Rapid Spanning Tree port states

Unlike STP, RSTP has three port states, Discarding, Learning, and Forwarding. They don't function with timers like classic STP does. The Learning state exists only momentarily during synchronization between the proposal and agreement BPDUs being exchanged. The Learning state will have a longer duration if RSTP determines that an STP switch is connected to it. It will automatically fall back to STP since it is backward compatible.

The transition from one state to another is governed by the STP - RSTP proposal-agreement process.