[Commotion-dev] Possible hardware defect with POE passthru on recent Ubiquiti Nanostation M2 and M5's

[Ben West]

I observed a problem on a recent generation 00:27:... Nanostation M5
(mfg date ~August 2011) bricking itself upon enabling the POE
passthrough feature (via firmware) shortly after boot.

The unit did not become bricked simply from flashing it, but rather
failed upon the passthrough enable.  Also, nothing was connected to
its secondary LAN port at the time; it was sitting on the bench.

I have not experienced this failure upon enabling the POE passthru
feature, with stock firmware and otherwise, on older NSM5 units.
Maybe there was a BOM change.

I found recent reports of other UBNT users experiencing the same
failure enabling the POE passthrough feature on Nanostation M2 and
M5s, when using stock firmware too:
https://forum.ubnt.com/showthread.php?p=270549

The suggested work-around, which I have so far tested successfully, is
to NOT enable POE passthrough, presumably with any firmware.  Rather,
swap the Main and Secondary LAN ports, i.e. so that whatever secondary
POE device is connected to Main.  This will have the effect of the 2nd
POE device being always on.

This work-around comes with caveat of possibly reduced power noise
filtering, since the unit will not be receiving its power from the
Main port.

Also, do please note UBNT's warranty policy of not supporting 3rd
party firmware, even despite their wiki providing instructions for
flashing OpenWRT onto their products:
http://www.ubnt.com/support/warranty

(So, recommendation is to prove out all units with UBNT stock firmware
first, especially POE passthru, to screen for any problems.)

-- 
Ben West
me at benwest.name