POE out - why do most MikroTik products not follow the standards?

Hardware MikroTik hardware general
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I recently received a hardware PBX that can only be powered via POE. No problem, I thought, my RB2011Uias supports POE after all, and the required 11W the PBX needs should be no problem to supply. But no matter which cable I used, the PBX just wouldn’t start up. I still had a RBGPOE injector lying around, that one must work for sure, I thought. But the PBX remained off, and went back to the supplier with the request to send me a working device.

Many of you will understand where this is headed. The PBX worked perfectly fine, of course. It just wouldn’t work with my Mikrotik devices. So I spent the best part of the day today reading up on what POE actually is, what standards exist, and how Mikrotik takes care of all that.

The PBX in question has the following POE specifications: 11W, 802.3at POE class 3. After reading up on the various POE standards, it’s clear that this is a type 1 device, also called 802.3af. And, indeed, the supplier sent me a picture of the PBX being powered by a regular 802.3af POE switch.

So, why doesn’t it work with Mikrotik? First and foremost, to my very big surprise, most Mikrotik routers and switches do not follow the 802.3af/at standard, also called active POE. Instead, they provide so called passive POE. There seem to be two major differences.

  • First, the voltage provided to the powered device (PD): 802.3af requires a voltage of at least 37V at POE IN of the device which translates in a voltage of at least 44V needed at the power sourcing equipment (PSE). Mikrotik passive POE is available in two versions, low voltage up to 30V, and high voltage above 30V, depending on the device and power adapter use.
  • Secondly, between compliant devices, a negotiation takes place and only the power needed by the PD is sent through by the PSE. Since my devices are not compliant, no such negotiation takes place.

Both my RB2011uias and the injector are using passive POE out with 30V so it is clear now why they won’t power the PBX. After researching this topic a lot, I do have a better understanding of this but I also have some questions left.


  • I’m really interested to understand, why did Mikrotik choose not to follow the standard, what was there to gain? Even some new routers such as RB4011 only support passive POE.
  • It seems that some Mikrotik PSEs can be powered by different power adapters. For example, the specification for RB4011 says that it accepts an input voltage of 12V - 57V, yet it is being sold together with a 24V adapter. According to the Mikrotik Wiki on POE, the voltage provided by the PSE depends on the power adapter so by using an adapter with 48V output voltage, I could fulfill the 802.3af requirement of providing 37V to the PD. For some reason, the hardware product pages don’t point to the higher powered adapters, though. Am I correct that I would need the 48POW adapter for the RB4011?
  • According to the Mikrotik Wiki on POE, by using a higher powered adapter, 802.3af/at devices can be powered that do not require negotiation. Some questions here:
  • At least from reading the respective Wikipedia article it seems that compliant devices always perform some sort of negotiation. Type 1 devices, i.e. the typical 802.3af devices, do a negotiation by way of power signature, i.e. hardware-based negotiation, type 2 (POE+) devices may but don’t have to implement a separate protocol called LLDP to negotiate power, i.e. software based negotiation. Are both types of negotiation out of bonds for Mikrotik passive POE or just LLDP?
    • If Mikrotik doesn’t support any type of negotiation, how can we make sure that the correct power is transmitted?
    • How can I find out if a compliant device requires POE negotiation or not? This information does not seem readily available for most devices. Is there some rule of thumb which devices will work and which won’t?
    • What are the risks, if any, of providing power to a compliant, non-Mikrotik PD through a non-compliant switch such as the RB4011, especially when the higher power adapters are used?

Some of the sources used for my research:

Mikrotik Manual on POE Out: https://wiki.mikrotik.com/wiki/Manual:PoE-Out
Netgear Blog on passive POE: https://blog.netgear.com/blog/active-or-passive-poe-that-is-the-question/
Wikipedia on POE: https://en.wikipedia.org/wiki/Power_over_Ethernet
Versatek on POE negotiation: https://www.versatek.com/blog/poe-negotiation-of-power-power-step-down-of-the-poe-protocol/
Extreme Networks on POE device classification: https://gtacknowledge.extremenetworks.com/articles/Q_A/How-does-PoE-device-classification-work
Product page RB2011: https://mikrotik.com/product/RB2011UiAS-2HnD-IN (max input and output voltage 30V)
Product page RB4011: https://mikrotik.com/product/rb4011igs_rm (can be powered by higher voltage power supply)
Product page RBGPOE: https://mikrotik.com/product/RBGPOE (can be powered by higher voltage power supply)
Product page 48POW: https://mikrotik.com/product/48POW

1 Like
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Which standards? Your PBX probably requires 802.3af, but Mikrotik devices can power each other with Passive PoE. There are all kinds of PoE implementations.

Anyway, the PoE standard is mentioned in the specifications page of each product. We also have devices that could power your PBX, but you don’t need to assume, just check the spec sheet.

3

Which standards?

Wikipedia: Standards-based Power over Ethernet is implemented following the specifications in IEEE 802.3af-2003 (which was later incorporated as clause 33 into IEEE 802.3-2005) or the 2009 update, IEEE 802.3at.


Mikrotik devices can power each other with Passive PoE

Wikipedia: Passive POE is listed as a non-standard implementation.


We also have devices that could power your PBX, but you don’t need to assume, just check the spec sheet.

As mentioned, your own manual says that 802.3af devices can be powered by your passive POE PSEs under certain circumstances. Your statement seems to contradict this.


I’m not sure why you decided to dismiss the research and questions of a Mikrotik user and reseller so quickly. Mikrotik seems proud for following standards in many areas, such as offering standards-compliant SFP and SFP+ ports which can be used with modules from third party vendors. With POE, Mikrotik decided to go another way apparently, at least in the devices mentioned. I think all of my questions remain valid and I hope someone will take the time to answer at least some of them.

4

Mikrotik has always used passive Poe, presumably because of lower cost to implement. I don’t know how non-standardised it is. UBNT and other manufacturers support the same standard.

But you won’t be the first or last person to try plug something in expecting it to be powered, but tbh that comes down to a lack of understanding the product. No offence intended, I experienced this too

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No offense taken, on the opposite, I agree. It is a lack of understanding. Hence my hours of research, hence my questions here - yet to be answered.

With regards to being standardized or not, it makes a big difference. Switches and routers made for the SOHO market, such as the RBS260GSP, will most likely not be bought in order to power just more Mikrotik switches and routers, but IP cameras, IP phones and the like. Out of curiosity, I checked the technical specs for a few brands for IP cameras and phones that are popular in my market and they all require 802.3af or 802.3at compliant POE. What’s more, I just checked the network equipment in one of the biggest warehouses here for technical equipment and out of 450 (!) POE routers and switches, Mikrotik is the only brand far and wide that has devices without support for the standard. Yes, there are UBNT that come with some proprietary POE, too, but they always have the standard on board as well. Mikrotik really disappoints here. The defensive reaction by their representative doesn’t make things better.

6

People have to realize that Passive POE has no voltage standard. Both 24v and 48v are in popular usage.

One simple check of the specs would have seen that your PBX is 48V and the Mikrotik units you tried are 24V.

I have successfully powered up 803.af devices with 48V passive POE using my Netonix switches. BTW Netonix is passive POE only also.

7

For a long time, MikroTik had devices only with POE input. I think few of the first ones did support standard 802.3af POE (I never used it with them), but later it was only lower-voltage passive POE. Most likely because wireless CPE on the roof didn’t need anything fancy, so passive POE was good enough. It’s not like any home user would have had some POE switch anyway. Then they added some devices with POE output, but the intended use was probably to power another MikroTik device and passive POE was again enough for that. But 802.3af/at is also showing up in new products, so it should be better in future.

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if you know that 802.3af means 48V and that passive POE may mean less, then yes, I agree. If you, like me, don’t know that POE from vendor X means something else than POE from vendor Y, you’re not even going to check for that.


I have successfully powered up 803.af devices with 48V passive POE using my Netonix switches.

Hence my question: How likely is it that a 802.3af device will work if I just power the passive POE device with 48V instead of 24V? Or, to make the question more complete, what’s the difference between powering a 802.3af device with another standards-compliant device, or a passive POE device with 48V? Can you list some of the devices you managed to power using passive POE?

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That was my original assumption, too. That’s why I was quite surprised to see that even very recent products such as the RB4011 and the RBS260 “only” have passive POE.

Here’s a thing I don’t understand and it’s part of my original questions: It’s obviously possible to increase the output voltage from 24V to 48V just by changing the power supply. So if you now have a device supporting 48V (after having changed the PS), why can’t you make it standards-compliant, too? I can only assume that couldn’t be that complicated. Or did it in fact become standards-compliant with the 48V PS but just not allowed to say so “on the box”?

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I’m no expert, but passive POE is as simple at it could be. Connect wires, there’s power, the end. Active POE has some kind of negotiation, so it will clearly be more complicated to add that. I can’t say how much more.

11

That’s the question though, isn’t it? 802.3af is active POE. According to the standard, a negotiation takes place between the PSE and the PD to determine the power class of the PD:

Class 1: PSE sends 4W
Class 2: PSE sends 7W
Class 3: PSE sends 15.4W

Since with 802.3af the voltage always remains the same 48V, a higher wattage simply means higher currents.

The main questions here are, is the negotiation even required and if not, what does that mean for the sent currents? I would simply assume that a class 3 PD will always be fine but I’m not so sure about classes 1 and 2.

12

Active POE is mostly active from the power supply side. It first checks for specific resistance and then ramps up the current. That’s required for higher power levels, because if other end would be shorted, wiring would be damaged.
But the active POE client/powered device usually doesn’t have any higher intelligence, unless it’s one of the really fancy ones that communicate power requirements over ethernet.
You can use passive POE 48V (or say gigabit POE + external PSU) to power most of the 802.3af devices and they will work. I have yet to find a device that would be damaged or not work with this simple setup.

That said, Mikrotik vs. 802.3af compatibility is still very bad, as PSU in most products simply can’t handle 48V. And POE outputs are only passive and only limited to lower voltages, so they can’t be used to power 48V devices. You have to look elsewhere for proper active POE switches…

13

Today, I put all theories to the test. I received a new POE switch (non-Mikrotik) and used the enclosed 48V power supply to power my Mikrotik RB4011. Of course, I checked the output voltage and power, all fits, and so does the plug.

After all the discussions, it didn’t come as a complete surprise that all the 802.3af devices I tried to power through the POE port of the RB4011 now indeed powered up and stayed powered on. So it really was just a matter of the right voltage, and not one of passive POE vs active POE.

With regards to the question of safety, I believe the Mikrotik manual answers this already. In spite of being called passive POE, the Mikrotik PSE actually does perform several checks (resistance range 3kΩ to 26.5kΩ, overload protection, short circuit detection). I assume that means only the correct amount of power is transmitted but if someone could confirm that, I’d appreciate that.

By the way, what didn’t work for me is monitoring the power output using the command

/interface ethernet poe monitor [find]

For me, this command just returns that the state is powered-on on eth10. That’s what I also see in webfig and winbox. Any pointers here?

14

@r00t, thanks for chiming in. I was in the middle of editing my previous post so didn’t see yours before sending it off.

It indeed looks as if 802.3af devices (needing not more than 40V) can be powered fine as long as a 48V power supply is attached to the router or the injector.

Concerning PDs with higher voltage requirements, some Mikrotik devices, including the injector and the RB4011 seem to accept 57V DC input. I would assume that, in theory, using such a higher powered PSU you may be able to power some 48V PDs as long no software-based handshake is necessary. In practice, I have no idea where to find such a PSU. I found one from Veratek, extremely expensive. Makes actually more sense to just buy proper POE+ hardware, from Mikrotik or another vendor.

15

For POE injectors, Ubiquity makes a full range including gigabit passive poe at 48V and also 52V (for AirFiber). They are quite cheap and even cheaper second hand. TP-Link also makes some.
Or use MikroTik RBGPOE, it is rated 9-48V (and works OK over 50V) and pair it with some decent industrial switching PSU (like Meanwell) and you are set.
Usually on these PSUs you can adjust output voltage slightly, so 48V PSU may go up to 50-55V if you need that.
From my experience devices that require 48V 802.3af POE starts working at around 40V, so unless you have really long cables or higher power requirements (thus voltage drop gets higher), using classic 48V gigabit POE is enough for most devices.

16

Sorry for barging in like this but I have a question too, in similar manner:
Why do I need to turn “Forced On” on Ominitk 5 PoE ac, to be able to power Hikvision camera ? Auto ON simply doesn’t work.
Both are 802.3af compatible and I have 48V PSU on Omnitik.

17

Typically that’s an indication that the camera is not properly negotiating its demand for POE. Maybe you have a bad one.

18

I would say that. But, I have 3 Omnitiks and 10 different Hikvision cameras connected to them and all of them need “forced on” to be able to properly work. I saw similar issue raised few years ago.

19

It looks like this problem is being reported by many people. One post estimates a 1:4 failure rate for Hikvision units in powering up, and the same problem is reported with many models of POE gear.

My only suggestion would be for you to power up other 802.3af units from the OmniTik port and satisfy yourself that the Hikvision is the odd man out. And then perhaps try to power up the Hikvision from other models of POE-out switches. I know this isn’t the easy solution you want to hear.

20

Well, I’m satisfied with the fact that they are working with “Forced On” option, some of them are working 3 years now without issues. I just wanted to know if there’s some sort of explanation behind it. Odds are very low that 10 out of 10 cameras won’t work on “Auto ON” (different models and different years).
When cameras were installed, they were tested with Hikvision PoE switch, but that’s not relevant because it was unmanaged switch.