> Unfortunately, only the yellow light (=> 802.3af) and not the green light (=> 802.3at) is lit on the switch,
I assume we are talking about the right-hand LED on port 5 - and not the left-hand LED which indicates the negotiated current speed on the ethernet connection.
> although this PoE injector should be 30W. Can someone explain to me why this is so?
802.11af/802.11at etc. performs a rather complex handshake when the link is powered up (plug in the cable, switch on, etc. ) - although there are also several legacy variants of this. This process regulates how much power is made available at the PSE (Power Sourcing Equipment) and how much power is available and can be drawn at the PD (Powered Device). Unfortunately, the fact that the switch is supposed to support both variants does not make it any easier.
> Is the injector supplying too little power? Is the switch defective?
Probably neither. As @Final has already pointed out, this is probably a compatibility problem, which typically leads to problems with more or less good injectors. Switches with built-in IEEE-compliant PoE/PoE+ and higher power levels usually work perfectly with the GS105PE.
The effective problem is that if the switch only displays an 802.11af power supply, only a single Class 1 or Class 2 (no Class 0!) PD can be operated.
https://kb.netgear.com/25541...
Since we don't know which firmware is installed in the box, there may be an additional hurdle to the recommended update. Possibly the bootloader (which contains a lot more that is relevant for PoE problems) has to be updated - but the latest firmware kits do not contain this bootloader. Maybe we'd better have a look at
https://community.netgear.com/t5... - there the paths are a bit easier.
> connecting only one PoE consumer (Ubiquiti UniFi AP AC-PRO), which uses a maximum of 9W according to the data sheet, it is actually not a problem.
Unfortunately, this is also a miscalculation and comes from an omission of correct information in Ubiquity's datasheet. Simple wattage mathematics does not work for IEEE PoE.
As mentioned, a PoE handshake takes place which not only confirms the presence of a PoE device before voltage is applied. The PoE class is also exchanged.
The Ubiquiti UniFi AP AC-PRO is an 802.3af device and reports as class 0. The 802.3at specification is simply wrong because the marketing people there do not understand IEEE PoE and Ubiquity also uses three or four completely different so-called passive non-IEEE PoE versions, each of which requires a special switch or injector variant. This means that with .3af the part requires 15.4W from the PSE. If only less is available - i.e. in the case that the GS105PE is only powered from .3af - it only provides class 1 and 2, so the AP cannot be operated reliably. Even if the data sheet speaks of 9W maximum required power, IEEE 802.3af supports PoE type 1 (class 0..3), IEEE 802.3at supports type 1 and type 2 (class 0..4), and the further extended IEEE 802.3b standard supports type 1, 2, 3 (max. 60W ports, class 0...6) or type 1, 2, 3 and 4 (max. 100W ports, class 0..8) - all power specifications always on the PSE. A guaranteed 12.95W (type 1), 25.5W (type 2), 51W (type 3) and 71W (type 4) are available at the units.
Actually quite simple 8-)
