dk6971's profile

New Poster

 • 

4 Messages

Mon, Jan 4, 2021 8:00 PM

Intermittent Internet Modenm Connectivity Issues

I'm having trouble with my XB6 Comcast modem with Gig-speed subscription.  Periodically throughout a typical day I lose connectivity (five to ten times a day or more).  The result is that consumer-level network applications (e.g., zoom, iPhone wifi calling, Android wifi calling, etc) are disrupted for short periods of time.

 

I've tried contacting front-line support, they run their remote diagnostics and determine that everything is fine, and that there is nothing to be done.

 

I've logged into the administration tool on the XB6 and have looked at SNR and strength, both seem OK:

 

IndexLock StatusFrequencySNRPower LevelModulation

Downstream
Channel Bonding Value
5
2
3
4
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
37
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
555000000
525000000
531000000
543000000
561000000
567000000
573000000
579000000
585000000
591000000
597000000
603000000
609000000
615000000
621000000
627000000
633000000
639000000
645000000
651000000
657000000
663000000
669000000
675000000
681000000
687000000
693000000
699000000
705000000
711000000
717000000
764800000
40.946209
40.366287
38.983261
40.366287
40.366287
40.366287
40.366287
40.366287
40.366287
40.366287
40.946209
40.946209
40.946209
40.366287
40.946209
40.946209
40.946209
40.366287
40.366287
40.366287
40.946209
40.366287
40.946209
40.366287
40.366287
40.946209
40.946209
40.366287
40.366287
40.946209
40.366287
NA
1.500000
-0.400002
0.299999
1.000000
1.900002
2.500000
2.700001
3.500000
3.500000
3.500000
3.799999
3.299999
3.400002
3.400002
3.599998
3.400002
3.400002
4.199997
3.599998
3.700001
4.699997
3.799999
3.500000
4.500000
3.700001
3.000000
4.000000
3.099998
2.900002
3.400002
2.799999
NA
QAM256
QAM256
QAM256
QAM256
QAM256

 

IndexLock StatusFrequencySymbol RatePower LevelModulation

Upstream
Channel Bonding Value
1
2
3
4
5
Locked
Locked
Locked
Locked
Locked
16400000
39600000
22800000
29200000
35600000
5120 KSym/sec
1280 KSym/sec
5120 KSym/sec
5120 KSym/sec
5120 KSym/sec
53.270599
49.750000
53.770599
53.520599
52.770599
64QAM
64QAM
64QAM
64QAM
64QAM

 

I have noticed that there appear to be repeating errors in the logs however:

ti_dhcp6c[7710]: 72001011-DHCPv6 - Missing Required Option 82 
	2021/1/04 22:10:58	Critical 

ti_dhcp6c[7710]: 72001011-DHCPv6 - Missing Required Option 24 
	2021/1/04 22:10:58	Critical 

ti_dhcp6c[7710]: 72001004-DHCPv6 Provision - 0 Retries Attempted with Last attempt at Tue Jan  5 03:10:57 2021 
	2021/1/04 22:10:58	Critical 

ti_dhcp6c[7710]: 72001011-DHCPv6 - Missing Required Option 82 
	2021/1/04 22:10:57	Critical 

ti_dhcp6c[7710]: 72001011-DHCPv6 - Missing Required Option 24 
	2021/1/04 22:10:57	Critical 

Can anyone shed any light or possibly connect me to higher-level support that can help debug the issue?

 

 

Responses

EG

Expert

 • 

86.5K Messages

4 m ago

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.
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!tick

New Poster

 • 

4 Messages

3 m ago

Thanks for the reply!

 

Since I posted this question, I've spent countless hours on phone support going through useless remote test after useless remote test.

 

Support told me to upgrade my modem, which I did to the very latest.  No improvement.

 

I've eliminated splitters of any kind, and plugged the coax coming into the house directly into the cable modem. No improvement.

 

I think that I've finally made it into next level support, which is supposed to be investigating the problem remotely, and if they can't figure things out will supposedly send an actual repair person out to investigate.

EG

Expert

 • 

86.5K Messages

3 m ago

O/k good luck with it ! Please post back here with how things turn out.

 

P.S. Also 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.

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!tick
EG

Expert

 • 

86.5K Messages

3 m ago

Here are the modem status values from the pinned "Internet Troubleshooting Tips" post 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 Ratio35dB-
Upstream Power Level+35dBmV+50dBmV
Upstream Signal to Noise Ratio31dB-
Upstream Receive Power-2dBmV+2dBmV

 

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!tick

New Poster

 • 

4 Messages

3 m ago

Just out of curiosity (and for others stumbling onto this thread), what is an acceptable range for power levels on the upstream channels?

New Poster

 • 

4 Messages

3 m ago

So I just looked at the stats for my new modem (XB7)...

 

Downstream
Channel Bonding Value
5
2
3
4
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
37
 
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
555000000
525000000
531000000
543000000
561000000
567000000
573000000
579000000
585000000
591000000
597000000
603000000
609000000
615000000
621000000
627000000
633000000
639000000
645000000
651000000
657000000
663000000
669000000
675000000
681000000
687000000
693000000
699000000
705000000
711000000
717000000
762000000
665600000
40.946209
40.366287
40.366287
40.946209
40.366287
40.366287
40.366287
40.946209
40.946209
40.946209
40.946209
40.946209
40.946209
40.366287
40.366287
40.946209
40.946209
40.946209
40.946209
40.946209
40.366287
40.946209
40.946209
40.946209
40.946209
40.366287
40.366287
40.946209
40.366287
40.946209
40.366287
7.593062
NA
13.000000
12.800003
12.900002
12.900002
13.099998
12.900002
13.000000
13.199997
13.300003
13.300003
13.500000
13.300003
13.199997
13.199997
13.199997
13.099998
13.199997
13.099998
13.099998
13.199997
13.099998
13.099998
13.000000
13.199997
13.099998
13.099998
13.000000
13.000000
12.800003
12.900002
12.900002
-60.000000
NA
QAM256
QAM256
QAM256
QAM256
QAM256

 

 

Upstream
Channel Bonding Value
1
2
3
4
5
Locked
Locked
Locked
Locked
Locked
39600000
16400000
22800000
29200000
35600000
1280 KSym/sec
5120 KSym/sec
5120 KSym/sec
5120 KSym/sec
5120 KSym/sec
42.500000
44.770599
45.270599
45.270599
44.520599
64QAM
64QAM
64QAM
64QAM
64QAM
US_TYPE_ATDMA
US_TYPE_ATDMA
US_TYPE_ATDMA
US_TYPE_ATDMA
US_TYPE_ATDMA

 

For the xb7 modem, it appears that (according to your table), the DOWNSTREAM power levels and SNRs are out of spec, but upstream looks OK.  I've already sandpaper-cleaned the copper on the coax, and eliminated any splitters that I can find.  I'm assuming this means that I will need to wait for techs to diagnose beyond the house.

 

EG

Expert

 • 

86.5K Messages

3 m ago

The SNR is fine. Re-visit the chart. There is no max SNR. Higher is better. Yours is very good. The downstream power level is now kind of high, but it still may or may not be a problem. Looks like you improved the connection.

 

You could try using a minus -6dB Forward Path Only attenuator pad such as this one to knock that downstream power down by the same amount;

 

https://www.amazon.com/line-Signal-Forward-Attenuator-FPA6-54/dp/B07882H96R

 

It will not affect the upstream power which is now in spec. They make a 9dB one as well. Or you could let a tech properly balance the line.

 

This may or may not be the direct cause of the problem. YMMV. Good luck !

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!tick

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