Kaos116 is correct, it is pin 2 and 3. There is a row of pins next to each Ethernet port. There is most likely a "Factory reset" label right next to them. Should be the two pins closest to the Ethernet controller. Short them with a paperclip and there will be an LED that will flash notifying you that it has reset.

After that connect the blades one at a time to set each one's IP address to something useful. Make sure that you set it to 192.168.x.y with x being the same as the computer/router you want the blade to be able to communicate with. (your computer will need to be 192.168.1.y to access the config menu the first time after performing factory reset.)