U

Visitor

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8 Messages

Tue, Sep 20, 2022 1:00 PM

Motorola MB8611 Randomly and Continuously Drops Connection

First I want to make it clear this is NOT a router/wireless question. Those are working just fine. However, I recently swapped out an older Netgear Modem for a newer Motorola MB8611 modem to set myself up for future >1 Gbps service. However, this new modem appears to drop and reset the connection multiple times a day at random intervals. While it is resetting I cannot access the modem but once it comes back up I always see CRITICAL alerts in the event log.

Critical (3)    SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=00:XX:XX:XX:XX:XX;CMTS-MAC=00:00:00:00:00:00;CMQOS=1.1;CM-VER=3.1;
Critical (3)    No Ranging Response received - T3 time-out; CMMAC=00:XX:XX:XX:XX:XX;CMTS-MAC=00:XX:XX:XX:XX:XX;CMQOS=1.1;CM-VER=3.1;
Critical (3)    SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=00:XX:XX:XX:XX:XX;CMTS-MAC=00:00:00:00:00:00;CMQOS=1.1;CM-VER=3.1;
Critical (3)    Started Unicast Maintenance Ranging - No Response received - T3 timeout; CM-MAC=00:XX:XX:XX:XX:XX;CMTS-MAC=00:XX:XX:XX:XX:XX;CMQOS=1.1;CM-VER=3.1;
Critical (3)    Started Unicast Maintenance Ranging - No Response received - T3 timeout; CM-MAC=00:XX:XX:XX:XX:XX;CMTS-MAC=00:XX:XX:XX:XX:XX;CMQOS=1.1;CM-VER=3.1;
Critical (3)    Started Unicast Maintenance Ranging - No Response received - T3 timeout; CM-MAC=00:XX:XX:XX:XX:XX;CMTS-MAC=00:XX:XX:XX:XX:XX;CMQOS=1.1;CM-VER=3.1;
Critical (3)    Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out; CMMAC=00:XX:XX:XX:XX:XX; CMTS-MAC=00:0X:XX:XX:XX:XX; CMQOS=1.1;CM-VER=3.1;
Critical (3)    SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=00:XX:XX:XX:XX:XX;CMTS-MAC=00:00:00:00:00:00; CMQOS=1.1;CM-VER=3.1;
Critical (3)    No Ranging Response received - T3 time-out; CMMAC=00:XX:XX:XX:XX:XX; CMTS-MAC=00:XX:XX:XX:XX:XX; CMQOS=1.1;CM-VER=3.1;
Notice (6)     Honoring MDD; IP provisioning mode = IPv6

The previous Netgear modem did not have disconnect issues. It was very stable. Although I had been experiencing some increased latency lately. I am wondering if there is some sort of provisioning error or if this modem is faulty.

I have the complete event log and connection screens in PDF files if they are needed.

Also I note that this problem seems to be common to the MB8611 modem but none of the other posts really have any solutions I can try myself. This house was built in 2006 and the cable infrastructure was put in place at the same time. There are no splitters on the line (at least within the house).

EG

Expert

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96.9K Messages

3 months ago

Please also copy all of the text in its entirety of the *Downstream Power Levels*, the *SNR's* (Signal to Noise Ratios), and the *Upstream Power Level* numbers and paste them into your next post.

Visitor

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8 Messages

3 months ago

Above are my power levels after the modem reset

(edited)

Visitor

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8 Messages

3 months ago

And again as of right now (3 hrs later)

(edited)

EG

Expert

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96.9K Messages

3 months ago

In the second set of pics, some of the downstream channel SNR values are too low / out of spec. It looks like you have intermittent spurious noise at those channel frequencies leaking into the lines somewhere. The large number of uncorrected bit errors and the error log entries confirm that something is going on.  It may be best to get a tech to come out and investigate / find the source of the problem and correct it. Good luck with it !

(edited)

Visitor

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8 Messages

@EG​ Thanks. I scheduled an appointment

EG

Expert

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96.9K Messages

3 months ago

@user_f80d18 

My pleasure ! Please post back here with how things turn out, thanks.

Visitor

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8 Messages

3 months ago

So some back and forth and things are not perfect but much improved. The junction box at street side, was run over by my neighbor backing out of their driveway and some of the components contained within were smashed. They replaced those and things improved greatly.

I have gone from 16+ resets a day down to maybe one or two. 

EG

Expert

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96.9K Messages

3 months ago

@user_f80d18 

Thanks for posting back ! For curiosity, what do the signal stats look like now ?

Visitor

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8 Messages

3 months ago

Still pretty poor but slightly better

CCLuis

Problem Solver

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493 Messages

Greetings, @user_f80d18. Thank you for taking the time to keep us updated on the matter. I was reading through your posts and I wanted to ask, have you trie testing your old (Netgear) modem to see if the issues persist? If so, did you see any further improvements in the status of your connection?

I no longer work for Comcast

EG

Expert

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96.9K Messages

3 months ago

Some of the SNR's are still on the low side, and there's a large number of uncorrected bit errors. Looks like more work needs to be done....

Visitor

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8 Messages

2 months ago

So something changed on Saturday and I have no idea what it was. However, I have had a stable connection now for almost 6 days which is a far cry from the connection resets every 2 to 4 hrs before.

So I wish I could tell you what I did or what comcast did but I have no idea. :( But it did not require anyone to come out to the house.

Visitor

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1 Message

2 months ago

I am having the same issue too. Connection keeps dropping 5-6 times in an hour.I called them at least 20 times this month and they keep telling me that it is a glitch or signal leakeage. They sent dozens of technician to my house and the problem persists. 

Maybe it's a modem thing. I am going to try a new modem

Visitor

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8 Messages

1 month ago

So this issue came back. And got progressively worse with time. I reverted back to my older NetGear modem and have had zero issues since. I highly suspect that the Motorola Modem is much more sensitive or has some sort of bug where it is resetting under certain circumstances. 

EG

Expert

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96.9K Messages

@user_f80d18​ 

I must agree with that ! We've been seeing many many posts here lately about the 8611 having good signal status values but accumulating many errors and spontaneous re-booting. Seem that it doesn't play nice with Comcast.......

(edited)

I am not a Comcast Employee.
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