Basic Internet Connectivity And Modem Help

[kayber76]

Ok so I bought a Motorola Surfboard SB6121 and a Cisco Linksys E1550 Router (about six months ago). We were having all kind of internet dropping issues with our comcast modem and our old linksys router. Anyway the new stuff has been dropping on and off for the past 6 months. The past few weeks its gotten worse, during peak hours its been dropping almost daily. 

So I called Comcast I've had 3 techs into our apartment (its the LAN that's disconnecting not the Wireless, and sometimes yes both disconnect).  Each has checked the lines the last was a supervisor and he pulled the splitter from the wall told me it was wired wrong and rewired it. He said this should fix it. As soon as he walked out the door my modem (about 10 mins) goes offline, all the lights go off and it drops our net connection.  I'm baffeled. I have no idea what the issue is.

I looked the logs and all I see is critital disconnects. The guy told me if it continues it has to be the modem. I can't tell if its the modem or the router.  I don't even know where to start at this point. He says all the tests should the lines from comcast are fine. I'm a little ticked I mean I bought new equipment to keep this from happening.

Any suggestions? I dont want to keep bothering comcast if its not their issue.

[kayber76]

It looks like now the modem is rebooting. It keeps turning off (all the lights) and restarts.

[EG]

Remove the router from the mix temporarily and connect the computer directly to the modem to narrow things down to the modem or a coax line problem. You'll need to powercycle the modem when doing so and then again when you re-add the router.

What are the indicator lights doing on the modem when this happens ?

[Edit]

Disregard the above. Didn't see your latest post.

What do the modem's signal stats look like ? Get them here; http://192.168.100.1

Please post the *Downstream Power Level*, the *Upstream Power Level*, and the *SNR* (Signal to Noise Ratio) numbers.

[kayber76]

I just called Motorala and they told me the status seems correct and it seems to be recycling. They said this is a comcast issue with the line. The line needs to be split so it doesnt overload the modem if that makes sense? They said they cant do nothign and to screen shot the logs to show the tech.

Its turned off four times in the past 10 minutes. Total Recycles.

I feel like I'm getting the run around from comcast and motorola. I've just about had it up to here with both of them!

[kayber76]

upstream when online and not dropped:

Power Level 44 dBmV

downstream:

5 dBmV 

The guy at motorola said its normal but to screen shot it after it disconnects. I dont see how that will help cause its recylcing so i cant even get to it when it starts doing it.

[kayber76]

Signal to Noise Ratio 38 dB

[AnarchyAo]

Yeah they want to schedule a technician to come out and plug a splitter up between your modem and the wall, which is avoiding the real issue that needs to be resolved at the lines with maintenance.

If you add a splitter or an attenuator to your line you'll decrease your downstream dBmV by approximately 3.0-3.5 dBmV and your upstream dBmV will rise approximately the same amount.

Because both your downstream and upstream dBmV values are too high, you cannot band-aid the issue with a splitter or an attenuator. You need Comcast to fix it, but good luck with that. I've had them saying that they'll send someone out each day this week and it hasn't happened yet.

[kayber76]

Tell me about it. I've had 3 techs out for basically no real reason at all. Most of the time they say "its working".

[EG]

---

AnarchyAo wrote:

Because both your downstream and upstream dBmV values are too high, you cannot band-aid the issue with a splitter or an attenuator.

---

FWIW, his upstream power will allow for the additional 3.5 dB of attenuation a two way splitter as long as that power level is not intermittently fluctuating higher out of spec. But besides that, his downstream power is not even really that hot to need any additional attenuation in the first place.. I understand your frustration going by your issue in your own thread but let's keep it real please.

To the OP.  There are two additional signal stats which can't be read at the modem level. They can only be read from their end by them polling the CMTS (Cable Modem Termination System) at the local headend facility.

They are the 'Upstream Receive Power Level' and the 'Upstream uSNR' (upstream Signal To Noise Ratio). Both of these are as equally important in diagnosing connectivity issues as are the modem's stats.

You can call in and ask what these figures are. The Upstream Receive Power Level should fall within the range of -10dB to +10dB with 0dB being in the middle and perfect.

The Upstream SNR should be least 30dB, and the higher it is the better. You could have a noise ingress issue in the upstream channel.

[kayber76]

I'm not sure I fully understand the issue.

All I know is i get random reboots now since the comcast guy came in and rewired the splitter behind the wall. Which he told me would fix the issue.  He said if it didnt it was my modem?

So what do I do at this point?

[EG]

Have you found out about the uSNR and the receive power figures ?

[kayber76]

How do I go about that?

[EG]

I outlined it in post #9.

[kayber76]

Power Level 43 dBmV .

reading the rest of the post again. Just had a power recycle yet agian.

[kayber76]

I would say all my levels and such look correct, thats what comcast tells me. I dont know the modem randomly reboots.

I wish I understood this more..

[#16]

pass few weeks my modem has been drop connection and rebooting.. change the splitter going to the tv and the modem, works fine then bam it drops.. change the splitter 3 times and still drops after ten mins.. removed the splitter and hooked direct to the modem it works fine.. upstream SNR 34db ..  upsream receive power -8db

[#17]

now i can't watch tv..  signal too weak????

[kayber76]

Sounds familar (well all but the TV).

I've had it I called Comcast and told them to send me one of their modems.

Though my Motorola Surfboard SB6121 is 5 months old I'm about ready to throw it out the window.  5 reboots in 20 minutes. I think this thing is a piece of junk. If comcast's modem fixes the issue then I say Motorola is getting a long nasty email.