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Internet issues with Netgear C3700-100NAS

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Frequent Visitor

Internet issues with Netgear C3700-100NAS

Hello lately I am having problem with the internet. My connection is not reliable at all.

I want to know why this is happening? All of this started like 4 to 5 months ago.

My internet plan is 300mbps. and currently I'm getting like 35mbps.

Startup Procedure
ProcedureStatusComment
Acquire Downstream Channel723000000 HzLocked
Connectivity StateOKOperational
Boot StateOKOperational
SecurityEnabledBPI+
IP Provisioning ModeHonor MDDhonorMdd(4)

 

Downstream Bonded Channels
ChannelLock StatusModulationChannel IDFrequencyPowerSNRCorrectablesUncorrectables
1LockedQAM25638723000000 Hz-0.6 dBmV40.8 dB00
2LockedQAM25639729000000 Hz-1.1 dBmV31.5 dB25071091409492
3LockedQAM25640735000000 Hz-1 dBmV32.4 dB3464899534918
4LockedQAM25641741000000 Hz-0.3 dBmV31.4 dB2470
5LockedQAM25642747000000 Hz-0.2 dBmV34.6 dB00
6LockedQAM25643753000000 Hz-0.1 dBmV33.1 dB13440
7LockedQAM25644759000000 Hz-0.3 dBmV37.9 dB00
8LockedQAM25645765000000 Hz-0.4 dBmV35.9 dB2820

 

Upstream Bonded Channels
ChannelLock StatusUS Channel TypeChannel IDSymbol RateFrequencyPower
1LockedATDMA45120 Ksym/sec17300000 Hz46 dBmV
2LockedATDMA15120 Ksym/sec36500000 Hz43.5 dBmV
3LockedATDMA35120 Ksym/sec23700000 Hz44.8 dBmV
4LockedATDMA25120 Ksym/sec30100000 Hz44.5 dBmV

 

thanks and let me know if I need to post more information. 

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Gold Problem Solver

Re: Internet issues with Netgear C3700-100NAS

There are at least 2 problems:

  • https://www.xfinity.com/support/devices/ rates the C3700-100NAS for use with plan speeds "Up to 283 Mbps". Using devices on speed tiers for which they are not approved tends to produce unpredictable results.
  • Half of the downstream channel quality readings (SNR) are out-of-spec (too low).

Signal quality problems are often due to poor coax connections or damaged coax cable, usually in or near your home.

If you want to troubleshoot this yourself, please see Internet Troubleshooting Tips. If you can't find the problem or you'd rather have Comcast take care of it, call them at the phone number on your bill or 1-800-Comcast, or use one of the options on https://www.xfinity.com/support/contact-us/. If they can't fix the problem remotely (unlikely), insist they send a tech out to identify the cause and correct it.

If the tech finds bad coax, splitters, amplifiers, or connections in your home (even if Comcast originally supplied them) you'll probably have to pay for the visit unless you have their Service Protection Plan (https://www.xfinity.com/support/articles/service-protection-plan, closed to customers that don't already have it). If the trouble is due to a faulty Comcast rental device or anything outside your home you shouldn't be charged.

 

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Frequent Visitor

Re: Internet issues with Netgear C3700-100NAS

Hello, and thanks for the information.

I got a new coaxial cable and now it looks like this. Is this better? what supposed to be normal or acceptable?

 

Startup Procedure
ProcedureStatusComment
Acquire Downstream Channel555000000 HzLocked
Connectivity StateOKOperational
Boot StateOKOperational
SecurityEnabledBPI+
IP Provisioning ModeHonor MDDhonorMdd(4)
 
Downstream Bonded Channels
ChannelLock StatusModulationChannel IDFrequencyPowerSNRCorrectablesUncorrectables
1LockedQAM2569555000000 Hz4.2 dBmV41.9 dB00
2LockedQAM2568549000000 Hz4.3 dBmV41.9 dB00
3LockedQAM25610561000000 Hz4.7 dBmV42.2 dB00
4LockedQAM25611567000000 Hz4.3 dBmV41.9 dB00
5LockedQAM25612573000000 Hz4.6 dBmV41.8 dB00
6LockedQAM25613579000000 Hz4.5 dBmV41.4 dB00
7LockedQAM25614585000000 Hz4.7 dBmV41.7 dB00
8LockedQAM25615591000000 Hz4.7 dBmV40.7 dB00
 
Upstream Bonded Channels
ChannelLock StatusUS Channel TypeChannel IDSymbol RateFrequencyPower
1LockedATDMA35120 Ksym/sec23700000 Hz42.5 dBmV
2LockedATDMA15120 Ksym/sec36500000 Hz41 dBmV
3LockedATDMA45120 Ksym/sec17300000 Hz43.5 dBmV
4LockedATDMA25120 Ksym/sec30100000 Hz41.8 dBmV
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Gold Problem Solver

Re: Internet issues with Netgear C3700-100NAS


@jodarove wrote: ... Is this better? what supposed to be normal or acceptable? ...

Yes, the signals the modem is reporting and improved and now withing spec, but please note that, if this is still the C3700-100NAS on a 300 Mbps plan, that combination is not one that Comcast approves.

 

The allowable signal level ranges (some of which cannot be read at the modem) are available at Internet Troubleshooting Tips previously linked.

 

Are you still having problems? If so, please post the modem's error log.

 

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Frequent Visitor

Re: Internet issues with Netgear C3700-100NAS

Thanks @BruceW ! So far everything is working fine. 

I'm planing on getting this modem SURFboard® SB8200 DOCSIS® 3.1 Gigabit Cable Modem. 

I get this upgrade should be ok?

 

Oh and here is the log:

TimePriorityDescription
2020-11-10, 20:23:32Critical (3)Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC="changed";CMTS-MAC="changed";CM-QOS=1.1;CM-VER=3.0;
1970-1-1, 00:00:48Notice (6)Honoring MDD; IP provisioning mode = IPv6
1970-1-1, 00:00:42Critical (3)No Ranging Response received - T3 time-out;CM-MAC="changed";CMTS-MAC="changed";CM-QOS=1.0;CM-VER=3.0;
1970-1-1, 00:00:37Notice (6)WiFi Interface [wl1] set to Channel 149 (Side-Band Channel:153) - Reason:INIT
1970-1-1, 00:00:37Notice (6)WiFi Interface [wl0] set to Channel 8 (Side-Band Channel:N/A) - Reason:INIT
1970-1-1, 00:00:34Critical (3)SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC="changed";CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;

 

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Gold Problem Solver

Re: Internet issues with Netgear C3700-100NAS


@jodarove wrote: ... So far everything is working fine. ...

Good to hear!

 

Quite a few posters here who upgraded to DOCSIS 3.1 modems capable of Gigabit service have reported an odd problem: all the modem's signal specs look good, but the modem experiences a lot of unexpected and unexplained dropouts. There's no way to know if that will happen to you except by trying it.

 

Not sure what to make of the error log you posted. The entries may represent a normal startup. I'd suggest keeping an eye on it to see what new entries appear.

 

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Re: Internet issues with Netgear C3700-100NAS

Thanks again @BruceW! I will update this when I get the new modem.

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Gold Problem Solver

Re: Internet issues with Netgear C3700-100NAS


@jodarove wrote: ... I will update this when I get the new modem.

Please do! We always like to hear how these thing turn out.

 

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Frequent Visitor

Re: Internet issues with Netgear C3700-100NAS

Hi @BruceW 

Hope you are doing well.

My problem is just getting worse. I did not upgrade yet my modem.

 

I check the connections outside my apartment.  

First pic: the cable is coming through neighborhs backyard and you can see in the pic that have that union there.

https://ibb.co/gMwvG1M

 

Second pic: Is the splitter.  In line goes to the landord house and the other one goes to my apt the basement.

https://ibb.co/8Y9rSdF

 

that line that it goes to my aparment go to a wall plate and from there to my router.

I dont think that little union (on the first pic)  is very helpful to my connection. 

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Re: Internet issues with Netgear C3700-100NAS

Update: Technician is coming tomorrow to check out the connections. I will update after that.

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Gold Problem Solver

Re: Internet issues with Netgear C3700-100NAS


@jodarove wrote: Update: Technician is coming tomorrow to check out the connections. ...

That's probably best. Unless there is obvious damage, it just isn't possible to evaluate the RF performance of coax cable, splitters, or connectors without special equipment.

 

Good luck!

 

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Re: Internet issues with Netgear C3700-100NAS

Update

The technician came. He tested the connection with a modem and an app on his phone. He connected his modem to the cable before the splitter. Then he told me that the connections was good and that on his app show that I have 4 bars and that normally other people only has 3 bars.( I have no idea what he means about that)

I came to my laptop to check out the SNR, power, etc. and show to him, but he has no clue about any of this ( I was shocked.) but any ways so far is working.

My modem has been up for: 1 day 04:53:41 and this is how the numbers looks like:

Startup Procedure
ProcedureStatusComment
Acquire Downstream Channel603000000 HzLocked
Connectivity StateOKOperational
Boot StateOKOperational
SecurityEnabledBPI+
IP Provisioning ModeHonor MDDhonorMdd(4)
 
Downstream Bonded Channels
ChannelLock StatusModulationChannel IDFrequencyPowerSNRCorrectablesUncorrectables
1LockedQAM25617603000000 Hz3.4 dBmV41.3 dB00
2LockedQAM25615591000000 Hz4.4 dBmV41.2 dB00
3LockedQAM25616597000000 Hz3.9 dBmV40.8 dB00
4LockedQAM25618609000000 Hz2.6 dBmV40.8 dB00
5LockedQAM25619615000000 Hz3.3 dBmV40.9 dB00
6LockedQAM25620621000000 Hz3.2 dBmV36.7 dB00
7LockedQAM25621627000000 Hz3.7 dBmV33.6 dB00
8LockedQAM25622633000000 Hz3.3 dBmV39.1 dB00
 
Upstream Bonded Channels
ChannelLock StatusUS Channel TypeChannel IDSymbol RateFrequencyPower
1LockedATDMA15120 Ksym/sec36500000 Hz40.5 dBmV
2LockedATDMA45120 Ksym/sec17300000 Hz44.3 dBmV
3LockedATDMA35120 Ksym/sec23700000 Hz42.5 dBmV
4LockedATDMA25120 Ksym/sec30100000 Hz41.3 dBmV

 

And I have no new event logs.

Now that I'm posting this I realized that the SNRs in the channels, 6, 7 & 8 are fluctuating betweeen 41 to 33 dB.

 

Thanks for reading. 

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Gold Problem Solver

Re: Internet issues with Netgear C3700-100NAS


@jodarove wrote: ... I came to my laptop to check out the SNR, power, etc. and show to him, but he has no clue about any of this ...

Wow. I hope that it continues to work for you, but if it was me, I'd insist that they send out another tech, preferably one who has a basic understanding of cable Internet signals.