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Archive for the ‘Networking’ Category

Automatically reset your cable modem when the Internet goes missing — part 2

My previous post was about writing a script to automatically reset a cable modem when the Internet dies.  My cable modem goes nuts from time to time and needs to be reset to get the Internet connection back.  This isn’t that big a deal, in fact it’s not an uncommon problem to have; but, I do access services running at home remotely and I’d like to have it set up to fix itself whenever this happens.

As noted in my previous post, I discovered that my particular cable modem has a web interface and you can reset it from the web interface.  However, I’ve already discovered instances where it’s gone crazy and does not respond to the http reset command, requiring a full power cycle to get things back in order.  Also, some people may not be able to reset the modem from the web interface, so this new method will help them out as well.

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Automatically reset your cable modem when the Internet goes missing

So…  I have Comcast cable Internet service at home, and a Motorola SB6120 cable modem that I own myself.  I’m not sure if it is Comcast, the modem, the combination of the two, or something else altogether… but, every now and then, the modem goes into a funk and the Internet stops working, and the only way to fix it is to power-cycle the modem.

This doesn’t happen terribly often, maybe once a month or so.  (Occasionally it will happen, say, twice in one week and thus cause me to think about it a little more.)  Power-cycling the modem is not a big deal, but I do access stuff that I have at home remotely, so if the connection dies while I am at work or away someplace, I can’t fix it until I return home.

It would be great if there was a way for a computer at the house to, say, periodically check and see if the Internet is working and if it is not, somehow reset the modem.  So, I did some searching on the topic, and… it turns out that it is possible to do this, and in fact, it is pretty simple.

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WDS and WPA with Apple Airport Extreme

Apple Airport Extreme (and Express) wireless base stations support WPA encryption, and also WDS, which allows you to use multiple access points to create one big wireless network (so you don’t actually have to connect each access point to the same “backbone” network, as they will create wireless links between each other).

In this day and age, you’d be silly to use anything less than WPA encryption (WEP is fundamentally flawed), but there are a few caveats with setting up WPA and WDS together on Apple’s devices that I ran into while setting this up for someone recently.

  • WPA only works with Airport Express or Extreme access points. (It does not work with the original Airports, or the “snow” models.)
  • Upgrade your access points to the latest firmware, some earlier versions have a bug that prevents WPA and WDS from working together.
  • Your wireless network name (SSID) must be the same on all access points participating in WDS. (This doesn’t seem to be documented anywhere, and without WPA, you can use different SSIDs.)