Monitoring DSL diagnostics on a ZyXEL P-600 Series modem

The DSL at the house has been really flakey the past 3 days. The line seems to periodically drop and I also noticed that the voice line had a lot of static.

I suspected a line problem so I called Earthlink support last night to try to get it straightened out. Surprisingly, the line tested good up until the point where it came into the house. But the diagnostics on the DSL modem were showing low noise margin (signal-to-noise ratio) and high attenuation (degradation), so there was definitely a problem somewhere. The trouble had to be inside the house: either the DSL modem or some wiring somewhere had gone bad or both.

I tried changing out some cables and tweaking the way the phone and fax (my housemate runs her own business) were all hooked up into the line. That seems to have fixed the problem. The line’s been steady for almost 24 hours now. I’ve been watching the diagnostics and researching what the numbers mean, and they seem to be within acceptable-to-good ranges. So far so good.

It was annoying to have to load the web interface on the ZyXEL P-600 Series modem (it’s a P-660R-ELNK) and continually refresh the page to watch the diagnostics. Plus I had to remember if any of the numbers changed and by how much. So I whipped up a little python script to fetch the data from the web interface and do some logging.

There were some interesting peculiarities in the ZyXEL web interface. After authenticating with a password, only that computer’s IP can use the interface, apparently; requests from other hosts get locked out until a few minutes of inactivity. Also, the way the interface refreshed the diagnostics page was a bit odd: it used a form submission to set some state that would cause another page to update its contents.

The script output looks like this:

Sun Jan 17 19:15:37 2010 noise = 16 (good) outputPower = 11 attenuation = 31 (very good)
Sun Jan 17 19:16:37 2010 noise = 17 (good) outputPower = 11 attenuation = 31 (very good)
Sun Jan 17 19:17:38 2010 noise = 17 (good) outputPower = 11 attenuation = 31 (very good)
Sun Jan 17 19:18:38 2010 noise = 17 (good) outputPower = 11 attenuation = 31 (very good)
Sun Jan 17 19:19:38 2010 noise = 17 (good) outputPower = 11 attenuation = 31 (very good)
Sun Jan 17 19:20:39 2010 noise = 17 (good) outputPower = 11 attenuation = 31 (very good)
Sun Jan 17 19:21:39 2010 noise = 17 (good) outputPower = 11 attenuation = 31 (very good)
Sun Jan 17 19:22:39 2010 noise = 17 (good) outputPower = 11 attenuation = 31 (very good)
Sun Jan 17 19:23:39 2010 noise = 18 (good) outputPower = 11 attenuation = 31 (very good)
Sun Jan 17 19:24:39 2010 noise = 17 (good) outputPower = 11 attenuation = 31 (very good)

A copy of the script is available here. You may need to do some tweaking to get it to work with your setup. It works with python 2.5 and 2.6.

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