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Rakeesh

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

Re: [AZ] Motorola SB6121 flapping HARD

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_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?