# Comcast Cable Modem Problem



## Dartmanrod (Oct 21, 2005)

I am a long time Comcast customer in NW Indiana and have experienced a major drop in service since August 8th. I have had 6 technician vists, 3 linesman visits, 2 line technician visits, and the head of the local Comcast office out twice. I have covered most everything I can think of, so I now ask for your help. My original modem was a Motorola Surfboard model SB5120. That has been replaced not once, not twice, not thrice, but four times. I now have a Motorola Surfboard model SB5101.

My old modem logs were displaying this error message:
Received Response to Broadcast Maintenance Request, but no Unicast Maintenance opportunities received - T4 timeout
It would then cycle through the lights on the front and after 10-15 seconds I would be back online. Unfortunately this would happen every 3 to 5 minutes. Also, I do not have the exact signal-to-noise DB numbers from the old modem.

The techs that were out have replaced the terminator block on the mainline, the cable going under the street, the cable from the street to my house, and the cable from inside the house to the modem. There is one splitter on the line where a second drop comes into my house for digital cable TV. (which has worked flawlessly the entire time)

The current modem logs show this error message:
2005-10-21 01:17:27	3-Critical	R005.0	Started Unicast Maintenance Ranging - No Response received - T3 time-out
This message appears over and over again with a different time stamp. Even though it is happening about every 3 to 5 minutes I do not see the lights cycle on the front of the modem. However, my downloads are interrupted constantly so I know I am losing connection.

Here is the current firmware version and a snapshot of the signal numbers:
Software Version: SB5101-2.4.1.6-SCM02-NOSH
Hardware Version: 1
MIB Version: II
GUI Version: 1.0

Frequency	711000000 Hz
Signal To Noise Ratio	35.7 dB
Power Level	1.7 dBmV

Channel ID	8
Frequency	24000000 Hz
Power	37.0 dBmV

I have tried every scenario possible. Up until August I had been running a USR wireless router just fine. I have tried a new Netgear router, I have tried not using any router at all, I have even unplugged the ethernet cable from the back of the modem and it still "cycles" on its own. The folks at Comcast have admittedly said they do not know what else to do since none of my Comcast neighbors are having any problems. I even searched for the possibility that a virus or DOS worm made its way into my PC creating the problem. I have use three different PC's, one of which was fresh out of the box (all Win XP Pro).

Can someone end my misery? I can't switch to DSL because I live between two cities and SBC and Verizon won't budge on a teritory issue. The only way I am able to enter this post is by hacking into my neighbor's wireless signal. Suggestions? Do you need more information?

-Rodney


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## Resolution (Sep 17, 2005)

Interesting. I had a similar problem with a 2wire DSL modem (SBC Global) doing the same thing every 3 to 5 minutes. It went on for about 2 months, however, I never went to the extremes that you went to. I finally ended up solving the problem when I noticed that in my modem's configuration, both the wireless and ethernet settings were enabled. I'm only using ethernet, so I just disabled the wireless setting, and the problem is now nonexistent. One of the neighbors over here also have a wireless connection, so i'm not sure if there was some kind of interference with that, or if the wireless and ethernet adapters just couldn't play well together. Actually, I didn't even have a wireless adapter installed in the computer. Perhaps it had something to do with the Wireless Zero Configuration built into XP. In any case, I don't know anything about your modem settings (or if you have any), but make sure this isn't happening to you.

This is actually what the config looks like...

http://www.2wire.com/imgs/pages/198.jpg

I had to disable the wireless setting. I also disabled USB also.


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## Dartmanrod (Oct 21, 2005)

The type of modem I am using has two connection choices, USB and Ethernet. Comcast disabled the USB connetion already. There is no wireless setting for this model of modem, but thank you for the reply. I may still be overlooking something simple.
-Rodney


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## johnwill (Sep 26, 2002)

Since the modem is going nuts with nothing connected to it, this is 100% certain to be a Comcast issue. I really doubt that it'll be solved by anyone other than Comcast.

Have you taken the modem to the entrance for the cable service and connected it DIRECTLY to the line, removing all other splitters, etc. for a test?


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## Dartmanrod (Oct 21, 2005)

Well I spoke with a Comcast technician again today (they called me!) and they have an even newer firmware version to upload to my modem. They are going to stop out tomorrow morning and perform the upgrade at my home in person. (Like I said, they know me by name now!) We'll see if this changes anything.

To answer your question, Yes - I have taken the modem out to the post in my yard which is pre-any kind of splitter or connector and with a laptop directly connected it still cycled.

I have done a fair amount of investigation and it seems that the problem may be due to the firmware (according to Motorola). Which leads me to the question "Why didn't Comcast distribute them with the most current firmware?!"

I will update this thread after tomorrow's "intervention".
-Rodney


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## JamesO (Mar 30, 2005)

Many of the cable companies are running scared now that Verizon is offering fiber optic service is some areas. In order to compete, cable companies are upgrading the cable plant and network equipment and this sometimes causes certain modems to quit working and/or to become intermittent and unstable. Many cable companies can upload firmware over the network, but this is usually for modems the cable company directly supports.

Your levels look pretty good, nothing sticks out as an issue. If the modem is dropping in and out, I would rule out any of your equipment. If the modem is unstable, it has nothing to do with your network equipment.

The Motorola SB5120 is a pretty solid and up to date modem. If you are the only person with a problem in your area, you probably have some form of signal impairment in the form of a non-linearity, interference, noise ingress, intermod, or a line amplifier that is phase unstable or taking phase hits. The problem may actually be on the return path and the modem may not be able to respond correctly back to the head end!

The smartest thing Comcast could do is bring you a "known good" modem that works solidly on their network at a different location and connected it to your house drop and see what happens. 

JamesO


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## Dartmanrod (Oct 21, 2005)

Well not one but two Comcast techs were out today. They gave me a new modem (#5 if anyone is keeping count!) which had the newest firmware. Lo and behold, no more T4 timeouts!! So they must have heeded your suggestion:


JamesO said:


> The smartest thing Comcast could do is bring you a "known good" modem that works solidly on their network at a different location and connected it to your house drop and see what happens.


Anyway, now they are addressing another problem in my area that affects not only me but everyone on my node. There is a T3 error which everyone in my neighborhood is having. I don't lose connection now and neither do my neighbors, but we receive slow repsonse to internet requests due to "noise on the line" as they put it. Here is the error:
2005-10-22 20:46:48	3-Critical	R005.0	Started Unicast Maintenance Ranging - No Response received - T3 time-out
The best thing about the new error is it doesn't affect just me but everyone on the node, and more importantly I now have reliable service once again! (I did just knock on wood and spin around in my chair 7 times and toss some salt over my shoulder just to be safe :wink: )
They also said that per the specs of the firmware on my old modem that it was not able to respond. Hey JamesO, where were you 2-1/2 months ago?!


JamesO said:


> The problem may actually be on the return path and the modem may not be able to respond correctly back to the head end!


Ultimately only time will tell if this truly has solved the problem. I have free internet access for the next couple months as a way of them saying "sorry". I will report back to this post in one week to let everyone know if it actually still works. Hopefully this will be the end of problems for a while.
-Rodney


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## JamesO (Mar 30, 2005)

I really do not understand these cable guys, they really do not get it. Managing a cable network with bi-directional cable boxes can really be easy if they use their head!! The problem is these jokers barely have a handle on what they are being paid for.

Not sure of the network setup, but they really need some "reference" modems at key locations that they can communicate with and monitor. This might be as simple as a few extra modems at customer houses in key locations. At $50 per modem, or less at wholesale, this really would not break the bank! Something as simple as a free software program on a PC pinging the boxes is a place to start. Signal level variations and modem lock status is also something that could tracked. The cable company could then monitor their network nodes and spans and know exactly what is going on. But this takes a little thought on someones part!

I managed a lot of satellite internet links and had receivers in key monitoring points at the uplink earth stations and also on the ground in many spots. I could tell in seconds if there was a problem, what part of the transmission path I had problems with and where to start to look for the problem. I would find problems the customers and the network management system would not detect and sort them before they became customer problems or outages! This was for a service that broadcast over 1 Gig of internet traffic globally from multiple location, through multiple pieces of hardware, so we really had to keep tabs on what was happening.

Good luck and let your cable company know I have an hourly rate!!

Good luck and slam them for the outage credits!!

JamesO


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