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Internet cutting off multiple times daily - T2, T3, Failed to acquire QAM/QPSK symbol timing

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Internet cutting off multiple times daily - T2, T3, Failed to acquire QAM/QPSK symbol timing

Help! My Xfinity internet has been cutting of very often these days. Today has been really bad. I had to reset my modem multiple times already, and after every reset, it only works fine for a few minutes before the internet is cut off again. Wi-fi connection to the router/modem is fine, only the internet is bad. I am using Netgear C7800 modem/router.

 

Here are some event logs I got from the netgear modem:

Warning (5) MDD message timeout
Critical (3) No Maintenance Broadcasts for Ranging opportunities received - T2 time-out
Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing
Critical (3) No Ranging Response received - T3 time-out
Critical (3) No Maintenance Broadcasts for Ranging opportunities received - T2 time-out
Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing

Critical (3) No Ranging Response received - T3

 

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Gold Problem Solver

Re: Internet cutting off multiple times daily - T2, T3, Failed to acquire QAM/QPSK symbol timing

Please post your gateway's signal information, especially downstream power levels and SNR, upstream power levels, and the complete error log with date and time info. Also see Internet Troubleshooting Tips.

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New Poster

Re: Internet cutting off multiple times daily - T2, T3, Failed to acquire QAM/QPSK symbol timing

@BruceW Previously I was resetting the modem physically. After resetting the gateway from xfinity web page, it seems to be okay now (have been running for 1hr uninterrupted).

Here is the status currently:

Startup Procedure
Procedure Status Comment
Acquire Downstream Channel 483000000 Hz Locked
Connectivity State OK Operational
Boot State OK Operational
Security ENABLED BPI+
IP Provisioning Mode Honor MDD IPv6 only

Downstream Bonded Channels
Channel Lock Status Modulation Channel ID Frequency Power SNR Correctables Uncorrectabables
1 Locked QAM256 20 483000000 Hz 4.4 dBmV 42.5 dB 0 0
2 Locked QAM256 8 411000000 Hz 4.1 dBmV 42.8 dB 0 0
3 Locked QAM256 9 417000000 Hz 3.8 dBmV 42.8 dB 0 0
4 Locked QAM256 10 423000000 Hz 3.9 dBmV 42.7 dB 0 0
5 Locked QAM256 11 429000000 Hz 3.9 dBmV 42.6 dB 0 0
6 Locked QAM256 12 435000000 Hz 3.8 dBmV 42.7 dB 0 0
7 Locked QAM256 13 441000000 Hz 3.9 dBmV 42.7 dB 0 0
8 Locked QAM256 14 447000000 Hz 4.0 dBmV 42.6 dB 0 0
9 Locked QAM256 15 453000000 Hz 4.1 dBmV 42.4 dB 0 0
10 Locked QAM256 16 459000000 Hz 4.1 dBmV 42.2 dB 0 0
11 Locked QAM256 17 465000000 Hz 4.2 dBmV 42.4 dB 0 0
12 Locked QAM256 18 471000000 Hz 4.3 dBmV 42.4 dB 0 0
13 Locked QAM256 19 477000000 Hz 4.4 dBmV 42.3 dB 0 0
14 Locked QAM256 21 489000000 Hz 4.4 dBmV 42.5 dB 0 0
15 Locked QAM256 22 495000000 Hz 4.3 dBmV 42.4 dB 0 0
16 Locked QAM256 23 507000000 Hz 4.4 dBmV 42.4 dB 0 0
17 Not Locked Unknown 0 0 Hz 0.0 dBmV 0.0 dB 0 0
18 Not Locked Unknown 0 0 Hz 0.0 dBmV 0.0 dB 0 0
19 Not Locked Unknown 0 0 Hz 0.0 dBmV 0.0 dB 0 0
20 Not Locked Unknown 0 0 Hz 0.0 dBmV 0.0 dB 0 0
21 Not Locked Unknown 0 0 Hz 0.0 dBmV 0.0 dB 0 0
22 Not Locked Unknown 0 0 Hz 0.0 dBmV 0.0 dB 0 0
23 Not Locked Unknown 0 0 Hz 0.0 dBmV 0.0 dB 0 0
24 Not Locked Unknown 0 0 Hz 0.0 dBmV 0.0 dB 0 0
25 Not Locked Unknown 0 0 Hz 0.0 dBmV 0.0 dB 0 0
26 Not Locked Unknown 0 0 Hz 0.0 dBmV 0.0 dB 0 0
27 Not Locked Unknown 0 0 Hz 0.0 dBmV 0.0 dB 0 0
28 Not Locked Unknown 0 0 Hz 0.0 dBmV 0.0 dB 0 0
29 Not Locked Unknown 0 0 Hz 0.0 dBmV 0.0 dB 0 0
30 Not Locked Unknown 0 0 Hz 0.0 dBmV 0.0 dB 0 0
31 Not Locked Unknown 0 0 Hz 0.0 dBmV 0.0 dB 0 0
32 Not Locked Unknown 0 0 Hz 0.0 dBmV 0.0 dB 0 0

Upstream Bonded Channels
Channel Lock Status US Channel Type Channel ID Symbol Rate Frequency Power
1 Locked ATDMA 3 5120 Ksym/sec 30300000 Hz 43.3 dBmV
2 Locked ATDMA 1 5120 Ksym/sec 17300000 Hz 42.5 dBmV
3 Locked ATDMA 2 5120 Ksym/sec 23700000 Hz 42.8 dBmV
4 Locked ATDMA 4 5120 Ksym/sec 36700000 Hz 43.3 dBmV
5 Not Locked Unknown 0 0 Ksym/sec 0 Hz 0 dBmV
6 Not Locked Unknown 0 0 Ksym/sec 0 Hz 0 dBmV
7 Not Locked Unknown 0 0 Ksym/sec 0 Hz 0 dBmV
8 Not Locked Unknown 0 0 Ksym/sec 0 Hz 0 dBmV

Downstream OFDM Channels
Channel Channel ID Indicator Subcarrier Zero Frequency Active Subcarrier Number Range Total Codewords Uncorrectable Codewords
1 48 Non-Primary 623600000 Hz 1108 ~ 2987 4309181 0
2 0 Other 0 Hz 0 ~ 0 0 0

Upstream OFDMA Channels
Channel UpstreamIsMuted Ranging Status Subcarrier Zero Frequency Active Subcarrier Number Range Symbols Per Frame Tx Power
1   Other 0 Hz 0 ~ 0 0 0 dBmV
2   Other 0 Hz 0 ~ 0 0 0 dBmV

 

And here are the complete logs when the internet was down:

Time Priority Description
2020-07-16, 11:29:22 Warning (5) MDD message timeout;CM-MAC=28:80:88:ab:de:28;CMTS-MAC=00:01:5c:b6:20:7a;CM-QOS=1.1;CM-VER=3.1;
2020-07-16, 11:29:16 Critical (3) No Maintenance Broadcasts for Ranging opportunities received - T2 time-out;CM-MAC=28:80:88:ab:de:28;CMTS-MAC=00:01:5c:b6:20:7a;CM-QOS=1.1;CM-VER=3.1;
2020-07-16, 11:29:07 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=28:80:88:ab:de:28;CMTS-MAC=00:01:5c:b6:20:7a;CM-QOS=1.1;CM-VER=3.1;
2020-07-16, 11:28:38 Critical (3) No Ranging Response received - T3 time-out;CM-MAC=28:80:88:ab:de:28;CMTS-MAC=00:01:5c:b6:20:7a;CM-QOS=1.1;CM-VER=3.1;
2020-07-16, 11:28:32 Critical (3) No Maintenance Broadcasts for Ranging opportunities received - T2 time-out;CM-MAC=28:80:88:ab:de:28;CMTS-MAC=00:01:5c:b6:20:7a;CM-QOS=1.1;CM-VER=3.1;
2020-07-16, 11:28:24 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=28:80:88:ab:de:28;CMTS-MAC=00:01:5c:b6:20:7a;CM-QOS=1.1;CM-VER=3.1;
2020-07-16, 11:28:05 Critical (3) No Ranging Response received - T3 time-out;CM-MAC=28:80:88:ab:de:28;CMTS-MAC=00:01:5c:b6:20:7a;CM-QOS=1.1;CM-VER=3.1;
2020-07-16, 11:27:58 Warning (5) MDD message timeout;CM-MAC=28:80:88:ab:de:28;CMTS-MAC=00:01:5c:b6:20:7a;CM-QOS=1.1;CM-VER=3.1;
2020-07-16, 11:27:56 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=28:80:88:ab:de:28;CMTS-MAC=00:01:5c:b6:20:7a;CM-QOS=1.1;CM-VER=3.1;
2020-07-16, 11:27:56 Warning (5) MDD message timeout;CM-MAC=28:80:88:ab:de:28;CMTS-MAC=00:01:5c:b6:20:7a;CM-QOS=1.1;CM-VER=3.1;
2020-07-16, 11:27:53 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=28:80:88:ab:de:28;CMTS-MAC=00:01:5c:b6:20:7a;CM-QOS=1.1;CM-VER=3.1;
2020-07-16, 11:21:02 Critical (3) No Ranging Response received - T3

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New Poster

Re: Internet cutting off multiple times daily - T2, T3, Failed to acquire QAM/QPSK symbol timing

It just went down again... I noticed the upstream and online lights on the modem was off this time.

Here is the status when that happened:

 

Downstream Bonded Channels (Partial Service)
Channel Lock Status Modulation Channel ID Frequency Power SNR Correctables Uncorrectabables
1 Locked QAM256 20 483000000 Hz 4.8 dBmV 42.3 dB 0 0
2 Locked QAM256 8 411000000 Hz 4.4 dBmV 42.9 dB 220 338
3 Locked QAM256 9 417000000 Hz 4.1 dBmV 42.7 dB 284 506
4 Locked QAM256 10 423000000 Hz 4.2 dBmV 42.5 dB 229 518
5 Locked QAM256 11 429000000 Hz 4.2 dBmV 42.7 dB 270 445
6 Locked QAM256 12 435000000 Hz 4.2 dBmV 42.7 dB 215 387
7 Locked QAM256 13 441000000 Hz 4.2 dBmV 42.4 dB 304 472
8 Locked QAM256 14 447000000 Hz 4.4 dBmV 42.6 dB 353 561
9 Locked QAM256 15 453000000 Hz 4.4 dBmV 42.5 dB 294 494
10 Locked QAM256 16 459000000 Hz 4.4 dBmV 42.3 dB 306 447
11 Locked QAM256 17 465000000 Hz 4.5 dBmV 42.3 dB 212 362
12 Locked QAM256 18 471000000 Hz 4.6 dBmV 42.4 dB 236 487
13 Locked QAM256 19 477000000 Hz 4.8 dBmV 42.5 dB 199 483
14 Locked QAM256 21 489000000 Hz 4.7 dBmV 42.5 dB 270 469
15 Locked QAM256 22 495000000 Hz 4.7 dBmV 42.3 dB 241 528
16 Locked QAM256 23 507000000 Hz 4.7 dBmV 42.4 dB 261 563
17 Locked QAM256 24 513000000 Hz 4.6 dBmV 42.4 dB 200 522
18 Locked QAM256 25 519000000 Hz 4.4 dBmV 42.2 dB 220 469
19 Locked QAM256 26 525000000 Hz 4.4 dBmV 42.2 dB 221 419
20 Locked QAM256 27 531000000 Hz 4.3 dBmV 41.9 dB 260 518
21 Locked QAM256 28 543000000 Hz 3.8 dBmV 41.9 dB 247 562
22 Locked QAM256 29 549000000 Hz 3.6 dBmV 42.0 dB 258 604
23 Locked QAM256 30 555000000 Hz 3.4 dBmV 41.9 dB 283 587
24 Locked QAM256 31 561000000 Hz 3.3 dBmV 41.8 dB 310 469
25 Locked QAM256 32 567000000 Hz 3.2 dBmV 41.7 dB 278 664
26 Locked QAM256 33 573000000 Hz 3.2 dBmV 41.6 dB 230 418
27 Locked QAM256 34 579000000 Hz 3.4 dBmV 41.8 dB 229 585
28 Locked QAM256 35 585000000 Hz 3.3 dBmV 41.6 dB 293 516
29 Locked QAM256 36 591000000 Hz 3.3 dBmV 41.6 dB 288 615
30 Locked QAM256 37 597000000 Hz 3.3 dBmV 41.5 dB 326 750
31 Locked QAM256 38 603000000 Hz 3.2 dBmV 41.5 dB 420 508
32 Not Locked Unknown 0 0 Hz 0.0 dBmV 0.0 dB 0 0
 

 
Upstream Bonded Channels  
Channel Lock Status US Channel Type Channel ID Symbol Rate Frequency Power
1 Locked ATDMA 3 5120 Ksym/sec 30300000 Hz 42.5 dBmV
2 Locked ATDMA 1 5120 Ksym/sec 17300000 Hz 41.8 dBmV
3 Locked ATDMA 2 5120 Ksym/sec 23700000 Hz 42.0 dBmV
4 Locked ATDMA 4 5120 Ksym/sec 36700000 Hz 42.5 dBmV
5 Not Locked Unknown 0 0 Ksym/sec 0 Hz 0 dBmV
6 Not Locked Unknown 0 0 Ksym/sec 0 Hz 0 dBmV
7 Not Locked Unknown 0 0 Ksym/sec 0 Hz 0 dBmV
8 Not Locked Unknown 0 0 Ksym/sec 0 Hz 0 dBmV
 

 
Downstream OFDM Channels  
Channel Channel ID Indicator Subcarrier Zero Frequency Active Subcarrier Number Range Total Codewords Uncorrectable Codewords
1 48 Non-Primary 623600000 Hz 1108 ~ 2987 5638992 0
2 0 Other 0 Hz 0 ~ 0 0 0
 

 
Upstream OFDMA Channels  
Channel UpstreamIsMuted Ranging Status Subcarrier Zero Frequency Active Subcarrier Number Range Symbols Per Frame Tx Power
1   Other 0 Hz 0 ~ 0 0 0 dBmV
2   Other 0 Hz 0 ~ 0 0 0 dBmV
 
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Gold Problem Solver

Re: Internet cutting off multiple times daily - T2, T3, Failed to acquire QAM/QPSK symbol timing


@hendolim wrote: It just went down again...

The signal info you've posted looks OK, but obviously there's a problem somewhere.

 

If you can't find the problem call Comcast 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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Diamond Problem Solver

Re: Internet cutting off multiple times daily - T2, T3, Failed to acquire QAM/QPSK symbol timing

@hemdolin
I’m not sure if you noticed but the first pic had no levels after downstream channel 16 but were there In the second. As suggested, start with a tech visit.

I am a Retired Official Comcast Employee
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