Which of the following is NOT a port state in RSTP?

In Rapid Spanning Tree Protocol (RSTP), the port states define the various roles that a port can take on a switch in the context of loop prevention and bridge topology management.

The correct answer is that "Blocking" is NOT a port state in RSTP. Instead, RSTP utilizes the states of Discarding, Learning, and Forwarding to manage the traffic flow and loop prevention effectively. The Discarding state renders the port inactive for forwarding frames and also prevents the port from learning MAC addresses. This is a transition state that helps RSTP assess the network topology before moving forward.

The Learning state enables the port to build its MAC address table, allowing it to learn the devices on the network but not to forward frames just yet. The Forwarding state is where the port actively participates in the network by forwarding frames to other ports.

Thus, in RSTP, Blocking is not used as it was in the older Spanning Tree Protocol (STP) because RSTP streamlines the process with the Discarding state instead. This fundamental difference emphasizes RSTP's improvements in convergence speed and efficiency in managing network changes.