Can Power over Ethernet (PoE) be passed over non-PoE switches ?
Generally, no. PoE doesn't carry through additional switches/hubs, it will only be supplied to devices that are directly connected to a PoE switch (and only by request).
If you have a PoE switch, and want to pass PoE to cliend devices, you should not use non-PoE switches in between. There are a couple of possible issues if you do:
1. Most PoE switches will not turn on power to ports that are connected to non-PoE client devices at all.
2. Some older non-PoE switches not only fail to pass power, but they may make matters worse by shorting unused pairs 1 and 4 (connecting them to ground)!
Note: If only a few devices require PoE, instead of changing all switches to PoE, it is sometimes more cost effective to use PoE injectors on the ports that need PoE.