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Cyndee

join:2001-02-03
Chicago, IL

[Connectivity] Connection turns on and off for a few second -- b

I'm not sure this is the right forum for this question; if not, please let me know and I'll post elsewhere.

I have Comcast HSI. I have a Motorola Surfboard SB5120 modem which I own. I have a business-related Juniper box that plugs into the modem. My Linksys E4200 plugs into the Juniper and then the computers on the network plug into the Linksys.

For the past few days, I've found that my internet connectivity has been turning off for a few seconds and then reconnecting. In normal usage, I probably wouldn't even notice it, but I use a business program that runs from the cloud and it stops and notifies me each time it disconnects and reconnects.

I am trying to isolate the problem. I've called Comcast and they say there's no problem with my service. I've power cycled all above mentioned devices. I have now bypassed both the Juniper and the Linksys router and have my system connected directly to the modem and the problem continues. I have also noticed that the modem's status lights do not change when connectivity goes out.

Does this mean the modem is likely bad (it is by far the oldest component involved)? If so, what should I buy to replace it?

Thanks.



pflog
Bueller? Bueller?
Premium,MVM
join:2001-09-01
El Dorado Hills, CA
kudos:3

Re: [Connectivity] Connection turns on and off for a few second

Please start here: »Comcast High Speed Internet FAQ »How To Get Help!

In particular, it would be good to see the modem's signal levels, traceroute/ping/pingplotter results, etc.
--
"I drank what?" -Socrates


Cyndee

join:2001-02-03
Chicago, IL

Click for full size
Signal levels
Click for full size
Pingplotter results
I am in Chicago, IL, problem described above. Issue seems to be constant but only for a few seconds at a time.

Modem is Motorola SB5120:
Software Version: SB5120-2.19.0.16-SCM00-NOSH
Hardware Version: 4

Other home networking describe above.

Firewall/Anti-virus is Norton Security Suite Version 20.2.0.19 from Comcast.

Signal levels and pingplotter results are above.

Please let me know if any other information is needed.

Thank you.


pflog
Bueller? Bueller?
Premium,MVM
join:2001-09-01
El Dorado Hills, CA
kudos:3

Your downstream SNR is quite low (32 dB). It is quite likely that it is fluctuating enough that your modem is losing sync.

You should call tech support and have them come out to investigate the signal.

Is the cable modem behind any splitter(s)?
--
"I drank what?" -Socrates


Cyndee

join:2001-02-03
Chicago, IL

No splitters behind cable modem. The cable comes through the wall of the house directly into the modem.

So, you think it could be a Comcast problem rather than the modem going?



pflog
Bueller? Bueller?
Premium,MVM
join:2001-09-01
El Dorado Hills, CA
kudos:3

Looks like something you need to have Comcast come out and investigate, yes.
--
"I drank what?" -Socrates


Cyndee

join:2001-02-03
Chicago, IL

Thanks, I'll get on it then.


Cyndee

join:2001-02-03
Chicago, IL

Comcast was here today. After checking inside the tech went outside and looked at the connections. He replaced all of them reporting that they looked "nasty". All seems well now.

I am also inclined to replace my modem. I presently have a Motorola SB5120 which I own.

I was looking at the Motorola SB6141 -- I am on Blast -- will I benefit additionally from a DOCSIS 3 modem?



pflog
Bueller? Bueller?
Premium,MVM
join:2001-09-01
El Dorado Hills, CA
kudos:3

Yes, a Docsis 3 modem would be a good idea. Even if you're on a lower plan, it can still benefit you by spreading things across multiple channels (assuming your CMTS is D3). This means you're less likely to experience issues during peak times.

»Re: DOCSIS 3.0 Available in Valparaiso, IN
--
"I drank what?" -Socrates


Cyndee

join:2001-02-03
Chicago, IL

I think I spoke too fast that everything was working again -- my service just blinked out again for a few seconds (I can only tell so easily because I'm running a VPN which notifies me as soon as the connection is out).

I am going to order the SB6141 now. We do have D3 here in Chicago as far as I know.



pflog
Bueller? Bueller?
Premium,MVM
join:2001-09-01
El Dorado Hills, CA
kudos:3

Can you post your signal levels now, post-visit from the tech?
--
"I drank what?" -Socrates


DanM64

join:2013-01-10
Mokena, IL
Reviews:
·Comcast

2 edits
reply to Cyndee

All of the Chicago area is DOCSIS 3.0. I'm on the Romeoville headend- I have 8 downstream channels and 3 upstream (I'm pretty sure the entire Chicago area has 8/3). You should notice a difference with the 6141 since you're on Blast- you old modem's single channel capability is barely fast enough to keep up with the Blast package's PowerBoost download speed 30Mb/s. With the channel bonding not only should it be much easier to hit your PB top speed, you won't notice as much congestion either.


andyross
Premium,MVM
join:2003-05-04
Schaumburg, IL
reply to Cyndee

Can you post the modem logs? If it only goes out for a few seconds, you could be getting DCC's (Dynamic Channel Change). Since you have an older D2 modem with only one channel, Comcast may occasionally tell it to change channels to help balance the load. That can take a few seconds for the modem itself. Some software may take longer to retry.


Cyndee

join:2001-02-03
Chicago, IL
reply to pflog

Click for full size
New Signal Levels
The only thing that looks really different from before is Power Levels.

And, other than that one quick outage Friday afternoon, the connection has been solid since.

I think I will still get a new modem though.

ExoticFish

join:2008-08-31
Stuarts Draft, VA

Ew. Still not liking those signals and SNR.


Cyndee

join:2001-02-03
Chicago, IL

Will a new modem make a difference?


ExoticFish

join:2008-08-31
Stuarts Draft, VA

Nope. The tech needs to fix them.


Cyndee

join:2001-02-03
Chicago, IL

1 edit
reply to andyross

Click for full size
Click for full size
Modem Logs
Here are the logos -- only shows the current day; don't know how helpful that is.

Your explanation about DCC's makes sense. Often I wouldn't even have noticed the connection go out except that I am running a Net Extender for a VPN that exits or I'm running a program in the Cloud that beeps whenever it doesn't have a connection.

andyross
Premium,MVM
join:2003-05-04
Schaumburg, IL

The next time you notice the dead spot, check the log as soon as possible.

Also, if DCC's are the issue, then going to a newer D3 modem will help. Since they bond channels, they typically do not have to worry about DCC's. If you have a D3 modem that only does 4-down, it could get DCC's if it's in an area with more than 4 downstream available, but I don't know if that's ever done, yet.


Cyndee

join:2001-02-03
Chicago, IL

It isn't possible to check to log as soon as the connection goes out. Normally I connect through a router. So to get to the logs I need to bypass the router and connect directly to the computer and reboot the modem to get a connection; I guess that wipes the log. I can't stay connected directly to the modem for any amount of time as my printers are all connected to the network and there are other users that need to be connected.



fuziwuzi
Not born yesterday
Premium
join:2005-07-01
Atlanta, GA

I have my SB5120 modem connected to my Linksys E3000 router. My computers are then connected via the router. I can access the modem logs without disconnecting the router, just put in the modem's IP address, 192.168.100.1.

I'm not seeing those disconnects you mention, here in Atlanta our system has gone "D3", but my old 5120 still chugs along just fine. I think your problem is terrible signal levels from Comcast.
--
Teabaggers: Destroying America is Priority #1


Cyndee

join:2001-02-03
Chicago, IL

I just tried that and I can get to the log. I'll post it shortly.


Cyndee

join:2001-02-03
Chicago, IL

There isn't much in the log now. I'll let it run until later and then post it.

However, note that I have NOT been getting the constant disconnects since the tech was here on Friday (one right after, but none since that).

It seems that the disconnects are fixed; there was just a concern mentioned above that my SNR is still low.

However, if I am not disconnecting and my speed is good (around 34/6), should I worry about the SNR?



pflog
Bueller? Bueller?
Premium,MVM
join:2001-09-01
El Dorado Hills, CA
kudos:3

Wait so the disconnects are gone? You had replied:

said by Cyndee:

I think I spoke too fast that everything was working again -- my service just blinked out again for a few seconds (I can only tell so easily because I'm running a VPN which notifies me as soon as the connection is out).

I am going to order the SB6141 now. We do have D3 here in Chicago as far as I know.

If it's not disconnecting anymore, that's a good start, but a SNR of 33 and power level of -9 dBmV is not good. The signal needs to be looked at by a tech and fixed. The fact that they came out and didn't address the low signal level is unfortunately, but not surprising. Next time a tech comes out, specifically ask them to address the "low downstream power level and signal to noise ratio".
--
"I drank what?" -Socrates

Cyndee

join:2001-02-03
Chicago, IL

I neglected to report that after that one disconnect after the tech left, it has been fine since (I thought I'd posted that).

I am going to get the new modem, then after it's running for a bit, will check the diagnostics and then get a tech out again.

Thanks for all the help.