Autonomous Management

‘Downgrading’ a Cisco Lightweight AP to Autonomous mode

 

Intro

This article will run through an automatic downgrading of an Autonomous AP to Lightweight mode.

Before you start

You will need the following:

  1. An autonomous IOS for your Access Point from http://software.cisco.com/download. You’ll need to be logged in with a registered account linked to a Cisco support contract.
  2. Be connected to your AP via a console connection and Ethernet connection.
  3. Configure your local machine IP within the range 10.0.0.2 – 10.0.0.30 255.255.255.0
  4. Be running a local TFTP server with the IOS image in the root directory. I use tftpd32 as it is nice and free and Solarwinds used to max out at a certain file size.
  5. Rename the IOS image to cXXXX-k9w7-tar.default with XXXX being the model number, e.g c1142-k8w7-tar.default in my example below.
  6. Turn off your local firewall (if you feel it is safe to do so).

If you are in the office it can be quite irritating to keep physically and virtually switching between your company network and the AP you are configuring. I bought a few cheap USB to Ethernet adapters off ebay that suit the job perfectly as I don’t need them to perform Gigabit uplinks but simply have enough clout to transfer some IOS images. So far my first one hasn’t died after four years use so that was $2 very well spent.

The Process

  1. Re-IP your NIC

Screenshot_1.png

  1. Turn off the power to your AP and then power it back on with your finger on the mode button at the back. After around 20 seconds the LED on the front should turn solid red and you can let go.
  2. If you are watching on the serial connection then you’ll see the AP report the mode button was pressed down and it will reset its IP to 10.0.0.1 and enter the image recovery process.
LW-Auto1
Resetting the AP

In the example above we can see the AP has reset to 10.0.0.1 and is looking for the file c1140-k9w7-tar.default.

Seeing as you setup everything perfectly the local TFTP server will tell you it is sending a file over to the AP. A couple of common things that prevent this occurring are:

  1. Ensure your windows firewall is turned off (again)
  2. If you are using Solarwinds I recall the default option to send files upon request (or something along those lines) is turned off so just go into the properties and make sure that is turned on. My apologies for the vagueness on that one.
  3. When you put the image in your TFTP root make sure that file extensions are enabled as viewable in windows as often it will append a hidden .tar to the name and mess up your transfer. This extra .tar must be removed.

Screenshot_2.png

Here we can see the file within the TFTP Root directory

LW-Auto2
TFTP Root directory

And this is once the AP begins to transfer the image:

LW-Auto3
Flash transfer via TFTP

Upon completion of the transfer the AP will reboot itself et voila you can log in with the default credentials – Cisco / Cisco – and go autonomous configure crazy! To verify you can always do a show version to see what IOS the AP booted off.

Lw-Auto4
AP booted into Autonomous mode

Final thoughts

Whilst there are other ways to copy the image over e.g. via  a static ‘archive download-sw’ command, this requires the image to transfer before the LW AP resets its CAPWAP discovery process which resets its IP and breaks the process. If locally available I always prefer the TFTP method.

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