Hi All,

       A heads up/request for assistance, it appears that it is not possible to downgrade current production Ubiquiti NanoBeams (at least not the M2) to 5.5 in order to successfully install OpenWRT.

Based on some analysis of the fwupdate binary (ubntbox actually I think) it seems that the issue is that the firmware updater checks against a bunch of OUIs and the OUI of this one isn't supported for installing 5.5. firmwares.

Raised a ticket with UBNT and they provided some suggestions, eventually got to Tier 2 who checked with engineering and they confirmed the NanoBeam I have is "too new" to install AirOS 5.5.

A further complication in all of this is the fact that my NanoBeam doesn't seem to want to enter TFTP recovery, the LEDs do all the right things (verified process and result against a PowerBeam), but nothing responds on 192.168.1.20.

At this point I'm looking at a brute force approach in patching the firmware updater binary to change the check for an OUI I know works (a fairly recent PowerBeam M2) and patch over that with the OUI of this NanoBeam, not sure if that'll be enough or not (the firmware update logic is rather convoluted and my MIPS assembly is pretty rusty).

Unfortunately if it goes sideways, due to the TFTP recovery issue, I will be stuck with only one option, namely to crack open the NanoBeam (compromising it's weatherproofing) to connect to the onboard UART

If anybody can provide alternative suggestions that would be greatly appreciated.

Thanks,

-J

A follow up on this one, it seems that TFTP recovery only works from 6.0.6-beta onwards on these particular devices, very strange... And does potentially rather complicate matters vis the "brute force" method I mentioned above.

So I caved and cracked it open, unfortunately the header is directly under part of the mounting feature so you can't just drill through the case to gain access

You can load older firmware using urescue in TFTP but for some reason it's not overwriting the u-boot partition, I might have to do that manually...

And now that I have access to the UART I decided "why not, might as well just throw the openwrt image at it and see what happened"... Lo and behold, from the 6.0.6-beta AirOS firmware I loaded a current 15.05.1 openwrt image and it works...

So it appears that whatever changed in AirOS 5.6 to break OpenWRT has now been "fixed" in 6.0.6-beta...

So you could simply flash from the stock OS web interface after all?

I'd like to buy a couple more Nanobeam M5 to use with OpenWrt but not sure if they will flash.  They look impossible to open the case without damaging something.

Yes, but with caveats...

If you can downgrade to AirOS 5.5 do it that way. The last M5 I installed openwrt on happily downgraded to 5.5.10, seems to be particular OUIs that do or don't work.

I've found there has been some breakage with flashing from 6.0.6-beta on my M2;
- There was an issue where the ethernet interface wasn't turning up on 192.168.1.1 in spite of br-lan being configured with that address, but I didn't think to try wifi.
- I attempted to roll back to AirOS so I could validate the process again and the rollback failed, I'm going to restore from a known good flash image and try again, once I've validated it I'll add the details to the NanoBeam page in the Wiki.

(Last edited by jrandombob on 15 Jan 2018, 22:24)