Which three of the following components must be elected before the Spanning Tree Protocol can converge in a switched LAN? (Choose three.)

Question

Options

• Adesignated ports
• Bduplex operating mode
• Cfast mode ports
• Droot bridge
• Eroot ports
• FBDPU priority

• A
  95% (21)
• F
  5% (1)

Explanation

STP convergence depends on three sequential elections: choosing a root bridge (D) first - the switch with the lowest Bridge ID becomes the central reference point for the entire topology. From there, each non-root switch elects one root port (E) - the port with the lowest-cost path back to the root bridge. Finally, designated ports (A) are elected on every network segment - the port closest to the root on each link that forwards traffic, with all other ports moved to blocking state.

Why the distractors are wrong:

• B (duplex mode) is a physical link configuration, not an STP election - it's negotiated independently of topology decisions.
• C (fast mode ports / PortFast) is a Cisco-specific feature that bypasses STP states for edge ports; it plays no role in STP's convergence election process.
• F (BPDU priority) - BPDUs are the messages STP uses to communicate; they aren't elected. BPDU priority values are inputs to the root bridge election, not a separate elected component.

Memory tip: Use the acronym "RRD" - Root bridge → Root ports → Designated ports. STP always works outward from the root, so the elections follow that same logical order.

No community discussion yet for this question.