[Outages-discussion] RoadRunner/Bright House cablemodem problems

[Jeremy Chadwick]

On Mon, Sep 16, 2013 at 04:11:15PM -0400, Jay Ashworth wrote:
> On a new install for a client, we're seeing that the cable modem drops
> out on us, and in a very interesting way.
> 
> Every so randomly often, it apparently does an uncommanded reboot (this
> according to a guy who was logged into the CMTS looking at it one time it
> did so), and when it does, 2 connected devices see the ethernet drop for 3-5 
> seconds, come back up for 15, then drop again for 3-5, and then go back 
> to normal.  I see this behavior logged exactly to the second on both the
> attached Fortigate router and my Linux laptop; we've replaced the cable
> modem and the ethernet cables coming out of it.
> 
> Oddly, it only seems to happen when there's traffic on the link; I haven't
> seen a drop get logged when the link is idle (overnight/weekends).
> 
> The cablemodem is a DOCSIS3, Motorola Surfboard Extreme (that's not exact, 
> but I can provide a model number if anyone thinks it's critical).  Everything
> in the cage is on a brand new 2000VA UPS.
> 
> Anyone ever seen a cablemodem misbehave in this particularly peculiar way
> before?

I can probably help (I just spent nearly 5 months getting Comcast to
deal with replacing some actual runs of cable between poles that were
accepting interference -- in the end things were successful), but I
need the following things:

- Exact model of Motorola modem (SBxxxx) you're using and its firmware
  *and* hardware version (visible via http://192.168.100.1/cmHelp.htm)
- Whether DOCSIS 3.x is in use or not -- no, actually, i'll redact that
  and just request this: a screenshot or PDF of the /cmSignal.htm page
- Same as before, but for /cmLogs.htm
- A topology diagram of things (don't need IPs/etc., just general
  what's-connected-to-what) -- I'm mainly interested in the device which
  hooks up to your cable modem's Ethernet port.  You mention "4 ports"
  (discussed with Frank) which is a device I haven't used before; I'm
  used to the consumer models which have 1 Ethernet port.  Knowing
  what's connected (brand/device/driver-wise) to all those Ethernet
  ports would be of interest

If this turns out to be what my issue was (very hard to track down),
I can give you a perl script that I wrote that polls the cable modem
periodically and stores SNRs in CSV which you can graph using dygraphs
(very very easy, I can include a working .html and relevant .js file).
I can put up a demo for you online (with real data) if you want to see
it first.

I do have a gut feeling about what the issue is, but a topology diagram
would help to rule out that feeling.

-- 
| Jeremy Chadwick                                   jdc at koitsu.org |
| UNIX Systems Administrator                http://jdc.koitsu.org/ |
| Making life hard for others since 1977.             PGP 4BD6C0CB |