I'm having issues with a HP 8206zl switch not delivering PoE+ to a PoE+ device, a Meraki MR42 WAP to be exact. The WAP reports that it's operating in 802.03af fallback mode, which restricts it's capabilities. The port it's connected to is part of a HP J9534A 24p Gig-T PoE+ v2 zl Module. The switch says that the device requested class 4. Attached output of the PoE port info. enter image description here


Here's the output of the PoE supply status on the switch, ample amounts of power available: enter image description here


I tried connecting the devices directly to the the switch, and they still operate in "low-power mode" so for some reason they don't seem to be able to negotiate 802.03at. Any ideas?

  • How many other PoE devices are connected to the switch? Normally, a 48-port switch has a limit based on its power supply, and you could exceed the limit by using PoE on all the ports. Just because it's a PoE switch doesn't mean you could load all the ports with PoE. You may need to see if there is an upgraded/additional PS option for the switch.
    – Ron Maupin
    Jun 21, 2016 at 14:11
  • The switch has 2 1500 watt PoE+ supplies running in full redundancy mode, and it has around 750 watts available still. See my edit for more info.
    – Stuggi
    Jun 21, 2016 at 14:17
  • What errors / log messages are generated when the device is attached? (some debug's might be necessary.)
    – Ricky
    Jun 21, 2016 at 20:02
  • Any chance your cable length is too long and causing a voltage drop resulting in the fallback to 802.03af mode? Jun 21, 2016 at 21:59
  • 1
    Well, I believe it's still 100 meters. If I were in your shoes I would temporarily connect the device to the same switchport using a patch cable and see what happens. If it works you know the cable or cable length is the problem. Of course this may be impossible depending on what the device is and how it's installed. Jun 23, 2016 at 17:41

1 Answer 1


I found the issue, it has to do with the device itself, specifically an Meraki MR42 AP. When the 802.03at Meraki APs first powers up, it does so in 802.03af mode, thus limiting the power it can draw. Then later in the boot sequence it tries to request more power to be delivered, and for some reason the HP switches does not understand to give it the full 33 watts it needs. The solution is to force the port to allocate power based on a configured value instead of what's negotiated over LLDP. The Meraki documentation shows you how to do it through the GUI, which in my book isn't that useful. Instead, the following commands does the exact thing but for several ports at once.

interface [port_range] poe-value 33
interface [port_range] poe-allocate-by value
interface [port_range] power-over-ethernet critical

The first command sets the "value" for the port to 33W, maximum under the IEEE 802.03at standard.

The second command forces the port to forget about LLDP and just give the device connected to the port whatever it chooses to consume, instead of limiting it.

The third command is probably not necessary, all it should do is to list the port as "critical", aka. tell the switch to shut something else down if it experiences shortage of available PoE power, but I left it in as Cisco Meraki specifically listed it in their fix.

The most amusing thing is that the APs doesn't actually draw any more power after this, at least when they are on standby with no connected clients, but they probably operate better at higher loads, and you get rid of that annoying error in the Meraki dashboard.


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