salvi,
You mentioned in an earlier post that the controller shows a root port instead of being a root bridge. These are 2 different things. Can you post the output of stp status on both the Aruba controller and your Cisco root bridge switch?
On Aruba:
- show spanning-tree
- show spanning-tree interface
On Cisco:
- show spanning-tree (I believe -- haven't done this in a while on Cisco).
With regards to recommendation, I usually disable STP on the Aruba controller if you do not have a need for it - i.e. you are not uplinking 2 ports from the controller (non-LACP/LAG/Aggregated) to your network.
-Mike