CRS112-8p needs secondary 48V2A power supplpy for powering PoE devices.
With two power supply connected, if I remove the primary one (in-the-box 28V) the router remains powered.
Is the ONLY second one (48V) enough to provide router+PoE supply or I need both connected anyway ??

However, the dual power supply is a silly choice....

However, the dual power supply is a silly choice....

Like you.


The device uses 10W alone, the connected PoE devices can use up to 86W total.

Is the ONLY second one (48V) enough to provide router+PoE supply or I need both connected anyway ??

你的设备只能提供输入电压对P (s)oE-out. When both power supplies are connected, then CRS can select (or you can set manually) to provide either low- or high-voltage on each PoE-out port separately. Your CRS doesn't do voltage regulation for PoE-out, so if you have some passive PoE client that requires low-voltage, it'll be cut off when you disconnect the low-voltage power supply. If you have none PoE clients that would require low-voltage, then you can safely disconnect the corresponding power supply. The same is true if all PoE clients were low-voltage ones, in this case you could disconnect high-voltage power supply.
Note that router itself can run on either power supply and will down-convert supplied voltage to levels actually needed (probably that woukd be 3.3V and 5V, possibly also some lower voltages). If both power supplies are connected, then router will[*] use the higher voltage source for own consumption. Both power sources will then act as redundant power supplies of the router itself (redundant against failures of power adapters, the rest of redundancy depends on how those power adapters are connected to AC power supply).
[*]This at least happens with other MT devices which accept multiple power sources, they always draw pover from highest-voltage source available at any time. If highest-voltage source goes AWOL, then device starts to draw power from the remaining source providing then highest voltage.

I say that it's a great feature to be able to power both 24V and 48V systems with the same device, depending on what powersupply you use. If you don't use any PoE at all then you can just use a simple 12V/1A plug to power the switch itself.

But I see the hassle then someone is buying a "PoE switch" and then you realize that your .at/.af devices doesn't work. They should probably shipped the device with a 48V PSU instead or 24V.

My biggest complaint is that regular DC barrel-jacks are a bit whimpy and unreliable for higher wattages.

First of all I find disrespectful answer to a point of view not directed to you with an offense.
CRS328-24p is a little masterpiece , it can power-up both voltages devices with a single power supply ,and better with mains one, not ac to dc then dc to switch.
I still find silly , in projecting phase, to create a device without an embedded regulation system like 328 one, it seems mostly like a post-production patch.
I can't imagine the dual power supply as a feature or added value, it's a nuisance instead. Moreover for just 8 ports.
Thank you for informations.

I still find silly ...

That's your subjective view from today's perspective. CRS1xx devices were engineered a decade or so ago with some other objectives in mind. And is almost EOL now. CRS3xx family was designed much later with different obectives in mind.

You as customer / potential user are free to either use CRS112 or skip it. No amount if subjective judgement will change the way CRS1xx are engineered.

CRS 112-8p is a very sucessfull device, flying from shelves up on arrival, a workhorse for WISP around the world

My biggest complaint is that regular DC barrel-jacks are a bit whimpy and unreliable for higher wattages.

remember this switch has only 8 PoE out ports, in fact separate barrel-jack connectos for each voltaje improve reliability distributing load

in this switch:
for 28 volts max supported current is only 2.8 amp
for 56 volts max supported current is only 1.4 amp

for sure barrel-jack connectors can provide this current

I can power the CRS112-8P (and CRS318-16P NetPower 16P) directly with clean, green energy obtained from solar panels.
I have dozens of radio tower turned on like this and I don't spend a dime to buy power.
I cannot use the CRS328 because I am forced to waste energy to power an inverter to have 230V to power that device, or I would have to take it apart and modify it.

A friend of mine has modified many MT devices to utilize his on-site 12V or 24V battery systems. In most of the bigger routers, the boards use 12V natively, so it's a simple matter of jumping a pair of wires to the 12V rail on the board (or splicing to one of the power supply's 12V cables).

Usually he does it in such a way that it can use either AC or DC (or both) at the site, leaving as much of the original powering options intact.