Synchronization of Port Roles When the device receives a proposal message on one of its ports and that port is selected as the new root port, the RSTP forces all other ports to synchronize with the new root information. The device is synchronized with superior root information that is received on the root port if all other ports are synchronized. An individual port on the device is synchronized if: • That port is in the blocking state. • It is an edge port (a port that is configured to be at the edge of the network).
If a designated port is in the forwarding state and is not configured as an edge port, it transitions to the blocking state when the RSTP forces it to synchronize with new root information. In general, when the RSTP forces a port to synchronize with root information and the port does not satisfy any of the above conditions, its port state is set to blocking. Figure 5: Sequence of Events During Rapid Convergence After ensuring that all of the ports are synchronized, the device sends an agreement message to the designated device corresponding to its root port.
When the devices that are connected by a point-to-point link are in agreement about their port roles, the RSTP immediately transitions the port states to forwarding. Configuring Multiple Spanning-Tree Protocol Synchronization of Port Roles Configuring Multiple Spanning-Tree Protocol 12