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sharonSB
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Wednesday, July 30th, 2025

Connection issues - "Started Unicast Maintenance Ranging - No Response received - T3 time-out" and "SYNC Timing Synchronization failure"

Hi there,

Xfinity has recently been doing work in my area, and I've started experiencing connection issues. I checked the router (MB7621) logs and saw that there were Unicast and SYNC timing issues. Logs and signal strengths are posted below. Would appreciate help with this matter.

Logs:

Time Priority Description
Fri Jun 13 21:32:19 2025 Critical (3)
No Ranging Response received - T3 time-out;CM-MAC=[redacted];CMTS-MAC=[redacted];CM-QOS=1.1;CM-VER=3.0;
Fri Jul 18 18:28:14 2025 Critical (3)
Resetting the cable modem due to docsDevResetNow
Fri Jul 18 18:47:54 2025 Critical (3)
Resetting the cable modem due to docsDevResetNow
Tue Jul 29 21:54:00 2025 Critical (3)
Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=[redacted];CMTS-MAC=[redacted];CM-QOS=1.1;CM-VER=3.0;
Wed Jul 30 00:14:59 2025 Critical (3)
Unicast Ranging Received Abort Response - Re-initializing MAC;CM-MAC=[redacted];CMTS-MAC=[redacted];CM-QOS=1.1;CM-VER=3.0;
Wed Jul 30 00:13:23 2025 Critical (3)
No Ranging Response received - T3 time-out;CM-MAC=[redacted];CMTS-MAC=[redacted];CM-QOS=1.1;CM-VER=3.0;
Wed Jul 30 00:13:27 2025 Critical (3)
SYNC Timing Synchronization failure - Failed to acquire FEC framing;CM-MAC=[redacted];CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Wed Jul 30 00:14:55 2025 Critical (3)
SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=[redacted];CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Wed Jul 30 00:14:56 2025 Critical (3)
SYNC Timing Synchronization failure - Failed to acquire FEC framing;CM-MAC=[redacted];CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Wed Jul 30 00:15:00 2025 Critical (3)
SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=[redacted];CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Wed Jul 30 00:15:01 2025 Critical (3)
SYNC Timing Synchronization failure - Failed to acquire FEC framing;CM-MAC=[redacted];CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Wed Jul 30 00:15:12 2025 Critical (3)
SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=[redacted];CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Wed Jul 30 00:15:12 2025 Critical (3)
SYNC Timing Synchronization failure - Failed to acquire FEC framing;CM-MAC=[redacted];CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Wed Jul 30 00:15:17 2025 Critical (3)
SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=[redacted];CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Wed Jul 30 00:15:19 2025 Critical (3)
SYNC Timing Synchronization failure - Failed to acquire FEC framing;CM-MAC=[redacted];CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Wed Jul 30 00:15:21 2025 Critical (3)
SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=[redacted];CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Wed Jul 30 00:15:21 2025 Critical (3)
SYNC Timing Synchronization failure - Failed to acquire FEC framing;CM-MAC=[redacted];CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Wed Jul 30 00:15:27 2025 Critical (3)
SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=[redacted];CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Wed Jul 30 00:15:29 2025 Critical (3)
SYNC Timing Synchronization failure - Failed to acquire FEC framing;CM-MAC=[redacted];CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Wed Jul 30 00:15:59 2025 Critical (3)
SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=[redacted];CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Wed Jul 30 00:16:00 2025 Critical (3)
SYNC Timing Synchronization failure - Failed to acquire FEC framing;CM-MAC=[redacted];CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Wed Jul 30 00:16:01 2025 Critical (3)
SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=[redacted];CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Wed Jul 30 00:16:01 2025 Critical (3)
SYNC Timing Synchronization failure - Failed to acquire FEC framing;CM-MAC=[redacted];CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Wed Jul 30 00:16:03 2025 Critical (3)
SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=[redacted];CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Wed Jul 30 00:16:04 2025 Critical (3)
SYNC Timing Synchronization failure - Failed to acquire FEC framing;CM-MAC=[redacted];CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Wed Jul 30 00:16:06 2025 Critical (3)
SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=[redacted];CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Wed Jul 30 00:16:06 2025 Critical (3)
SYNC Timing Synchronization failure - Failed to acquire FEC framing;CM-MAC=[redacted];CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Wed Jul 30 00:16:38 2025 Critical (3)
SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=[redacted];CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Wed Jul 30 00:16:38 2025 Critical (3)
SYNC Timing Synchronization failure - Failed to acquire FEC framing;CM-MAC=[redacted];CMTS
-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Wed Jul 30 00:16:40 2025 Critical (3)
SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=[redacted];CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.0;CM-VER=3.0;
Wed Jul 30 00:17:13 2025 Critical (3)
No Ranging Response received - T3 time-out;CM-MAC=[redacted];CMTS-MAC=[redacted];CM-QOS=1.1;CM-VER=3.0;
Time Not Established Notice (6)
Honoring MDD; IP provisioning mode = IPv6

Signal Strengths:

Downstream Bonded Channels
Channel Lock Status Modulation Channel ID Freq. (MHz) Pwr (dBmV) SNR (dB) Corrected Uncorrected
1 Locked QAM256 28 597 0 40.2 0 0
2 Locked QAM256 21 555 -0.9 40 0 0
3 Locked QAM256 22 561 -1.8 39.6 0 0
4 Locked QAM256 23 567 -1.7 39.7 0 0
5 Locked QAM256 24 573 -2 39.5 0 0
6 Locked QAM256 25 579 -1.8 39.7 0 0
7 Locked QAM256 26 585 -1 39.9 0 0
8 Locked QAM256 27 591 -0.4 40 0 0
9 Locked QAM256 29 603 -1 39.8 0 0
10 Locked QAM256 30 609 -0.9 39.9 0 0
11 Locked QAM256 31 615 -1.5 39.6 0 0
12 Locked QAM256 32 621 -1.4 39.1 0 0
13 Locked QAM256 33 627 -0.9 39.8 0 0
14 Locked QAM256 34 633 -1.3 39.5 0 0
15 Locked QAM256 35 639 -0.5 40.1 0 0
16 Locked QAM256 36 645 -1.1 39.7 0 0
17 Locked QAM256 37 651 -1.2 40.8 0 0
18 Locked QAM256 38 657 -1.4 40.5 0 0
19 Locked QAM256 39 663 -1.5 40.4 0 0
20 Locked QAM256 40 669 -0.9 40.7 0 0
21 Locked QAM256 41 675 -1 40.6 0 0
22 Locked QAM256 42 681 -0.2 41.1 0 0
23 Locked QAM256 43 687 -0.2 41.2 0 0
24 Locked QAM256 44 693 0 40.9 0 0
Total 0 0
Upstream Bonded Channels
Channel Lock Status Channel Type Channel ID Symb. Rate (Ksym/sec) Freq. (MHz) Pwr (dBmV)
1 Locked ATDMA 18 5120 22.8 47.8
2 Locked ATDMA 17 5120 16.4 46.2
3 Locked ATDMA 19 5120 29.2 47.7
4 Locked ATDMA 20 5120 35.6 47.7
5 Locked ATDMA 21 2560 40.4 47.7
6 Not Locked Unknown 0 0 0 0
7 Not Locked Unknown 0 0 0 0
8 Not Locked Unknown 0 0 0 0

Question

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Updated 

20 days ago

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XfinitySara

Official Employee

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2K Messages

27 days ago

Hello, @sharonSB! You've come to a great place for help :) Our Digital Care Team is awesome to work with because we'll always do whatever we can to review and resolve issues quickly. I'm sorry to hear about this concern, and I'd like to ask a quick question to start - how are the connection issues presenting themselves (i.e. intermittent/unstable connection, slow speeds, no service at all, etc.)?

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sharonSB

Visitor

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3 Messages

Hi Sara, thanks for following up. The issues are most present as intermittent drops in service for the full network.

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27 days ago

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XfinitySara

Official Employee

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2K Messages

Thanks for confirming, @sharonSB! Have you already reviewed our Connection Troubleshooting Tips?

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

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27 days ago

sharonSB

Visitor

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3 Messages

Yes I have reviewed those tips.

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22 days ago

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XfinityOrlandoM

Official Employee

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2.4K Messages

@sharonSB

Awesome,  have you done any troubleshooting steps by rebooting the modem checking all the connections or jumping on our Xfinity app and using the remote troubleshooting functions within the app

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

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20 days ago

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