# Modem constantly dropping internet connection - Comcast



## Scythe Studios (Jul 24, 2012)

Good Evening,

Normally, I would consider myself a solid troubleshooter as I'm pretty familiar with desktops and PC's. However, the field of networking is completely foreign to me. I'm having this issue and it has got me totally stumped. My cable modem is always power cycling itself. This happens a couple times a day and I have no idea why. I've contacted Comcast on several occasions and usually they "rest the settings" remotely which will "resolve" the problem and they are confident in that fix, but it never lasts. I've tried multiple/different Coaxial cables and splitters, eliminating the router and just plugging directly from the modem to the desktop, but to no avail it is still power cycling.

With my inability to resolve the issue, I am hoping someone here can help me find a solution. I will be as detailed as possible with my hardware and the logs from my cable modem itself.


```
My Hardware:
[URL="http://www.amazon.com/ARRIS-Motorola-SurfBoard-SB6121-DOCSIS/dp/B004XC6GJ0/ref=sr_1_1?ie=UTF8&qid=1423878262&sr=8-1&keywords=Motorola+Surfboard+sb+6121"]Motorola Surfboard SB6121[/URL]
[URL="http://www.amazon.com/NETGEAR-Wireless-Router-Gigabit-WNDR3700/dp/B002HWRJY4/ref=sr_1_1?ie=UTF8&qid=1423878361&sr=8-1&keywords=WNDR3700v4"]Netgear N600 Dual-Band Router - WNDR3700v4[/URL]
```


```
Logs from the cable modem:
Feb 13 2015 18:25:24	3-Critical	R02.0	No Ranging Response received - T3 time-out;CM-MAC=7c:bf:b1:d8:a4:86;CMTS-MAC=00:01:5c:64:14:56;CM-QOS=1.1;CM-VER=3.0;
Feb 13 2015 18:25:23	5-Warning	Z00.0	MIMO Event MIMO: Stored MIMO=-1 post cfg file MIMO=-1;CM-MAC=7c:bf:b1:d8:a4:86;CMTS-MAC=00:01:5c:64:14:56;CM-QOS=1.1;CM-VER=3.0;
Jan 01 1970 00:00:23	3-Critical	R02.0	No Ranging Response received - T3 time-out;CM-MAC=7c:bf:b1:d8:a4:86;CMTS-MAC=00:01:5c:64:14:56;CM-QOS=1.1;CM-VER=3.0;
Jan 01 1970 00:00:14	6-Notice	N/A	Cable Modem Reboot due to T4 timeout ;CM-MAC=7c:bf:b1:d8:a4:86;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.0;
Feb 13 2015 18:24:30	3-Critical	R06.0	Unicast Maintenance Ranging attempted - No response - Retries exhausted;CM-MAC=7c:bf:b1:d8:a4:86;CMTS-MAC=00:01:5c:64:14:56;CM-QOS=1.1;CM-VER=3.0;
Feb 13 2015 18:24:30	3-Critical	R03.0	Ranging Request Retries exhausted;CM-MAC=7c:bf:b1:d8:a4:86;CMTS-MAC=00:01:5c:64:14:56;CM-QOS=1.1;CM-VER=3.0;
Feb 13 2015 18:24:29	3-Critical	R02.0	No Ranging Response received - T3 time-out;CM-MAC=7c:bf:b1:d8:a4:86;CMTS-MAC=00:01:5c:64:14:56;CM-QOS=1.1;CM-VER=3.0;
Feb 13 2015 18:24:01	3-Critical	R06.0	Unicast Maintenance Ranging attempted - No response - Retries exhausted;CM-MAC=7c:bf:b1:d8:a4:86;CMTS-MAC=00:01:5c:64:14:56;CM-QOS=1.1;CM-VER=3.0;
Feb 13 2015 18:24:01	3-Critical	R03.0	Ranging Request Retries exhausted;CM-MAC=7c:bf:b1:d8:a4:86;CMTS-MAC=00:01:5c:64:14:56;CM-QOS=1.1;CM-VER=3.0;
Feb 13 2015 18:24:00	3-Critical	R02.0	No Ranging Response received - T3 time-out;CM-MAC=7c:bf:b1:d8:a4:86;CMTS-MAC=00:01:5c:64:14:56;CM-QOS=1.1;CM-VER=3.0;
Feb 13 2015 18:23:26	3-Critical	R06.0	Unicast Maintenance Ranging attempted - No response - Retries exhausted;CM-MAC=7c:bf:b1:d8:a4:86;CMTS-MAC=00:01:5c:64:14:56;CM-QOS=1.1;CM-VER=3.0;
Feb 13 2015 18:23:26	3-Critical	R03.0	Ranging Request Retries exhausted;CM-MAC=7c:bf:b1:d8:a4:86;CMTS-MAC=00:01:5c:64:14:56;CM-QOS=1.1;CM-VER=3.0;
Feb 13 2015 18:23:25	3-Critical	R02.0	No Ranging Response received - T3 time-out;CM-MAC=7c:bf:b1:d8:a4:86;CMTS-MAC=00:01:5c:64:14:56;CM-QOS=1.1;CM-VER=3.0;
Feb 13 2015 18:23:04	3-Critical	R06.0	Unicast Maintenance Ranging attempted - No response - Retries exhausted;CM-MAC=7c:bf:b1:d8:a4:86;CMTS-MAC=00:01:5c:64:14:56;CM-QOS=1.1;CM-VER=3.0;
Feb 13 2015 18:23:04	3-Critical	R03.0	Ranging Request Retries exhausted;CM-MAC=7c:bf:b1:d8:a4:86;CMTS-MAC=00:01:5c:64:14:56;CM-QOS=1.1;CM-VER=3.0;
Feb 13 2015 18:23:02	3-Critical	R02.0	No Ranging Response received - T3 time-out;CM-MAC=7c:bf:b1:d8:a4:86;CMTS-MAC=00:01:5c:64:14:56;CM-QOS=1.1;CM-VER=3.0;
Feb 13 2015 17:59:28	5-Warning	Z00.0	MIMO Event MIMO: Stored MIMO=-1 post cfg file MIMO=-1;CM-MAC=7c:bf:b1:d8:a4:86;CMTS-MAC=00:01:5c:64:14:56;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=7c:bf:b1:d8:a4:86;CMTS-MAC=00:01:5c:64:14:56;CM-QOS=1.1;CM-VER=3.0;
Jan 01 1970 00:00:14	6-Notice	N/A	Cable Modem Reboot due to T4 timeout ;CM-MAC=7c:bf:b1:d8:a4:86;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.0;
Feb 13 2015 17:58:17	3-Critical	R06.0	Unicast Maintenance Ranging attempted - No response - Retries exhausted;CM-MAC=7c:bf:b1:d8:a4:86;CMTS-MAC=00:01:5c:64:14:56;CM-QOS=1.1;CM-VER=3.0;
```


```
Information from signal page on modem:
Channel ID	11 	12 	13 	16 
Frequency	615000000 Hz 	621000000 Hz 	627000000 Hz 	645000000 Hz 
Signal to Noise Ratio	36 dB 	36 dB 	36 dB 	36 dB 
Downstream Modulation	QAM256 	QAM256 	QAM256 	QAM256 
Power Level
The Downstream Power Level reading is a snapshot taken at the time this page was requested. Please Reload/Refresh this Page for a new reading
4 dBmV  	4 dBmV  	4 dBmV  	4 dBmV  
Upstream	Bonding Channel Value
Channel ID	36 	33 	34 	35 
Frequency	17300000 Hz 	36500000 Hz 	30100000 Hz 	23700000 Hz 
Ranging Service ID	9137 	9137 	9137 	9137 
Symbol Rate	5.120 Msym/sec 	5.120 Msym/sec 	5.120 Msym/sec 	5.120 Msym/sec 
Power Level	44 dBmV 	46 dBmV 	45 dBmV 	44 dBmV 
Upstream Modulation	[3] QPSK
[3] 64QAM
 	[3] QPSK
[3] 64QAM
 	[3] QPSK
[3] 64QAM
 	[3] QPSK
[3] 64QAM
 
Ranging Status	Success 	Success 	Success 	Success 
Signal Stats (Codewords)	Bonding Channel Value
Channel ID	11 	12 	13 	16 
Total Unerrored Codewords	63184695 	62048320 	62048497 	62048588 
Total Correctable Codewords	149 	9 	11 	8 
Total Uncorrectable Codewords	1597 	554 	515 	579
```

I formatted the information and post as best as I could. If there's any further questions or information any of you need from me to help me out, I would gladly provide it. I appreciate any insight that anyone has to offer.

Thank you in advance.


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## Old Rich (May 31, 2007)

Have you asked Comcast to replace the modem? . . they are usually willing to do that


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## Scythe Studios (Jul 24, 2012)

Well, Comcast wants me to pay $10 a month to rent a modem from them. I said forget that and bought my own modem that was on their approved list. I have neighbors and friends with the same modem who aren't having any issue. When I bring the modem to their house, the modem doesn't power cycle itself like it does for me and works as it should.


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## Scythe Studios (Jul 24, 2012)

Really? Over 90 views and only one person replies?


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## abdol (Feb 8, 2015)

Ask Comcast to send tech to make sure all your fitting and splitter and the signal good in your house and to change the port at the tap outside. Thanks


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## cgc018 (Jan 22, 2012)

Greetings!

Whenever you say that your modem is power cycling itself, are the lights on the modem blinking and it is losing all power and then coming back on?

Would it be possible for you to get another modem to test? 

Can you plug the modem into a different electrical socket to see if it power cycles itself there as well?


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## Old Rich (May 31, 2007)

What is the Modem plugged into? have you tried a different wall plug?


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## Fred Garvin (Sep 4, 2010)

I would look into your coax wiring from the pole to your modem, including any splitters or filters. If the wiring is old, it may even be RG59 instead of RG6. Comcast will probably have to do that for you since you'd need a meter to test the lines. The SnR at your modem seems to be at the bottom of the threshold which would indicate line noise. That will result in more packet retransmission which you'll see as disconnects or delays.


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