Refer to the exhibit, An engineer is deploying a Cisco ACI environment but experiences a...

To break the STP loop between switch1 and switch2 in a Cisco ACI environment, enabling BPDU filtering on the interfaces facing the MST (Multiple Spanning Tree) switches is the necessary step. BPDU filtering prevents BPDUs from being sent or received through a port, which effectively stops the STP process on those ports and breaks the loop1.

When BPDU filtering is enabled on an interface, the switch does not send any BPDUs and ignores any BPDUs it receives on that interface. This can be used to prevent unwanted STP negotiations on ports where loops are not expected to happen or where STP is not desired1.

References :=

Use of ACI Operation with L2 Switches and Spanning Tree Link Types - Cisco1