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Cisco Certified Network Associate (CCNA) · Cisco
Select one answer.
Written by other learners. Comments can disagree with the marked answer — check the official documentation when in doubt.
The correct answer is B. PortFast. PortFast is a feature in the Spanning Tree Protocol (STP) that is used to quickly transition a port from the blocking state to the forwarding state. This feature is typically used for access ports that connect to end devices (such as PCs or servers), which do not generate Spanning Tree Protocol (BPDUs) messages. By using PortFast, the STP learning and listening states are skipped and the port is immediately placed into the forwarding state, reducing the amount of time it takes for the port to transition from a blocking to a forwarding state.
A. BPDUfilter: This feature disables the processing of received BPDUs on a port, but it does not change the operation of the Spanning Tree Protocol. C. Backbonefast: This feature is used to quickly detect and recover from indirect failures in the network, but it does not change the operation of the Spanning Tree Protocol on individual ports. D. BPDUguard: This feature helps to prevent unauthorized switches from being connected to the network by disabling a port if it receives a BPDU message. This can help to prevent unauthorized switches from affecting the operation of the Spanning Tree Protocol.
PortFast: allows the port to go straight to a forwarding state because there is no danger of a loop. BPDU Guard: If an interface with this enabled receives BPDU from another switch, the interface will be shut down to prevent a loop from forming. Root Guard*: even if it receives a superior BPDU (lower bridge ID) on that interface, the switch will not accept the new switch as the root bridge. The interface will be disabled. Loop Guard*: even if the interface stops receiving BPDUs, it will not start forwarding. The interface will be disabled. * = not mentioned in objectives.