Has anyone got any experience with Cisco Aironet 1200 series (yes, I know these are ancient, but they still work for us and being a Scout campsite, we don’t have limitless budgets for IT equipment unfortunately).
We’ve just replaced an old switch (blew up after a power cut) with a new Mikrotik CRS328-24P-4S+RM.
The other PoE devices that we have in the building (VoIP phone, CCTV Camera etc) have powered up fine with the default PoE settings on the Switch.
The Cisco Access Points don’t want to - even when I changed the interface PoE settings to “Force On” and “Voltage High” (the access points say that they need 48V input), still they seemed to do nothing.
Anyone ever experienced the same or similar? Previously, these were powered from a PoE Midline type thing (basically, just a big rack mounted injector) so, I am assuming that this is something to do with the PoE settings somewhere.
Very likely it is one of the (usual) issues with PoE standards (or non-standards and the way each manufacturer has implemented or not implemented them).
While the (oldish) Cisco are definitely “passive” 48 V only, I think there are several Aironet models maybe they exceed the 450 mA limit of the Mikrotik switch, as in theory with poe-out=forced-on and poe-voltage=high they should work, in practice everything (and the contrary of it) is possible.
Hi,
Thanks for the reply. I too think this is a problem with the implementation of the PoE “Standards”.
What I did find in the last few minutes googling is that the access points use Mode A and the switch provides power using Mode B, but I guess this is overridden by setting the force-On etc, or?
According to the label on the back of the AP, it needs 380mA / 48V… I’d like to think that the current value stated is not exceeded at boot-up, but it’s possible.
I’m going to try with a “normal” power injector just to make sure that the APs themselves haven’t died the same way that the old switch did in the morning.
No, mode A vs mode B is about the cabling, from the already mentioned documentation page:
PoE Out polarity
All MikroTik PSE uses the same PoE-Out pin polarity Mode B4,5 (+) and 7,8 (-), however other vendors can use opposite or Mode A pinout on PD. Reverse polarity would require using a crossover cable but Mode A PD would require Mode B to Mode A converter.
Mode B has + on pins 4 and 5 and - on 7 and 8. (but it can also have polarity reversed)
Mode A has + on pin 1 and 2 and - on 3 and 6. (but it can also have polarity reversed)
Mode B to mode A (but not mode A to mode B) should be possible, you could split the power from the unused pairs (mode B) and then reinject it via a “normal” PoE injector (mode A) as Sindy suggested in the above.