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user_19jk63
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Sunday, December 14th, 2025 12:56 AM

UCD invalid or channel unusable

I am experiencing daily modem resets in the morning between around 5:40 AM and 5:50 AM. My modem (Motorola MB8600) log shows repeating Critical Errors at this exact time, specifically "CMSTATUS:US_Diplexer_Mode_Change" and "UCD invalid or channel unusable". This indicates a command or maintenance action is likely being sent from the CMTS, forcing my modem offline. Is it possible that some scheduled maintenance or a repeated daily CMTS reconfiguration is affecting my node around 5:45 AM almost every day?

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EG

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2 days ago

Please also copy all of the text in its entirety of the *Downstream Power Levels*, the *SNR's* (Signal to Noise Ratios), and the *Upstream Power Level* numbers and paste them into your next post.



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user_19jk63

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Thanks for the suggestion!  I don't have the values from the time of the issue, as the modem is restarting.  These tables are from a few hours later:

Downstream Bonded Channels

Channel Lock Status Modulation Channel ID Freq. (MHz) Pwr (dBmV) SNR (dB) Corrected Uncorrected
   1 Locked QAM256 20 495.0 -1.7 44.5 0 0
   2 Locked QAM256 13 453.0 -0.2 45.3 2 0
   3 Locked QAM256 14 459.0 -0.4 45.1 2 0
   4 Locked QAM256 15 465.0 -0.8 44.9 2 0
   5 Locked QAM256 16 471.0 -0.4 45.2 2 0
   6 Locked QAM256 17 477.0 -1.2 44.7 2 0
   7 Locked QAM256 18 483.0 -1.0 44.7 6 0
   8 Locked QAM256 19 489.0 -1.3 44.7 6 0
   9 Locked QAM256 21 501.0 -1.2 44.7 10 0
   10 Locked QAM256 22 507.0 -1.9 44.1 9 0
   11 Locked QAM256 23 513.0 -1.6 44.2 7 0
   12 Locked QAM256 24 519.0 -1.7 44.4 6 0
   13 Locked QAM256 25 525.0 -2.3 44.0 6 0
   14 Locked QAM256 26 531.0 -1.8 44.3 10 0
   15 Locked QAM256 27 537.0 -2.5 43.9 9 0
   16 Locked QAM256 28 543.0 -2.4 43.8 7 0
   17 Locked QAM256 29 549.0 -2.2 44.0 8 0
   18 Locked QAM256 30 555.0 -3.0 43.6 7 0
   19 Locked QAM256 31 561.0 -2.0 44.0 7 0
   20 Locked QAM256 32 567.0 -2.7 43.5 2 0
   21 Locked QAM256 33 573.0 -2.7 43.6 2 0
   22 Locked QAM256 34 579.0 -2.4 43.6 3 0
   23 Locked QAM256 35 585.0 -3.3 43.0 2 0
   24 Locked QAM256 36 591.0 -2.7 43.3 2 0
   25 Locked QAM256 37 597.0 -3.3 42.9 7 0
   26 Locked QAM256 38 603.0 -3.5 42.6 3 0
   27 Locked QAM256 39 609.0 -3.1 43.0 2 0
   28 Locked QAM256 40 615.0 -4.2 42.4 3 0
   29 Locked QAM256 41 621.0 -3.5 42.7 2 0
   30 Locked QAM256 42 627.0 -4.0 42.4 1 0
   31 Locked QAM256 43 633.0 -4.7 42.0 1 0
   32 Locked QAM256 44 639.0 -4.1 42.0 0 0
   33 Locked OFDM PLC 193 722.0 -6.4 40.4 1391886032 0
   34 Locked OFDM PLC 194 957.0 -12.6 36.1 1315436808 67330753

Upstream Bonded Channels

Channel Lock Status Channel Type Channel ID Symb. Rate (Ksym/sec) Freq. (MHz) Pwr (dBmV)
   1 Locked SC-QAM 17 5120 16.4 46.3
   2 Locked SC-QAM 18 5120 22.8 46.5
   3 Locked SC-QAM 19 5120 29.2 46.8
   4 Locked SC-QAM 20 5120 35.6 47.3

And here is the event log I captured from the event on Friday morning:

05:46:39
Fri Dec 12 2025		 Critical (3) CMSTATUS:US_Diplexer_Mode_Change:TLV-84.1, 5-42MHz.
05:46:41
Fri Dec 12 2025		 Critical (3) CMSTATUS:DS_Diplexer_Mode_Change_Ignored:TLV-21.2, 258MHz.
05:46:41
Fri Dec 12 2025		 Critical (3) CMSTATUS:DS_Diplexer_Mode_Change_Ignored:TLV-21.3, 1002MHz.
05:46:41
Fri Dec 12 2025		 Critical (3) CMSTATUS:US_Diplexer_Mode_Change_Ignored:TLV-21.1, 85MHz.
05:46:42
Fri Dec 12 2025		 Critical (3) UCD invalid or channel unusable;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
05:46:45
Fri Dec 12 2025		 Notice (6) Honoring MDD; IP provisioning mode = IPv6
05:46:54
Fri Dec 12 2025		 Critical (3) CMSTATUS:DS_Diplexer_Mode_Change_Ignored:TLV-84.2, 108MHz.
05:46:54
Fri Dec 12 2025		 Critical (3) CMSTATUS:DS_Diplexer_Mode_Change_Ignored:TLV-84.3, 1002MHz.
05:46:54
Fri Dec 12 2025		 Critical (3) CMSTATUS:US_Diplexer_Mode_Change:TLV-84.1, 5-42MHz.
05:47:00
Fri Dec 12 2025		 Notice (6) DS profile assignment change. DS Chan ID: 32; Previous Profile: ; New Profile: 1 2 3.;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
05:47:01
Fri Dec 12 2025		 Notice (6) DS profile assignment change. DS Chan ID: 33; Previous Profile: ; New Profile: 1 2 3.;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
05:47:08
Fri Dec 12 2025		 Critical (3) UCD invalid or channel unusable;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
05:47:41
Fri Dec 12 2025		 Notice (6) CM-STATUS message sent. Event Type Code: 16; Chan ID: 194; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: 3.;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;

(edited)

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2 days ago

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EG

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114.9K Messages

2 days ago

At that snapshot in time, the downstream channels 28 to 33 were on the low / weak side and channel 34's power and SNR values are out of spec. Also, the upstream is a bit on the high side and they may be intermittently fluctuating even higher to out of spec levels. That can cause random disconnects, spontaneous re-booting of the modem, speed, packet loss, latency problems, and the un-bonding of channels.

In an effort to try to obtain better connectivity / more wiggle room, check to see if there are any excess/unneeded coax cable splitters in the line leading to the modem that can be eliminated/reconfigured. Any splitters that remain should be high quality and cable rated for 5-1002 MHz, bi-directional, and no gold colored garbage from Home Depot, Target, Wal-Mart, etc. Splitters should be swapped with known to be good / new ones to test.

Also, check the coax cable for any damage such as cuts, nicks, abrasions, kinks, sharp bends, or animal chews.

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. Good luck !

(edited)

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