I have three SG300 switches that are connect over Ubiquiti microwave links. I am trying to create a redundant layer 2 link to form a ring with the switches. The issue I am having is that the switches will only negotiate at STP and not RSTP. And when I connect the last part of the ring it will not go into blocking and will create a loop on the network. I want to use RSTP and not MSTP. I have try MSTP also and have no luck at getting it to work. Its like the BPDUs are not being seen. I have BPDU flooding turned on.