Which port state is introduced by Rapid-PVST?

Which port state is introduced by Rapid-PVST?
A . learning
B . listening
C . discarding
D . forwarding

Answer: C

Explanation:

Spanning Tree from PVST+ to Rapid-PVST Migration Configuration Example

Reference 1:

http://www.cisco.com/en/US/products/hw/switches/ps708/products_configuration_example09186a00807b0670.shtml

Reference 2:

http://www.cisco.com/en/US/tech/tk389/tk621/technologies_white_paper09186a0080094cfa.shtml

PVST+ is based on IEEE802.1D Spanning Tree Protocol (STP). But PVST+ has only 3 port states (discarding, learning and forwarding) while STP has 5 port states (blocking, listening, learning, forwarding and disabled). So discarding is a new port state in PVST+.