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Modem constantly dropping internet connection - Comcast

Frankentek

Reputable
Feb 14, 2015
2
0
4,510
0
Hello,

I'm not sure if I"m posting this in the right section or not, but I figured networking was the best way to go until somebody adjusts otherwise.

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:
Motorola Surfboard SB6121
Netgear N600 Dual-Band Router - WNDR3700v4

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 as best as I could. I posted this on another forum, but got absolutely nowhere as there were over 100 views but only one reply saying "contact Comcast to replace your modem". Even though this modem was supplied by myself since I refuse to pay $10 a month to rent one. I greatly appreciate any insight any of you have to offer and will furnish other information if it is needed.

Thank you
 

Clayto1332

Reputable
Feb 10, 2015
151
0
4,710
19
Sounds a whole lot like your cable modem is defective or not compatible. "Contact Comcast to replace your modem" is unbelievably good and spot-on advice however their service up to your residence might be bad. Did you purchase this modem recently? Was it working for some time before having these problems? Are you putting things on or around the modem that might be causing it to overheat?

A quick look at Comcast folks like yourself that don't want to lease say this is your best option:

http://www.amazon.com/gp/product/B00AJHDZSI/ref=ox_sc_act_title_1?ie=UTF8&psc=1&smid=ATVPDKIKX0DER
 

Frankentek

Reputable
Feb 14, 2015
2
0
4,510
0
Thank you for actually replying. I will address your comments in order.

1.) This is a compatible modem since I took it to other friends locations who have comcast and it works fine and it is also on their list of compatible modems.

2.) This modem is about a year old and has been working flawlessly until this issue started occurring which is about a month ago

3.) The modem is currently sitting by itself next to the router and nothing is preventing it from getting a decent airflow and it doesn't feel warm or hot to the touch so I don't believe it to be overheating.
 

Clayto1332

Reputable
Feb 10, 2015
151
0
4,710
19
Have you tried it at your friends house since you have been having problems?

Looking at your logs it looks like your connection is dropping and your modem automatically reboots to try to fix. Not sure if you are in a house, apartments, dorm or what have you but bad or weak coax terminations can cause internet problems. If you raise enough hell, Comcast might re-terminate or run new cable from the telephone pole to you (you may or may not have a demarcation outside your building, this is where their responsibility stops and yours starts). If you do have a demarc, you might possibly try plugging your modem straight into it and see if it times out and boots like it does inside. If all is good outside, this would point to the inside wiring which would be your responsibility. Coax tools are cheap and it is pretty easy to watch videos and research on the internet how to terminate. I had two dead coax drops in my house when I bought it and I had to terminate one and run a new cable from the wall outlet to the main splitter near my satellite service.

 

Ryan C

Reputable
Jun 25, 2015
1
0
4,510
0
I have the exact same issue. SB6121 on Comcast and the N600 WNDR3700v3. And the modem is about a year old, I also refuse to rent a modem, and the problem started around the same time as yours. At first, I would never get the internet light to start up, and the light above it would just blink endlessly. Finally I called Comcast and they did their magic and voila. Til the next day.

Now I get all my lights on so it appears as if I have internet. However, whenever a device is plugged in the connection logo blinks endlessly. Have tried hooking it up directly to the computer to no avail. The logs that you have reported are exactly like mine. I've read one forum where it said the end result was for the foreman to replace the lines leading to his house because apparently they were chewed on by some squirrel. Bizarre. The problem is, my lines are underground. And apparently that forum guy came to that conclusion after 8 appointments with Comcast technicians. So, I suppose I'll just call Comcast again. What else am I going to do?

Please let me know if you've come to a resolution at this point. Thank you

(I'm typing this using my phone's hotspot)
 

switlikbob

Reputable
Jul 30, 2015
1
0
4,510
0
I hate to say it, but I have comcast, the same cable modem, and same problems. They started today. They are sending someone to check the lines, and hopefully someone to swap out cable modem to test.

Jul 30 2015 20:10:14 3-Critical R02.0 No Ranging Response received - T3 time-out;CM-MAC=a4:7a:a4:b7:eb:6f;CMTS-MAC=00:01:5c:22:7e:d2;CM-QOS=1.1;CM-VER=3.0;
Jul 30 2015 20:10:13 5-Warning Z00.0 MIMO Event MIMO: Stored MIMO=-1 post cfg file MIMO=-1;CM-MAC=a4:7a:a4:b7:eb:6f;CMTS-MAC=00:01:5c:22:7e:d2;CM-QOS=1.1;CM-VER=3.0;

 

Alex_88

Reputable
Nov 9, 2015
1
0
4,510
0
SAME PROBLEM.... SOLVED!!!!

I had the same issue starting 10 days ago.

The internet connection to the xfinity modem started to come and go, each time it went it would be out longer. I dealt with tech support both on the phone and via chat (with my phone), they rebooted, reset etc, nothing.. They said i had a perfect signal and bad modem.

Monday i went to the comcast office just a few blocks from me and swapped out the modem for a new one. Worked for an hour or so and went out again. Swapped it out 3 more times and called tech support to send out a technician. The technician showed up the next day and said the modems needed a software update which he performed. He told me that of the 500 xfinity modems they get in each batch easily 200 of them are bad and that it was a crap shoot. The modem worked and he left. Thirty minutes later the internet connection went out again. I promptly went back and swapped it out for another modem thinking it was just bad luck and was getting all the bad ones.

Nothing, the new (5th) modem had connection issues too.

PROBLEM SOLVED WHEN....A couple hours later i figured it had to be the connection from the street to my house. So i put the ladder up a tree close enough to the line where i could reach it and shake the heck out of it... when i say shake i mean little girl playing jump rope with it shaking.

It's been 3 days and the connection hasn't dropped once.

Maybe i'm just lucky, but i think the weak link in the cable modem signal to your house is the one sitting out in the rain above your house. If the issue ever comes back i'll have a technician come back and make him disconnect, clean and reconnect the line to the house from the street.


hope this helps

 

Rochelle_1

Commendable
Mar 22, 2016
1
0
1,510
0



Long time issues with Comcast. My experience is that:

1.) Installers, do just that install. They will get things up and running but soon there may be issues that crop up.

2.) Service technicians, are the fine tuners of equipment - Cables, Signal Amplifiers, Filters, Interference

3.) After 4 years of trouble shooting multiple rental properties these are the things to have Service Tech look into

a. Connectors are properly installed on coaxial cable (ours were not cut correctly)
b. Too many outlets connected to your cable (needed an amplifier) 5 televisions, phone, internet ~ Smart TV's pull internet and cable connections
c. If they install a signal amplifier in the box, you will also need a filter (they fine tune the amplified signal - over amplifying causes interference)
d. Modems to need replacement, from time to time. Even top of the line Motorola Surfboards. When you have multiple crashes or reboots a week, plan on once a year replacements.

4.) Ask Comcast to monitor the drops on your modem for a week. This will escalate the issue and they will respond. If you have the 2 in one phone / wireless gateway the documented fail rate is 6 in 10. You will need to keep trying till you get one that is not defective.

Good Luck!
 

housey

Commendable
Jul 31, 2016
1
0
1,510
0


 

Fred_49

Prominent
Apr 6, 2017
1
0
510
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I HAVE SAME PROBLEM WITH COMCAST
MY INTERNET KEEPS LOSING CONNECTION
I HAVE THE COMCAST GATEWAY MODEM WITH TELEPHONE
ARRIS MODEL TG1682G
COMCAST TRIED TO SAY IT WAS MY MOCA SETTINGS
SO THEY TURN THAT OFF BUT I STILL KEEP LOSING CONNECTIONS AT TIMES




 

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