBmV	39.1 dB	64720231	1325	4830
10	Locked	QAM256	9	531000000 Hz	-3.1 dBmV	39.3 dB	64724479	5480	26491
11	Locked	QAM256	10	537000000 Hz	-3.0 dBmV	39.4 dB	64723792	5836	27966
12	Locked	QAM256	11	543000000 Hz	-3.1 dBmV	39.3 dB	64729815	5170	24677
13	Locked	QAM256	12	549000000 Hz	-2.9 dBmV	39.4 dB	64735703	782	1044
14	Locked	QAM256	13	555000000 Hz	-2.6 dBmV	39.6 dB	64739574	5608	27443
15	Locked	QAM256	14	561000000 Hz	-2.7 dBmV	39.3 dB	64742700	5930	28637
16	Locked	QAM256	15	567000000 Hz	-2.9 dBmV	39.4 dB	64745371	5661	27281
17	Locked	QAM256	16	573000000 Hz	-2.7 dBmV	39.5 dB	64769644	9418	25081
18	Locked	QAM256	18	585000000 Hz	-2.8 dBmV	39.5 dB	64774172	17178	15246
19	Locked	QAM256	19	591000000 Hz	-2.7 dBmV	39.5 dB	64783828	22025	5417
20	Locked	QAM256	20	597000000 Hz	-2.3 dBmV	39.6 dB	64794547	18760	2065
21	Locked	QAM256	21	603000000 Hz	-2.4 dBmV	39.5 dB	64793880	21515	4126
22	Locked	QAM256	22	609000000 Hz	-2.3 dBmV	39.5 dB	64798198	21891	3794
23	Locked	QAM256	23	615000000 Hz	-1.8 dBmV	39.8 dB	64808961	15205	1087
24	Locked	QAM256	29	459000000 Hz	-2.8 dBmV	39.4 dB	64797187	5564	27605
25	Locked	QAM256	34	465000000 Hz	-2.8 dBmV	39.3 dB	64798205	5915	28846
26	Locked	QAM256	35	471000000 Hz	-2.7 dBmV	39.4 dB	64792486	5790	27849
27	Locked	QAM256	36	477000000 Hz	-3.0 dBmV	39.1 dB	64794992	5871	28804
28	Locked	QAM256	38	429000000 Hz	-2.3 dBmV	39.4 dB	64767490	5246	25934
29	Locked	QAM256	39	435000000 Hz	-2.8 dBmV	39.1 dB	64779295	423	514
30	Locked	QAM256	40	441000000 Hz	-3.1 dBmV	39.1 dB	64774997	920	2066
31	Locked	QAM256	41	453000000 Hz	-2.6 dBmV	39.5 dB	64777052	5852	28958
32	Not Locked	Unknown	0	0 Hz	0.0 dBmV	0.0 dB	0	0	0

<tabindex=-1>Upstream Bonded Channels</tabindex=-1>

Channel	Lock Status	Modulation	Channel ID	Frequency	Power
1	Locked	ATDMA	1	35800000 Hz	47.0 dBmV
2	Locked	ATDMA	2	29400000 Hz	46.8 dBmV
3	Locked	ATDMA	3	23000000 Hz	46.5 dBmV
4	Not Locked	Unknown	0	0 Hz	0.0 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	37	690000000 Hz	0.4 dBmV	32.0 dB	1228 ~ 2867	298986550	236769966	17558813
2	Not Locked	0	0	0 Hz	0.0 dBmV	0.0 dB	0 ~ 4095	0	0	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

Current System Time: Sun May 17 19:54:51 2020System Up Time: 26:39:57

plemans · ‎2020-05-18

You have a bunch of errors in your line. Not a few, a bunch.

If you don't have any splitters, attenuators, amplifiers, or extended runs, then your isp needs to check the line.

goal is to connect right where the coax enters the home to prevent the isp from saying the issues is the wiring within the home.

G0atHax0r · ‎2020-05-18

@plemans wrote:
You have a bunch of errors in your line. Not a few, a bunch.
If you don't have any splitters, attenuators, amplifiers, or extended runs, then your isp needs to check the line.
goal is to connect right where the coax enters the home to prevent the isp from saying the issues is the wiring within the home.

I appreciate your feedback, @plemans! Could you please share some more specific information? I'm assuming you're talking about these sample errors that keep repeating below, right? I'm pretty decent at deciphering windows server errors and whatnot, but cable modem/communication-specific errors are not my expertise. What typically are the cause for these kinds of errors, and what should I be looking out for? For instance, could this be an physical cable problem? If so, why would it only happen intermittently? Could it be the CM1000 flaking out? Why or why not? Would I see different errors? Is it an upstream hardware issue not producing enough voltage, or not supplying what's necessary to maintain a sync connection, or timing hardware failures?

2020-05-14, 10:41:35	Critical (3)	No Ranging Response received - T3 time-out;CM-MAC=a0:04:60:fc:37:50;CMTS-MAC=00:01:5c:a2:6a:51;CM-QOS=1.1;CM-VER=3.1;
2020-05-14, 10:41:29	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=a0:04:60:fc:37:50;CMTS-MAC=00:01:5c:a2:6a:51;CM-QOS=1.1;CM-VER=3.1;
2020-05-14, 10:41:28	Critical (3)	Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=a0:04:60:fc:37:50;CMTS-MAC=00:01:5c:a2:6a:51;CM-QOS=1.1;CM-VER=3.1;

I don't have any splitters, attenuators, amplifiers or extended runs. I appreciate your help! 🙂

plemans · ‎2020-05-18

I'm talking your codewords. Some are correctable and some aren't. Tie those in together with your logs and there's usually line issues causing it.

It could be damage to a coax line, bends, wear, or even moisture in the line. It could be corrosion to a connector. it could be a poorly installed connector. it could be an issues at the box. Its tough to say exactly.

but if you have the modem directly connected to where the coax is entering the home and you're still getting those, your isp needs to check the line.

It always potentially can be a modem. connectors/hardware does go bad sometimes.

And sometimes the isp will say "our lines fine, its your 3rd party modem". I've had to rent an ISP modem for a month to prove it wasn't the modem so they'd fix a line before. Problem with that is that some isp's are locking down their modem page so the home user can't even check anymore.

G0atHax0r · ‎2020-05-18

Ahhh! Understood. So the codewords are some type of CRC. What do these correctable/uncorrectable codeword values normally look like? Just extremely low numbers right that indicate no noise on the line, right? Seeing that there's a similar range of errors like this across most of the channels, then I guess that could be indicative of a line/connector problem.

Lol... that's exactly what the isp said... they don't see any problems with the line when they run their tests, but after sharing some of these SYNC/No ranging response errors from the logs, they seemed a little more willing to admit to it possibly being a cable or upstream equipment issue. If it was the latter, you'd think more neighbors would be complaining though. So it must be a cable/connector. I believe the next step is begging them to come out and do a hands-on test. Thanks again for your help @plemans!

@plemans wrote:
I'm talking your codewords. Some are correctable and some aren't. Tie those in together with your logs and there's usually line issues causing it.
It could be damage to a coax line, bends, wear, or even moisture in the line. It could be corrosion to a connector. it could be a poorly installed connector. it could be an issues at the box. Its tough to say exactly.
but if you have the modem directly connected to where the coax is entering the home and you're still getting those, your isp needs to check the line.

It always potentially can be a modem. connectors/hardware does go bad sometimes.

And sometimes the isp will say "our lines fine, its your 3rd party modem". I've had to rent an ISP modem for a month to prove it wasn't the modem so they'd fix a line before. Problem with that is that some isp's are locking down their modem page so the home user can't even check anymore.

FURRYe38 · ‎2020-05-18

Have you factory reset the modem?

Be sure your using good quality RG6 coax cable up to the modem.

I would contact NG support and ask for additional help and information. Ask about a RMA if thats an option.

https://www.netgear.com/support/#

G0atHax0r · ‎2020-05-18

I thought about factory resetting... but wasn't sure if that was going to cause me to have to work with XFinity support to get it hooked back up again, if it wasn't automatically going to be able to reconnect after the factory reset? Any ideas?

Cable quality is good up to the modem... I really feel it's either cable from the street to the house, or a connector somewhere. These things don't seem to last our in the hot, humid, wet florida weather eventhough they're in a box.

@FURRYe38 wrote:
Have you factory reset the modem?
Be sure your using good quality RG6 coax cable up to the modem.

I would contact NG support and ask for additional help and information. Ask about a RMA if thats an option.
https://www.netgear.com/support/#

FURRYe38 · ‎2020-05-18

Resets are ok. They only reset the modem and don't deactivate the ISP side. The ISP just has the mac address associated with there services. You can factory reset or reboot the modem all day long. ISP doesn't care.

Have a friend or family member you can take the modem to and connect it at a different location to see if the problem follows?

G0atHax0r · ‎2020-05-29