the cnPilot e430 Access Point ships with a short ethernet jumper cable in its packaging:
This cable is meant to loopback across the two ports at the back of the unit:
The pass-through port and the eth1/PoE port should be connected this way.
This is useful in cases where the AP is installed using one of its optional accessories such as the on-wall bracket, or the desktop stand. In both of these cases the ports at the back of the AP become inaccessible and the just the ports at the bottom are available to the user. The jumper cable here helps to make the Eth1/PoE-in port accessible from the bottom by completing the circuit/path through the passthrough port. Basically the Passthrough port at the bottom now becomes Eth1/PoE-In.