I have several 411's and 433's with failing ethernet ports. It seems to me it has to do with the POE.
Even managed to upload new ros and firmware by serial upload (takes an hour or so) and installed the new software. After that everything works fine but it didn't bring the failing port back.
And only affects the POE ports. The other ports (if physical available) work normal.
I have two rb433's working in production with the only execption the POE port cannot transport data.
The 411's are waiting for a smart move from my end. That might be a move to the waist bin though...
Sending back for RMA, mostly even out of the warrenty period, is costing the same or more then a new board.
Also, you need to find the original supplyer witch is difficult if you bought through several channels over the last years. Some boards fail after an upgrade or after short lived power cuts after a working live of severalyears....
These POE ports are definately the weakest part in the total physical design of these boards.
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Rudy R. Puister
WISP operator based on MT routerboard & ROS.