Intermittent Modem Restarts

Modem: Arris SBG7400AC2

Starting 8/16 modem began randomly rebooting, all lights off for a second before starting with the power indicator and proceeding with normal bootup sequence. Once complete normal internet connectivity was restored. However another reboot would occur sometimes within 5 minutes sometimes not for several hours. I have been successfully using this modem for at least 3 years without issue up to this point.

I have attempted:

1. Modem reboot (intentionally this time).

2. Modem powercycle.

3. Modem factory reset.

4. Logging into the modem I have captured some status read outs and logs:

Downstream

	DCID	Freq	Power	SNR	Modulation	Octets	Correcteds	Uncorrectables
Downstream 1	28	579.00 MHz	2.50 dBmV	40.37 dB	256QAM	27411536	31	0
Downstream 2	21	537.00 MHz	2.70 dBmV	40.95 dB	256QAM	19744338	0	0
Downstream 3	22	543.00 MHz	2.80 dBmV	40.37 dB	256QAM	19611523	12	0
Downstream 4	23	549.00 MHz	2.30 dBmV	40.95 dB	256QAM	19659134	0	0
Downstream 5	24	555.00 MHz	2.30 dBmV	40.37 dB	256QAM	19606943	0	0
Downstream 6	25	561.00 MHz	2.80 dBmV	40.95 dB	256QAM	28158250	11	0
Downstream 7	26	567.00 MHz	2.60 dBmV	40.95 dB	256QAM	28392035	0	0
Downstream 8	27	573.00 MHz	2.10 dBmV	40.37 dB	256QAM	28373425	27	5
Downstream 9	29	585.00 MHz	2.70 dBmV	40.37 dB	256QAM	23195646	13	0
Downstream 10	30	591.00 MHz	2.00 dBmV	40.37 dB	256QAM	23264771	29	0
Downstream 11	31	597.00 MHz	2.00 dBmV	40.95 dB	256QAM	23101069	0	0
Downstream 12	32	603.00 MHz	2.40 dBmV	40.95 dB	256QAM	23170311	25	0
Downstream 13	33	609.00 MHz	1.70 dBmV	40.95 dB	256QAM	24972455	25	0
Downstream 14	34	615.00 MHz	1.60 dBmV	40.95 dB	256QAM	24957361	0	0
Downstream 15	35	621.00 MHz	2.30 dBmV	40.95 dB	256QAM	25140739	3	0
Downstream 16	36	627.00 MHz	2.20 dBmV	40.37 dB	256QAM	22854932	0	0
Downstream 17	37	633.00 MHz	1.90 dBmV	40.37 dB	256QAM	21580414	0	0
Downstream 18	38	639.00 MHz	2.70 dBmV	40.37 dB	256QAM	21726144	0	0
Downstream 19	39	645.00 MHz	2.90 dBmV	40.95 dB	256QAM	21662075	0	0
Downstream 20	40	651.00 MHz	2.30 dBmV	40.37 dB	256QAM	21882479	0	0
Downstream 21	41	657.00 MHz	2.60 dBmV	40.95 dB	256QAM	21122233	0	0
Downstream 22	42	663.00 MHz	3.20 dBmV	40.95 dB	256QAM	21101243	0	0
Downstream 23	43	669.00 MHz	3.00 dBmV	40.37 dB	256QAM	20887674	0	0
Downstream 24	44	675.00 MHz	2.80 dBmV	40.37 dB	256QAM	19491237	0	0

Upstream

	UCID	Freq	Power	Channel Type	Symbol Rate	Modulation
Upstream 1	17	16.20 MHz	54.00 dBmV	DOCSIS2.0 (ATDMA)	5120 kSym/s	64QAM
Upstream 2	20	35.60 MHz	52.50 dBmV	DOCSIS2.0 (ATDMA)	5120 kSym/s	64QAM
Upstream 3	19	29.20 MHz	53.00 dBmV	DOCSIS2.0 (ATDMA)	5120 kSym/s	64QAM
Upstream 4	18	22.80 MHz	53.75 dBmV	DOCSIS2.0 (ATDMA)	5120 kSym/s	64QAM

DOCSIS(CM) Events

Date Time	Event ID	Event Level	Description
8/19/2023 18:24	82000200	3	No Ranging Response received - T3 time-out;CM-MAC=<REDACTED>;CMTS-MAC=<REDACTED>;CM-QOS=1.1;CM-VER=3.0;
8/19/2023 18:26	73040100	6	TLV-11 - unrecognized OID;CM-MAC=<REDACTED>;CMTS-MAC=0<REDACTED>;CM-QOS=1.1;CM-VER=3.0;
8/19/2023 18:35	82000200	3	No Ranging Response received - T3 time-out;CM-MAC=<REDACTED>;CMTS-MAC=<REDACTED>;CM-QOS=1.1;CM-VER=3.0;
8/19/2023 18:44	73040100	6	TLV-11 - unrecognized OID;CM-MAC=a8:97:cd:22:e0:41;CMTS-MAC=00:90:f0:12:05:00;CM-QOS=1.1;CM-VER=3.0;
8/19/2023 18:52	82000200	3	No Ranging Response received - T3 time-out;CM-MAC=<REDACTED>;CMTS-MAC=<REDACTED>;CM-QOS=1.1;CM-VER=3.0;
8/19/2023 18:55	73040100	6	TLV-11 - unrecognized OID;CM-MAC=<REDACTED>;CMTS-MAC=<REDACTED>;CM-QOS=1.1;CM-VER=3.0;
8/19/2023 19:01	82000200	3	No Ranging Response received - T3 time-out;CM-MAC=<REDACTED>;CMTS-MAC=<REDACTED>;CM-QOS=1.1;CM-VER=3.0;

I am no expert but the upstream power seems to be out of acceptable range. Is that a possible cause of the connection instability and if so what is the best approach to correcting it.

Thanks,

Dave

Responses

Accepted Solution

EG

Expert

•

110.4K Messages

2 years ago

Yes. The upstream power is too high / out of spec. And it may be intermittently fluctuating even farther out of spec. That can cause random disconnects, spontaneous re-booting of the modem, speed, packet loss, latency problems, and the un-bonding of channels.

In an effort to try to obtain better connectivity / more wiggle room, check to see if there are there any excess/unneeded coax cable splitters in the line leading to the modem that can be eliminated/re-configured. Any splitters that remain should be high quality and cable rated for 5-1000 MHz, bi-directional, and no gold colored garbage from Home Depot, Target, Wal-Mart, etc. Splitters should be swapped with known to be good / new ones to test.

Also check the coax cable for any damage such as cuts, nicks, abrasions, kinks, sharp bends, etc.

If there aren't any unneeded splitters that can be eliminated and if your coax wiring setup can't be reconfigured so that there is a single two-way splitter connected directly off of the drop from the street / pole with one port feeding the modem and the other port feeding the rest of the house/equipment with additional splits as needed and you've checked all the wiring and fittings for integrity and tightness and refresh them by taking them apart then check for and clean off any corrosion / oxidation on the center wire and put them back together again, then perhaps it's best to book a tech visit to investigate and correct.

Good luck with it !

2

U

user_173817

2 Messages

Thank you @EG,

For anyone experiencing a similar issue I had a tech come out and verify the power readings. We then tracked down a nest of splitters installed by the previous homeowners. Removing the splitters and connecting the house without any splitters and the power draw has dropped to the low 40 dBmV range. So far for the last 8 hours no uninitiated modem restarts.

~ Dave

2 years ago

0

XfinityMichaelC

Administrator

•

4.3K Messages

Awesome explanation, @EG! We just wanted to follow up with you @user_173817 to see how the services are running since you and the tech were able to narrow it down to some old splitters since it has been some time since your last update.

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2 years ago

EG

Expert

•

110.4K Messages

2 years ago

Good to hear that you found something ! Hope things hold up for you. Good luck !

0

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user_173817

Intermittent Modem Restarts

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EG

user_173817

XfinityMichaelC

EG

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