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ARRIS : SB6121 : No Ranging Response received - T3 time-out

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ARRIS : SB6121 : No Ranging Response received - T3 time-out

Internet is very irratic today. 

My modem(SB6121) can't be restarted using the App.

When restarted manually... it shows on modme page : 


Signal : 


Downstream Bonding Channel Value
Channel ID40 41 42 43 
Frequency645000000 Hz 651000000 Hz 657000000 Hz 663000000 Hz 
Signal to Noise Ratio36 dB 36 dB 36 dB 36 dB 
Downstream ModulationQAM256 QAM256 QAM256 QAM256 
Power Level
The Downstream Power Level reading is a snapshot taken at the time this page was requested. Please Reload/Refresh this Page for a new reading
-1 dBmV  -1 dBmV  -1 dBmV  -1 dBmV  


Upstream Bonding Channel Value
Channel ID
Frequency22800000 Hz 35600000 Hz 29200000 Hz 16400000 Hz 
Ranging Service ID8569 8569 8569 8569 
Symbol Rate5.120 Msym/sec 5.120 Msym/sec 5.120 Msym/sec 5.120 Msym/sec 
Power Level51 dBmV 51 dBmV 51 dBmV 51 dBmV 
Upstream Modulation[2] QPSK
[1] 32QAM
[3] 64QAM
[2] QPSK
[1] 32QAM
[3] 64QAM
[2] QPSK
[1] 32QAM
[3] 64QAM
[2] QPSK
[1] 16QAM
[3] 32QAM
Ranging StatusSuccess Success Success Success 


Signal Status (Codewords) Bonding Channel Value
Channel ID40 41 42 43 
Total Unerrored Codewords96157306 95252173 95252175 95252264 
Total Correctable Codewords15 
Total Uncorrectable Codewords648 569 546 538 


Logs :


Feb 02 2021 18:57:413-CriticalR02.0No Ranging Response received - T3 time-out;CM-MAC=38:6b:bb:16:0a:4a;CMTS-MAC=00:01:5c:9e:8e:71;CM-QOS=1.1;CM-VER=3.0;
Feb 02 2021 18:26:335-WarningZ00.0MIMO Event MIMO: Stored MIMO=-1 post cfg file MIMO=-1;CM-MAC=38:6b:bb:16:0a:4a;CMTS-MAC=00:01:5c:9e:8e:71;CM-QOS=1.1;CM-VER=3.0;
Jan 01 1970 00:00:166-NoticeN/ACable Modem Reboot due to power reset ;CM-MAC=38:6b:bb:16:0a:4a;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.0;


Also it seems the app see's my modem's serial number all wrong.




Re: ARRIS : SB6121 : No Ranging Response received - T3 time-out

The upstream power is on the high side and it 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 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 perhaps it's best to book a tech visit to investigate and correct.

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