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From: E Johnson <iris.gates@gmail.com>
To: Worcester Linux Users Group <wlug@mail.wlug.org>
Sent: Thursday, September 27, 2012 10:36 AM
Subject: Re: [Wlug] Test needed on declared-ill Modem. Who has a lab?

I don't know how much of the recent comments are directed to me, or which were responding to Richard.

This here:

> Make sure that you update the MAC address with charter, and that
> they actually update it. I've had a few problems where they
> haven't even though they said they did.

Yes! That happened to me, and the modem had to be re-registered two or three times. It depends on the tech you talk to. My modem was incorrectly or incompletely registered here by the install tach on the day the service was hooked up. The internet generally worked as it should anyway, but during times when there were connectivity problems here (see below), in phone calls to tech support, every once in a while the tech would tell me "I" had the wrong MAC address, that I was running an unauthorized modem, etc.. Then I would have to explain why that seemed to be, and they would try again to get that corrected.

My history here:

Charter here needs a DOCSYS3-compliant modem. I was running a Motorola SB6120, which worked fine for 27 months. This has several nice diagnostic pages, accessed at 192.168.100.1, including logs which give details of any exceptions and error messages.

Connectivity problems in summer of 2010 were caused by new lines (coax) from the pole to the box. I was able to prove to the provider that the intermittant problems were not in my setup, but outside. There were several issues, which they gradually seemed to fix. One had to do with connectivity interruptions on the days following a big rainstorm. The connectors in the new lines (at the pole) had not been weatherproofed, which they did.  Line techs eventually checked and improved the weatherproofing throughout the whole neighborhood.

Note that I have no other services (such as TV) which run on the incoming line. Also note: I have no extra connectors in the coax running between the box and my modem.

The sick modem I experienced here a few weeks ago may have simply been due to a failing power supply (wall wart) running the modem.  Somehow that had never occurred to me. I could have tested that by replacing it with an equivalent new power supply.

Meanwhile 2 Charter techs had diagnosed my modem as 'dying', shook their heads when they learned it was 2+ years old, replaced it with one of theirs, and left. This is a Cisco, which sounded reasonable to me. But there is only one page available to customers, at 192.168.100.1 and this only shows that the modem is connected, a few power levels, SNR, how many channels are running. Further diagnostic pages can be accessed through a password, but the usual logins and passwords don't work.

My ultimate solution is to get another modem which I will own and have provisioned when I set it up. The one I'm planning to get is the Motorola SB 6121, their replacement for the 6120, which they no longer manufacture.

A further note on the SB6120, in case anyone gets one on ebay or whatever:
These are very sensitive to incoming power levels. If the signal is too "hot", such as 15 dBmV, they start throwing errors. These power levels seem to vary according to temperature and humidity. Once I installed a 3db attenuator pad between the incoming coax and my modem,  the power levels the modem experienced came down to 10 or 12 dBmV, which allowed the modem to operate without interruption for many months at a time.

I haven't heard if the SB6121 has the same sensitivity to hot power levels or not. I'm still reading reviews and forum posts about this unit. I can report on it once I get one in here and running. It will be nice to be able to see the diagnostics pages and service logs again.

Liz