I recently came across a solution for a small problem I was working on, and I thought I would share.
I have a Cisco 1131 AG lightweight access point that I wanted to downgrade to autonomous mode. Now this is easy if you have a WLC (Wireless LAN Controller) that these APs are designed for, but if you don’t you have to perform a downgrade manually.
There are lots of instructions on the Internet, but this is the Cisco documentation for this issue.
What Cisco leaves out is what the AP is expecting out of your TFTP server. When the AP loads up into recovery mode it is going to be attempting to connect to a tftp server at the broadcast address: tftp://255.255.255.255 — essentially this means that the AP will attempt to connect to an address that every device on the LAN has.
My laptop is running Ubuntu (a flavour of Linux) and I have the tftpd-hpa package as my TFTP server. Normally I like the setup I have, but today it wasn’t enough — the AP wasn’t connecting.
The CLI was throwing this error:
And when I used wireshark to look at the traffic I found that the tftp server wasn’t responding to the requests from the AP. So I configured tftpd-hpa to specifically listen on the broadcast address like this:
And restarted tftpd with
Once I did that, the AP was able to connect and all was well in the world.