The device is small and convenient for plug and forget usage in many ways. Therefore it is shame it does not have a PoE capability. As it has only Fast ethernet 100 Mbps (WAN and LAN ports), we can manually take unusued ethernet conductors and use them for do-it-yourself PoE.
What you need
Some thin wires
Power switch or relay (to prevent reverse current flow to ethernet in case of using microUSB power delivery)
Multimeter and patience
DO NOT FORGET, THAT ALL PARTS OF THE CIRCUIT MUST HANDLE MAXIMUM CURRENT DELIVERY. NEXX ITSELF HAS 1.2 ADC, for me the weakest part is DC-DC converter that can handle 1.7 A, but it is still higher than the limit.
The basic idea
PoE mod pic, I can not upload it here
PoE uses unusued ethernet pins 5-6 (blue; +DC) and 7-8 (brown; GND) to power delivery in case you have only fast ethernet 10/100 Mbit. So you can unsolder them from the board and use them for PoE. For that task, I used small scissors and ripped them off the board :P
You can use pins from WAN or LAN ports or both if you wish. I used pins from WAN port (in the picture 1a with GND connected to ethernet shield and 1b).
You can power PoE by many voltage sources, so there is step down DC-DC converter (2.) which can handle 5-17 VDC input and is set up to 5 VDC output. Therefore you can PoE it from 5 to 17 volts power sources.
From there, the left side output GND is again connected to (not visible) ethernet shield (not necessary, 1a GND is also connected so this is «just in case») and the +5 VDC output goes to power switch. The power switch is important if you do not have reverse current protection! There you choose between PoE and microUSB power delivery. You can also use some relay to do this automaticaly.
I connected the +5 VDC output to female USB-A +5 VDC pin as it was the largest part that you can use for this ;)
You also need to «adjust» the above router cover if you use the power switch — I fixed the switch on the USB-A port. And remember to isolate all moving parts to prevent unwanted short-circuit. I used glue gun for that (see the bottom of DC-DC converter).
Use multimeter resistance measurement to see, which parts are connected to which. The 5 VDC are short-circuited on both microUSB and USB-A ports, same with the GND.
Do not use diode for reverse current protection as there will be voltage drop and unnecessary power losses.
And the last thing — this is only my idea how to do PoE on Nexx WT3020. Do it as you wish if you like to.
И как это выглядит