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Forum Discussion
PoE 802.3af Standards A or B
Does the M4300-28G-PoE+ support PoE 802.3af with variant A or B, or maybe both?
A or B refers to https://en.wikipedia.org/wiki/Power_over_Ethernet#Pinouts
I have PoE device which in particular re...
Hi,
I believe this access point supports both Passive 24V ou Active 802.3af PoE modes and any standard PoE switch will work just fine in standard 802.3af mode. As such, the M4300 switches should be OK.
I hope this will help,
Regards,
Thank You for a quick reply, but I still have doubts.
This device (UniFi AP) supports passive PoE, as stated in datasheet:
24V Passive PoE (Pairs 4, 5+; 7, 8 Return)
802.3af Alternative A (Pairs 1, 2+; 3, 6 Return)
So if switch will power device on pins 4,5;7,8 (variant B), may not detect it properly, or even damage by putting 50V, where 24V is expected.
If switch puts power on pins 1,2;3,6, then all should be fine. That's why is so important for me, which variant is implemented.
As a last resort solution is possible to connect device with only 1,2,3,6 pins, but then connection speed will be down to 100Mbit, what i want to avoid.
I think the access point manufacturer datasheet is leading to some confusion, and I can attest you will find many reports and feedback on other forums with this access point working fine with perfectly standard 802.3af switches.
Thank You. I'll get the mentioned hardware in about month or so, then report back.
WojtekC wrote:
So if switch will power device on pins 4,5;7,8 (variant B), may not detect it properly, or even damage by putting 50V, where 24V is expected.... That's why is so important for me, which variant is implemented.
This problem isn't a problem, absolutley not important, and not applicable at all as long as using IEEE standards PoE standards: Different from most of these passive (dumb, cheap, ...) proprietary schemes, a 802.3af or 802.3at PoE source does not blindly supply any power without a proper negotiation to the PD (powered device).
schumaku wrote:
WojtekC wrote:
So if switch will power device on pins 4,5;7,8 (variant B), may not detect it properly, or even damage by putting 50V, where 24V is expected.... That's why is so important for me, which variant is implemented.
This problem isn't a problem, absolutley not important, and not applicable at all as long as using IEEE standards PoE standards: Different from most of these passive (dumb, cheap, ...) proprietary schemes, a 802.3af or 802.3at PoE source does not blindly supply any power without a proper negotiation to the PD (powered device).
I'm perfectly aware about that, and using non-standard device because it cheap, and know the risk.
As far as I know, standard compliant device can suply power with variant A or B, or even both. Just wanna know, how that standard is implemented in my particular switch. Unfortunately, nobody can tell so far.
WojtekC wrote:
As far as I know, standard compliant device can suply power with variant A or B, or even both.Again: Unless there is a standard compliant PoE device plugged, NO power will be supplied by the switch. There is an (amazingly complex!) handshaking happen when a PoE device is plugged - before power will be supplied.
Don't waste your time about a problem which does not exist on 802.11af and 802.11at swiches - they will power your UniFi without blackening them.
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