Refer to the exhibit. What does the output confirm about the switch's spanning tree configuration?

Question

Exhibits

Options

• AThe spanning-tree mode stp ieee command was entered on this switch
• BThe spanning-tree operation mode for this switch is PVST.
• CThe spanning-tree operation mode for this switch is PVST+.
• DThe spanning-tree operation mode for this switch is IEEE

• A
  2% (1)
• B
  5% (3)
• C
  91% (50)
• D
  2% (1)

Explanation

Explanation

When viewing the show spanning-tree output on a Cisco switch, the protocol field displays "ieee" alongside the VLAN information, which specifically indicates PVST+ (Per-VLAN Spanning Tree Plus) - Cisco's default and enhanced STP implementation that runs a separate spanning tree instance for each VLAN. Option C is correct because PVST+ is identified by the IEEE 802.1D protocol designation shown in the output, and it is the default mode on Cisco Catalyst switches.

Why the distractors are wrong:

• Option A is incorrect because spanning-tree mode stp ieee is not a valid Cisco IOS command; the correct command would be spanning-tree mode pvst.
• Option B is incorrect because legacy PVST (without the "+") used Cisco's proprietary ISL encapsulation and is essentially obsolete; the output shown reflects PVST+, not the older PVST.
• Option D is incorrect because "IEEE" is not a standalone spanning-tree operation mode on Cisco switches - it's a protocol descriptor visible in the output, not the mode name itself.

Memory Tip

Remember: Cisco switches default to PVST+, and when you see "ieee" in the show spanning-tree output, think PVST+ - Cisco took the IEEE 802.1D standard and enhanced it ("plus") to support per-VLAN instances.

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