Cable modem resets when both PC/Internet & Phone are in use

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rohpks
Posts: 4
Joined: Thu Oct 04, 2012 5:23 am

Cable modem resets when both PC/Internet & Phone are in use

Post by rohpks » Thu Oct 04, 2012 5:42 am

I have been using Ooma for the past 8 months and I notice that whenever I am connected to internet (wired/wireless) and also talking on the phone, periodically I loose internet connection (internet and dropped call) and can see the cable modem resetting. After a minute or so, the internet is back and also the phone line. This is more frequent during the day.
I have Cox internet with a Motorola SB5101u cable modem connected to a Linksys router.
Any suggestions as to the rootcause and possible fix to this problem? Appreciate your help.

murphy
Posts: 7205
Joined: Tue Jan 27, 2009 12:49 pm
Location: Pennsylvania

Re: Cable modem resets when both PC/Internet & Phone are in use

Post by murphy » Thu Oct 04, 2012 5:57 am

Connect to

http://192.168.100.1

which is a web page inside of your modem.

Find the signal strength screen and report

Downstream signal level
Downstream Signal to Noise Ratio (SNR)
Upstream power level

Modem reboots are usually caused by signal levels that are either too low or too high.
Customer since January 2009
Telo with 2 Handsets, a Linx, and a Safety Phone
Telo2 with 2 Handsets and a Linx

rohpks
Posts: 4
Joined: Thu Oct 04, 2012 5:23 am

Re: Cable modem resets when both PC/Internet & Phone are in use

Post by rohpks » Thu Oct 04, 2012 8:59 am

Following are the values I see ...

Downstream Value
--------------------------------------------------
Frequency 855000000 Hz
Signal To Noise Ratio 32.4 dB
Power Level -11.8 dBmV

murphy
Posts: 7205
Joined: Tue Jan 27, 2009 12:49 pm
Location: Pennsylvania

Re: Cable modem resets when both PC/Internet & Phone are in use

Post by murphy » Thu Oct 04, 2012 9:18 am

The signal level is on the low side although within the modem's spec of -15 to +15 dBmV.
The SNR should be at least 35.

There should only be one two way splitter between your incoming cable line and the modem.
The splitter should be rated from 5 MHz to 1000 MHz.
Customer since January 2009
Telo with 2 Handsets, a Linx, and a Safety Phone
Telo2 with 2 Handsets and a Linx

rohpks
Posts: 4
Joined: Thu Oct 04, 2012 5:23 am

Re: Cable modem resets when both PC/Internet & Phone are in use

Post by rohpks » Thu Oct 04, 2012 9:50 am

There is only one two way splitter between the incoming cable line from the outlet and modem. It is rated as you mentioned: 5MHz - 1000MHz. Should I not use the splitter?

Thanks for your help in trying to troubleshoot the problem.

thunderbird
Posts: 6388
Joined: Mon Nov 08, 2010 4:41 pm

Re: Cable modem resets when both PC/Internet & Phone are in use

Post by thunderbird » Thu Oct 04, 2012 11:34 am

rohpks wrote:I have been using Ooma for the past 8 months and I notice that whenever I am connected to internet (wired/wireless) and also talking on the phone, periodically I loose internet connection (internet and dropped call) and can see the cable modem resetting. After a minute or so, the internet is back and also the phone line. This is more frequent during the day.
I have Cox internet with a Motorola SB5101u cable modem connected to a Linksys router.
Any suggestions as to the rootcause and possible fix to this problem? Appreciate your help.
It appears that the Motorola SB5101u is prone to do what you discribe. See this thread: http://forums.comcast.com/t5/Connectivi ... -p/1360539

If that Motorola SB5101u is rented, get Cox to give you another one, or better yet, give you a later more up to date model Modem.

murphy
Posts: 7205
Joined: Tue Jan 27, 2009 12:49 pm
Location: Pennsylvania

Re: Cable modem resets when both PC/Internet & Phone are in use

Post by murphy » Thu Oct 04, 2012 11:44 am

rohpks wrote:There is only one two way splitter between the incoming cable line from the outlet and modem. It is rated as you mentioned: 5MHz - 1000MHz. Should I not use the splitter?

Thanks for your help in trying to troubleshoot the problem.
The splitter should be fine.
You may want to have your cable company check your signal.
They should be supplying a higher signal level that you are seeing.
Customer since January 2009
Telo with 2 Handsets, a Linx, and a Safety Phone
Telo2 with 2 Handsets and a Linx

rohpks
Posts: 4
Joined: Thu Oct 04, 2012 5:23 am

Re: Cable modem resets when both PC/Internet & Phone are in use

Post by rohpks » Fri Oct 05, 2012 9:30 am

I removed the splitter and directly connected the modem to the cable outlet. I get the following values..

Downstream Value
Frequency: 855000000 Hz
Signal To Noise Ratio: 34.1 dB
Power Level: -7.0 dBmV

Its too early to tell, but I am hoping this will solve my problem. If not, I will buy a new DOCSIS 3.0 modem.

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