Modem issue - internet intermittently dropping

Hi All,

I'm trying to figure out if this is a modem issue or a cable issue - my internet keeps dropping intermittently. I reset my router (Orbi mesh) and restarted my modem multiple times. Disconnected and reconnected the coax cable but still having the issue. Here is what my cable modem status is looking like:

Downstream

Bonding Channel Value

Channel ID

5

1

2

3

4

6

7

8

Frequency

459000000 Hz

435000000 Hz

441000000 Hz

447000000 Hz

453000000 Hz

465000000 Hz

471000000 Hz

477000000 Hz

Signal to Noise Ratio

39 dB

40 dB

39 dB

Downstream Modulation

QAM256

Power Level

The Downstream Power Level reading is a snapshot taken at the time this page was requested. Please Reload/Refresh this Page for a new reading

14 dBmV

13 dBmV

Upstream	Bonding Channel Value
Channel ID	5	4	3	2
Frequency	35600000 Hz	29200000 Hz	22800000 Hz	16400000 Hz
Ranging Service ID	6061	6061	6061	6061
Symbol Rate	5.120 Msym/sec	5.120 Msym/sec	5.120 Msym/sec	5.120 Msym/sec
Power Level	34 dBmV	34 dBmV	34 dBmV	34 dBmV
Upstream Modulation	[2] QPSK [1] 32QAM [3] 64QAM	[2] QPSK [1] 32QAM [3] 64QAM	[2] QPSK [1] 32QAM [3] 64QAM	[2] QPSK [1] 32QAM [3] 64QAM
Ranging Status	Success	T4 TimeOut	T4 TimeOut	T4 TimeOut

Signal Status (Codewords)	Bonding Channel Value
Channel ID	5	1	2	3	4	6	7	8
Total Unerrored Codewords	24202603	24209953	24218747	24194110	24181896	24182472	24183282	24184257
Total Correctable Codewords	24	0	7	5	48	16	12	43
Total Uncorrectable Codewords	650	1499	1329	518	1556	583	1506	1501

Any thoughts on whether this is a modem vs. cable issue?

TIA

Responses

Accepted Solution

hkp703

Regular Visitor

•

12 Messages

3 years ago

In case anyone stumbles upon this thread - the issue was finally resolved by Comcast techs who came on site. Apparently there was a filter on the line at the pole which needed to be removed. This fixed the connection in that my upstream channels were able to bond. Prior to this, only one out of 4 channels or so were bonding.

0

U

user_bb801b

Contributor

•

167 Messages

3 years ago

Hey unfortunate to hear that internet is spotty.. To understand issue, what gateway are we talking about here? Is this WIFI or ethernet connected device that's having issues?

Before going down the rabbit hole, what does https://internet.xfinity.com/network/health output say?

Just my .2 cents.

Thanks and good luck.

1

0

EG

Expert

•

110.1K Messages

3 years ago

@hkp703

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

The downstream power is too high. It may be over-driving the front-end receiver circuit of the modem. That can cause random disconnects, spontaneous re-booting of the modem, speed, packet loss, latency problems, and the un-bonding of channels.

Is there a drop amplifier on the coax cable line leading to the modem ? If so, try removing / bypassing it and see. If not, you can try installing a -6 dB attenuator pad such as this one to knock that power level down and see;

https://www.amazon.com/6db-Attenuator-Pad-1-each/dp/B0013L48XA

Good luck !

5

0

hkp703

Regular Visitor

•

12 Messages

@EG

Awesome, thank you. This is cheap enough for me to try it out and see if it works. We had a Comcast tech come out today but I was on a Zoom call and couldn't talk to him. I think he looked at the drop and left - didn't change anything and my stats still look the same:

Downstream

Bonding Channel Value

Channel ID

33

34

35

36

37

38

39

40

Frequency

627000000 Hz

633000000 Hz

639000000 Hz

645000000 Hz

651000000 Hz

657000000 Hz

663000000 Hz

669000000 Hz

Signal to Noise Ratio

38 dB

Downstream Modulation

QAM256

Power Level

The Downstream Power Level reading is a snapshot taken at the time this page was requested. Please Reload/Refresh this Page for a new reading

8 dBmV

7 dBmV

Upstream	Bonding Channel Value
Channel ID	5	4	3	2
Frequency	35600000 Hz	29200000 Hz	22800000 Hz	16400000 Hz
Ranging Service ID	6061	6061	6061	6061
Symbol Rate	5.120 Msym/sec	5.120 Msym/sec	5.120 Msym/sec	5.120 Msym/sec
Power Level	34 dBmV	34 dBmV	34 dBmV	34 dBmV
Upstream Modulation	[2] QPSK [1] 32QAM [3] 64QAM	[2] QPSK [1] 32QAM [3] 64QAM	[2] QPSK [1] 32QAM [3] 64QAM	[2] QPSK [1] 32QAM [3] 64QAM
Ranging Status	Success	T4 TimeOut	T4 TimeOut	T4 TimeOut

Signal Status (Codewords)	Bonding Channel Value
Channel ID	33	34	35	36	37	38	39	40
Total Unerrored Codewords	553560655	553590347	553588057	553615013	553553969	553552781	553550091	553546336
Total Correctable Codewords	68	18	21	12	62	20	32	33
Total Uncorrectable Codewords	2273	3047	3075	2914	2228	3149	3028	3010

3 years ago

0

EG

Expert

•

110.1K Messages

Actually, the downstream power is now 6 to 7dB lower. The tech may have already installed an attenuator pad or removed an amp. The bottom line is to see if the problem is now gone or not.

I am not a Comcast Employee.
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We ask that you post publicly so people with similar questions may benefit from the conversation.

Was your question answered? Please mark an Accepted Answer! tick

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3 years ago

0

hkp703

Regular Visitor

•

12 Messages

Sadly I still have the issue. I'm thinking of buying a new modem and trying it out to see if it fixes the issue. Still getting T4 timeouts. I've to scour the basement to see if we have any splitters that I can replace/get rid of.

3 years ago

0

EG

Expert

•

110.1K Messages

Please post the error log entries as well in their entirety (copy and paste them, don't post a screenshot) but redact the CM MAC and the CMTS MAC addresses for your privacy. They are considered to be personal information. Personally identifying information is a violation of their forum guidelines. The forum bot will not allow your post to be seen publically.

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? Please mark an Accepted Answer! tick

3 years ago

hkp703

Regular Visitor

•

12 Messages

Here are the latest log entries:

Time	Priority	Code	Message
Jan 21 2022 17:10:07	3-Critical	R04.0	Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;;CM-QOS=1.1;CM-VER=3.0;
Jan 21 2022 17:09:57	3-Critical	R05.0	Started Unicast Maintenance Ranging - No Response received - T3 time-out;;CM-QOS=1.1;CM-VER=3.0;
Jan 21 2022 17:09:47	3-Critical	R04.0	Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;;CM-QOS=1.1;CM-VER=3.0;
Jan 21 2022 17:09:37	3-Critical	R05.0	Started Unicast Maintenance Ranging - No Response received - T3 time-out;;CM-QOS=1.1;CM-VER=3.0;
Jan 21 2022 17:09:17	3-Critical	R04.0	Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;;CM-QOS=1.1;CM-VER=3.0;
Jan 21 2022 17:09:17	3-Critical	R05.0	Started Unicast Maintenance Ranging - No Response received - T3 time-out;;CM-QOS=1.1;CM-VER=3.0;
Jan 21 2022 17:09:07	3-Critical	R04.0	Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;;CM-QOS=1.1;CM-VER=3.0;
Jan 21 2022 17:08:37	3-Critical	R05.0	Started Unicast Maintenance Ranging - No Response received - T3 time-out;;CM-QOS=1.1;CM-VER=3.0;
Jan 21 2022 17:08:27	3-Critical	R04.0	Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;;CM-QOS=1.1;CM-VER=3.0;
Jan 21 2022 17:08:17	3-Critical	R05.0	Started Unicast Maintenance Ranging - No Response received - T3 time-out;;CM-QOS=1.1;CM-VER=3.0;
Jan 21 2022 17:07:57	3-Critical	R04.0	Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;;CM-QOS=1.1;CM-VER=3.0;
Jan 21 2022 17:07:57	3-Critical	R05.0	Started Unicast Maintenance Ranging - No Response received - T3 time-out;;CM-QOS=1.1;CM-VER=3.0;
Jan 21 2022 17:07:47	3-Critical	R04.0	Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;;CM-QOS=1.1;CM-VER=3.0;
Jan 21 2022 17:07:17	3-Critical	R05.0	Started Unicast Maintenance Ranging - No Response received - T3 time-out;;CM-QOS=1.1;CM-VER=3.0;
Jan 21 2022 17:07:08	3-Critical	R04.0	Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;;CM-QOS=1.1;CM-VER=3.0;
Jan 21 2022 17:06:57	3-Critical	R05.0	Started Unicast Maintenance Ranging - No Response received - T3 time-out;;CM-QOS=1.1;CM-VER=3.0;
Jan 21 2022 17:06:38	3-Critical	R04.0	Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;;CM-QOS=1.1;CM-VER=3.0;
Jan 21 2022 17:06:38	3-Critical	R05.0	Started Unicast Maintenance Ranging - No Response received - T3 time-out;;CM-QOS=1.1;CM-VER=3.0;
Jan 21 2022 17:06:28	3-Critical	R04.0	Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;;CM-QOS=1.1;CM-VER=3.0;
Jan 21 2022 17:05:58	3-Critical	R05.0	Started Unicast Maintenance Ranging - No Response received - T3 time-out;;CM-QOS=1.1;CM-VER=3.0;

3 years ago

0

EG

Expert

•

110.1K Messages

3 years ago

So, 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) / an upstream channel-return path impairment 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 !

3

hkp703

Regular Visitor

•

12 Messages

@EG Awesome, thank you so much. I appreciate you diving into this and escalating to Comcast!

3 years ago

0

EG

Expert

•

110.1K Messages

Quite welcome ! Please post back with how things turn out.

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? Please mark an Accepted Answer! tick

3 years ago

CCValerie

Official Employee

•

974 Messages

Hi there, @hkp703, thank you for reaching out through our Xfinity Forums and working with our Customer Experts! They really are amazing! I know how important it is to have a reliable connection and I can definitely take a look at your modem and signals further. Please send us a direct message with your full name and service address.

Here's the detailed steps to direct message us:

• Click "Sign In" if necessary

• Click the "Peer to peer chat" icon (upper right corner of this page)

• Click the "New message" (pencil and paper) icon

• Type "Xfinity Support" in the to line and select "Xfinity Support" from the drop-down list

• Type your message in the text area near the bottom of the window

• Press Enter to send your message

I no longer work for Comcast.

I am an Official Xfinity Employee.
Official Employees are from multiple teams within Xfinity: CARE, Product, Leadership.
We ask that you post publicly so people with similar questions may benefit from the conversation.
Was your question answered? Please, mark a reply as the Accepted Answer. tick

3 years ago

0

EG

Expert

•

110.1K Messages

3 years ago

Glad it got squared away ? For curiosity, would you please post what the signal values look like now ?

1

hkp703

Regular Visitor

•

12 Messages

@EG Here you go - I have more channels for upstream and downstream now as I'm finally able to use the Docsis 3.1 modem I bought 2 years ago but couldn't use because of the cable issue:

Downstream Bonded Channels
Channel ID	Lock Status	Modulation	Frequency	Power	SNR/MER	Corrected	Uncorrectables
41	Locked	QAM256	675000000 Hz	6.7 dBmV	39.4 dB	0	0
13	Locked	QAM256	507000000 Hz	10.9 dBmV	41.9 dB	0	0
14	Locked	QAM256	513000000 Hz	10.7 dBmV	41.9 dB	0	0
15	Locked	QAM256	519000000 Hz	10.7 dBmV	41.9 dB	0	0
16	Locked	QAM256	525000000 Hz	10.3 dBmV	41.5 dB	0	0
17	Locked	QAM256	531000000 Hz	10.2 dBmV	41.6 dB	0	0
18	Locked	QAM256	537000000 Hz	10.3 dBmV	41.7 dB	0	0
19	Locked	QAM256	543000000 Hz	10.0 dBmV	41.6 dB	0	0
20	Locked	QAM256	549000000 Hz	10.0 dBmV	41.6 dB	0	0
21	Locked	QAM256	555000000 Hz	9.8 dBmV	41.5 dB	0	0
22	Locked	QAM256	561000000 Hz	9.9 dBmV	41.5 dB	0	0
23	Locked	QAM256	567000000 Hz	9.8 dBmV	41.4 dB	0	0
24	Locked	QAM256	573000000 Hz	9.5 dBmV	41.3 dB	0	0
25	Locked	QAM256	579000000 Hz	9.6 dBmV	41.3 dB	0	0
26	Locked	QAM256	585000000 Hz	9.1 dBmV	41.2 dB	0	0
27	Locked	QAM256	591000000 Hz	8.9 dBmV	41.2 dB	0	0
28	Locked	QAM256	597000000 Hz	8.5 dBmV	40.9 dB	0	0
29	Locked	QAM256	603000000 Hz	8.4 dBmV	40.8 dB	0	0
30	Locked	QAM256	609000000 Hz	8.0 dBmV	40.7 dB	0	0
31	Locked	QAM256	615000000 Hz	7.6 dBmV	40.5 dB	0	0
32	Locked	QAM256	621000000 Hz	7.6 dBmV	40.4 dB	0	0
33	Locked	QAM256	627000000 Hz	7.4 dBmV	40.3 dB	0	0
34	Locked	QAM256	633000000 Hz	7.5 dBmV	40.3 dB	0	0
35	Locked	QAM256	639000000 Hz	7.1 dBmV	39.9 dB	0	0
36	Locked	QAM256	645000000 Hz	6.9 dBmV	40.1 dB	0	0
37	Locked	QAM256	651000000 Hz	6.8 dBmV	40.0 dB	0	0
38	Locked	QAM256	657000000 Hz	6.7 dBmV	39.9 dB	0	0
39	Locked	QAM256	663000000 Hz	6.8 dBmV	40.1 dB	0	0
40	Locked	QAM256	669000000 Hz	6.6 dBmV	39.8 dB	0	0
42	Locked	QAM256	681000000 Hz	6.9 dBmV	40.0 dB	0	0
43	Locked	QAM256	687000000 Hz	7.0 dBmV	40.1 dB	0	0
44	Locked	QAM256	693000000 Hz	6.8 dBmV	40.0 dB	0	0
159	Locked	Other	702000000 Hz	7.9 dBmV	39.2 dB	1293748687	0

Upstream Bonded Channels
Channel	Channel ID	Lock Status	US Channel Type	Frequency	Width	Power
1	3	Locked	SC-QAM Upstream	22800000 Hz	6400000 Hz	29.0 dBmV
2	2	Locked	SC-QAM Upstream	16400000 Hz	6400000 Hz	29.0 dBmV
3	4	Locked	SC-QAM Upstream	29200000 Hz	6400000 Hz	31.0 dBmV
4	5	Locked	SC-QAM Upstream	35600000 Hz	6400000 Hz	31.0 dBmV
5	6	Locked	SC-QAM Upstream	40400000 Hz	3200000 Hz	30.0 dBmV

3 years ago

0

EG

Expert

•

110.1K Messages

3 years ago

Thank you ! Looks good ! Happy surfing ! Now closing your marked "Solved" topic.

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hkp703

Modem issue - internet intermittently dropping

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EG

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EG

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EG

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EG

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