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Intermittent T3 disconnects

Regular Visitor

Intermittent T3 disconnects

Over the past few months I've been getting a lot of disconnects on my Cable modem. sometimes 2-3 a day and the only thing that helps is rebooting my modem. It's getting a little annoying having to do this multiple times each day. Modem model is Netgear C7000v2

 

Looking through the router logs, every time it happens its showing a T3 timeout. 

Time Priority Description
1970-1-1, 00:00:52 Notice (6) Honoring MDD; IP provisioning mode = IPv6
1970-1-1, 00:00:45 Critical (3) No Ranging Response received - T3 time-out;CM-MAC=10:0c:6b:8a:d0:a8;CMTS-MAC=00:01:5c:62:ba:53;CM-QOS=1.0;CM-VER=3.0;
1970-1-1, 00:00:41 Notice (6) WiFi Interface [wl1] set to Channel 157 (Side-Band Channel:N/A) - Reason:INIT
1970-1-1, 00:00:41 Notice (6) WiFi Interface [wl0] set to Channel 11 (Side-Band Channel:N/A) - Reason:INIT
1970-1-1, 00:00:39 Critical (3) SYNC Timing Synchronization failure - Failed to acquire FEC framing;CM-MAC=10:0c:6b:8a:d0:a8;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=10:0c:6b:8a:d0:a8;CMTS-MAC=00:01:5c:62:ba:53;CM-QOS=1.0;CM-VER=3.0;
1970-1-1, 00:00:37 Critical (3) SYNC Timing Synchronization failure - Failed to acquire FEC framing;CM-MAC=10:0c:6b:8a:d0:a8;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=10:0c:6b:8a:d0:a8;CMTS-MAC=00:01:5c:62:ba:53;CM-QOS=1.0;CM-VER=3.0;
1970-1-1, 00:00:39 Critical (3) SYNC Timing Synchronization failure - Failed to acquire FEC framing;CM-MAC=10:0c:6b:8a:d0:a8;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=10:0c:6b:8a:d0:a8;CMTS-MAC=00:01:5c:62:ba:53;CM-QOS=1.0;CM-VER=3.0;
1970-1-1, 00:00:39 Critical (3) SYNC Timing Synchronization failure - Failed to acquire FEC framing;CM-MAC=10:0c:6b:8a:d0:a8;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
2019-11-21, 09:04:39 Critical (3) Resetting the cable modem due to docsDevResetNow
1970-1-1, 00:00:43 Critical (3) No Ranging Response received - T3 time-out;CM-MAC=10:0c:6b:8a:d0:a8;CMTS-MAC=00:01:5c:62:ba:53;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=10:0c:6b:8a:d0:a8;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
2019-11-19, 08:40:54 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=10:0c:6b:8a:d0:a8;CMTS-MAC=00:01:5c:62:ba:53;CM-QOS=1.1;CM-VER=3.0;

 

I've done some research on this error and so far what I've done is checked the wire connections in the home, made sure that I don't have any splitters, put a signal amplifier on the cable line to the router to help with any signal noise upstream, and still haven't had improvement. 

Startup Procedure
Procedure Status Comment
Acquire Downstream Channel 513000000 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 24 513000000 Hz 5.1 dBmV 39.8 dB 0 0
2 Locked QAM256 25 519000000 Hz 5.3 dBmV 39.9 dB 0 0
3 Locked QAM256 26 525000000 Hz 5.1 dBmV 39.8 dB 0 0
4 Locked QAM256 27 531000000 Hz 5.1 dBmV 39.7 dB 0 0
5 Locked QAM256 28 543000000 Hz 4.9 dBmV 39.6 dB 0 0
6 Locked QAM256 29 555000000 Hz 5 dBmV 39.5 dB 0 0
7 Locked QAM256 30 561000000 Hz 5 dBmV 39.2 dB 0 0
8 Locked QAM256 31 567000000 Hz 5.1 dBmV 39.5 dB 0 0
9 Locked QAM256 32 573000000 Hz 4.9 dBmV 39.4 dB 0 0
10 Locked QAM256 33 579000000 Hz 5.2 dBmV 39.5 dB 0 0
11 Locked QAM256 34 585000000 Hz 5.4 dBmV 39.4 dB 0 0
12 Locked QAM256 35 591000000 Hz 5.7 dBmV 39.4 dB 0 0
13 Locked QAM256 36 597000000 Hz 5.8 dBmV 39.4 dB 0 0
14 Locked QAM256 37 603000000 Hz 5.7 dBmV 39.2 dB 0 0
15 Locked QAM256 38 609000000 Hz 5.8 dBmV 39.3 dB 0 0
16 Locked QAM256 39 615000000 Hz 5.8 dBmV 39.2 dB 0 0
17 Locked QAM256 40 621000000 Hz 5.4 dBmV 39.5 dB 0 0
18 Locked QAM256 41 627000000 Hz 5.4 dBmV 39.4 dB 0 0
19 Locked QAM256 42 633000000 Hz 5.6 dBmV 39.8 dB 0 0
20 Locked QAM256 43 639000000 Hz 5.5 dBmV 39.5 dB 0 0
21 Locked QAM256 44 645000000 Hz 5.4 dBmV 39.4 dB 0 0
22 Locked QAM256 45 651000000 Hz 5.3 dBmV 39.4 dB 0 0
23 Locked QAM256 46 657000000 Hz 5.4 dBmV 39.4 dB 0 0
24 Locked QAM256 47 663000000 Hz 5.3 dBmV 39.4 dB 0 0
 
Upstream Bonded Channels
Channel Lock Status US Channel Type Channel ID Symbol Rate Frequency Power
1 Locked ATDMA 4 5120 Ksym/sec 36500000 Hz 45.8 dBmV
2 Locked ATDMA 1 5120 Ksym/sec 17300000 Hz 46.8 dBmV
3 Locked ATDMA 2 5120 Ksym/sec 23700000 Hz 46.3 dBmV
4 Locked ATDMA 3 5120 Ksym/sec 30100000 Hz 46.3 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

 

I've reached the extent of what I can figure out on my own. Any assistance or ideas on what else I can do to help fix this issue would be appreciated.

Expert

Re: Intermittent T3 disconnects

Even though the signal stats looked o/k at that snapshot in time, the error log entries confirm that something is going on. Perhaps there is noise ingress into the line(s) somewhere.

 

There are other signal stat figures that can't be read by the modem. They are the "Upstream Rx Power" (Upstream Receive Power Level), the "Upstream SNR Ch." (Upstream Signal To Noise Ratio), and the "Upstream ICFR" (In Channel Frequency Response). These are as equally important in diagnosing connectivity issues as are the modem's stats.


I'm going to escalate your issue to the Comcast corporate employees that are available to these boards. They can check the CMTS (Cable Modem Termination System) for any real time degradation and / or error reports, see your node / cable plant and modem health, and see whether or not everything is in the green zone. They can also see a history plot for the modem and poll for those upstream receive signal stats.

You should get a reply here in your topic. Good luck !



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I am a Customer Expert volunteering my time to help other customers here in the Forums.
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Regular Visitor

Re: Intermittent T3 disconnects

Thanks for your help. The stats I posted were right after a restart of my modem from one of those issues. I can try to post the stats during the next time I have an issue if that would be helpful.

Expert

Re: Intermittent T3 disconnects

Comparisons can't hurt !



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I am a Customer Expert volunteering my time to help other customers here in the Forums.
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Official Employee

Re: Intermittent T3 disconnects

Greetings, Jedivestis! We appreciate you taking the time to reach out to us here on the forums. We hope you are having an amazing day. We apologize to hear of the issues you are running into with the drop connection. This is certainly frustrating. We would like to look closer into this for you. Can you please send us a PM with your first and last name so we may further assist you?

 

To send a private message, please click the name "Comcast_Support" then select "Send a Message" on the right side.


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Regular Visitor

Re: Intermittent T3 disconnects

Still waiting on Comcast, said they were going to watch things on their end for a few days. But I did get the cable connection stats for while I was having an issue.

 

Channel

Lock Status

Modulation

Channel ID

Frequency

Power

SNR

Correctables

Uncorrectables

1

Locked

QAM256

24

513000000 Hz

5.7 dBmV

39.9 dB

44

144

2

Locked

QAM256

25

519000000 Hz

5.9 dBmV

40 dB

61

234

3

Locked

QAM256

26

525000000 Hz

5.8 dBmV

39.9 dB

46

183

4

Locked

QAM256

27

531000000 Hz

5.8 dBmV

39.9 dB

49

196

5

Locked

QAM256

28

543000000 Hz

5.7 dBmV

39.8 dB

67

317

6

Locked

QAM256

29

555000000 Hz

5.9 dBmV

39.7 dB

38

153

7

Locked

QAM256

30

561000000 Hz

5.9 dBmV

39.4 dB

35

140

8

Locked

QAM256

31

567000000 Hz

6 dBmV

39.7 dB

61

291

9

Locked

QAM256

32

573000000 Hz

5.7 dBmV

39.6 dB

39

167

10

Locked

QAM256

33

579000000 Hz

6 dBmV

39.7 dB

36

163

11

Locked

QAM256

34

585000000 Hz

6.1 dBmV

39.6 dB

31

175

12

Locked

QAM256

35

591000000 Hz

6.3 dBmV

39.6 dB

50

211

13

Locked

QAM256

36

597000000 Hz

6.4 dBmV

39.6 dB

32

191

14

Locked

QAM256

37

603000000 Hz

6.2 dBmV

39.4 dB

69

283

15

Locked

QAM256

38

609000000 Hz

6.3 dBmV

39.5 dB

34

150

16

Locked

QAM256

39

615000000 Hz

6.2 dBmV

39.4 dB

32

124

17

Locked

QAM256

40

621000000 Hz

5.9 dBmV

39.8 dB

0

0

18

Locked

QAM256

41

627000000 Hz

5.9 dBmV

39.9 dB

0

0

19

Locked

QAM256

42

633000000 Hz

6.1 dBmV

39.9 dB

0

0

20

Locked

QAM256

43

639000000 Hz

6.1 dBmV

39.9 dB

0

0

21

Locked

QAM256

44

645000000 Hz

6.1 dBmV

39.8 dB

0

0

22

Locked

QAM256

45

651000000 Hz

5.9 dBmV

39.8 dB

0

0

23

Locked

QAM256

46

657000000 Hz

6.1 dBmV

39.8 dB

0

0

24

Locked

QAM256

47

663000000 Hz

5.9 dBmV

39.8 dB

0

0

 

Upstream Bonded Channels (Partial Service)

Channel

Lock Status

US Channel Type

Channel ID

Symbol Rate

Frequency

Power

1

Locked

ATDMA

2

5120 Ksym/sec

23700000 Hz

47.3 dBmV

2

Locked

ATDMA

1

5120 Ksym/sec

17300000 Hz

48 dBmV

3

Not Locked

Unknown

3

0 Ksym/sec

30100000 Hz

0.0 dBmV

4

Not Locked

Unknown

4

0 Ksym/sec

36500000 Hz

0.0 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

Expert

Re: Intermittent T3 disconnects

So there are only 2 upstream channels locked now where there was 4 before. Something is going on in the return path. I'm going to re-escalate your issue.


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