Which result occurs when PortFast is enabled on an interface that is connected to another switch? 

Answer options:

A. Root port choice and spanning-tree recalculation are accelerated when a switch link goes down.
B. After spanning-tree converges, PortFast shuts down any port that receives BPDUs.
C. VTP is allowed to propagate VLAN configuration information from switch to switch automatically.
D. Spanning-tree may fail to detect a switching loop in the network that causes broadcast storms.

D

Enabling the PortFast feature causes a switch or a trunk port to enter the STP forwarding-state immediately or upon a linkup event, thus bypassing the listening and learning states. Note: To enable portfast on a trunk port you need the trunk keyword spanning-tree portfast trunk