Which two port states are classified as 'transitional' in STP?

In Spanning Tree Protocol (STP), the two port states classified as 'transitional' are Listening and Learning. These states are part of the process that a port goes through as it transitions from being ineffective in the network to an operational state.

During the Listening state, a port does not forward any frames but is actively learning about the network topology. It listens to the Bridge Protocol Data Units (BPDU) to understand which ports should be forwarded or blocked based on the current topology. This state helps ensure that the port can respond appropriately to network changes, which is crucial for preventing loops.

The Learning state follows Listening and allows the port to start learning MAC addresses by examining the source addresses of the frames that are received. While still not forwarding frames, the port prepares itself to eventually become a Forwarding state port by building the MAC address table.

This transitional nature of Listening and Learning is vital for STP's loop-prevention mechanism, allowing the network to adapt and recover from topology changes without causing broadcast storms or inefficient routing of packets. The other port states—like Blocking and Forwarding—are either inactive in frame transmission or fully operational, rather than transitional.