The correct answer: Blocking state
A blocked port won't forward frames; it just listens to BPDUs and will drop all other frames. The purpose of the blocking state is to prevent the use of looped paths. All ports are in blocking state by default when the switch is powered up.
In a spanning-tree network, you might need to configure BPDU protection on interfaces that are not explicitly configured as edge interfaces. In such cases, use the set ethernet-switching-options bpdu-block configuration command for BPDU protection. When you use this command, you can configure for the interface to either shutdown, or to only drop the BPDU packets and retain its state as up, on receiving incompatible BPDU packets.
