POE with Arduino Leonardo Eth
From the arduino.cc website.

"The optional PoE module is designed to extract power from a conventional twisted pair Category 5 Ethernet cable. PoE module features are as follows: IEEE802.3af compliant Input voltage range 36V to 57V Overload and short-circuit protection 12V Output High efficiency DC/DC converter: typ 85% @ 80% load 1500V isolation (input to output)"

It sounds like you need the 12V PoE module