Question D-Link DGS-1008P PoE Switch is working as a passthrough switch (not supposed to happen) ?

[ricf99]

Hello

I have a D-Link DGS-1008P PoE switch working as a passthrough switch (receiving power from PoE injector and feeding two IP cams, not using the powercord that came with it). The question here is if this is correct to keep it as it is as the switch itself is not advertised as a passthrough switch (supposed only PoE OUT ports) and came with a power source of it's own. Can it damage the switch or the connected devices over time?
Thanks

 

[bill001g]

That is a interesting thing to happen. It is actually fairly rare to find a device that can do poe passthrough.
There are multiple hardware revisions of that device making it even more confusing but the ones that I looked at seem to say you could only power it via the power adapters.

There are a couple reasons this should not work. This switch uses 802.3af/at form of poe. This is a active protocol where the "client" asks the "server" to provide a certain amount of power. The switch should always act as a server and never request power from your power injector.

Next most times there is not enough power to accomplish this. Lets say your injector is 15watts. So the switch now uses say 5 watts of power for overhead. This barely leaves the 7watt minimum a switch could provide to a single poe device it will not be able to provide 2. Now I guess if the injector was a 802.3at and provides 30 watts the switch could then provide power to 2 7 watt cameras.

The switch though (depends on the exact hardware revisions) says it can provide 80 watts. From the power requirement it appears it take 10 watts for overhead. This would mean for the switch to fully function it would need 90 watts of power over the poe cable and the max for 802.3at is 30.

I have no idea how you managed to accomplish what you did it should not be possible.