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mclitle1074
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Friday, December 4th, 2020 2:00 PM

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loss of connectivity every few days

I've had my personal netgear cable modem connected fairly stable for about 5 years.  I recently upgraded bandwidth and took advantage of a promotion with a new XB3 modem provided by XFINITY and in the last month I've had about 8 instances where traffic simply stops.  The modem lights indicate connected with upload and download, but there is a complete loss of connectivity for any usable sessions.  Unplugging the modem, waiting 30 seconds, then plugging it in restores connectivity, but it sure is a nuisance to have a work and school disrupted.

Could it be interface errors building up?

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Updated 

4 years ago

2.3K

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BruceW

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26.3K Messages

4 years ago

If you want to troubleshoot this yourself, please see Internet Troubleshooting Tips. If you still need help, please post the following information from your XB3:

  • model number
  • downstream power levels and SNR
  • upstream power levels
  • error log

 

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mclitle1074

Frequent Visitor

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9 Messages

4 years ago

Thank you.  The internet troubleshooting recommendations work everytime; wait 30 seconds, plug it in and let it reconnect, but it doesn't return to the stability I was experiencing before upgrading to the Xfinity owned modem.  I don't see a place to identify the downstream power and signal to noise ratio...the troubleshooting tools in the modem GUI are packet sent / received to test connectivity to www.comcast.net, check for IP addresses, and traceroute.  there is an MoCA diagnostics option, but "currently MoCA devices are not connected to the gateway".  I downloaded the logs and the only item is the administrator log on.  I'll see if I get a different IP address via DHCP next time I lose connectivity; maybe there is a DHCP conflict.  

Thanks again for your input.

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mclitle1074

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9 Messages

4 years ago

@BruceW I found the section you must've been referring to.  It's a Cisco model DPC3941T.  

IndexLock StatusFrequencySNRPower LevelModulation
Downstream
Channel Bonding Value
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
591 MHz
543 MHz
549 MHz
555 MHz
561 MHz
567 MHz
573 MHz
579 MHz
585 MHz
597 MHz
603 MHz
609 MHz
615 MHz
621 MHz
627 MHz
633 MHz
639 MHz
645 MHz
651 MHz
657 MHz
663 MHz
669 MHz
675 MHz
681 MHz
40.366 dB
40.946 dB
40.366 dB
40.946 dB
40.366 dB
38.983 dB
38.605 dB
38.983 dB
40.946 dB
40.366 dB
40.366 dB
40.366 dB
40.946 dB
40.366 dB
40.946 dB
40.366 dB
38.983 dB
40.366 dB
40.366 dB
40.366 dB
40.946 dB
40.366 dB
40.946 dB
40.946 dB
2.200 dBmV
1.900 dBmV
2.000 dBmV
1.600 dBmV
1.100 dBmV
-0.100 dBmV
-0.200 dBmV
1.400 dBmV
2.500 dBmV
1.400 dBmV
1.300 dBmV
1.600 dBmV
2.000 dBmV
1.800 dBmV
1.400 dBmV
0.800 dBmV
0.900 dBmV
1.600 dBmV
2.300 dBmV
2.400 dBmV
2.500 dBmV
2.400 dBmV
2.600 dBmV
2.700 dBmV
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
IndexLock StatusFrequencySymbol RatePower LevelModulationChannel Type
Upstream
Channel Bonding Value
1
2
3
4
5
Locked
Locked
Locked
Locked
Locked
36 MHz
41 MHz
30 MHz
23 MHz
17 MHz
5120 KSym/sec
1280 KSym/sec
5120 KSym/sec
5120 KSym/sec
5120 KSym/sec
37.500 dBmV
37.500 dBmV
37.500 dBmV
37.500 dBmV
37.500 dBmV
64 QAM
64 QAM
64 QAM
64 QAM
64 QAM
ATDMA
ATDMA
ATDMA
ATDMA
ATDMA
Unerrored CodewordsCorrectable CodewordsUncorrectable Codewords
CM Error Codewords
0
12396790
0
0
12369032
12370898
12367559
0
0
0
0
0
0
0
0
0
0
0
0
0
0
12172896
0
0
0
3
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0

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BruceW

Gold Problem Solver

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26.3K Messages

4 years ago

@mclitle1074 wrote: ... I found the section you must've been referring to.  ...

The signal levels and SNR at the moment were OK. Can you also post the event log if the device has one?

 

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mclitle1074

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9 Messages

4 years ago

Thanks @BruceW 

Here is the event log for the past week, lost connectivity twice during this timeframe:

 

[Dhcpc][1874]: erouter0 T1 Expired, Enter Renew State 
2020/12/09 09:59:41Notice 
 
[Dhcpc][1874]: erouter0 T1 Expired, Enter Renew State 
2020/12/09 08:59:41Notice 
 
[Dhcpc][1874]: erouter0 T1 Expired, Enter Renew State 
2020/12/09 07:59:41Notice 
 
[Dhcpc][1874]: erouter0 T1 Expired, Enter Renew State 
2020/12/09 06:59:41Notice 
 
[Dhcpc][1874]: erouter0 T1 Expired, Enter Renew State 
2020/12/09 05:59:40Notice 
 
[Dhcpc][1874]: erouter0 T1 Expired, Enter Renew State 
2020/12/09 04:59:40Notice 
 
[Dhcpc][1874]: erouter0 T1 Expired, Enter Renew State 
2020/12/09 03:59:40Notice 
 
[Dhcpc][1874]: erouter0 T1 Expired, Enter Renew State 
2020/12/09 02:59:40Notice 
 
[Dhcpc][1874]: erouter0 T1 Expired, Enter Renew State 
2020/12/09 01:59:39Notice 
 
[Dhcpc][1874]: erouter0 T1 Expired, Enter Renew State 
2020/12/09 00:59:39Notice 
 
[Dhcpc][1874]: erouter0 T1 Expired, Enter Renew State 
2020/12/08 23:59:38Notice 
 
[Dhcpc][1874]: erouter0 T1 Expired, Enter Renew State 
2020/12/08 22:59:38Notice 
 
[Dhcpc][1874]: erouter0 T1 Expired, Enter Renew State 
2020/12/08 21:59:37Notice 
 
[Dhcpc][1874]: erouter0 T1 Expired, Enter Renew State 
2020/12/08 20:59:37Notice 
 
[Dhcpc][1874]: erouter0 T1 Expired, Enter Renew State 
2020/12/08 19:59:36Notice 
 
[Dhcpc][1874]: erouter0 T1 Expired, Enter Renew State 
2020/12/08 18:59:37Notice 
 
[Dhcpc][1874]: erouter0 T1 Expired, Enter Renew State 
2020/12/08 17:59:36Notice 
 
[Dhcpc][1874]: erouter0 T1 Expired, Enter Renew State 
2020/12/08 16:59:36Notice 
 
[Dhcpc][1874]: erouter0 T1 Expired, Enter Renew State 
2020/12/08 15:59:36Notice 
 
[Dhcpc][1874]: erouter0 T1 Expired, Enter Renew State 
2020/12/08 14:59:30Notice 
 
[Dhcpc][1874]: erouter0 T1 Expired, Enter Renew State 
2020/12/08 13:59:30Notice 
 
[Dhcpc][1874]: erouter0 T1 Expired, Enter Renew State 
2020/12/08 12:59:31Notice 
 
[Dhcpc][1874]: erouter0 T1 Expired, Enter Renew State 
2020/12/08 11:59:30Notice 
 
[Dhcpc][1874]: erouter0 T1 Expired, Enter Renew State 
2020/12/08 10:59:29Notice 
 
[Dhcpc][1874]: erouter0 T1 Expired, Enter Renew State 
2020/12/08 09:59:28Notice 
 
[Dhcpc][1874]: erouter0 T1 Expired, Enter Renew State 
2020/12/08 08:59:29Notice 
 
[Dhcpc][1874]: erouter0 T1 Expired, Enter Renew State 
2020/12/08 07:59:28Notice 
 
[Dhcpc][1874]: erouter0 T1 Expired, Enter Renew State 
2020/12/08 06:59:28Notice 
 
[Dhcpc][1874]: erouter0 T1 Expired, Enter Renew State 
2020/12/08 05:59:28Notice 
 
[Dhcpc][1874]: erouter0 got new IP ###.###.###.### (removed)
2020/12/07 23:42:16Notice 
 
[Harvester][839]:  Harvester StartRadioTrafficHarvesting Starting Thread to start RadioTraffic Data Harvesting   
2020/12/07 23:41:56Notice 
 
[Harvester][839]:  Harvester StartAssociatedDeviceHarvesting : Started Thread to start DeviceData Harvesting   
2020/12/07 23:41:55Notice 
 
[Docsis][964]: No Ranging Response received - T3 time-out 
2020/12/07 21:11:37Warning 
 
[Docsis][964]: No Ranging Response received - T3 time-out 
2020/12/07 21:00:52Warning 
 
[Dhcpc][1857]: erouter0 got new IP ###.###.###.### (removed) 
2020/12/07 20:59:51Notice 
 
[Harvester][842]:  Harvester StartRadioTrafficHarvesting Starting Thread to start RadioTraffic Data Harvesting   
2020/12/07 20:59:36Notice 
 
[Harvester][842]:  Harvester StartAssociatedDeviceHarvesting : Started Thread to start DeviceData Harvesting   
2020/12/07 20:59:36Notice 
 
[Dhcpc][1811]: erouter0 T1 Expired, Enter Renew State 
2020/12/07 12:16:38Notice 
 
[Dhcpc][1811]: erouter0 T1 Expired, Enter Renew State 
2020/12/07 00:16:36Notice 
 

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BruceW

Gold Problem Solver

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26.3K Messages

4 years ago

@mclitle1074 wrote: ... Here is the event log for the past week, lost connectivity twice during this timeframe ...

Apparently the device does not log the items I would expect to see when connectivity is lost and regained. But just as Comcast has access to signal characteristics that the modem does not report, they also have access to other performance information.

 

I'd recommend you have a Comcast tech out to take a look at the problem. Call them at the phone number on your bill or 1-800-Comcast, or use one of the options on https://www.xfinity.com/support/contact-us/. Insist they send a tech out to identify the cause and correct it.

If the tech finds bad coax, splitters, amplifiers, or connections in your home (even if Comcast originally supplied them) you'll probably have to pay for the visit unless you have their Service Protection Plan (https://www.xfinity.com/support/articles/service-protection-plan, closed to customers that don't already have it). If the trouble is due to a faulty Comcast rental device or anything outside your home you shouldn't be charged.

 

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mclitle1074

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9 Messages

4 years ago

Probably more relevant, this was in the event log 11 times in a row at the exact time that I lost LAN side DHCP and about 30 minutes before the modem lights went out (except the power lights).

 

[Docsis][961]: Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out

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mclitle1074

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9 Messages

4 years ago

I had an interesting observation during this mornings outage (8am PST).  All my hosts lost their DHCP issued IP even though the XB3 modem said there was 2days left on the DHCP lease.  I noticed the iOS, Windows, and 2 Meraki devices self assign an IP address in the 169 network (meaning they weren't getting a response via DHCP).  I waited about 10 minutes then they did get an IP out of the DHCP pool (default pool from 10.0.0.5-253) and their connectivity was restored for about 8-10 minutes before the modem lights all went out except the power light.  Troubleshooting steps of unplug, wait 30 seconds and plug the modem back into power restored service...UGH.  I might go through the pain of moving all the hosts except a router and one adminstrative PC behind another router providing DHCP in another RFC1918 network and then manually assign IP's to the two hosts directly connected to the XB3, but that is NOT what I intended to do with this new, fancy modem.

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EG

Expert

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110K Messages

4 years ago

Start with the modem's signal stats. Perhaps they already are, or they are close to being out of spec and intermittently they go completely of spec. Try getting them here http://192.168.100.1 or here http://10.0.0.1

Please post the *Downstream Power Level*, the *Upstream Power Level*, and the *SNR* (Signal to Noise Ratio) numbers.


[EDIT]

 

Disregard.

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mclitle1074

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9 Messages

4 years ago

Thanks EG...they were already posted in the thread above.

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EG

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110K Messages

4 years ago

@mclitle1074 wrote:

Thanks EG...they were already posted in the thread above.

My bad. I posted my reply to the wrong thread, sorry. Disregard it.

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BruceW

Gold Problem Solver

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26.3K Messages

4 years ago

@mclitle1074 wrote: ... they were already posted in the thread above.

But those are from a week ago. The signal and log readings may be different now. Please post them.

 

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BruceW

Gold Problem Solver

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26.3K Messages

4 years ago

@mclitle1074 wrote: Here you go, thanks for looking at this ...

The last few Uncorrectable Codeword counts are on the high side, otherwise the information is similar to what you posted last week. As before, I'd suggest having Comcast send a premise tech out to take a look at this.

 

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mclitle1074

Frequent Visitor

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9 Messages

4 years ago

Here you go, thanks for looking at this:

IndexLock StatusFrequencySNRPower LevelModulation
Downstream
Channel Bonding Value
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
Locked
663 MHz
543 MHz
549 MHz
555 MHz
561 MHz
567 MHz
573 MHz
579 MHz
585 MHz
591 MHz
597 MHz
603 MHz
609 MHz
615 MHz
621 MHz
627 MHz
633 MHz
639 MHz
645 MHz
651 MHz
657 MHz
669 MHz
675 MHz
681 MHz
40.946 dB
40.366 dB
40.366 dB
40.366 dB
40.366 dB
38.605 dB
38.983 dB
38.983 dB
40.366 dB
40.946 dB
40.366 dB
40.366 dB
40.366 dB
40.366 dB
40.366 dB
38.983 dB
38.983 dB
38.983 dB
38.983 dB
40.366 dB
40.366 dB
40.366 dB
40.946 dB
40.366 dB
3.300 dBmV
2.900 dBmV
2.900 dBmV
2.500 dBmV
2.100 dBmV
1.100 dBmV
0.200 dBmV
1.200 dBmV
3.700 dBmV
3.500 dBmV
2.400 dBmV
2.300 dBmV
2.700 dBmV
3.000 dBmV
2.300 dBmV
1.600 dBmV
1.200 dBmV
1.700 dBmV
2.600 dBmV
3.300 dBmV
3.400 dBmV
3.200 dBmV
3.300 dBmV
3.400 dBmV
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
256 QAM
IndexLock StatusFrequencySymbol RatePower LevelModulationChannel Type
Upstream
Channel Bonding Value
1
2
3
4
5
Locked
Locked
Locked
Locked
Locked
36 MHz
41 MHz
30 MHz
23 MHz
17 MHz
5120 KSym/sec
1280 KSym/sec
5120 KSym/sec
5120 KSym/sec
5120 KSym/sec
35.750 dBmV
35.750 dBmV
35.750 dBmV
35.750 dBmV
34.250 dBmV
64 QAM
64 QAM
64 QAM
64 QAM
64 QAM
ATDMA
ATDMA
ATDMA
ATDMA
ATDMA
Unerrored CodewordsCorrectable CodewordsUncorrectable Codewords
CM Error Codewords
4058949929
4050869924
4050859216
4050839216
4055047505
4050860264
4055050831
4055053440
4050849575
4055056448
4055057597
4050855208
4055063870
4055068268
4055071260
4055072556
4055066296
4050844661
4055075197
4055076437
4050834217
4055077871
4055076877
4055078145
188
11
7
1
1
0
1
16
273
37
15
14
11
28
30
0
26
67
77
109
138
193
958
849
9
0
0
0
0
0
0
0
0
0
0
0
0
0
4
0
0
28
68
26
29
1016
4674
4827

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mclitle1074

Frequent Visitor

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9 Messages

4 years ago

Lost network connectivity, I couldn't even ping the router with a computer that was connected to the switch on the back of the router and still had the DHCP issued IP in the same network as the router.  This started and persisted during the time below where it was "Received Response to Broadcast Maintenance...."  Restarted the modem but didn't quite wait 30 seconds and restored LAN connectivity, but couldn't get to the internet, it took the full 30 second wait.  

I guess I'll ask for a replacement modem, but it seems like the issue is that it's receiving a maintenance that is not needed and then it locks up.  Maybe they have me recorded as having the wrong modem in their network management tool?

 

[Dhcpc][1849]: erouter0 got new IP ###.###.###.###2020/12/19 16:29:01Notice
[Harvester][827]: Harvester StartRadioTrafficHarvesting Starting Thread to start RadioTraffic Data Harvesting2020/12/19 16:28:47Notice
[Harvester][827]: Harvester StartAssociatedDeviceHarvesting : Started Thread to start DeviceData Harvesting2020/12/19 16:28:46Notice
[Docsis][961]: Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out2020/12/19 16:18:09Warning
[Docsis][961]: Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out2020/12/19 16:16:59Warning
[Docsis][961]: Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out2020/12/19 16:16:39Warning
[Docsis][961]: Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out2020/12/19 16:16:19Warning
[Docsis][961]: Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out2020/12/19 16:15:59Warning
[Docsis][961]: Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out2020/12/19 16:15:39Warning
[Docsis][961]: Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out2020/12/19 16:14:29Warning
[Docsis][961]: Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out2020/12/19 16:14:09Warning
[Docsis][961]: Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out2020/12/19 16:13:49Warning
[Docsis][961]: Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out2020/12/19 16:13:29Warning
[Docsis][961]: Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out

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