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Internet connection flapping (No Ranging Response Received)

jchristmas
Regular Visitor

Internet connection flapping (No Ranging Response Received)

For the past 2 weeks I have had random moments where my internet just stops working. It usually happens for 15-30 minutes at a time and can happen anywhere from once a day to 5 or more times a day.

When it happens my router is no longer able to communicate and sees the connection between the modem and itself as down.

When it comes back up I am able to see the logs and I see during that time all these critical notices for No Ranging Responses Received. I called support one day when it lasted a lot longer than normal and since they couldnt reach my modem they opted to just get a tech out here.

The tech checked the lines and what not and everything he saw looked good. He wanted to reset my router and eventually reset it to factory defaults. I have a AC-5300 and with all the new firmware updates it can take some time to reboot. His diagnosis was the router must be at fault as sometimes it was taking a bit longer to come up and normal. It always came back up in the end and the logs on it indicate no issues at all.

Really interested in seeing if someone here can get a comcast engineer to look at the VCMTS logs and stats to determine if the problem is there or some other potential noise in the line.

 

One final note I own both my router and my modem the modem is a Netgear CM1000 if it makes a difference.


Cheers thanks

EG
Expert

Re: Internet connection flapping (No Ranging Response Received)

What do the modem's signal stats look like ? Try getting 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.





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jchristmas
Regular Visitor

Re: Internet connection flapping (No Ranging Response Received)

Acquire Downstream Channel 697750000 Hz Locked
Connectivity State OK Operational
Boot State OK Operational
Security Enable BPI+
IP Provisioning Mode Honor MDD IPv6 only

<tabindex=-1>Downstream Bonded Channels</tabindex=-1>
Channel Lock Status Modulation Channel ID Frequency Power SNR / MER Unerrored Codewords Correctable Codewords Uncorrectable Codewords
1 Locked QAM256 34 697750000 Hz -3.6 dBmV 38.9 dB 3994186240 34065 7027
2 Locked QAM256 10 559750000 Hz -1.1 dBmV 40.3 dB 3946225153 66843 9570
3 Locked QAM256 11 565750000 Hz -1.2 dBmV 40.3 dB 3946328623 55597 8059
4 Locked QAM256 12 571750000 Hz -1.0 dBmV 40.3 dB 3946436295 53089 7238
5 Locked QAM256 13 577750000 Hz -1.0 dBmV 40.3 dB 3946600935 46933 7319
6 Locked QAM256 14 583750000 Hz -1.0 dBmV 40.4 dB 3946750203 45397 7521
7 Locked QAM256 15 589750000 Hz -1.0 dBmV 40.2 dB 3946859997 44237 7005
8 Locked QAM256 16 595750000 Hz -1.0 dBmV 40.1 dB 3946979884 41878 6659
9 Locked QAM256 17 601750000 Hz -0.9 dBmV 40.2 dB 3947172357 39352 6468
10 Locked QAM256 18 607750000 Hz -1.5 dBmV 39.9 dB 3947295389 33859 6277
11 Locked QAM256 19 613750000 Hz -1.7 dBmV 39.8 dB 3947472487 23939 5864
12 Locked QAM256 20 619750000 Hz -1.3 dBmV 39.9 dB 3947595734 20704 5897
13 Locked QAM256 21 625750000 Hz -1.4 dBmV 39.8 dB 3947740118 16790 6111
14 Locked QAM256 22 631750000 Hz -1.7 dBmV 39.8 dB 3947937727 14571 6093
15 Locked QAM256 23 637750000 Hz -1.7 dBmV 39.8 dB 3948046567 13871 6025
16 Locked QAM256 24 643750000 Hz -1.6 dBmV 39.9 dB 3948194920 13019 6121
17 Locked QAM256 25 649750000 Hz -1.7 dBmV 39.8 dB 3809042778 9337 5734
18 Locked QAM256 26 655750000 Hz -2.1 dBmV 39.6 dB 3809112966 9891 5877
19 Locked QAM256 27 661750000 Hz -2.2 dBmV 39.5 dB 3809164809 9654 5667
20 Locked QAM256 28 667750000 Hz -2.4 dBmV 39.4 dB 3809174900 7574 5293
21 Locked QAM256 30 673750000 Hz -2.8 dBmV 38.9 dB 3809301320 6694 5084
22 Locked QAM256 31 679750000 Hz -3.1 dBmV 39.1 dB 3809426453 5376 4678
23 Locked QAM256 32 685750000 Hz -3.0 dBmV 39.2 dB 3809554912 4802 4442
24 Locked QAM256 33 691750000 Hz -3.5 dBmV 38.9 dB 3809704585 4148 4437
25 Locked QAM256 35 703750000 Hz -3.7 dBmV 38.9 dB 3809848874 4091 3915
26 Locked QAM256 36 709750000 Hz -4.2 dBmV 38.7 dB 3809948800 3534 3952
27 Locked QAM256 37 715750000 Hz -4.5 dBmV 38.6 dB 3810018764 3465 3191
28 Locked QAM256 38 721750000 Hz -4.9 dBmV 38.5 dB 3810043624 3397 2850
29 Locked QAM256 39 727750000 Hz -5.1 dBmV 38.2 dB 3809595338 3976 3392
30 Locked QAM256 40 733750000 Hz -5.9 dBmV 37.8 dB 3809656127 3376 2689
31 Locked QAM256 41 739750000 Hz -6.6 dBmV 37.4 dB 3809808648 3866 1959
32 Not Locked Unknown 0 0 Hz 0.0 dBmV 0.0 dB 0 0 0

<tabindex=-1>Upstream Bonded Channels</tabindex=-1>
Channel Lock Status Modulation Channel ID Frequency Power
1 Locked ATDMA 5 36500000 Hz 50.0 dBmV
2 Locked ATDMA 6 30100000 Hz 50.3 dBmV
3 Locked ATDMA 7 23700000 Hz 49.3 dBmV
4 Locked ATDMA 8 17300000 Hz 48.0 dBmV
5 Not Locked Unknown 0 0 Hz 0.0 dBmV
6 Not Locked Unknown 0 0 Hz 0.0 dBmV
7 Not Locked Unknown 0 0 Hz 0.0 dBmV
8 Not Locked Unknown 0 0 Hz 0.0 dBmV

<tabindex=-1>Downstream OFDM Channels</tabindex=-1>
Channel Lock Status Modulation / Profile ID Channel ID Frequency Power SNR / MER Active Subcarrier Number Range Unerrored Codewords Correctable Codewords Uncorrectable Codewords
1 Locked 0 29 780000000 Hz -8.8 dBmV 31.8 dB 1108 ~ 2987 6983670905 527890005 2
2 Not Locked 0 0 0 Hz 3.7 dBmV 0.0 dB 0 ~ 4095 0 0 0

<tabindex=-1>Upstream OFDMA Channels</tabindex=-1>
Channel Lock Status Modulation / Profile ID Channel ID Frequency Power
1 Not Locked Unknown 0 0 Hz 0 dBmV
2 Not Locked Unknown 0 0 Hz 0 dBmV
EG
Expert

Re: Internet connection flapping (No Ranging Response Received)

The upstream power is too high and it may be intermittently fluctuating even farther out of spec. That can cause random disconnects, spontaneous re-booting of the modem, speed, packet loss, and latency problems.

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 it's best to get the techs re-involved until it is fixed properly. Good luck !!



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jchristmas
Regular Visitor

Re: Internet connection flapping (No Ranging Response Received)

My current connection is using a splitter per your specs (one installed by the comcast installation expert). Its currently connected directly from the street and splits off as you suggested should be done.

I will clean up the cables and order a replacement splitter to see if perhaps that fixes it otherwise I guess its time to get the techs back out here again...

I looked online and according so several sites because I am a multi-channel ATDMA the power should be

Three or more TDMA 1280 Ksym/sec +55 dBmV  45 dBmV
ATDMA 2560 Ksym/sec +52 dBmV  45 dBmV
5120 Ksym/sec +51 dBmV  45 dBmV

I am within these ranges so I am a bit confused on what you believe the power level should be for the upstream? Also isnt this something they could configure on the modem directly similar to wifi signal power?

Thanks for the help I will give it another go or two for now.

 

EG
Expert

Re: Internet connection flapping (No Ranging Response Received)

The Comcast plant / engineering specs are the only ones that matter. Not something found on the internet... From the Troubleshooting Tips sticky topic at the top of this board;

 

Specification      Min             Max
Downstream Power Level    
Cable Modems -10dBmV +10dBmV
Gateways and EMTAs -7dBmV +7dBmV
Downstream Signal to Noise Ratio 35dB -
Upstream Power Level +35dBmV +50dBmV
Upstream Signal to Noise Ratio 31dB -
Upstream Receive Power -2dBmV +2dBmV

 

And I guess that you overlooked the part that I stated about "may be intermittently fluctuating higher out of spec" (many readers do) ? Wiggle room is always needed !

 

As stated, if you can't get it to be any better, get a tech out to investigate / correct it.  Bear in mind that if the premises facing techs can not find or fix a problem at your home, it is they who are responsible for escalating it to their line / network / maintenance dept. techs. The problem may lie beyond your home in the local neighborhood infrastructure somewhere but it is their S.O.P. to start at the home.


Good luck with it !



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Xephyr
New Poster

Re: Internet connection flapping (No Ranging Response Received)

Thanks to @EG 

 

After upgrading to 1Gbps internet since June 2020. Been smooth for a few months, with occational internet drops, that required reboot the CM1200 Netgear modem. Started with once a month, then once a week, to last weeks (Dec. 2020) twice to 3 times a day. Finally started troubleshooting by looking at logs 192.168.100.1 signals and lots of searches to find signal problems. This thread where the upstream power is too high (50-50.3 dBmv) and near the spec boundries seems to be off for my signals (besides for some reason my modem only locks to 9 downstream bonded channels from 543000000 most of the time). After reroute cable directly to cable box, removing 1 unnecessary spliter, and hook up cable modem to only 1 spliter at the -3.5dB output.  The upstream power is now down to 41.3~41.5 dBmv). All channels has 0 correctable and 0 uncorrectable packages before and after this cable reroute, also download speed with wired internet is around 940mbps (when its working.)

 

Will continue to monitor and see if any drop occurs. I also tried to view the modem after an hour live online, seems to connect more downstream channels at higher frequencies. 603-675000000hz. I don't have any clue if this has any impact as when i started troubleshooting it only had 9 channels from 543-597000000. For some reason frequency 483-531000000 never locks.

 

thanks again for this great spec. on the upstream bonding channel signal power!

 

Sincerely!

 

 
EG
Expert

Re: Internet connection flapping (No Ranging Response Received)

Quite welcome  ! Glad you got it figured out !  9 month old dead thread now being closed.



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