200-301 Question #652: Real Exam Question with Answer & Explanation

Question

Which command entered on a switch configured with Rapid PVST+ listens and learns for a specific time period?

Options

• Aswitch(config)#spanning-tree vlan 1 max-age 6
• Bswitch(config)#spanning-tree vlan 1 hello-time 10
• Cswitch(config)#spanning-tree vlan 1 priority 4096
• Dswitch(config)#spanning-tree vlan 1 forward-time 20

Explanation

The forward-time command in Rapid PVST+ configures the duration a switch port spends in the listening and learning states, during which it processes BPDUs and populates its MAC table.

Common mistakes.

• A. max-age defines the maximum amount of time a switch stores BPDU information before discarding it and potentially initiating a topology change, not the duration of the listening and learning phases.
• B. hello-time specifies the interval at which the root bridge sends Bridge Protocol Data Units (BPDUs), which is unrelated to the duration a port spends in listening and learning states.
• C. priority is a value used in the root bridge election process for a specific VLAN, where a lower priority value increases the likelihood of a switch becoming the root bridge, and does not control state transition timers.

Concept tested. Rapid PVST+ forward-time timer

Reference. https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3750x_3560x/software/release/12_2_55_se/configuration/guide/3750x_3560x_scg/swstp.html#wp1010377

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