200-301 Question #1179: Real Exam Question with Answer & Explanation

Question

What are two features of PortFast? (Choose two.)

Options

• AConvergence is fast after a link failure.
• BSTP loops are mitigated for uplinks to other switches.
• CPorts transition directly from the blocking state to the forwarding state.
• DPorts operate normally without receiving BPDUs.
• EPorts that connect to the backbone automatically detect indirect link failures.

Explanation

PortFast is a Cisco switch feature that enables rapid Spanning Tree Protocol (STP) convergence on edge ports by transitioning them directly to the forwarding state, and it is part of overall fast convergence strategies.

Common mistakes.

• B. PortFast is designed for end-device ports, and applying it to uplinks to other switches can create STP loops if not properly managed, as it bypasses loop prevention mechanisms.
• D. Ports configured with PortFast still receive and process BPDUs; if a BPDU is received, PortFast is disabled on that port to prevent loops, indicating it does not operate normally without receiving them.
• E. PortFast does not automatically detect indirect link failures; features like UplinkFast and BackboneFast are designed for such scenarios in STP.

Concept tested. Spanning Tree PortFast features

Reference. https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3850/software/release/3se/consolidated/configuration_guide/b_consolidated_3850_3se_config_guide/b_consolidated_3850_3se_config_guide_chapter_01000.html#concept_06C787265F9341409F36FB1421448A43

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