352-001 · Question #86
If a network design must support rapid convergence on half-duplex interfaces, which IEEE 802.1w capability should be used?
The correct answer is B. proposal-agreement handshake. IEEE 802.1w (RSTP) achieves rapid convergence through the proposal-agreement handshake, which allows adjacent switches to negotiate port state transitions without waiting for legacy STP timers.
Question
If a network design must support rapid convergence on half-duplex interfaces, which IEEE 802.1w capability should be used?
Options
- Aroot guard
- Bproposal-agreement handshake
- Cloop guard
- DUplinkFast
How the community answered
(27 responses)- A11% (3)
- B81% (22)
- C4% (1)
- D4% (1)
Why each option
IEEE 802.1w (RSTP) achieves rapid convergence through the proposal-agreement handshake, which allows adjacent switches to negotiate port state transitions without waiting for legacy STP timers.
Root guard is a protective feature that rejects superior BPDUs on specific ports to enforce root bridge placement and does not accelerate convergence.
The proposal-agreement handshake lets an RSTP switch immediately send a Proposal BPDU on a designated port; the downstream switch synchronizes its non-edge ports and replies with an Agreement BPDU, allowing the upstream port to transition to Forwarding without the 30-second listening and learning delays of 802.1D. This is the defining convergence mechanism in 802.1w.
Loop guard prevents ports from transitioning to Forwarding when BPDUs are lost, serving as a protection mechanism rather than a convergence accelerator.
UplinkFast is a Cisco-proprietary extension to legacy 802.1D STP, not a feature of the IEEE 802.1w standard.
Concept tested: RSTP proposal-agreement rapid convergence mechanism
Source: https://www.cisco.com/c/en/us/support/docs/lan-switching/spanning-tree-protocol/24062-146.html
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