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Intermittent Disconnects

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Intermittent Disconnects

I've had recurrent disconnects on my Internet connection ever since moving to a new apartment last June. The pattern with these disconnects is always the same: loss of upstream channels, followed by a modem reboot, at which point the modem searches for channels (which can take up to an hour or more).

 

I changed my modem from an Arris to a NETGEAR CM500 figuring it would fix the issue but to no avail. I've also asked for a tech to check the outlet, and according to him, the signal-to-noise ratio is just fine and there are no issues with the coax outlet itself.

 

Logs and data from CM500 attached. Wondering if anyone can figure out what the problem specifically is.

 

Time

Priority

Description

2020-7-4, 17:33:10

Notice (6)

Honoring MDD; IP provisioning mode = IPv6

2020-7-4, 17:33:03

Warning (5)

B-INIT-RNG Failure - Retries exceeded;CM-MAC=08:36:c9:4f:ee:38;CMTS-MAC=00:01:5c:a5:cc:53;CM-QOS=1.0;CM-VER=3.0;

2020-7-4, 17:26:57

Critical (3)

No Ranging Response received - T3 time-out;CM-MAC=08:36:c9:4f:ee:38;CMTS-MAC=00:01:5c:a5:cc:53;CM-QOS=1.0;CM-VER=3.0;

2020-7-4, 17:26:50

Critical (3)

SYNC Timing Synchronization failure - Failed to acquire FEC framing;CM-MAC=08:36:c9:4f:ee:38;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;

2020-7-4, 17:26:49

Critical (3)

Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=08:36:c9:4f:ee:38;CMTS-MAC=00:01:5c:a5:cc:53;CM-QOS=1.0;CM-VER=3.0;

2020-7-4, 17:18:49

Critical (3)

No Ranging Response received - T3 time-out;CM-MAC=08:36:c9:4f:ee:38;CMTS-MAC=00:01:5c:a5:cc:53;CM-QOS=1.0;CM-VER=3.0;

2020-7-4, 17:18:26

Critical (3)

Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=08:36:c9:4f:ee:38;CMTS-MAC=00:01:5c:a5:cc:53;CM-QOS=1.1;CM-VER=3.0;

2020-7-4, 17:14:06

Critical (3)

Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=08:36:c9:4f:ee:38;CMTS-MAC=00:01:5c:a5:cc:53;CM-QOS=1.1;CM-VER=3.0;

2020-7-4, 17:14:06

Critical (3)

16 consecutive T3 timeouts while trying to range on upstream channel 1;CM-MAC=08:36:c9:4f:ee:38;CMTS-MAC=00:01:5c:a5:cc:53;CM-QOS=1.1;CM-VER=3.0;

2020-7-4, 17:14:06

Critical (3)

Unicast Maintenance Ranging attempted - No response - Retries exhausted;CM-MAC=08:36:c9:4f:ee:38;CMTS-MAC=00:01:5c:a5:cc:53;CM-QOS=1.1;CM-VER=3.0;

2020-7-4, 17:12:59

Critical (3)

Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=08:36:c9:4f:ee:38;CMTS-MAC=00:01:5c:a5:cc:53;CM-QOS=1.1;CM-VER=3.0;

2020-6-29, 14:37:56

Notice (6)

Honoring MDD; IP provisioning mode = IPv6

2020-6-29, 14:37:51

Warning (5)

B-INIT-RNG Failure - Retries exceeded;CM-MAC=08:36:c9:4f:ee:38;CMTS-MAC=00:01:5c:a5:cc:53;CM-QOS=1.0;CM-VER=3.0;

2020-6-29, 14:31:47

Critical (3)

No Ranging Response received - T3 time-out;CM-MAC=08:36:c9:4f:ee:38;CMTS-MAC=00:01:5c:a5:cc:53;CM-QOS=1.0;CM-VER=3.0;

2020-6-29, 14:31:31

Critical (3)

Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=08:36:c9:4f:ee:38;CMTS-MAC=00:01:5c:a5:cc:53;CM-QOS=1.1;CM-VER=3.0;

2020-6-29, 14:27:16

Critical (3)

Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=08:36:c9:4f:ee:38;CMTS-MAC=00:01:5c:a5:cc:53;CM-QOS=1.1;CM-VER=3.0;

2020-6-29, 14:27:16

Critical (3)

16 consecutive T3 timeouts while trying to range on upstream channel 1;CM-MAC=08:36:c9:4f:ee:38;CMTS-MAC=00:01:5c:a5:cc:53;CM-QOS=1.1;CM-VER=3.0;

2020-6-29, 14:27:16

Critical (3)

Unicast Maintenance Ranging attempted - No response - Retries exhausted;CM-MAC=08:36:c9:4f:ee:38;CMTS-MAC=00:01:5c:a5:cc:53;CM-QOS=1.1;CM-VER=3.0;

2020-6-29, 14:26:47

Critical (3)

Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=08:36:c9:4f:ee:38;CMTS-MAC=00:01:5c:a5:cc:53;CM-QOS=1.1;CM-VER=3.0;

2020-6-29, 14:26:46

Critical (3)

16 consecutive T3 timeouts while trying to range on upstream channel 2;CM-MAC=08:36:c9:4f:ee:38;CMTS-MAC=00:01:5c:a5:cc:53;CM-QOS=1.1;CM-VER=3.0;

2020-6-29, 14:26:46

Critical (3)

Unicast Maintenance Ranging attempted - No response - Retries exhausted;CM-MAC=08:36:c9:4f:ee:38;CMTS-MAC=00:01:5c:a5:cc:53;CM-QOS=1.1;CM-VER=3.0;

2020-6-29, 14:25:39

Critical (3)

Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=08:36:c9:4f:ee:38;CMTS-MAC=00:01:5c:a5:cc:53;CM-QOS=1.1;CM-VER=3.0;

2020-6-28, 14:25:16

Notice (6)

Honoring MDD; IP provisioning mode = IPv6

2020-6-28, 14:20:55

Critical (3)

No Ranging Response received - T3 time-out;CM-MAC=08:36:c9:4f:ee:38;CMTS-MAC=00:01:5c:a5:cc:53;CM-QOS=1.0;CM-VER=3.0;

2020-6-28, 14:20:28

Critical (3)

Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=08:36:c9:4f:ee:38;CMTS-MAC=00:01:5c:a5:cc:53;CM-QOS=1.1;CM-VER=3.0;

2020-6-28, 14:15:53

Critical (3)

Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=08:36:c9:4f:ee:38;CMTS-MAC=00:01:5c:a5:cc:53;CM-QOS=1.1;CM-VER=3.0;

2020-6-28, 14:15:52

Critical (3)

16 consecutive T3 timeouts while trying to range on upstream channel 3;CM-MAC=08:36:c9:4f:ee:38;CMTS-MAC=00:01:5c:a5:cc:53;CM-QOS=1.1;CM-VER=3.0;

2020-6-28, 14:15:52

Critical (3)

Unicast Maintenance Ranging attempted - No response - Retries exhausted;CM-MAC=08:36:c9:4f:ee:38;CMTS-MAC=00:01:5c:a5:cc:53;CM-QOS=1.1;CM-VER=3.0;

2020-6-28, 14:14:45

Critical (3)

Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=08:36:c9:4f:ee:38;CMTS-MAC=00:01:5c:a5:cc:53;CM-QOS=1.1;CM-VER=3.0;

 

Downstream Bonded Channels

Channel

Lock Status

Modulation

Channel ID

Frequency

Power

SNR

Correctables

Uncorrectables

1

Locked

QAM256

32

597000000 Hz

1.8 dBmV

39.2 dB

912

153

2

Locked

QAM256

33

603000000 Hz

2 dBmV

39.6 dB

832

215

3

Locked

QAM256

34

609000000 Hz

1.9 dBmV

39.5 dB

1048

221

4

Locked

QAM256

35

615000000 Hz

1.1 dBmV

39.4 dB

701

214

5

Locked

QAM256

36

621000000 Hz

1.1 dBmV

39.6 dB

658

121

6

Locked

QAM256

37

627000000 Hz

1.2 dBmV

39.6 dB

658

229

7

Locked

QAM256

38

633000000 Hz

1.2 dBmV

39.6 dB

613

209

8

Locked

QAM256

39

639000000 Hz

2.3 dBmV

39.6 dB

668

141

9

Locked

QAM256

40

645000000 Hz

2.2 dBmV

39.7 dB

670

185

10

Locked

QAM256

41

651000000 Hz

1.6 dBmV

39.8 dB

682

136

11

Locked

QAM256

42

657000000 Hz

2.2 dBmV

39.9 dB

559

286

12

Locked

QAM256

43

663000000 Hz

1.3 dBmV

39.7 dB

695

130

13

Locked

QAM256

44

669000000 Hz

1.8 dBmV

39.9 dB

498

184

14

Locked

QAM256

45

675000000 Hz

2.9 dBmV

39.6 dB

564

207

15

Locked

QAM256

46

681000000 Hz

2.2 dBmV

39.9 dB

389

237

16

Locked

QAM256

47

687000000 Hz

1.8 dBmV

39.9 dB

381

122

 

Upstream Bonded Channels

Channel

Lock Status

US Channel Type

Channel ID

Symbol Rate

Frequency

Power

1

Locked

ATDMA

7

5120 Ksym/sec

23000000 Hz

52.3 dBmV

2

Locked

ATDMA

5

5120 Ksym/sec

36100000 Hz

53.5 dBmV

3

Locked

ATDMA

6

5120 Ksym/sec

29600000 Hz

53 dBmV

4

Locked

ATDMA

8

5120 Ksym/sec

16500000 Hz

52.5 dBmV

Highlighted
Expert

Re: Intermittent Disconnects

The upstream power is too high / out of spec.. 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.



I am not a Comcast Employee.
I am a Customer Expert volunteering my time to help other customers here in the Forums.
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New Poster

Re: Intermittent Disconnects

Hi EG,

 

Thanks for the response. I'll try and take a look behind the outlets to see if there are excess splitters, but I can't really do anything about removing splitters since I'm just renting and not owning my current place at the moment. (Not sure if the rental company would be fine with me doing that.)

 

For cleaning corrosion, what do you recommend for that (like cleaning agents)? Or would it be better to just replace the cables? I'm currently just using the Comcast-provided coax cables so it could be a cable quality problem.

Highlighted
Expert

Re: Intermittent Disconnects

Vinegar or Isopropyl alcohol should suffice. With really bad pitting, very fine emery cloth may be needed, but don't unnecessarily use too much rubbing.



I am not a Comcast Employee.
I am a Customer Expert volunteering my time to help other customers here in the Forums.
We ask that you post publicly so people with similar questions may benefit from the conversation.
Was your question answered? Mark the post as Best Answer!