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sirlight

join:2007-01-05
Glendale, AZ

2 edits

[AZ] Motorola SB6121 flapping HARD

Peoples,

I got a Motorola SB6121 modem that for a long while has been flapping and last night it started going into this hard loop of boot boot boot for a solid 40 or so mins. I did get a firmware update which seems to fix this problem but it's back and it's doing it HARD....

Here is the log entry that starts off the boot....

Aug 31 2013 18:47:17 3-Critical R02.0 No Ranging Response received - T3 time-out;CM-MAC=;CMTS-MAC=;CM-QOS=1.1;CM-VER=3.0;

Then this....

Jan 01 1970 00:00:13 6-Notice N/A Cable Modem Reboot due to T4 timeout ;CM-MAC=;CMTS-MAC=;CM-QOS=1.1;CM-VER=3.0;

Cox techs, I KNOW you people want my MAC to get the flap report.

Sirlight


some bozo

@cox.net
Had a similar problem a while back.

Two visits from contractors who could tell something was wrong, but not what.

Finally they sent a guy out with test equipment who figured out my cable to the pedestal had gone bad.

Cable was replaced, no more problems for the last two or three years.


Optimus2357
Premium
join:2010-11-21
West Warwick, RI
kudos:3
reply to sirlight
Define flapping? Do you mean just any short instance of random connectivity? Or do you literally mean a cable modem flap? A T4 would suggest a problem in the area, and if it warranted a general push of a firmware patch, I would think it was a big issue. Do you have some history with this issue that the Cox techs know you? I sense backstory.

Rakeesh

join:2011-10-30
Mesa, AZ
Reviews:
·Sprint Mobile Br..
·Cox HSI
said by Optimus2357:

Define flapping? Do you mean just any short instance of random connectivity? Or do you literally mean a cable modem flap? A T4 would suggest a problem in the area, and if it warranted a general push of a firmware patch, I would think it was a big issue. Do you have some history with this issue that the Cox techs know you? I sense backstory.

In network terminology, flapping refers to a link that keeps going up and down (simply referred to as a "flapping link" or "flapping interface.")

Can cause serious problems in enterprise or ISP environments if appropriate countermeasures aren't taken beforehand (namely route poisoning-like problems even though redundant paths are available, effectively making your expensive resilient network not so resilient after all) though most newer equipment (Cisco anyways) come configured with these countermeasures by default.


Optimus2357
Premium
join:2010-11-21
West Warwick, RI
kudos:3
Im sorry, i don't fallow. Are you saying something specific happened in Glendale AZ? Route Poisoning?

I thought he meant more like

Cable modem flap
»en.wikipedia.org/wiki/Cable_mode ··· le_modem

Cable modems can have a problem known in industry jargon as "flap" or "flapping". A modem flap is when the connection by the modem to the head-end has been dropped (gone offline) and then comes back online. The time offline or rate of flap is not typically recorded, only the incidence. While this is a common occurrence and usually unnoticed, if a modem's flap is extremely high, these disconnects can cause service to be disrupted. If there are usability problems due to flap the typical cause is a defective modem or very high amounts of traffic on the service provider's network (upstream utilization too high).[17] Types of flap include reinsertions, hits and misses, and power adjustments.

sirlight

join:2007-01-05
Glendale, AZ
reply to Rakeesh
Rakeesh,

You got it right, my modem will every so often just drop connection and get back up. And every once in a while, it will get into a very hard cycle where it will just keep booting constantly for 20 or so mins and it will do it at a drop of a hat and I have to wait for the bloody modem to make it's own mind to be happy!!!

Sirlight

Rakeesh

join:2011-10-30
Mesa, AZ
Reviews:
·Sprint Mobile Br..
·Cox HSI
reply to Optimus2357
said by Optimus2357:

Im sorry, i don't fallow. Are you saying something specific happened in Glendale AZ? Route Poisoning?

No, flapping itself simply refers to a link that is going up and down on its own. It is almost always caused by a hardware fault in the physical interface.

In his case, I don't think it is truly a flapping link though, I think it is more likely a signaling issue that is causing layer 2 connectivity to periodically drop (flapping happens at layer 1,) though I don't know enough about DOCSIS to know what is going on here.


Optimus2357
Premium
join:2010-11-21
West Warwick, RI
kudos:3
Ahh ok, I thought you were talking about some kind of flapping happening at the switch level. I agree, its more a signal issue causing modem to reboot. I would need to know the light sequence of the boot and where the boot fails to wager a guess on the cause. Maybe a ingress issue on the DS frequencies?

OP Still going on? Signal levels?


DrDrew
That others may surf
Premium
join:2009-01-28
SoCal
kudos:20
reply to sirlight
Post your signal levels.

If the signal levels are bad, that's a problem.

If the signal levels are good, then your problem is probably noise related interruptions of upstream communications.
--
If you need help, I'm here for you. If you're wrong, expect to be called out on it. If it's important, have a back up or two. Don't complain in public if you don't want an answer...

sirlight

join:2007-01-05
Glendale, AZ
DrDrew,

Signal page coming at ya.....

Downstream Bonding Channel Value
Channel ID 85 86 87 88
Frequency 825000000 Hz 831000000 Hz 837000000 Hz 843000000 Hz
Signal to Noise Ratio 35 dB 35 dB 35 dB 35 dB
Downstream Modulation QAM256 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
-9 dBmV -9 dBmV -9 dBmV -9 dBmV

Upstream Bonding Channel Value
Channel ID 2 1 3
Frequency 29600000 Hz 23300000 Hz 36100000 Hz
Ranging Service ID 338 338 338
Symbol Rate 5.120 Msym/sec 2.560 Msym/sec 5.120 Msym/sec
Power Level 47 dBmV 45 dBmV 47 dBmV
Upstream Modulation [3] 16QAM
[3] 64QAM
[3] QPSK
[2] 16QAM
[3] 64QAM
[3] 16QAM
[3] 64QAM

Ranging Status Success Success Success

Signal Stats (Codewords) Bonding Channel Value
Channel ID 85 86 87 88
Total Unerrored Codewords 11164880 10397148 10397413 10397415
Total Correctable Codewords 23 0 0 0
Total Uncorrectable Codewords 713 594 499 642

The incoming signal levels are ok from what I know but the outgoing levels OUCH... and it varies from 45 to 51. So it's running running a bit hot.

Here is the firmware info....

Model Name: SB6121
Vendor Name: Motorola
Firmware Name: SB_KOMODO-1.0.6.12-SCM00-NOSH
Boot Version: PSPU-Boot(25CLK) 1.0.12.18m3
Hardware Version: 5.0
Serial Number:
Firmware Build Time: Mar 12 2013 17:48:19

Sirlight


dvd536
as Mr. Pink as they come
Premium
join:2001-04-27
Phoenix, AZ
kudos:4
downstream power is low and almost out of spec[-10 to +10]
--
Despises any post with strings.


Optimus2357
Premium
join:2010-11-21
West Warwick, RI
kudos:3
I agree, especially with that DS SNR. 35 is spec, but really should be above 36 IMHO for best performance. But I don't see those signal levels causing the symtoms you described. Is the problem still happening or did it get better after the new firmware? Also, happen to know what the old firmware was? Odd they would need a new firmware to fix a problem when they can just fix it with a config. Either the firmware issue caused the problem to begin with, or it's unrelated IMHO.


DrDrew
That others may surf
Premium
join:2009-01-28
SoCal
kudos:20

1 edit
reply to sirlight
What kind of splitter do you have between the modem and demarc? A 4-way or 8-way or do you live in a apt/condo?

6 db of upstream signal variation is too much


dvd536
as Mr. Pink as they come
Premium
join:2001-04-27
Phoenix, AZ
kudos:4
apartments are FUN specially the large complexes due to huge media closets that the tennant doesn't have access to. usually a ratsnest of cabling and splitters in there.
--
Despises any post with strings.

sirlight

join:2007-01-05
Glendale, AZ
reply to DrDrew
DrDrew,

No splitter on the cable. It's a straight shot from the demarc to the modem. And I live in a home.

Sirlight


DrDrew
That others may surf
Premium
join:2009-01-28
SoCal
kudos:20

1 edit
said by sirlight:

DrDrew,

No splitter on the cable. It's a straight shot from the demarc to the modem. And I live in a home.

Sirlight

If those signals are a straight shot, then something is wrong with the incoming signal. Call for a tech visit. This isn't something that can be fixed over the phone or remotely.

A straight shot usually has downstream signals close to around +5-10 and upstream signals in the 35-40 range.
--
If you need help, I'm here for you. If you're wrong, expect to be called out on it. If it's important, have a back up or two. Don't complain in public if you don't want an answer...

sirlight

join:2007-01-05
Glendale, AZ
DrDrew,

For a long while, I think I have a very hot ground that is making a LOT of noise coming thru the grounds and it is mucking up the modem. Didn't think of it too much but that now I got a doccis 3.0 modem and it's just a bit more sensitive and it is killing my internet connection whenever a big noise storm comes. I'm going to have a friend look at my natural ground connection because all of the grounds are tied to one spot and it's the only place that is common.

What you think?


DrDrew
That others may surf
Premium
join:2009-01-28
SoCal
kudos:20
said by sirlight:

DrDrew,

For a long while, I think I have a very hot ground that is making a LOT of noise coming thru the grounds and it is mucking up the modem. Didn't think of it too much but that now I got a doccis 3.0 modem and it's just a bit more sensitive and it is killing my internet connection whenever a big noise storm comes. I'm going to have a friend look at my natural ground connection because all of the grounds are tied to one spot and it's the only place that is common.

What you think?

fix the signals first
--
If you need help, I'm here for you. If you're wrong, expect to be called out on it. If it's important, have a back up or two. Don't complain in public if you don't want an answer...