Slowness, service discruption with down arrow light blinking

This is an ongoing issue that happened after a “service upgrade” few months back. The service upgrade caused an outage in our area and after that my internet has been expereincing periodcally slowness and disconnect. I also notice the down arrow light blinking when the issue occcurs.

I’ve called Xfinity support many times but they were unable to even indentify the problem. The solution given to me was to power cycle the modem. But this only resolve the issue for couple days or hours and the issue will reappear. They also told me that I need to update my modem firmware and pass me the number to contact Motorla support. Interestingly, when I spoke with Motorla support, they said only the ISP (Xfinity) can upgrade the firmware. This problem has been ongoing for months now, with no meaningful help from Xfinty support.

Here is the log I‘ve gather form the modem and I hope someone can shed some light on how to resovle this problem.

Thanks in advance.

02:42:08 Sat Nov 26 2022		Notice (6)		CM-STATUS message sent. Event Type Code: 20; Chan ID: 193; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: N/A.;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
	02:42:52 Sat Nov 26 2022		Notice (6)		CM-STATUS message sent. Event Type Code: 22; Chan ID: 193; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: N/A.;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
	06:52:39 Sat Nov 26 2022		Critical (3)		Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
	06:52:55 Sat Nov 26 2022		Warning (5)		RNG-RSP CCAP Commanded Power Exceeds Value Corresponding to the Top of the DRW;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
	06:52:55 Sat Nov 26 2022		Warning (5)		Dynamic Range Window violation
	06:53:14 Sat Nov 26 2022		Critical (3)		Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
	06:53:51 Sat Nov 26 2022		Warning (5)		RNG-RSP CCAP Commanded Power Exceeds Value Corresponding to the Top of the DRW;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
	06:53:51 Sat Nov 26 2022		Warning (5)		Dynamic Range Window violation
	07:03:48 Sat Nov 26 2022		Critical (3)		UCD invalid or channel unusable;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=0

Responses

Accepted Solution

EG

Expert

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110K Messages

2 years ago

@user_f891cf

Please redact all of the CM MAC and the CMTS MAC addresses in your error log entries for your privacy. They are considered to be personal information. The posting of personally identifiable information is a violation of their forum guidelines. The forum bot will not allow your post to be seen publically. It flagged your post as "Private".

That said. The upstream power is too high. The downstream power is a bit on the low / weak side as well. 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 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 5-1000 MHz, bi-directional, and no gold colored garbage from Radio Shack, Home Depot, Target, 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, etc.

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 with it !

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EG

Expert

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110K Messages

2 years ago

What do the modem's signal stats look like ?

Please 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.

What is the exact model number of the Motorola device ?

(edited)

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user_f891cf

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6 Messages

2 years ago

HI EG:

Thank you for you reply

1. Here is the output from connection page. This was capture after the reset of the modem that was done on its own and the down arrow again is blue and blinking. All other lights look normal.

Connection

Startup Sequence

Startup Step	Status	Comment
Acquire Downstream Channel	549000000 Hz	Locked
Upstream Connection	OK	Operational
Boot State	OK	Operational
Configuration File	OK
Security	Enabled	BPI+

Connection Status

System Up Time	0 days 20h:27m:36s
Network Access	Allowed

Downstream Bonded Channels

Channel	Lock Status	Modulation	Channel ID	Freq. (MHz)	Pwr (dBmV)	SNR (dB)	Corrected	Uncorrected
1	Locked	QAM256	20	549.0	-4.3	39.3	0	0
2	Locked	QAM256	13	507.0	-4.5	39.5	31	34
3	Locked	QAM256	14	513.0	-4.2	35.9	93	518
4	Locked	QAM256	15	519.0	-4.4	35.5	106	458
5	Locked	QAM256	16	525.0	-4.5	41.1	90	482
6	Locked	QAM256	17	531.0	-5.0	37.0	91	481
7	Locked	QAM256	18	537.0	-5.4	36.6	97	475
8	Locked	QAM256	19	543.0	-5.0	29.6	610	465
9	Locked	QAM256	21	555.0	-3.6	42.2	103	483
10	Locked	QAM256	22	561.0	-3.8	41.9	92	493
11	Locked	QAM256	23	567.0	-4.3	35.8	74	512
12	Locked	QAM256	24	573.0	-5.0	32.5	96	490
13	Locked	QAM256	25	579.0	-5.1	38.8	111	479
14	Locked	QAM256	26	585.0	-5.4	38.4	99	489
15	Locked	QAM256	27	591.0	-5.2	31.5	115	500
16	Locked	QAM256	28	597.0	-4.9	35.0	107	479
17	Locked	QAM256	29	603.0	-4.9	36.6	100	507
18	Locked	QAM256	30	609.0	-4.5	39.3	109	499
19	Locked	QAM256	31	615.0	-4.8	40.9	1043191	14660
20	Locked	QAM256	32	621.0	-5.1	40.8	109	498
21	Locked	QAM256	33	627.0	-5.6	40.2	90	517
22	Locked	QAM256	34	633.0	-5.9	40.4	92	516
23	Locked	QAM256	35	639.0	-6.2	39.8	102	506
24	Locked	QAM256	36	645.0	-5.6	40.2	106	511
25	Locked	QAM256	37	651.0	-5.5	40.8	90	509
26	Locked	QAM256	38	657.0	-5.3	40.8	100	499
27	Locked	QAM256	39	663.0	-5.1	40.9	28639	590
28	Locked	QAM256	40	669.0	-5.4	41.0	83	516
29	Locked	QAM256	41	675.0	-5.2	40.4	91	524
30	Locked	QAM256	42	681.0	-5.3	41.0	96	519
31	Locked	QAM256	43	687.0	-5.5	40.8	88	527
32	Locked	QAM256	44	693.0	-5.4	40.7	80	535
33	Locked	OFDM PLC	193	957.0	-4.9	40.0	370655631	72

Upstream Bonded Channels

Channel	Lock Status	Channel Type	Channel ID	Symb. Rate (Ksym/sec)	Freq. (MHz)	Pwr (dBmV)
1	Locked	SC-QAM	1	5120	16.4	53.5
2	Locked	SC-QAM	2	5120	22.8	52.0
3	Locked	SC-QAM	3	5120	29.2	50.5
4	Locked	SC-QAM	4	5120	35.6	49.8

Downstream Frequency Setting

Downstream Frequency Select

LAG Enable/Disable

LAG(Link Aggregation Group, or Ethernet Port Bonding)

2. Here is the output from the event log

Here is the software output:

Software

Device Information

Cable Specification Version	DOCSIS 3.1
Hardware Version	V1.0
Software Version	8600-19.3.18
Cable Modem MAC Address	xxx
Cable Modem Serial Number	xxxx
CM Certificate	Installed
	Prod_19.3_d31

Thank you for your help.

(edited)

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user_f891cf

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6 Messages

2 years ago

Hi EG:

Thank you so much for your help!! I just check and notice the cables are connecting via a RCA splitter in the attic. I'm unsure if it was installed by Comcast or by the previous home owner. The splitter looks exactly like this:

https://www.walmart.com/ip/Rca-Vh49r-Splitter-4-Way/11600129?wmlspartner=wlpa&selectedSellerId=1609&adid=22222222227000000000&wl0=&wl1=g&wl2=c&wl3=42423897272&wl4=pla-51320962143&wl5=9027782&wl6=&wl7=&wl8=&wl9=pla&wl10=113487702&wl11=online&wl12=11600129_1609&veh=sem&gclid=Cj0KCQiAvqGcBhCJARIsAFQ5ke7icgDy4BL4dNca8XX7Tb4Nm5PUiRCKTv5kq-uLurWCwvO4O2_ovC8aAiIWEALw_wcB

Should I purchase a new splitter myself or would Comcast send me one that would work better?

Thank you again for your help, I really appreciate it!

(edited)

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EG

Expert

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110K Messages

2 years ago

Quite welcome ! That's a cheapie ! Comcast does not use that brand. You could pick one up for free at your local Xfinity / Comcast store. It would be an official quality one that they actually use in the field. But your existing splitter may or may not be malfunctioning. YMMV. Is it actually being used / needed ? It would be better to eliminate it altogether if you can and use an inline coax cable coupler instead.

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user_f891cf

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6 Messages

2 years ago

Ha.. yeah, that splitter doesn't look high quality at all. I'm just wondering now: Why didn't Comcast replace this "unofficial" splitter during the initial installation and why is the issue only happening after their "service upgrade"

I will get a coupler to test, but I need the splitter for flexibility to move to different rooms if needed. I will go to the store tonight and see if they have one available.

Thanks!

(edited)

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EG

Expert

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110K Messages

2 years ago

As I stated, a new splitter may not be the solution. You may want to consider getting a tech out to investigate / determine what is needed. The problem may be that the signal from the pole may be too weak in the first place. An active amplifier may need to be used rather than a passive splitter.

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user_f891cf

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6 Messages

2 years ago

Hi EG:

Just want to give an update. So Xfinity store said they only have splitter that looks like this:

https://www.amazon.com/Antronix-CMC2002H-Horizontal-Splitter-Performance/dp/B08LM96C2J/ref=sr_1_1_sspa?keywords=antronix+2+way+splitter&qid=1670090194&sr=8-1-spons&psc=1&smid=A3G1B2YUG70PQB&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUFJTk04TzJSUDJIVzcmZW5jcnlwdGVkSWQ9QTA3MTQwOTgxOFBQNFpQUVRLMURJJmVuY3J5cHRlZEFkSWQ9QTAyODg3NjJCQjNHSENDUDVJQTAmd2lkZ2V0TmFtZT1zcF9hdGYmYWN0aW9uPWNsaWNrUmVkaXJlY3QmZG9Ob3RMb2dDbGljaz10cnVlhttps://www.amazon.com/Antronix-CMC2002H-Horizontal-Splitter-Performance/dp/B08LM96C2J/ref=sr_1_1_sspa?keywords=antronix+2+way+splitter&qid=1670090194&sr=8-1-spons&psc=1&smid=A3G1B2YUG70PQB&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUFJTk04TzJSUDJIVzcmZW5jcnlwdGVkSWQ9QTA3MTQwOTgxOFBQNFpQUVRLMURJJmVuY3J5cHRlZEFkSWQ9QTAyODg3NjJCQjNHSENDUDVJQTAmd2lkZ2V0TmFtZT1zcF9hdGYmYWN0aW9uPWNsaWNrUmVkaXJlY3QmZG9Ob3RMb2dDbGljaz10cnVl

Here is the latest connection output, it seems the new splitter did improved the signal on both upload and download streams. I haven't experienced any connection issue since.

Connection

Startup Sequence

Startup Step	Status	Comment
Acquire Downstream Channel	597000000 Hz	Locked
Upstream Connection	OK	Operational
Boot State	OK	Operational
Configuration File	OK
Security	Enabled	BPI+

Connection Status

System Up Time	1 days 18h:50m:33s
Network Access	Allowed

Downstream Bonded Channels

Channel	Lock Status	Modulation	Channel ID	Freq. (MHz)	Pwr (dBmV)	SNR (dB)	Corrected	Uncorrected
1	Locked	QAM256	28	597.0	1.8	42.5	12	54
2	Locked	QAM256	13	507.0	2.5	43.9	14	64
3	Locked	QAM256	14	513.0	2.5	42.7	17	50
4	Locked	QAM256	15	519.0	2.4	40.8	27	38
5	Locked	QAM256	16	525.0	2.3	43.5	42	25
6	Locked	QAM256	17	531.0	2.0	44.1	43	3
7	Locked	QAM256	18	537.0	1.9	42.5	39	20
8	Locked	QAM256	19	543.0	2.0	38.6	49	26
9	Locked	QAM256	20	549.0	2.5	43.8	32	54
10	Locked	QAM256	21	555.0	2.9	44.8	47	23
11	Locked	QAM256	22	561.0	3.0	44.7	65	0
12	Locked	QAM256	23	567.0	2.8	43.6	35	32
13	Locked	QAM256	24	573.0	2.4	42.2	52	13
14	Locked	QAM256	25	579.0	2.0	43.2	61	0
15	Locked	QAM256	26	585.0	1.6	41.9	51	9
16	Locked	QAM256	27	591.0	1.6	41.2	19	48
17	Locked	QAM256	29	603.0	2.5	42.4	40	24
18	Locked	QAM256	30	609.0	2.7	43.8	51	15
19	Locked	QAM256	31	615.0	2.3	43.9	44	20
20	Locked	QAM256	32	621.0	1.7	43.6	60	0
21	Locked	QAM256	33	627.0	1.1	43.4	13	20
22	Locked	QAM256	34	633.0	0.8	43.3	48	1
23	Locked	QAM256	35	639.0	1.0	43.3	33	9
24	Locked	QAM256	36	645.0	1.4	43.5	65	0
25	Locked	QAM256	37	651.0	1.6	43.6	32	1
26	Locked	QAM256	38	657.0	1.5	43.6	58	0
27	Locked	QAM256	39	663.0	1.5	43.7	38	0
28	Locked	QAM256	40	669.0	1.6	43.7	28	0
29	Locked	QAM256	41	675.0	1.6	43.1	35	2
30	Locked	QAM256	42	681.0	1.7	43.7	33	0
31	Locked	QAM256	43	687.0	1.8	43.7	46	0
32	Locked	QAM256	44	693.0	1.7	43.7	21	29
33	Locked	OFDM PLC	193	957.0	-0.1	42.1	241422016	0

Upstream Bonded Channels

Channel	Lock Status	Channel Type	Channel ID	Symb. Rate (Ksym/sec)	Freq. (MHz)	Pwr (dBmV)
1	Locked	SC-QAM	1	5120	16.4	46.0
2	Locked	SC-QAM	2	5120	22.8	44.5
3	Locked	SC-QAM	3	5120	29.2	43.5
4	Locked	SC-QAM	4	5120	35.6	43.0

1. Are these levels sufficient or do I still need a signal booster?

2. There are still uncorrected errors in the downstreams, but are these errors within the acceptable level or they should be all 0?

2. I would like to replace this splitter that only has 1 in 2 outs (-3.5 on out) to one that has 1 in 3 outs, but this Antronix brand only has one that is -7 on two and -3.5 on one. Would that work?

Thank you so much for your help again!!

(edited)

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EG

Expert

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110K Messages

2 years ago

1. Looking good !

2. The uncorrectable bit error rates are low, but it all depends on the total amount of uptime that the modem has had. They are cumulative.

3. Yes. You can use a 3-way unbalanced splitter, but make sure that you put the modem on a -3.5 dB tap.

Bottom line. Live with it for a while now and see if the problem returns. You should be good to go as long as the signals remain stable.

P.S. Antronix is a very good quality brand of splitter !

(edited)

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user_f891cf

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6 Messages

2 years ago

Hi EG:

The slowness issue came back and the down arrow is blinking again. Here is the connection log.

Connection

Startup Sequence

Startup Step	Status	Comment
Acquire Downstream Channel	597000000 Hz	Locked
Upstream Connection	OK	Operational
Boot State	OK	Operational
Configuration File	OK
Security	Enabled	BPI+

Connection Status

System Up Time	4 days 02h:22m:13s
Network Access	Allowed

Downstream Bonded Channels

Channel	Lock Status	Modulation	Channel ID	Freq. (MHz)	Pwr (dBmV)	SNR (dB)	Corrected	Uncorrected
1	Locked	QAM256	28	597.0	1.3	41.9	12	54
2	Locked	QAM256	13	507.0	1.8	43.6	14	64
3	Locked	QAM256	14	513.0	1.8	42.4	17	50
4	Locked	QAM256	15	519.0	1.7	39.5	27	38
5	Locked	QAM256	16	525.0	1.7	42.4	42	25
6	Locked	QAM256	17	531.0	1.4	43.7	43	3
7	Locked	QAM256	18	537.0	1.2	41.8	39	20
8	Locked	QAM256	19	543.0	1.3	38.1	49	26
9	Locked	QAM256	20	549.0	1.9	43.6	32	54
10	Locked	QAM256	21	555.0	2.4	44.7	47	23
11	Locked	QAM256	22	561.0	2.4	44.7	65	0
12	Locked	QAM256	23	567.0	2.2	42.8	35	32
13	Locked	QAM256	24	573.0	1.9	41.2	52	13
14	Locked	QAM256	25	579.0	1.4	42.9	61	0
15	Locked	QAM256	26	585.0	1.0	40.9	51	9
16	Locked	QAM256	27	591.0	1.0	40.3	19	48
17	Locked	QAM256	29	603.0	2.0	42.5	40	24
18	Locked	QAM256	30	609.0	2.2	44.0	51	15
19	Locked	QAM256	31	615.0	1.9	44.0	44	20
20	Locked	QAM256	32	621.0	1.3	43.6	60	0
21	Locked	QAM256	33	627.0	0.6	43.2	13	20
22	Locked	QAM256	34	633.0	0.3	43.2	48	1
23	Locked	QAM256	35	639.0	0.5	43.3	33	9
24	Locked	QAM256	36	645.0	1.0	43.6	65	0
25	Locked	QAM256	37	651.0	1.2	43.7	32	1
26	Locked	QAM256	38	657.0	1.2	43.7	58	0
27	Locked	QAM256	39	663.0	1.2	43.8	38	0
28	Locked	QAM256	40	669.0	1.2	43.8	28	0
29	Locked	QAM256	41	675.0	1.3	43.0	35	2
30	Locked	QAM256	42	681.0	1.2	43.7	33	0
31	Locked	QAM256	43	687.0	1.4	43.6	46	0
32	Locked	QAM256	44	693.0	1.3	43.7	21	29
33	Locked	OFDM PLC	193	957.0	2.1	43.1	576013897	0

Upstream Bonded Channels

Channel	Lock Status	Channel Type	Channel ID	Symb. Rate (Ksym/sec)	Freq. (MHz)	Pwr (dBmV)
1	Locked	SC-QAM	1	5120	16.4	47.5
2	Locked	SC-QAM	2	5120	22.8	46.3
3	Locked	SC-QAM	3	5120	29.2	45.3
4	Locked	SC-QAM	4	5120	35.6	45.3

Downstream Frequency Setting

Downstream Frequency Select

LAG Enable/Disable

LAG(Link Aggregation Group, or Ethernet Port Bonding)

Disable
Enable

Is there anything else I can do, or it's time to ask Xfinity to send out a tech?

Thank you,

(edited)

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EG

Expert

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110K Messages

2 years ago

Hmmm..... The signal stats were still OK at that snapshot in time. As stated earlier, yes, you may want to consider getting a tech out to investigate / correct the problem.

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. And if the problem is found to be on their side of the demarcation point, there will not be any charge. Good luck with it !

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user_f891cf

Slowness, service discruption with down arrow light blinking

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