Occasionally I find myself with piece of information that is unlikely to help anybody other than me in future. But that never prevented me from making a post before, so why should it now. In the left corner, we have my existing Mikrotik Audience router that yearns for some power via passive PoE. And in the right corner we have Netgear GS305EP PoE switch that’ll give its best using 802.3af/at. Can we make them play together?

Short answer is no - you cannot power router that uses passive PoE from a switch that provides only 802.3af/at. But… Depending on both the exact passive PoE device and how the active PoE switch is doing detection, you might get lucky and things will work.

First prerequisite is for client device to support 56V on PoE input. Anything lower than that and you’ll probably fry your device if you attempt powering it. Second prerequisite is that active PoE device supports legacy mode where resistors are used to determine power level. And lastly, your client device needs to have those resistors even though it doesn’t support active PoE as such. In Settings this would look like this:

Power Mode .....: Pre-802.3at
Power Limit Type: User
Power Limit (W) : 30.0
Detection Type .: 4pt 802.3af + Legacy

If you are lucky with all that, you might have power flowing between two officially incompatible devices.

Caveat emptor!