Thanks for the reply,
We have 2 different appliances with the mentioned digi (with the same firmware). And both, when placed in the UDP sockets mode, behave exactly the same. That is - you need to specify the receivers list with respective ports.
Regarding the firmware upgrade: when flashing the POST firmware I think I killed one of my devices. I flashed it with this one: http://ftp1.digi.com/support/firmware/82001229_F.bin and it is signalling the green led, even with eth. cable disconnected, in such manner: 6-3-4 (6 meaning 6 consecutive quick blinks).