Rapid Spanning Tree Protocol (RSTP) Port States and Faster Convergence

RSTP Port States

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Which two spanning-tree port states does RSTP combine to allow faster convergence? (Choose two.)



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A. B. C. D. E.


The Rapid Spanning Tree Protocol (RSTP) is an updated version of the original Spanning Tree Protocol (STP) designed to reduce the time required for a network to converge after a topology change, such as a link failure or addition.

RSTP combines two port states to achieve faster convergence:

  1. Discarding (formerly blocking): This port state prevents loops by blocking traffic on the port while still listening for BPDU messages. During the blocking state, the port does not forward any frames, but it still monitors the network to determine if the topology has changed.

  2. Learning and Forwarding: RSTP combines the Learning and Forwarding port states, unlike STP, which treats them as separate states. In the Learning state, the switch learns the MAC addresses of devices on the network by examining the source address of frames received on the port. In the Forwarding state, the port forwards frames based on the forwarding table built during the Learning state.

By combining the Learning and Forwarding port states, RSTP can transition a port from a blocked state to forwarding state faster, reducing the time required for network convergence after a topology change.

Therefore, the correct answer to the question is C. forwarding and D. discarding.