Frequent Visitor
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6 Messages
SYNC Timing Synchronization failure
I have Xfinity 1Gb/s plan running with a Arris SB8200 modem. The rest of the network is a Unifi USG, 2x Unifi 8 POE switches and 2x Unifi AC-Pros. Most of my devices are connected via ethernet but every so often my internet just goes out; my wife and I work from home so this is not only embarrasing but incredibly depressing that moving is on the table just to no longer have to deal with Comcast as a whole. I've complained about these issues via their phone support at some point in the past three years and they sent a tech whom added a cap thats on the coax between the modem and the line running from outside the building which seemed to work but only for a very short amount of time. It dropped so frequently in the past that I had to buy a remote power IP switch that power cycles our modem whenever the device can no longer connect to the internet which is absolutely maddening. Below are the logs from the modem:
| Downstream Bonded Channels | |||||||
| Channel ID | Lock Status | Modulation | Frequency | Power | SNR/MER | Corrected | Uncorrectables |
| 1 | Locked | QAM256 | 441000000 Hz | -4.2 dBmV | 42.6 dB | 0 | 0 |
| 2 | Locked | QAM256 | 447000000 Hz | -3.5 dBmV | 42.6 dB | 0 | 0 |
| 3 | Locked | QAM256 | 453000000 Hz | -3.6 dBmV | 42.8 dB | 0 | 0 |
| 4 | Locked | QAM256 | 459000000 Hz | -3.5 dBmV | 42.8 dB | 0 | 0 |
| 5 | Locked | QAM256 | 465000000 Hz | -3.3 dBmV | 42.9 dB | 0 | 0 |
| 6 | Locked | QAM256 | 471000000 Hz | -3.7 dBmV | 42.6 dB | 0 | 0 |
| 7 | Locked | QAM256 | 477000000 Hz | -2.9 dBmV | 42.9 dB | 0 | 0 |
| 8 | Locked | QAM256 | 483000000 Hz | -3.3 dBmV | 42.7 dB | 0 | 0 |
| 9 | Locked | QAM256 | 489000000 Hz | -3.0 dBmV | 42.6 dB | 0 | 0 |
| 10 | Locked | QAM256 | 507000000 Hz | -2.5 dBmV | 43.1 dB | 0 | 0 |
| 11 | Locked | QAM256 | 513000000 Hz | -2.9 dBmV | 42.9 dB | 0 | 0 |
| 12 | Locked | QAM256 | 519000000 Hz | -2.7 dBmV | 42.7 dB | 0 | 0 |
| 13 | Locked | QAM256 | 525000000 Hz | -2.4 dBmV | 42.9 dB | 0 | 0 |
| 14 | Locked | QAM256 | 531000000 Hz | -2.4 dBmV | 43.1 dB | 0 | 0 |
| 15 | Locked | QAM256 | 537000000 Hz | -2.1 dBmV | 43.1 dB | 0 | 0 |
| 16 | Locked | QAM256 | 543000000 Hz | -2.1 dBmV | 43.1 dB | 0 | 0 |
| 17 | Locked | QAM256 | 549000000 Hz | -2.1 dBmV | 43.0 dB | 0 | 0 |
| 18 | Locked | QAM256 | 555000000 Hz | -1.8 dBmV | 43.1 dB | 0 | 0 |
| 19 | Locked | QAM256 | 561000000 Hz | -1.7 dBmV | 43.1 dB | 0 | 0 |
| 20 | Locked | QAM256 | 567000000 Hz | -1.9 dBmV | 43.1 dB | 0 | 0 |
| 21 | Locked | QAM256 | 573000000 Hz | -1.7 dBmV | 43.3 dB | 0 | 0 |
| 22 | Locked | QAM256 | 579000000 Hz | -1.9 dBmV | 42.9 dB | 0 | 0 |
| 23 | Locked | QAM256 | 585000000 Hz | -1.9 dBmV | 42.9 dB | 0 | 0 |
| 24 | Locked | QAM256 | 591000000 Hz | -2.0 dBmV | 42.6 dB | 0 | 0 |
| 25 | Locked | Other | 693000000 Hz | -1.7 dBmV | 41.0 dB | 25416696 | 0 |
| 26 | Not Locked | QAM256 | 0 Hz | 0.0 dBmV | 41.4 dB | 0 | 0 |
| 27 | Locked | QAM256 | 597000000 Hz | -1.9 dBmV | 41.8 dB | 0 | 0 |
| 28 | Locked | QAM256 | 603000000 Hz | -1.7 dBmV | 42.8 dB | 0 | 0 |
| 29 | Locked | QAM256 | 609000000 Hz | -2.0 dBmV | 43.1 dB | 0 | 0 |
| 30 | Locked | QAM256 | 615000000 Hz | -1.9 dBmV | 43.0 dB | 0 | 0 |
| 31 | Locked | QAM256 | 621000000 Hz | -2.0 dBmV | 42.4 dB | 0 | 0 |
| 32 | Locked | QAM256 | 627000000 Hz | -1.9 dBmV | 42.8 dB | 0 | 0 |
| Upstream Bonded Channels | |||||||
| Channel | Channel ID | Lock Status | US Channel Type | Frequency | Width | Power | |
| 1 | 2 | Locked | SC-QAM Upstream | 30100000 Hz | 6400000 Hz | 59.0 dBmV | |
| 2 | 1 | Locked | SC-QAM Upstream | 36500000 Hz | 6400000 Hz | 59.0 dBmV | |
| 3 | 3 | Locked | SC-QAM Upstream | 23700000 Hz | 6400000 Hz | 59.0 dBmV | |
| 4 | 4 | Locked | SC-QAM Upstream | 17300000 Hz | 6400000 Hz | 59.0 dBmV |
| Event Log | |||
Date Time | Event ID | Event Level | Description |
| 9/28/2020 9:24 | 84000500 | 3 | "SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;" |
| 9/28/2020 9:24 | 67061600 | 6 | "DS profile assignment change. DS Chan ID: 32; Previous Profile: ; New Profile: 1 2 3.;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;" |
| 9/28/2020 9:24 | 2436694066 | 6 | "Honoring MDD; IP provisioning mode = IPv6" |
| 9/28/2020 9:23 | 82000500 | 3 | "Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;" |
| 9/28/2020 9:22 | 67061600 | 6 | "DS profile assignment change. DS Chan ID: 32; Previous Profile: ; New Profile: 1 2 3.;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;" |
| 9/28/2020 9:22 | 2436694066 | 6 | "Honoring MDD; IP provisioning mode = IPv6" |
| 9/28/2020 9:22 | 84000100 | 3 | "SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;" |
| 9/28/2020 9:21 | 82000500 | 3 | "Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;" |
| 9/28/2020 9:20 | 67061600 | 6 | "DS profile assignment change. DS Chan ID: 32; Previous Profile: ; New Profile: 1 2 3.;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;" |
| 1/1/1970 0:00 | 2436694066 | 6 | "Honoring MDD; IP provisioning mode = IPv6" |
| 1/1/1970 0:00 | 84000100 | 3 | "SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;" |
| 8/17/2020 14:27 | 84000500 | 3 | "SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;" |
| 8/17/2020 14:27 | 82000200 | 3 | "No Ranging Response received - T3 time-out;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;" |
| 8/17/2020 14:27 | 84000100 | 3 | "SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;" |
| 8/17/2020 14:26 | 84000100 | 3 | "SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;" |
| 1/1/1970 0:02 | 84000100 | 3 | "SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;" |
| 8/16/2020 16:11 | 82000500 | 3 | "Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;" |
| 8/16/2020 16:11 | 84000500 | 3 | "SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;" |
| 1/1/1970 0:01 | 84000100 | 3 | "SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;" |
| 1/1/1970 0:01 | 84000100 | 3 | "SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;" |
| 8/16/2020 16:05 | 84000500 | 3 | "SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;" |
| 8/16/2020 16:04 | 84000500 | 3 | "SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;" |
| 8/16/2020 16:03 | 84000500 | 3 | "SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;" |
| 8/16/2020 9:55 | 84000500 | 3 | "SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;" |
| 1/1/1970 0:01 | 82000500 | 3 | "Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;" |
| 1/1/1970 0:00 | 82000200 | 3 | "No Ranging Response received - T3 time-out;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;" |
| 1/1/1970 0:00 | 84000100 | 3 | "SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;" |
| 8/16/2020 9:34 | 82000200 | 3 | "No Ranging Response received - T3 time-out;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;" |
| 8/16/2020 9:33 | 84000100 | 3 | "SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;" |
| 8/16/2020 9:33 | 82000200 | 3 | "No Ranging Response received - T3 time-out;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;" |
| 8/16/2020 9:33 | 84000500 | 3 | "SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;" |
| 8/16/2020 9:33 | 84000100 | 3 | "SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;" |
| 8/16/2020 9:33 | 84000500 | 3 | "SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;" |
| 8/16/2020 9:32 | 84000500 | 3 | "SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;" |
| 8/16/2020 9:32 | 82000200 | 3 | "No Ranging Response received - T3 time-out;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;" |
| 8/16/2020 9:31 | 84000500 | 3 | "SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;" |
| 8/16/2020 9:31 | 84000500 | 3 | "SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;" |
| 8/16/2020 9:30 | 84000100 | 3 | "SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;" |
| 8/16/2020 9:29 | 84000100 | 3 | "SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;" |
| 8/16/2020 9:26 | 82000200 | 3 | "No Ranging Response received - T3 time-out;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;" |
| 8/16/2020 9:26 | 84000500 | 3 | "SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;" |
| 8/16/2020 9:25 | 84000500 | 3 | "SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;" |
| 8/14/2020 20:35 | 82000500 | 3 | "Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;" |
| 8/13/2020 9:37 | 84000500 | 3 | "SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;" |
| 8/7/2020 1:36 | 82000500 | 3 | "Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;" |
| 8/6/2020 20:03 | 82000800 | 3 | "16 consecutive T3 timeouts while trying to range on upstream channel 2;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;" |
| 8/6/2020 20:03 | 82000600 | 3 | "Unicast Maintenance Ranging attempted - No response - Retries exhausted;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;" |
| 8/6/2020 20:03 | 82000500 | 3 | "Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;" |
| 8/6/2020 19:16 | 82000500 | 3 | "Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;" |
| 8/6/2020 19:15 | 82000800 | 3 | "16 consecutive T3 timeouts while trying to range on upstream channel 2;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;" |
EG
Expert
•
111.6K Messages
5 years ago
The upstream power is WAY 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 it's best to Get the techs involved again until it is fixed properly.
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.
Good luck !
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