Re: CM1200 Modem Upstream LED Flashing - Spectrum Internet

WaveWarper · ‎2021-01-11

I've had this modem for just over a year and it started dropping signal a couple days ago. The upstream LED was flashing green so I had a tech from Spectrum come out and check on everything. They promptly swapped my CM1200 out for one of their modems and everything worked. This is really frustrating considering I paid around $200 for the modem.

Any ideas what could be causing the issue and why the tech couldn't find a solution? Should I have "Enable Extended Upstream Transmit Power" checked in the modem options?

Hardware Version	1.01
Firmware Version	V1.02.01
CM Certificate	Installed

I'm getting a bunch of errors and warnings in the log like this when connecting the modem:

Critical (3)	Started Unicast Maintenance Ranging - No Response received - T3 time-out
Critical (3)	16 consecutive T3 timeouts while trying to range on upstream channel 8

Warning (5)	Dynamic Range Window violation
Warning (5)	RNG-RSP CCAP Commanded Power in Excess of 6 dB Below the Value Corresponding to the Top of the DRW

Error (4)

Missing BP Configuration Setting TLV Type

plemans · ‎2021-01-11

The full logs as well as the cable connection page helps.

Take a screen snip of them and post them here.

FURRYe38 · ‎2021-01-11

Please post the Connection status page that gives the power levels seen on each channel.

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.
Be sure to power OFF the modem for 1 minute them back ON.
https://community.netgear.com/t5/Cable-Modems-Routers/General-info-and-Troubleshooting-for-Cable-Mod...

WaveWarper · ‎2021-01-11

Thanks for the response.I'm assuming/hoping the tech made those checks when he was trying to get it working.

Connection status page attached.

FURRYe38 · ‎2021-01-11

You would need to check to be sure.

Your power levels seems a bit high...

Heres mine:

Startup Procedure

Procedure	Status	Comment
Acquire Downstream Channel	837000000 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	31	837000000 Hz	-2.5 dBmV	37 dB	0	0
2	Locked	QAM256	1	651000000 Hz	-2.5 dBmV	36.4 dB	0	0
3	Locked	QAM256	2	657000000 Hz	-2.6 dBmV	36.4 dB	0	0
4	Locked	QAM256	3	663000000 Hz	-2.3 dBmV	36.6 dB	0	0
5	Locked	QAM256	4	669000000 Hz	-2.3 dBmV	36.6 dB	0	0
6	Locked	QAM256	5	675000000 Hz	-2.1 dBmV	36.7 dB	0	0
7	Locked	QAM256	6	681000000 Hz	-2 dBmV	36.9 dB	0	0
8	Locked	QAM256	7	687000000 Hz	-1.8 dBmV	36.8 dB	0	0
9	Locked	QAM256	8	693000000 Hz	-1.7 dBmV	36.9 dB	0	0
10	Locked	QAM256	9	699000000 Hz	-1.5 dBmV	37 dB	0	0
11	Locked	QAM256	10	705000000 Hz	-1.5 dBmV	36.8 dB	0	0
12	Locked	QAM256	11	711000000 Hz	-1.3 dBmV	36.9 dB	0	0
13	Locked	QAM256	12	717000000 Hz	-0.8 dBmV	37.1 dB	0	0
14	Locked	QAM256	13	723000000 Hz	-1 dBmV	36.9 dB	0	0
15	Locked	QAM256	14	729000000 Hz	-0.7 dBmV	36.9 dB	0	0
16	Locked	QAM256	16	741000000 Hz	-0.6 dBmV	37.1 dB	0	0
17	Locked	QAM256	17	753000000 Hz	-0.7 dBmV	37.2 dB	0	0
18	Locked	QAM256	18	759000000 Hz	-0.9 dBmV	37.1 dB	0	0
19	Locked	QAM256	19	765000000 Hz	-1.3 dBmV	37.1 dB	0	0
20	Locked	QAM256	20	771000000 Hz	-1.3 dBmV	37.2 dB	0	0
21	Locked	QAM256	21	777000000 Hz	-1.5 dBmV	37.3 dB	0	0
22	Locked	QAM256	22	783000000 Hz	-1.7 dBmV	37.3 dB	0	0
23	Locked	QAM256	23	789000000 Hz	-1.7 dBmV	37.4 dB	0	0
24	Locked	QAM256	24	795000000 Hz	-1.9 dBmV	37.3 dB	0	0
25	Locked	QAM256	25	801000000 Hz	-2.1 dBmV	37.1 dB	0	0
26	Locked	QAM256	26	807000000 Hz	-2 dBmV	37.2 dB	0	0
27	Locked	QAM256	27	813000000 Hz	-2 dBmV	37.2 dB	0	0
28	Locked	QAM256	28	819000000 Hz	-2.4 dBmV	36.9 dB	0	0
29	Locked	QAM256	29	825000000 Hz	-2.3 dBmV	37.2 dB	0	0
30	Locked	QAM256	30	831000000 Hz	-2.3 dBmV	37.1 dB	0	0
31	Locked	QAM256	32	843000000 Hz	-2.5 dBmV	37 dB	0	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	1	5120 Ksym/sec	36000000 Hz	38.8 dBmV
2	Locked	ATDMA	2	5120 Ksym/sec	29000000 Hz	37.5 dBmV
3	Locked	ATDMA	5	5120 Ksym/sec	22000000 Hz	38 dBmV
4	Locked	ATDMA	6	2560 Ksym/sec	16000000 Hz	37 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	33	547000000 Hz	-4.0 dBmV	36.5 dB	1108 ~ 2987	107438938	87612859	0
2	Not Locked	0	0	0 Hz	0 dBmV	0.0 dB	0 ~ 4095	0	0	0

WaveWarper · ‎2021-01-11

Thanks for that. They said the power seems fine (I just asked again). Is there anything I can do on the modem side to rule out it is not faulty? I want to be able to bring some ammo back to Spectrum so they can't punt it back. As of now their provided modem is working, so I don't have a lot of leverage.

plemans · ‎2021-01-12

You're actually the first person with a locked upstream on the ofdma channels I've seen.

You're power levels are technically within spec. You didn't post your whole logs but the one had a dynamic window violation and t3 errors. Dynamic window violations usually occur when the power gets to high/low for a period of time. it can cause instabilities.

Your power levels are also a little backwards. Usually when you're power level on the upstream is high, it means you're close to the node so you tend to have a lower upstream level because it doesn't take as much power to communicate with the node.

Is there an amplifier in the line?

Also, have you tried checking off the "enable extended upstream transmit power"

WaveWarper · ‎2021-01-12

The "power" box is right outside the window from the modem, so the cable run is pretty short. I'm not sure if there is amp or not though. I will try giving the checkbox a try.

Thank you!

ctem81 · ‎2021-01-28

You are the victim of OFDMA being enabled on the upload channels. Modem running 1.02.01 breaks when OFDMA is enabled. You can read my journey here. https://www.dslreports.com/forum/r32832397-Netgear-CM1200-is-now-crap-OFDMA-just-enabled-on-upstream

FURRYe38 · ‎2021-01-28

Any progress on this?

@WaveWarper wrote:
The "power" box is right outside the window from the modem, so the cable run is pretty short. I'm not sure if there is amp or not though. I will try giving the checkbox a try.

Thank you!

WaveWarper · ‎2021-01-28

They came out and swapped my modem with theirs (which is free) and my speeds have been the same. I've honestly not put any more effort into it. Kind of a shame because this means NETGEAR is losing a customer and I probably wouldn't recommend someone get their own modem at this point.

FURRYe38 · ‎2021-01-28

You might try to contact NG support and your the ISP, have them push FW to the modem. Seems like the other user that posted reported v3 is working on there CM1200 thats on Spectrum. NG seems to have FW that would hopefully solve this for you. But its up to the ISP to push it. You might ask for escalated support from you ISP about this. I'm not on Spectrum, however my CM1200 works great.

Good Luck.

@WaveWarper wrote:
They came out and swapped my modem with theirs (which is free) and my speeds have been the same. I've honestly not put any more effort into it. Kind of a shame because this means NETGEAR is losing a customer and I probably wouldn't recommend someone get their own modem at this point.

Marksa17 · ‎2021-03-15

I read through your post, and one year later seems like the same issue is happening. Is the only recourse to buy another modem?!!? This one is slightly over a year old only just started having issues. Still running the same firmware too. Like OP I've had 3 tech visits, swapped out lines, added/removed/added again amplifier. But constant issues. ISP said maybe an issues with a Node, but to be honest I don't know what that means. I was given the number to the supervisor directly for updates, but I'll let you guess how many times I've spoken to him.

I'll take any/all suggestions, tips, magic enchament spells.. what ever you got.

Marksa17 · ‎2021-03-15

My specs if anyone cares to take a look.