Thursday, April 15, 2010

Reverting a Cisco LAP1142N to Atonomyous Mode

Wow, this was fun.

A friend of mine got in half-a-dozen Cisco AP's, and they all came with the wrong firmware. These are nice, slim flying saucers Wifi AP's with 2 radios supporting
2.4G and 5.0G operation. The focus of the line is to use a controller, my friend
chose to not buy a controller, but to buy autonomous units.

So when they came in. IOS was missing in action.

While there are notes on the web to do this, not appeared to work.

The basics is, to setup a tftp server at a magic address (10.0.0.2),
the ap will boot, setting it self to 10.0.0.1, and check for a default image
based on model.

Didnt work at all, despite shooting a day.

I tried several different tftp implementions, including linux tftp, atftpd, and
finally two different ones on windows.

So after two days of pain, and some inspiration from one of my friends, I figured out
the secret sause.

1. Press and hold the mode button
2. Let it boot till it notices (You can see the messages if you plug in the cisco cable) It will say the mode button is pressed in the logs
3. It will fail to find the image need and dump you to the bootloader
4. At the bootloader erase the flash - format flash:
5. Reboot
6. set the IP address, network mask, and router, as the instructions are given in the log
7. tftp_init
8. tar -xtract tftp://thefirmwarefilename.tar flash:

If you mess up start back at 1

tftp is very sensitive to traffic, and to extra overhead in the server side,
so be careful about switches.