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!