nerdexam
Cisco

350-401 · Question #758

Which two statements about the STP dispute function are true? (Choose two)

The correct answer is A. It compares the downstream port states reported in received BPDUs. B. The upstream switch uses received BPDUs to detect unidirectional link failures.. The STP Dispute function compares downstream port states reported in BPDUs to identify inconsistencies, allowing the upstream switch to detect unidirectional link failures.

Submitted by tom_us· Mar 6, 2026Infrastructure

Question

Which two statements about the STP dispute function are true? (Choose two)

Options

  • AIt compares the downstream port states reported in received BPDUs.
  • BThe upstream switch uses received BPDUs to detect unidirectional link failures.
  • CThe downstream switch uses received BPDUs to detect unidirectional link failures.
  • DWhen a designated port detects a conflict, it changes its role by reverting to a discarding state.

How the community answered

(21 responses)
  • A
    90% (19)
  • C
    5% (1)
  • D
    5% (1)

Why each option

The STP Dispute function compares downstream port states reported in BPDUs to identify inconsistencies, allowing the upstream switch to detect unidirectional link failures.

AIt compares the downstream port states reported in received BPDUs.Correct

The STP Dispute mechanism is activated when a designated port receives a BPDU from a downstream switch that reports a port state inconsistent with what the designated port expects, such as a forwarding state when it should be blocking.

BThe upstream switch uses received BPDUs to detect unidirectional link failures.Correct

When a designated port on an upstream switch detects a dispute, it often indicates a unidirectional link failure where the downstream switch is not correctly receiving the upstream BPDUs, leading to a conflicting port state reported by the downstream device.

CThe downstream switch uses received BPDUs to detect unidirectional link failures.

The dispute mechanism is primarily initiated by the upstream designated port upon receiving conflicting BPDUs, rather than by the downstream switch actively detecting the dispute.

DWhen a designated port detects a conflict, it changes its role by reverting to a discarding state.

When a designated port detects a conflict, it transitions its port state to discarding and sends Dispute BPDUs to resolve the conflict, rather than fundamentally changing its designated role.

Concept tested: STP Dispute mechanism

Source: https://www.cisco.com/c/en/us/support/docs/lan-switching/spanning-tree-protocol/24062-146.html

Topics

#STP#dispute mechanism#BPDU#unidirectional link

Community Discussion

No community discussion yet for this question.

Sign up to join the discussion
Full 350-401 Practice