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No internet, partial connection with Netgear CM500

New Poster

No internet, partial connection with Netgear CM500

Hello, my first post here. I'm switching to Comcast Xfinity Performance Plus 55 Mbps as my ISP, from Wave (formerly Astound, formerly RCN). Comcast technicians added a cable drop to my home (I put the details below under "The history"), but my self-installed owned Netgear CM500 cable modem won't connect. Its front panel lights indicate "One downstream channel is locked; The cable modem is scanning for an upstream channel; The cable modem is offline."

I connected to the cable modem's web administration, here's its status panel. The downstream power level and SNR are worse than what nerdburg recommends in the "Connection Troubleshooting Tips" post. Is that why the cable modem is offline?

Is there anything more I can do while I wait for a second Comcast installation technician's visit? Thanks!

 

 
Startup Procedure
Procedure Status Comment
Acquire Downstream Channel 693000000 Hz Locked
Connectivity State In Progress Upstream Parameters Acquired
Boot State In Progress Unknown
Security Disabled Disabled
IP Provisioning Mode In Progress Unknown
 
Downstream Bonded Channels
Channel Lock Status Modulation Channel ID Frequency Power SNR Correctables Uncorrectables
1 Locked QAM256 31 693000000 Hz -21.9 dBmV 29 dB 610 0
 
Upstream Bonded Channels
Channel Lock Status US Channel Type Channel ID Symbol Rate Frequency Power
1 Not Locked ATDMA 1 5120 Ksym/sec 19300000 Hz 32.5 dBmV
 

 

I also looked at the cable modem's logs. Each time I power it on results in a series of log lines like:

1970-1-1, 00:00:20 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=b0:b9:8a:77:08:f8;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
1970-1-1, 00:00:22 Critical (3) SYNC Timing Synchronization failure - Failed to acquire FEC framing;CM-MAC=b0:b9:8a:77:08:f8;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
1970-1-1, 00:00:22 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=b0:b9:8a:77:08:f8;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
1970-1-1, 00:00:23 Critical (3) SYNC Timing Synchronization failure - Failed to acquire FEC framing;CM-MAC=b0:b9:8a:77:08:f8;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
1970-1-1, 00:00:25 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=b0:b9:8a:77:08:f8;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
1970-1-1, 00:00:36 Critical (3) SYNC Timing Synchronization failure - Failed to acquire FEC framing;CM-MAC=b0:b9:8a:77:08:f8;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
1970-1-1, 00:00:37 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=b0:b9:8a:77:08:f8;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
1970-1-1, 00:00:38 Critical (3) SYNC Timing Synchronization failure - Failed to acquire FEC framing;CM-MAC=b0:b9:8a:77:08:f8;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
1970-1-1, 00:00:38 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=b0:b9:8a:77:08:f8;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
1970-1-1, 00:00:45 Critical (3) No Ranging Response received - T3 time-out;CM-MAC=b0:b9:8a:77:08:f8;CMTS-MAC=00:01:5c:62:cc:68;CM-QOS=1.0;CM-VER=3.0;
1970-1-1, 00:05:32 Warning (5) B-INIT-RNG Failure - Retries exceeded;CM-MAC=b0:b9:8a:77:08:f8;CMTS-MAC=00:01:5c:62:cc:68;CM-QOS=1.0;CM-VER=3.0;
1970-1-1, 00:05:34 Critical (3) No Ranging Response received - T3 time-out;CM-MAC=b0:b9:8a:77:08:f8;CMTS-MAC=00:01:5c:62:cc:68;CM-QOS=1.0;CM-VER=3.0;

 

The history

I signed up online for Comcast Xfinity internet. I ordered the self-install kit and bought a compatible Netgear CM500-1AZNAS DOCSIS 3.0 cable modem.

I couldn't see any way online to say "I have no Comcast service at my house" (bug?!), nor was there any guidance in the self-install kit, which assumes you have Comcast running to cable jacks in your house, so I telephoned Comcast support and arranged for a installer.

"Angel" came out and confirmed I had no Comcast. He installed the cable drop. Wave/Astound/RCN had installed a coax pair running into my house so he connected Comcast to the second coax cable and put a splitter on the inside. He called in my cable modem's MAC address. But his truck wasn't tall enough to reach the utility pole, so he called for another installer with a bigger truck, and said once the cable was connected to the pole I could plug in my cable modem and be good to go. The big truck installer hooked up the outside cable to the utility pole, but said a technician would have to come back to complete the install. I think he called "Angel", but he did not return.

I tried connecting the cable modem, and every time I power it on I get the results above: a downstream channel but no upstream, and not online.

I've called Comcast installation support twice. Both times the suggestions were the same, to power off the cable modem (done 5 times), swap the coaxial cable (done), and replace my brand new cable modem (!). Neither person was interested in my cable modem's diagnostics or logs, even though the second time I asked to speak to someone more knowledgeable about cable modems.

Other observations

  • Comcast's web-based installation services are very confused when you have a working internet connection but not through Comcast :-)
  • My cable modem appears under the My Xfinity Devices tab https://customer.xfinity.com/#/devices with its MAC address as its serial number. Does this mixup matter? That page has a button to restart the cable modem, which doesn't work.
  • The self-install kit suggests using the Xfinity Xfi app to set up cable, but that app seems to detect my existing Wi-Fi router and says it isn't good enough for Xfi, and thereafter won't let me proceed to set up devices or check my connection.
  • It's a shame Comcast doesn't have text support ("chat").
Official Employee

Re: No internet, partial connection with Netgear CM500

Hi skierpage,

 

I was able to review your account signal levels using the email address you registered with the forums. Everything looks good on our end. Can you tell me if there's a splitter on your line? I can try some troubleshooting on my end, but I am convinced as well this may be an issue with your actual modem. 

 

In regards to the xFi app, your current modem isn't compatible. You would need a Arris 1682G, Cisco 3941T or Arris TG3482G. To see more details about the xFi app, follow this link Xfinity xFi

 

 

 

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Diamond Problem Solver

Re: No internet, partial connection with Netgear CM500

FWIW, Che, I can't understand how "everything" can possibly "look good" on your end when their downstream power is horribly out of spec at (minus) -21 dB, and a 29 dB SNR, and only 1 DS CHANNEL ? Unless it's an intermittent fluctuation ?
Official Employee

Re: No internet, partial connection with Netgear CM500

Looking in tools we use to monitor signals, everything is showing good EG. 

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Official Employee

Re: No internet, partial connection with Netgear CM500

That could be a possibility as well, but from what I can tell, signal wise is good. It puzzles me further that I am not pulling or showing what you are. I'm happy to get a tech out and waive any charges associated. Either way, my main goal is to help get it resolved. 

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Diamond Problem Solver

Re: No internet, partial connection with Netgear CM500

What I am seeing is just what they posted here. It boggles the mind.. If it is an intermittent thing, I wonder what their modem is showing them now.
New Poster

Re: No internet, partial connection with Netgear CM500


I can't understand how "everything" can possibly "look good" on your end when their downstream power is horribly out of spec at (minus) -21 dB, and a 29 dB SNR, and only 1 DS CHANNEL ? Unless it's an intermittent fluctuation ?

It turns out the problem was in the second coax cable of the pair running into my house. Even after he replaced the terminator on it, "Glen" still found the signal strength was terrible. So he disconnected Wave's drop from the first coax cable, plugged in Comcast's drop, the signal on it was nice and strong, and when I plugged my new cable modem into that coax it quickly went online. The only downside was I couldn't run both ISPs side-by-side for a few hours.

BTW, when I called Wave to cancel service, their customer service rep offered 1 Gbps for $30/month, and first month free! A much better deal than when I only threatened to cancel Wave. But I was too worn out to pursue it and wait for another truck roll to swap drops on my one good coax cable

I'm on Xfinity, everything looks good, 65 Mbps down on a wired Ethernet connection to the router. Thanks everyone.

New Poster

Self-install kit assumes xFi wireless gateway


ComcastChe wrote:

In regards to the xFi app, your current modem isn't compatible. You would need a Arris 1682G, Cisco 3941T or Arris TG3482G. To see more details about the xFi app, follow this link Xfinity xFi.


I understand. The error is that the self-install kit I received (INT-V SIK 0717, "Wireless Gateway Internet/Voice") assumes the new customer is installing XFinity Internet/Voice with an xFi wireless gateway. It has no instructions for when your're using your own cable modem to get internet.

Official Employee

Re: Self-install kit assumes xFi wireless gateway

Understandable. If there's anything else we can assist you with, please reach out. 

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