Wired IoT sensor network with PoE? Objective: Maybe I'm a bad Googler, but I am finding very little on wired Internet of Things sensor networks using Arduino.

Project Goals:


Arduino based sensor nodes that connect to the local network (not out to the internet)
All the benefits of adding adding/removing nodes, moving nodes, adding new routers for more ports.
Black box sensors that don't take any soldering to plug into the network (although they contain soldered components in the black box.
Using a master Raspberry Pi on the network to identify the nodes and read data from them.
Using Power over Ethernet (PoE) to power my sensor nodes.
Don't want to actually connect to the outside internet, just want the convenience of assembling a network with node names and such.


Why not use wireless solutions (e.g. XBee):

Currently, it seems Xbee is the way to go, but I don't want a wireless solution.


I want the reliability of a wired connection.
I don't want to have to worry about batteries


What I'm doing right now:

Currently, I have all my sensors wired to a central Arduino MEGA using 4-conductor security cable (Vcc, GND, and two signal conductors). The MEGA communicates over serial with a Raspberry Pi. This is annoying for the following reasons:


I have to solder/unsolder every time I want to change something.
I have to figure out which digital I/O pins are available on the MEGA and have to write down which signal conductor goes to which pin on the MEGA and means what on the sensor.
There is a finite number of pins.
Each sensor is its own unique project. I want to start standardizing these sensors to clean up the code.


What I have found so far:

I've been looking at XPort sensors; however they are very expensive (i.e. $60 ea.) and don't support PoE. If there is a solution using Arduino and an Ethernet Shield, it brings down the base cost of a sensor by a lot.

Request:

Where can I find out more information about wired Arduino sensors? Are there any prebuilt solutions that already do what I am looking for?
I think I am using a setup like you wish at my home:


PoE Switch (for example Cisco SG300-28P) 
Arduino Ethernet's with PoE Module (https://www.arduino.cc/en/Main/ArduinoBoardEthernet) I bought one for every room ;-)
Use DHCP-Server on raspberry PI
Put your sensors on your Arduino ethernet board
I am also using MQTT as protokoll for example http://pubsubclient.knolleary.net/
Use MQTT broker Mosquitto on raspberry pi


For the case that you want to use your switch also for internet connectivity, define a vlan (search wikipedia) for your arduino sensor network.

Hope that helps.