CCNA R&S Question of the Week: Rapid STP

Which three statements about Rapid Spanning Tree Protocol (STP) are true? (Choose three.)

A. Rapid STP significantly reduces topology convergence time after a link failure.
B. Rapid STP adds the port roles of alternate and backup.
C. Rapid STP port states are blocking, discarding, learning or forwarding.
D. Rapid STP provides a faster transition to the forwarding state than traditional STP.
E. Rapid STP also uses the STP proposal-agreement sequence.
F. Rapid STP uses the same timer-based process as STP on point-to-point links.

Reveal Answer

Answer: A, B and D.

Rapid STP performes better compared to the traditional STP, mainly due to the introduction of port roles.

With RSTP, the forwarding ports are defined as either Designated ports or Root ports, indicating the direction of forwarding, relative to the root. Root ports forward towards root, Designated ports forward away from root. The blocking ports from STP are now identified as Non-Designated ports. Of those, they can also be deemed to be Alternate or Backup ports.

If a Root port fails, than either the Backup or Alternate can be promoted to become the Root port. If it’s a direct link failure, convergence can be within milliseconds. If it’s an indirect link failure (on another switch), than the Hellos are used as a keep alive and 3 failures will trigger a conference of the topology.

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