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Rmpondite
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Sun, Dec 27, 2020 1:00 PM

Nighthawk C7000 AC1900 how to test if modem/router vs Comcast issue?

All of our devices, both wired and wireless, are experiencing intermitten short access drops -- wired PC screen won't refresh, wifi Roku has connection delays (though it's just 3ft from router), etc. Then a minute later all will be fine. We have had a couple of moments where both wired PCs experienced delays at the same time when we were both just doing mundane browsing so we don't suspect the indiviual devices or wifi interferance. We have 200Mbps service, and typically get around 150 download speed wired, 50 wifi (measured using fast.com) which is usually fine for what we do (just two of us, never more than one movie streaming at a time, no gaming, etc.).

 

I'm trying to figure out how to determine whether this is an issue with the modem/router or with Comcast. All suggestions are much appreciated. I peeked at the logs for the router and didn't know how to make sense of what I was seeing.  The event log has a bunch of things dates 1970 and several "SYNC timing synchronization" errors so I'm guessing that's related! I'll c/p the event log below.

 

FYI

Hardware Version1.05
Firmware VersionV1.01.34
Model: C7000|Nighthawk - AC1900 WiFi Cable Modem Router
 
Event log:
Time Priority Description
1970-1-1, 01:41:35Notice (6)Honoring MDD; IP provisioning mode = IPv6
1970-1-1, 01:36:01Critical (3)No Ranging Response received - T3 time-out;CM-MAC=2c:30:33:8d:39:38;CMTS-MAC=00:01:5c:8e:3c:6e;CM-QOS=1.0;CM-VER=3.0;
1970-1-1, 01:35:59Warning (5)B-INIT-RNG Failure - Retries exceeded;CM-MAC=2c:30:33:8d:39:38;CMTS-MAC=00:01:5c:8e:3c:6e;CM-QOS=1.0;CM-VER=3.0;
1970-1-1, 01:28:49Critical (3)No Ranging Response received - T3 time-out;CM-MAC=2c:30:33:8d:39:38;CMTS-MAC=00:01:5c:8e:3c:6e;CM-QOS=1.0;CM-VER=3.0;
1970-1-1, 01:28:48Warning (5)B-INIT-RNG Failure - Retries exceeded;CM-MAC=2c:30:33:8d:39:38;CMTS-MAC=00:01:5c:8e:3c:6e;CM-QOS=1.0;CM-VER=3.0;
1970-1-1, 01:24:23Critical (3)No Ranging Response received - T3 time-out;CM-MAC=2c:30:33:8d:39:38;CMTS-MAC=00:01:5c:8e:3c:6e;CM-QOS=1.0;CM-VER=3.0;
1970-1-1, 01:24:22Warning (5)B-INIT-RNG Failure - Retries exceeded;CM-MAC=2c:30:33:8d:39:38;CMTS-MAC=00:01:5c:8e:3c:6e;CM-QOS=1.0;CM-VER=3.0;
1970-1-1, 01:18:01Critical (3)No Ranging Response received - T3 time-out;CM-MAC=2c:30:33:8d:39:38;CMTS-MAC=00:01:5c:8e:3c:6e;CM-QOS=1.0;CM-VER=3.0;
1970-1-1, 01:17:55Critical (3)SYNC Timing Synchronization failure - Failed to acquire FEC framing;CM-MAC=2c:30:33:8d:39:38;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
1970-1-1, 01:17:54Critical (3)No UCDs Received - Timeout;;CM-MAC=2c:30:33:8d:39:38;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
1970-1-1, 01:17:44Warning (5)Lost MDD Timeout;CM-MAC=2c:30:33:8d:39:38;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
1970-1-1, 01:17:37Critical (3)SYNC Timing Synchronization failure - Failed to acquire FEC framing;CM-MAC=2c:30:33:8d:39:38;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
1970-1-1, 01:17:36Critical (3)No UCDs Received - Timeout;;CM-MAC=2c:30:33:8d:39:38;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
1970-1-1, 01:17:26Warning (5)Lost MDD Timeout;CM-MAC=2c:30:33:8d:39:38;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
1970-1-1, 01:17:19Critical (3)SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=2c:30:33:8d:39:38;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
1970-1-1, 01:17:18Critical (3)No UCDs Received - Timeout;;CM-MAC=2c:30:33:8d:39:38;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
1970-1-1, 01:17:08Warning (5)Lost MDD Timeout;CM-MAC=2c:30:33:8d:39:38;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
1970-1-1, 01:17:01Critical (3)SYNC Timing Synchronization failure - Failed to acquire FEC framing;CM-MAC=2c:30:33:8d:39:38;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
1970-1-1, 01:16:59Warning (5)B-INIT-RNG Failure - Retries exceeded;CM-MAC=2c:30:33:8d:39:38;CMTS-MAC=00:01:5c:8e:3c:6e;CM-QOS=1.0;CM-VER=3.0;
1970-1-1, 01:10:51Critical (3)No Ranging Response received - T3 time-out;CM-MAC=2c:30:33:8d:39:38;CMTS-MAC=00:01:5c:8e:3c:6e;CM-QOS=1.0;CM-VER=3.0;
1970-1-1, 01:10:49Warning (5)B-INIT-RNG Failure - Retries exceeded;CM-MAC=2c:30:33:8d:39:38;CMTS-MAC=00:01:5c:8e:3c:6e;CM-QOS=1.0;CM-VER=3.0;
1970-1-1, 01:04:50Critical (3)No Ranging Response received - T3 time-out;CM-MAC=2c:30:33:8d:39:38;CMTS-MAC=00:01:5c:8e:3c:6e;CM-QOS=1.0;CM-VER=3.0;
1970-1-1, 01:04:48Warning (5)B-INIT-RNG Failure - Retries exceeded;CM-MAC=2c:30:33:8d:39:38;CMTS-MAC=00:01:5c:8e:3c:6e;CM-QOS=1.0;CM-VER=3.0;
1970-1-1, 00:59:02Critical (3)No Ranging Response received - T3 time-out;CM-MAC=2c:30:33:8d:39:38;CMTS-MAC=00:01:5c:8e:3c:6e;CM-QOS=1.0;CM-VER=3.0;
1970-1-1, 00:59:00Warning (5)B-INIT-RNG Failure - Retries exceeded;CM-MAC=2c:30:33:8d:39:38;CMTS-MAC=00:01:5c:8e:3c:6e;CM-QOS=1.0;CM-VER=3.0;
1970-1-1, 00:54:12Critical (3)No Ranging Response received - T3 time-out;CM-MAC=2c:30:33:8d:39:38;CMTS-MAC=00:01:5c:8e:3c:6e;CM-QOS=1.0;CM-VER=3.0;
1970-1-1, 00:54:06Critical (3)SYNC Timing Synchronization failure - Failed to acquire FEC framing;CM-MAC=2c:30:33:8d:39:38;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
1970-1-1, 00:53:56Critical (3)SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=2c:30:33:8d:39:38;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
1970-1-1, 00:53:55Critical (3)SYNC Timing Synchronization failure - Failed to acquire FEC framing;CM-MAC=2c:30:33:8d:39:38;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
1970-1-1, 00:00:39Critical (3)SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=2c:30:33:8d:39:38;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
1970-1-1, 00:00:39Notice (6)WiFi Interface [wl1] set to Channel 161 (Side-Band Channel:N/A) - Reason:INTERFERENCE
1970-1-1, 00:00:39Notice (6)WiFi Interface [wl0] set to Channel 11 (Side-Band Channel:N/A) - Reason:INIT
2020-12-23, 01:19:37Critical (3)SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=2c:30:33:8d:39:38;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
2020-12-23, 01:19:37Critical (3)SYNC Timing Synchronization failure - Failed to acquire FEC framing;CM-MAC=2c:30:33:8d:39:38;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
2020-12-23, 01:19:30Critical (3)Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=2c:30:33:8d:39:38;CMTS-MAC=00:01:5c:8e:3c:6e;CM-QOS=1.1;CM-VER=3.0;
2020-12-23, 01:18:57Critical (3)SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=2c:30:33:8d:39:38;CMTS-MAC=00:01:5c:8e:3c:6e;CM-QOS=1.1;CM-VER=3.0;
2020-12-23, 01:18:56Critical (3)Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=2c:30:33:8d:39:38;CMTS-MAC=00:01:5c:8e:3c:6e;CM-QOS=1.1;CM-VER=3.0;
2020-12-23, 01:18:32Critical (3)SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=2c:30:33:8d:39:38;CMTS-MAC=00:01:5c:8e:3c:6e;CM-QOS=1.1;CM-VER=3.0;
2020-12-23, 01:18:31Critical (3)Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=2c:30:33:8d:39:38;CMTS-MAC=00:01:5c:8e:3c:6e;CM-QOS=1.1;CM-VER=3.0;
2020-12-23, 01:18:30Critical (3)SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=2c:30:33:8d:39:38;CMTS-MAC=00:01:5c:8e:3c:6e;CM-QOS=1.1;CM-VER=3.0;
 
 

Responses

EG

Expert

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87K Messages

6 m ago

FWIW, that default 1970 date/time stamp happens when a modem is re-booted/power-cycled either deliberately by the end-user, or spontaneously because of connectivity / signal issues with the system, so it can not talk to the T.O.D. (Time Of Day) server. And it also spits out a number of random errors caused by the re-boot. Makes the entries look more numerous than they really are.

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


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Rmpondite

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7 Messages

6 m ago

NOTE: I just cleared out the event log to see if I get correct timestamps or 1970 time stamps.

Rmpondite

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7 Messages

6 m ago

Thank you! Is this what you're asking for? If not, where do I find that?

Startup Procedure
Procedure Status Comment
Acquire Downstream Channel639000000 HzLocked
Connectivity StateOKOperational
Boot StateOKOperational
SecurityEnabledBPI+
IP Provisioning ModeHonor MDDhonorMdd(4)
 
Downstream Bonded Channels
Channel Lock Status Modulation Channel ID Frequency Power SNR Correctables Uncorrectables
1LockedQAM25633639000000 Hz5.8 dBmV38.6 dB5671
2LockedQAM25613519000000 Hz6.3 dBmV39.9 dB2090
3LockedQAM25614525000000 Hz6.2 dBmV39.9 dB2080
4LockedQAM25615531000000 Hz5.5 dBmV39.6 dB2480
5LockedQAM25616537000000 Hz6.3 dBmV39.9 dB1480
6LockedQAM25617543000000 Hz5.2 dBmV39.5 dB2350
7LockedQAM25618549000000 Hz6 dBmV39.7 dB2220
8LockedQAM25619555000000 Hz6.4 dBmV39.7 dB2570
9LockedQAM25620561000000 Hz6 dBmV39.5 dB3030
10LockedQAM25621567000000 Hz7.1 dBmV39.8 dB2760
11LockedQAM25622573000000 Hz6.5 dBmV39.7 dB3480
12LockedQAM25623579000000 Hz6.5 dBmV39.5 dB2540
13LockedQAM25624585000000 Hz6.2 dBmV39.5 dB3690
14LockedQAM25625591000000 Hz5.5 dBmV39.3 dB3970
15LockedQAM25626597000000 Hz6.8 dBmV39.5 dB2820
16LockedQAM25627603000000 Hz6.3 dBmV39.2 dB4250
17LockedQAM25628609000000 Hz6.1 dBmV40.3 dB00
18LockedQAM25629615000000 Hz6.6 dBmV40.3 dB00
19LockedQAM25630621000000 Hz6 dBmV39.5 dB00
20LockedQAM25631627000000 Hz6.5 dBmV39.4 dB00
21LockedQAM25632633000000 Hz6 dBmV39.8 dB00
22LockedQAM25634645000000 Hz6.2 dBmV39.4 dB00
23LockedQAM25635651000000 Hz5.5 dBmV39.4 dB00
24LockedQAM25636657000000 Hz5.4 dBmV39.4 dB00
 
Upstream Bonded Channels
Channel Lock Status US Channel Type Channel ID Symbol Rate Frequency Power
1LockedATDMA45120 Ksym/sec36500000 Hz50 dBmV
2LockedATDMA15120 Ksym/sec17300000 Hz49.5 dBmV
3LockedATDMA25120 Ksym/sec23700000 Hz49.8 dBmV
4LockedATDMA35120 Ksym/sec30100000 Hz50.5 dBmV
5Not LockedUnknown00 Ksym/sec0 Hz0.0 dBmV
6Not LockedUnknown00 Ksym/sec0 Hz0.0 dBmV
7Not LockedUnknown00 Ksym/sec0 Hz0.0 dBmV
8Not LockedUnknown00 Ksym/sec0 Hz0.0 dBmV
 
EG

Expert

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87K Messages

6 m ago

Yep. The upstream power is on the high side and it may be intermittently fluctuating even higher to out of spec levels. That can cause random disconnects, spontaneous re-booting of the modem, speed, packet loss, latency problems, and the un-bonding of channels.

In a self troubleshooting effort to try to obtain better connectivity / more wiggle room, check to see if there are there any excess/unneeded coax cable splitters in the line leading to the modem that can be eliminated/re-configured. Any splitters that remain should be high quality and cable rated for 5-1002 MHz, bi-directional, and no gold colored garbage types like GE, RadioShack, RCA, Philips, Leviton, Magnavox, and Rocketfish from big box stores like Home Depot, Lowes, Target, Wal-Mart etc. Splitters should be swapped with known to be good / new ones to test

If there aren't any unneeded splitters that can be eliminated and if your coax wiring setup can't be reconfigured so that there is a single two way splitter connected directly off of the drop from the street/pole with one port feeding the modem and the other port feeding the rest of the house/equipment with additional splits as needed, and you've checked all the wiring and fittings for integrity and tightness and refresh them by taking them apart then check for and clean off any corrosion / oxidation on the center wire and put them back together again, then perhaps it's best to book a tech visit to investigate and correct.

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Rmpondite

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7 Messages

6 m ago

No splitters that I've installed, only those put in by Comcast. I'll disconnect and spruce up and  reconnect all that I can and see if anything improves.

 

I'm not clear which numbers are indicative of this problem - can you be specific as to what I should be looking at and what the values should be, so that once I do what I can I can check it on my own? Thanks!

EG

Expert

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87K Messages

6 m ago

The upstream power ideally should be between 40 and 45 dB. It's all in the pinned troubleshooting tips post at the top of this board.. No one ever looks... You, by no means, wouldn't be the first...

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Rmpondite

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7 Messages

5 m ago

FYI the response from the Netgear boards was "the t3/t4 errors indicate line issues. The B-INIT-RNG Failure and no ucds received upstream line issues. this indicates the ISP needs to check the line. "  So both the Comcast- and Netgear-knowledgeable folks are saying it's the line.

 

But of course Comcast technical support's response was "nope, it's the modem because only Netgear modems give those types of errors and look, you're connected just fine right now and what you really need to do is call us while you're having the issue [which only ever lasts for a minute or so] and also it will fix everything if you upgrade to a higher speed Internet so let me push you to do that several times during this conversation."  I pushed to get an appointment anyway, to which I got several variations on "I just want to warn you that when they determine that it's your own equipment, there will be a service charge."

 

So my question now is, when the tech comes here, what do I need to tell them and make sure that they test so that they don't also immediately say that it's the modem? I just have this fear that they will have zero incentive to actually troubleshoot since all they have to say is "not our equipment, not our problem."

 

Thanks!

EG

Expert

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87K Messages

5 m ago

Show them this thread, if they'll even look.... Good luck with it !!!

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Rmpondite

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7 Messages

5 m ago

Good news: The tech assigned here heard me out (including the information from here), verified my cable modem model and age, and declared that he can't imagine that it would be the modem. He then evaluated everything from the street all the way to the modem, and while he didn't find any one big problem he found 9 different little problems that combined could have easily been the culprit: Several loose connections, a couple of corroded connections, a 4" cable segment, and a part that they stopped using years ago because it was the cause of various intermitten problems. He was so confident that it's not the cable modem that he said that if the problem isn't resolved he'll put in the notes that they need to check the lines from even further back in our neighborhood .

 

So I haven't looked back at the logs yet but I'm happy with the service that I received today. Thanks again for all of your help!

EG

Expert

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87K Messages

5 m ago

Quite welcome ! 

 

For curiosity, what do the signal status values look like now ?

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