intermittent cable modem resets caused by signal drop
Hello all
Here's the lengthy status of my current problems with cox cable modem dropping.
Cable modem SB6121 will lose connectivity and reset, going down to one light, then rebuilding the connection after about a one minute outage. Happens regularly and randomly.
Here's an example of the logs found in the motorola cable modem. If you haven't checked your own cable modem logs and you're having this problem, here's the link to prove you're having the same problem as me: http://192.168.100.1/cmLogs.htm . I xxx'd out my MAC addresses in the logs.
| Jun 20 2012 01:57:47 | 6-Notice | I401.0 | TLV-11 - unrecognized OID;CM-MAC=xxxx;CMTS-MAC=xxxx;CM-QOS=1.1;CM-VER=3.0; |
| Jun 20 2012 01:57:46 | 5-Warning | D04.1 | ToD request sent - No Response received;CM-MAC=xxxx;CMTS-MAC=xxx;CM-QOS=1.1;CM-VER=3.0; |
| Jun 20 2012 01:57:34 | 3-Critical | R02.0 | No Ranging Response received - T3 time-out;CM-MAC=xxx;CMTS-MAC=xxx;CM-QOS=1.1;CM-VER=3.0; |
| Jun 20 2012 01:57:30 | 4-Error | T201.0 | Missing Mandatory MDD TLV on primary DS Channel;CM-MAC=xxx;CMTS-MAC=xxx;CM-QOS=1.1;CM-VER=3.0; |
When it comes to signal strength, this is apparently not the problem.
Here's what motorola says should be fine, according to Motorola Tech Support:
Downstream Signal to Noise Ratio (SNR): 25 dB or greater
Downstream Power Level: +15 to -15dBmV
Upstream Transmit Power Level: less than 58dBmV
My values, pasted from http://192.168.100.1/cmSignal.htm. I've sampled these values over time and they have never strayed much from these numbers.
| downstream Signal to Noise Ratio | 38 dB | 38 dB | 38 dB | 38 dB |
| downstream Power Level | 1 dBmV | 0 dBmV | 0 dBmV | 0 dBmV |
| upstream Power Level | 44 dBmV |
After multiple lengthy calls with Motorola Tech Support, who are surprisingly helpful, they told me that this problem is definitely at the service provider end (Cox), with the signal dropping out on the modem. They offered for free to replace my old Motorola SB6120 with a new SB6121, saying they're only doing this to prove that the cable modem isn't the problem, and to aide my case for Cox to fix it.
Now, I've been receiving these random restarts (which sometimes occur in bursts of 3-4 per hour) since I lived at my prior residence, three blocks away from my new place in the same neighborhood.
So, in summary.
Cable modem random restarts resulting in 1 minute outages.
Two different cable modems.
Two different HOUSES in the same neighborhood.
Signal strength to the cable modem is NOT a problem.
What does Cox do?
Schedule another technician to come out. The last scheduled appointment on Thursday from 5-7pm didn't call, didn't show. Got another one scheduled on Monday. We'll see.
I'm posting this because if anyone else has the same problems, they should check their Motorola cable modem logs and signal strengths and post here.
Terse-
It's not solved as in Cox has actually stopped dropping Docsis 3.0 modems when they switch frequencies.
It's solved as in Cox can manually set your modem to a single frequency, preventing it from using the find-best-frequency feature of Docsis 3.0.
So it's a total hack, we're not getting the performance we're paying for, but it works. I've had zero problems with cable modem connection since that one nice technician admitted the problem and fixed it for me.
