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user_4t7yl5
1st Topic

2 Messages

Saturday, September 14th, 2024 7:00 AM

Having connection issues with Netgear CM1200 (Started Unicast Maintenance Ranging - No Response received - T3 time-out)

As the subject says, I'm getting bad lag even when rebooting/restarting the modem. I get latency issues when doing ping test and getting packet loss of 20-50%. And as I see, I'm not the only one having this problem. 

I called Comcast Business earlier today and was basically told that since I don't have a Comcast modem, he wouldn't help me. He said he saw no issues in my area and that was that. He said he'd start a ticket, [Edited: "Personal Information"], but when I checked back later, it was marked "closed". 

Frequency start Value
This field below allows you to modify the frequency the cable modem start with its scan during initialization and registration. Enter the new start frequency and restart the cable modem for it to take effect.
Starting Frequency
 
Startup Procedure
Procedure Status Comment
Acquire Downstream Channel 555000000 Hz Locked
Connectivity State OK Operational
Boot State OK Operational
Security Enabled BPI+
IP Provisioning Mode Honor MDD honorMdd(4)
 
Downstream Bonded Channels
Channel Lock Status Modulation Channel ID Frequency Power SNR Correctables Uncorrectables
1 Locked QAM256 28 555000000 Hz 2.6 dBmV 46.8 dB 0 0
2 Locked QAM256 13 453000000 Hz 2.3 dBmV 47.1 dB 0 0
3 Locked QAM256 14 459000000 Hz 2.3 dBmV 47.1 dB 0 0
4 Locked QAM256 15 465000000 Hz 2.3 dBmV 47.1 dB 0 0
5 Locked QAM256 16 471000000 Hz 2.4 dBmV 47.1 dB 0 0
6 Locked QAM256 17 477000000 Hz 2.4 dBmV 47.1 dB 0 0
7 Locked QAM256 18 483000000 Hz 2.5 dBmV 47.1 dB 0 0
8 Locked QAM256 19 489000000 Hz 2.5 dBmV 47 dB 0 0
9 Locked QAM256 20 495000000 Hz 2.6 dBmV 47.1 dB 0 0
10 Locked QAM256 21 501000000 Hz 2.5 dBmV 47 dB 0 0
11 Locked QAM256 22 507000000 Hz 2.6 dBmV 47.1 dB 0 0
12 Locked QAM256 23 513000000 Hz 2.6 dBmV 47 dB 0 0
13 Locked QAM256 24 519000000 Hz 2.6 dBmV 47 dB 0 0
14 Locked QAM256 25 525000000 Hz 2.6 dBmV 46.9 dB 0 0
15 Locked QAM256 26 531000000 Hz 2.5 dBmV 46.7 dB 0 0
16 Locked QAM256 27 543000000 Hz 2.6 dBmV 46.7 dB 0 0
17 Locked QAM256 29 561000000 Hz 2.6 dBmV 46.7 dB 0 0
18 Locked QAM256 30 567000000 Hz 2.6 dBmV 46.6 dB 0 0
19 Locked QAM256 31 573000000 Hz 2.5 dBmV 46.6 dB 0 0
20 Locked QAM256 32 579000000 Hz 2.4 dBmV 46.4 dB 0 0
21 Locked QAM256 33 585000000 Hz 2.6 dBmV 46.6 dB 0 0
22 Locked QAM256 34 591000000 Hz 2.5 dBmV 46.5 dB 0 0
23 Locked QAM256 35 597000000 Hz 2.7 dBmV 46.6 dB 0 0
24 Locked QAM256 36 603000000 Hz 2.7 dBmV 46.5 dB 0 0
25 Locked QAM256 37 609000000 Hz 2.7 dBmV 46.5 dB 0 0
26 Locked QAM256 38 615000000 Hz 2.7 dBmV 46.5 dB 0 0
27 Locked QAM256 39 621000000 Hz 2.8 dBmV 46.5 dB 0 0
28 Locked QAM256 40 627000000 Hz 2.9 dBmV 46.6 dB 0 0
29 Locked QAM256 41 633000000 Hz 3 dBmV 46.7 dB 0 0
30 Locked QAM256 42 639000000 Hz 3 dBmV 46.6 dB 0 0
31 Locked QAM256 43 645000000 Hz 3 dBmV 46.6 dB 0 0
32 Locked QAM256 44 651000000 Hz 3.1 dBmV 46.1 dB 0 0
 
Upstream Bonded Channels
Channel Lock Status US Channel Type Channel ID Symbol Rate Frequency Power
1 Locked ATDMA 17 5120 Ksym/sec 16400000 Hz 50 dBmV
2 Locked ATDMA 18 5120 Ksym/sec 22800000 Hz 50.3 dBmV
3 Locked ATDMA 19 5120 Ksym/sec 29200000 Hz 50.8 dBmV
4 Locked ATDMA 20 5120 Ksym/sec 35600000 Hz 50.8 dBmV
5 Not Locked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV
6 Not Locked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV
7 Not Locked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV
8 Not Locked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV
 
Downstream OFDM Channels
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 ,1 ,2 ,3 193 690000000 Hz 3.6 dBmV 46.5 dB 908 ~ 3187 10241818 4065623 0
2 Not Locked 0 0 0 Hz 0 dBmV 0.0 dB 0 ~ 4095 0 0 0
 
Upstream OFDMA Channels
Channel Lock Status Modulation / Profile ID Channel ID Frequency Power
1 Not Locked 0 0 0 Hz 0 dBmV
2 Not Locked 0 0 0 Hz 0 dBmV
 
Extended Upstream Transmit Power
Enable Extended Upstream Transmit Power
 
Current System Time:Sat Sep 14 01:56:53 2024

System Up Time:00:42:53

Time Priority Description
Sat Sep 14 01:59:06 2024 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;

Question

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Updated 

2 months ago

 • Edited

61

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EG

Expert

 • 

107.1K Messages

2 months ago

This may or may not be the root cause of the problem (YMMV) but it should be addressed regardless. 

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 an effort to try to obtain better connectivity / more wiggle room, check to see if there are 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 from Home Depot, Target, Wal-Mart, etc. Splitters should be swapped with known to be good / new ones to test.

Also check the coax cable for any damage such as cuts, nicks, abrasions, kinks, sharp bends, etc.

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.


Good luck with it !

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user_4t7yl5

2 Messages

@EG​ Thanks, but there are no splitters on the line. We had a problem similar to this about a year ago, they sent out a technician who checked the line outside. Couldn't find any issues. Had a service rep get in touch with me all week to see if there were still problems, but they ultimately couldn't find anything. Then the line had no problems at all for the past year. But then about a week ago, I started getting packet loss again. Rebooting the CM1200 would clear it and it would be fine for 12 or 13 hours, but then it started with lag again. 

BTW, this is the same equipment I had a year ago. Nothing has changed. No new lines. No new hardware. Now, even rebooting the modem doesn't work and I still latency problems right away. I did a search, and it seems that the Netgear CM1200 is mentioned a lot with this exact same problem, but I don't see any solution listed here. I see Comcast reaches out to them to private message them, but then that's as far as I can find. 

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2 months ago

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XfinityBillie

Official Employee

 • 

2.8K Messages

@user_4t7yl5 We appreciate you giving the steps @EG provided a try. I would be more than happy to double check things on our side and assist with getting a technician scheduled out if we determine one is needed. Please send us a DM to Xfinity Support with your full name and address to get started.


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2 months ago

EG

Expert

 • 

107.1K Messages

2 months ago

If there is nothing more that can be done to improve the connection quality, then you'll need a tech visit as stated. 


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 up 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. And if the problem is found to be on their side of the demarcation point, there will not be any charge.


Good luck !

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