Exam 300-620 topic 1 question 215 discussion

https://www.linkedin.com/pulse/connecting-cisco-aci-mstp-lan-islam-elbaz/

I think is A

When Interacting with MST Switches ACI, BPDU frames for Per-VLAN Spanning Tree (PVST) and Rapid Per-VLAN Spanning Tree (RPVST) have a VLAN tag. The Cisco ACI leaf can identify the EPG on which the BPDUs need to be flooded based on the VLAN tag in the frame. MST (IEEE 802.1s), BPDU frames do not carry a VLAN tag, and the BPDUs are sent over the native VLAN. Typically, the native VLAN is not used to carry data traffic, and the native VLAN may not be configured for data traffic on the Cisco ACI fabric. As a result, to help ensure that MST BPDUs are flooded to the desired ports, the user must create an EPG (an MST EPG) for VLAN 1 as native VLAN to carry the BPDUs. This EPG connects to the external switches that run MST. Administrator must configure the mapping of MST instances to VLANs to define which MAC address table must be flushed when a Topology Change Notification (TCN) occurs. When a TCN event occurs on the external Layer 2 network, this TCN reaches the leafs to which it connects via the MST EPG, and flushes the local endpoint information associated with these VLANs on these leafs; as result, these entries are removed from the spine-proxy mapping database.