Implementing Cisco IP Switched Networks (SWITCH v2-0) (#194)

An administrator recently configured all ports for rapid transition using PortFast. After testing, it has been determined that several ports are not transitioning as they should. What is the reason for this?

RSTP has been enabled per interface and not globally.
The STP root bridge selection is forcing key ports to remain in non-rapid transitioning mode.
STP is unable to achieve rapid transition for trunk links.
The switch does not have the processing power to ensure rapid transition for all ports.