I've been experiencing an issue for a while now, with my modem constantly restarting itself... at least a dozen times a day I would estimate; when it's really bad it can be every 5-10 minutes for an hour. I've seen other threads on this, but the solutions provided (upstream signal too high, remove splitters, etc.) don't seem directly relevant to me.
- This has been somewhat of an ongoing problem ever since I've lived in this locaiton (about 2 years), from what I can remember. It did seem to cease entirely for about a year, but it's started back up within the last 6 months or so, and either it's gotten much worse in the last 1-2 months or I've simply lost patience with it, because it does seem to be excessively bad recently.
- My modem is a Motorola SB6141. It is relatively new - I was having connection issues with my previous modem, but since it was about 7 years old at that point I though it might be an issue with the modem itself and replaced it. I bought it myself, I don't lease it through Comcast. The frequency of connection issues didn't really change.
- My upstream/downstream power levels seem to consisently be within spec - they always are when I check the modem's status page at least, which is every time that I notice or suspect the modem has restarted.
- The coax cable it's connected to comes into that room directly from outside, and from outside I can see it runs down the exterior wall into the ground. I do have 2 other cable lines in my house, but neither of them work. I suspect they're not even connected to the outside line at all. If there's a splitter on the line, it's not inside the house and it's somewhere I can't see it. I do not have TV service, only internet, so it's only that one cable that's in use.
- I don't seem to be having any kind of speed issues. It seems I have the 'performance tier' plan and my speed tests seem to match up with that... I get around 25/4.
- My modem logs only keep around 20 entries and the entire fail/reboot sequence takes up about 10 so it's hard to see exactly how often this happens. It does happen when I'm not at the computer. I see the same error messages over and over, though I don't know if they're always the same exact number of messages in the same exact order.
- I had an 8db attenuator on the coax cable that I only noticed was there last month. I have no idea who put it there, or when, or why, but I took it off in the hopes that that was what was causing the issues. It made my signal strength numbers fall closer to the middle of the acceptible spectrum, and gave me 3 upstream channels instead of 1, but other than that had no effect.
Here's my log. The last entry here was just a minute ago.
Jul 13 2014 11:32:07 | 3-Critical | R02.0 | No Ranging Response received - T3 time-out;CM-MAC=;CMTS-MAC=;CM-QOS=1.1;CM-VER=3.0; Jul 13 2014 10:33:57 | 3-Critical | R06.0 | Unicast Maintenance Ranging attempted - No response - Retries exhausted;CM-MAC=;CMTS-MAC=;CM-QOS=1.1;CM-VER=3.0; Jul 13 2014 10:33:57 | 3-Critical | R03.0 | Ranging Request Retries exhausted;CM-MAC=;CMTS-MAC=;CM-QOS=1.1;CM-VER=3.0; Jul 13 2014 10:33:56 | 3-Critical | R02.0 | No Ranging Response received - T3 time-out;CM-MAC=;CMTS-MAC=;CM-QOS=1.1;CM-VER=3.0; Jul 13 2014 09:59:47 | 5-Warning | Z00.0 | MIMO Event MIMO: Stored MIMO=-1 post cfg file MIMO=-1;CM-MAC=;CMTS-MAC=;CM-QOS=1.1;CM-VER=3.0; Jan 01 1970 00:00:26 | 3-Critical | R02.0 | No Ranging Response received - T3 time-out;CM-MAC=;CMTS-MAC=;CM-QOS=1.1;CM-VER=3.0; Jan 01 1970 00:00:15 | 6-Notice | N/A Cable Modem Reboot due to T4 timeout ;CM-MAC=;CMTS-MAC=;CM-QOS=1.1;CM-VER=3.0; Jul 13 2014 09:58:48 | 3-Critical | R04.0 | Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=;CMTS-MAC=;CM-QOS=1.1;CM-VER=3.0; Jul 13 2014 09:58:16 | 3-Critical | R02.0 | No Ranging Response received - T3 time-out;CM-MAC=;CMTS-MAC=;CM-QOS=1.1;CM-VER=3.0; Jul 13 2014 09:58:06 | 3-Critical | R06.0 | Unicast Maintenance Ranging attempted - No response - Retries exhausted;CM-MAC=;CMTS-MAC=;CM-QOS=1.1;CM-VER=3.0; Jul 13 2014 09:58:06 | 3-Critical | R03.0 | Ranging Request Retries exhausted;CM-MAC=;CMTS-MAC=;CM-QOS=1.1;CM-VER=3.0; Jul 13 2014 09:58:04 | 3-Critical | R02.0 | No Ranging Response received - T3 time-out;CM-MAC=;CMTS-MAC=;CM-QOS=1.1;CM-VER=3.0; Jul 13 2014 09:44:42 | 5-Warning | Z00.0 | MIMO Event MIMO: Stored MIMO=-1 post cfg file MIMO=-1;CM-MAC=;CMTS-MAC=;CM-QOS=1.1;CM-VER=3.0; Jan 01 1970 00:00:25 | 3-Critical | R02.0 | No Ranging Response received - T3 time-out;CM-MAC=;CMTS-MAC=;CM-QOS=1.1;CM-VER=3.0; Jan 01 1970 00:00:15 | 6-Notice | N/A Cable Modem Reboot due to T4 timeout ;CM-MAC=;CMTS-MAC=;CM-QOS=1.1;CM-VER=3.0; Jul 13 2014 09:43:42 | 3-Critical | R04.0 | Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=;CMTS-MAC=;CM-QOS=1.1;CM-VER=3.0; Jul 13 2014 09:43:12 | 3-Critical | R02.0 | No Ranging Response received - T3 time-out;CM-MAC=;CMTS-MAC=;CM-QOS=1.1;CM-VER=3.0; Jul 13 2014 09:43:08 | 3-Critical | R06.0 | Unicast Maintenance Ranging attempted - No response - Retries exhausted;CM-MAC=;CMTS-MAC=;CM-QOS=1.1;CM-VER=3.0; Jul 13 2014 09:43:08 | 3-Critical | R03.0 | Ranging Request Retries exhausted;CM-MAC=;CMTS-MAC=;CM-QOS=1.1;CM-VER=3.0; Jul 13 2014 09:43:07 | 3-Critical | R02.0 | No Ranging Response received - T3 time-out;CM-MAC=;CMTS-MAC=;CM-QOS=1.1;CM-VER=3.0;
Downstream signal:
Frequency 651000000 Hz 657000000 Hz 663000000 Hz 669000000 Hz Signal to Noise Ratio 36 dB 35 dB 35 dB 35 dB Downstream Modulation QAM256 QAM256 QAM256 QAM256 Power Level -2 dBmV -3 dBmV -3 dBmV -3 dBmV
Frequency 675000000 Hz 681000000 Hz 687000000 Hz 693000000 Hz Signal to Noise Ratio 35 dB 36 dB 36 dB 36 dB Downstream Modulation QAM256 QAM256 QAM256 QAM256 Power Level -3 dBmV -3 dBmV -3 dBmV -3 dBmV
Upstream signal:
Frequency 29400000 Hz 36200000 Hz 22000000 Hz
Ranging Service ID 12979 12979 12979
Symbol Rate 5.120 Msym/sec 5.120 Msym/sec 2.560 Msym/sec
Power Level 39 dBmV 39 dBmV 38 dBmV
Upstream Modulation [3] QPSK [3] QPSK [3] QPSK
[3] 64QAM [3] 64QAM [2] 16QAM
[3] 64QAM
Ranging Status Success Success Success
It seems to me that "on paper", there is nothing wrong... yet clearly there is something wrong. I have never contacted Comcast support about this directly because I am not confident in my ability to extract any useful help out of the phone-answerer.