If PoE-in + DC power supply connected = redundant power?

RouterOS General
1

Quite a common question I hear around as people see MT hardware with external power supply and PoE-in port:

  • If I connect my router to DC supply and at the same time feed it with power over PoE-in port what happens when the DC suddenly go away?

As far as I understand there is no special circuit to deal with. Moreover, in CCR1009-8G-1S-1S+PC (http://routerboard.com/CCR1009-8G-1S-1SplusPC) description I see “The unit is powered by an external 24v 2.5A AC/DC adapter and supports power redundancy if you also power it from the PoE input port”, that is, this is some kind of special feature that may not be there on lower priced units, say, 951 or 2011 ones.

So, the question is: is it good idea to archive power redundancy by powering device both the PoE input and from DC sources? What kind of drawbacks I can see if I implement that? Did some tried to use that scheme?

Thanks in advance!

2

All our devices with POE-In and DC connector supports power redundancy, and it’s completely safe to use both power sources, as long they are in allowed voltage range.

3

So every device will do fine, even if it’s not marked as “supports power redundancy” in its description? And there is no need to enable it in config, it’ll run out of box, right?

Oh, great news, indeed! Sad to know it is not documented this way in the wiki.

4

yes! one word of advice, make the two power sources slightly different voltage. it could have some problems if they are identical voltage.

5

Muito bom saber disso… Tinha essa dúvida faz tempos e hoje resolvi procurar no google como “MIKROTIK POE + DC” e me apareceu essa resposta de primeira.

Parabéns a Equipe Mikrotik por esta solução maravilhosa!

Very good know this… I had this doubt have times and decided today search on GOOGLE “MIKROTIK POE + DC” and appeared to me this answer in first position!

Congratulations to Mikrotik Team for this wonderful solution!

6

PaulsMT and normis please comment on my topic also.

7

Would you clarify this, please? Your comment here is the only reference to using different voltage power supplies in a dual-power configuration I have found. If I can’t use a second 24V supply, a 48V power supply would be my next choice because they are common and I can get them from a reputable vendor. But 24V to 48V might not fit your definition of slightly different.

8

i use a laptop 18 volt power supply as second one. routerboard will take voltage from 24volt psu first if that fali then the 18volts one will kick instantly.