Motorola MB8611 keeps losing connection and rebooting throughout the day

My modem keeps rebooting throughout the day. I have had 4 different modems and modem/routers in the last 3 years and this continuously keeps happening regardless of what I try. I have rebooted it dozens of times, replaced almost every cable connecting to my system (excluding the ones running through the walls), and changed out various splitters. Normally this wouldn't bother me but I recently started working from home so a stable internet connection is crucial for my work.

Below are the latest Error Logs, Downstream, and Upstream Channels from about 30 minutes before posting this:

Time	Priority	Description
16:18:07 Mon Jun 27 2022	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-VER=3.1;
16:18:07 Mon Jun 27 2022	Critical (3)	Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-VER=3.1;
16:18:50 Mon Jun 27 2022	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-VER=3.1;
16:18:50 Mon Jun 27 2022	Critical (3)	Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-VER=3.1;
16:18:51 Mon Jun 27 2022	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-VER=3.1;
16:18:51 Mon Jun 27 2022	Critical (3)	Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-VER=3.1;
16:19:18 Mon Jun 27 2022	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-VER=3.1;
16:19:18 Mon Jun 27 2022	Critical (3)	Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-VER=3.1;
16:19:33 Mon Jun 27 2022	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-VER=3.1;
16:19:34 Mon Jun 27 2022	Critical (3)	Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-VER=3.1;
16:20:18 Mon Jun 27 2022	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-VER=3.1;
16:20:18 Mon Jun 27 2022	Critical (3)	Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-VER=3.1;
Time Not Established	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-VER=3.1;
16:26:30 Mon Jun 27 2022	Critical (3)	Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-VER=3.1;
16:26:30 Mon Jun 27 2022	Critical (3)	TFTP Failed - OUT OF ORDER packets;CM-VER=3.1;
16:26:30 Mon Jun 27 2022	Critical (3)	TFTP Request Retries exceeded, CM unable to register
16:26:44 Mon Jun 27 2022	Critical (3)	No Ranging Response received - T3 time-out;CM-VER=3.1;
Time Not Established	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-VER=3.1;
Time Not Established	Critical (3)	No Ranging Response received - T3 time-out;CM-VER=3.1;
Time Not Established	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-VER=3.1;
Time Not Established	Critical (3)	No Ranging Response received - T3 time-out;CM-VER=3.1;
Time Not Established	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-VER=3.1;
Time Not Established	Critical (3)	No Ranging Response received - T3 time-out;CM-VER=3.1;
Time Not Established	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-VER=3.1;
Time Not Established	Critical (3)	No Ranging Response received - T3 time-out;CM-VER=3.1;
10:19:44 Tue Jun 28 2022	Critical (3)	Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-VER=3.1;
Time Not Established	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-VER=3.1;
Time Not Established	Critical (3)	No Ranging Response received - T3 time-out;CM-VER=3.1;
Time Not Established	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-VER=3.1;
Time Not Established	Critical (3)	No Ranging Response received - T3 time-out;CM-VER=3.1;
Time Not Established	Notice (6)	Honoring MDD; IP provisioning mode = IPv6
11:10:51 Tue Jun 28 2022	Notice (6)	DS profile assignment change. DS Chan ID: 32; Previous Profile: ; New Profile: 1 2 3.;CM-VER=3.1;

Channel	Lock Status	Modulation	Channel ID	Freq. (MHz)	Pwr (dBmV)	SNR (dB)	Corrected	Uncorrected
1	Locked	QAM256	20	603.0	-6.4	37.2	0	0
2	Locked	QAM256	17	585.0	-5.4	37.7	0	0
3	Locked	QAM256	18	591.0	-5.7	37.8	0	0
4	Locked	QAM256	19	597.0	-5.8	37.7	0	0
5	Locked	QAM256	21	609.0	-6.7	37.0	0	0
6	Locked	QAM256	22	615.0	-6.8	37.0	0	0
7	Locked	QAM256	23	621.0	-6.3	37.4	0	0
8	Locked	QAM256	24	627.0	-5.8	37.7	0	0
9	Locked	QAM256	25	633.0	-6.0	37.8	0	0
10	Locked	QAM256	26	639.0	-6.4	37.5	0	0
11	Locked	QAM256	27	645.0	-6.6	37.2	0	0
12	Locked	QAM256	28	651.0	-7.1	37.0	0	0
13	Locked	QAM256	29	657.0	-6.4	37.2	0	0
14	Locked	QAM256	30	663.0	-6.0	37.5	0	0
15	Locked	QAM256	31	669.0	-5.6	37.9	0	0
16	Locked	QAM256	32	675.0	-5.7	37.2	0	0
17	Locked	QAM256	33	681.0	-5.6	37.7	0	0
18	Locked	QAM256	34	687.0	-5.6	37.5	0	0
19	Locked	QAM256	35	693.0	-5.7	37.4	0	0
20	Locked	QAM256	36	699.0	-5.4	37.5	0	0
21	Locked	QAM256	37	705.0	-5.0	38.0	0	0
22	Locked	QAM256	38	711.0	-5.1	38.3	0	0
23	Locked	QAM256	39	717.0	-5.2	38.0	0	0
24	Locked	QAM256	40	723.0	-6.0	37.6	0	0
25	Locked	QAM256	41	729.0	-5.9	37.5	0	0
26	Locked	QAM256	42	735.0	-5.7	37.7	0	0
27	Locked	QAM256	43	741.0	-5.8	37.8	0	0
28	Locked	QAM256	44	747.0	-5.3	38.2	0	0
29	Locked	QAM256	45	753.0	-5.0	38.5	0	0
30	Locked	QAM256	46	759.0	-5.2	38.3	0	0
31	Locked	QAM256	47	765.0	-5.9	38.0	0	0
32	Locked	OFDM PLC	48	805.0	-3.7	38.4	10003812	0

Channel	Lock Status	Channel Type	Channel ID	Symb. Rate (Ksym/sec)	Freq. (MHz)	Pwr (dBmV)
1	Locked	SC-QAM	1	2560	10.4	48.3
2	Locked	SC-QAM	2	5120	16.4	49.0
3	Locked	SC-QAM	3	5120	22.8	49.5
4	Locked	SC-QAM	4	5120	29.2	49.8
5	Locked	SC-QAM	5	5120	35.6	49.8
6	Locked	SC-QAM	6	2560	40.4	50.3

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Responses

EG

Expert

•

111.4K Messages

3 years ago

Both the downstream and the upstream power levels are marginal and they may be intermittently fluctuating even farther to out of spec levels. 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 Radio Shack, Home Depot, Target, 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, 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 !

1

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user_379362

Visitor

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4 Messages

@EG Thank you very much for replying I really appreciate it! I replaced the two splitters leading to my modem (one outside and one inside) with wideband splitters (5-1670 MHz range). I have a MoCA system on my network so I can have hard-line connections upstairs for my personal computer. I will update if I am still having issues.

Side note: When I replaced the outside splitter I also noticed that I have what appears to be a very old POE filter connected to the splitter's input. I didn't need to install a POE filter for my MoCA system when I installed it a year or so ago so I might also need to replace that with a new one as well. The POE filter is directly upstream from my modem which is why I believe it may be an issue. I can post a full network diagram I have created if needed to show where it is located.

3 years ago

0

EG

Expert

•

111.4K Messages

3 years ago

So what do the signal stat figures look like now ?

1

0

U

user_379362

Visitor

•

4 Messages

@EG

Here are the Downstream, Upstream, and Event Logs from today. I replaced the splitter this morning around 8 after it went out again at about 7:30ish

Channel	Lock Status	Modulation	Channel ID	Freq. (MHz)	Pwr (dBmV)	SNR (dB)	Corrected	Uncorrected
1	Locked	QAM256	20	603.0	-6.7	36.8	0	0
2	Locked	QAM256	17	585.0	-5.6	37.6	0	0
3	Locked	QAM256	18	591.0	-5.8	37.7	0	0
4	Locked	QAM256	19	597.0	-6.1	37.6	0	0
5	Locked	QAM256	21	609.0	-6.9	37.0	0	0
6	Locked	QAM256	22	615.0	-7.0	36.9	0	0
7	Locked	QAM256	23	621.0	-6.6	37.3	0	0
8	Locked	QAM256	24	627.0	-6.1	37.6	0	0
9	Locked	QAM256	25	633.0	-6.2	37.8	0	0
10	Locked	QAM256	26	639.0	-6.7	37.5	0	0
11	Locked	QAM256	27	645.0	-7.0	37.2	0	0
12	Locked	QAM256	28	651.0	-7.3	37.0	0	0
13	Locked	QAM256	29	657.0	-6.6	37.2	0	0
14	Locked	QAM256	30	663.0	-6.3	37.5	0	0
15	Locked	QAM256	31	669.0	-5.9	37.8	0	0
16	Locked	QAM256	32	675.0	-5.9	37.5	0	0
17	Locked	QAM256	33	681.0	-5.9	37.6	0	0
18	Locked	QAM256	34	687.0	-6.0	37.4	0	0
19	Locked	QAM256	35	693.0	-6.1	37.4	0	0
20	Locked	QAM256	36	699.0	-5.6	37.5	0	0
21	Locked	QAM256	37	705.0	-5.3	38.0	0	0
22	Locked	QAM256	38	711.0	-5.5	38.1	0	0
23	Locked	QAM256	39	717.0	-5.6	38.1	0	0
24	Locked	QAM256	40	723.0	-6.2	37.7	0	0
25	Locked	QAM256	41	729.0	-6.2	37.5	0	0
26	Locked	QAM256	42	735.0	-6.1	37.7	0	0
27	Locked	QAM256	43	741.0	-6.1	37.8	0	0
28	Locked	QAM256	44	747.0	-5.4	38.2	0	0
29	Locked	QAM256	45	753.0	-5.3	38.5	0	0
30	Locked	QAM256	46	759.0	-5.6	38.2	0	0
31	Locked	QAM256	47	765.0	-6.1	37.9	0	0
32	Locked	OFDM PLC	48	805.0	-4.0	38.4	7649403	0

Channel	Lock Status	Channel Type	Channel ID	Symb. Rate (Ksym/sec)	Freq. (MHz)	Pwr (dBmV)
1	Locked	SC-QAM	1	2560	10.4	49.0
2	Locked	SC-QAM	2	5120	16.4	49.3
3	Locked	SC-QAM	3	5120	22.8	49.8
4	Locked	SC-QAM	4	5120	29.2	50.5
5	Locked	SC-QAM	5	5120	35.6	50.5
6	Locked	SC-QAM	6	2560	40.4	50.5

Time	Priority	Description
Time Not Established	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-VER=3.1;
Time Not Established	Critical (3)	No Ranging Response received - T3 time-out;CM-VER=3.1;
Time Not Established	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-VER=3.1;
Time Not Established	Critical (3)	No Ranging Response received - T3 time-out;CM-VER=3.1;
Time Not Established	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-VER=3.1;
Time Not Established	Critical (3)	No Ranging Response received - T3 time-out;CM-VER=3.1;
Time Not Established	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-VER=3.1;
Time Not Established	Critical (3)	No Ranging Response received - T3 time-out;CM-VER=3.1;
Time Not Established	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-VER=3.1;
Time Not Established	Critical (3)	No Ranging Response received - T3 time-out;CM-VER=3.1;
07:49:08 Wed Jun 29 2022	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-VER=3.1;
07:49:14 Wed Jun 29 2022	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-VER=3.1;
07:49:20 Wed Jun 29 2022	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-VER=3.1;
07:51:35 Wed Jun 29 2022	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-VER=3.1;
07:51:35 Wed Jun 29 2022	Critical (3)	Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-VER=3.1;
07:51:36 Wed Jun 29 2022	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-VER=3.1;
07:51:37 Wed Jun 29 2022	Critical (3)	Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-VER=3.1;
07:51:42 Wed Jun 29 2022	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-VER=3.1;
07:51:42 Wed Jun 29 2022	Critical (3)	Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-VER=3.1;
07:53:34 Wed Jun 29 2022	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-VER=3.1;
07:53:41 Wed Jun 29 2022	Critical (3)	SYNC Timing Synchronization failure - Loss of Sync;CM-VER=3.1;
07:53:57 Wed Jun 29 2022	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-VER=3.1;
07:54:02 Wed Jun 29 2022	Critical (3)	No Ranging Response received - T3 time-out;CM-VER=3.1;
Time Not Established	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-VER=3.1;
Time Not Established	Critical (3)	No Ranging Response received - T3 time-out;CM-VER=3.1;
08:30:38 Wed Jun 29 2022	Critical (3)	SYNC Timing Synchronization failure - Loss of Sync;CM-VER=3.1;
08:30:47 Wed Jun 29 2022	Critical (3)	No Ranging Response received - T3 time-out;CM-VER=3.1;
Time Not Established	Critical (3)	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-VER=3.1;
Time Not Established	Critical (3)	No Ranging Response received - T3 time-out;CM-VER=3.1;
Time Not Established	Notice (6)	Honoring MDD; IP provisioning mode = IPv6
11:33:23 Wed Jun 29 2022	Notice (6)	DS profile assignment change. DS Chan ID: 32; Previous Profile: ; New Profile: 1 2 3.;CM-VER=3.1;
11:33:44 Wed Jun 29 2022	Notice (6)	CM-STATUS message sent. Event Type Code: 24; Chan ID: 48; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: 0.;CM-VER=3.1;

3 years ago

0

EG

Expert

•

111.4K Messages

3 years ago

It's still N/G. If there is nothing more that can be done to improve the connection quality, then you'll need a tech visit as stated.

Bear in mind that if the premises facing techs can not find or fix a problem at your home, it is they who are responsible for escalating it to their line / network / maintenance dept. techs. The problem may lie beyond your home in the local neighborhood infrastructure somewhere but it is their S.O.P. to start at the home. And if the problem is found to be on their side of the demarcation point, there will not be any charge.

Good luck !

3

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user_379362

Visitor

•

4 Messages

@EG I appreciate you trying to help me solve this. I will contact Xfinity this week and see when they can get someone out here to take a look.

Thanks!

3 years ago

CCDaryl

Problem Solver

•

828 Messages

@user_379362

Thank you for sharing your experience with us in the Forums. I see that you have been given some great advice from EG. If you need to set up a technician appointment, we are happy to accomodate. If you would like to set that up through here, just send us a direct message with your full name and address. You can send us a direct message but making sure you are first logged in to the Forums. After that, click on the "Chat" icon in the upper right (left of the notification bell), next click on the "pen/pad" icon, and lastly choose Xfinity Support. Thank you again for the time you have spent sharing your situation.

I no longer work for Comcast.

3 years ago

EG

Expert

•

111.4K Messages

@user_379362 Quite welcome !

I am not a Comcast Employee.
I am a Customer Expert volunteering my time to help other customers here in the Forums.
We ask that you post publicly so people with similar questions may benefit from the conversation.

Was your question answered? Please mark an Accepted Answer! tick

3 years ago

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Your Home Network

user_379362

Motorola MB8611 keeps losing connection and rebooting throughout the day

EG

user_379362

EG

user_379362

EG

user_379362

CCDaryl

EG

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