Selected Answer: B The default spanning-tree mode on a Cisco switch is PVST+. This spanning-tree mode is based on the IEEE 802.1D standard and Cisco proprietary extensions. PVST+ is the same as standard IEEE 802.1D, but it runs on each VLAN. In the output, we see the line “Spanning tree enabled protocol ieee” under “VLAN 20”, so it can be said the switch is running in PVST+ mode.

B - PVST+ adds support for IEEE Devices, "SPanning tree enabled protocol IEEE" output confirms PVST+

Selected Answer: B sw2(config)# sw2(config)#do s spanning-tree vl 1 summ | i mode Switch is in pvst mode sw2(config)# sw2(config)# sw2(config)#do s spanning-tree vl 1 det | i ieee VLAN0001 is executing the ieee compatible Spanning Tree protocol sw2(config)#do s spanning-tree vl 1 | i ieee Spanning tree enabled protocol ieee sw2(config)# sw2(config)#do s runn | s mode pv spanning-tree mode pvst sw2(config)# https://content.cisco.com/chapter.sjs?uri=/searchable/chapter/content/en/us/td/docs/routers/ncs5xx/ncs520/configuration/guide/LAN-switch/17-1-1/b-lanswitch-17-1-1-ncs520/b-lanswitch-17-1-1-ncs520_chapter_0110.html.xml

Selected Answer: B The reason for using PVST+ is that it is applied to VLAN 20. PVST does not exist, and IEEE is the same as STP.

Both PVST and PVST+ are per VLAN; after all, the abbreviation means Per VLAN Spanning Tree. See the differences here: - 802.1q (standard) supports only one single STP instance native VLAN (Common Spanning Tree) - (let's say channel 1) one STP instance - (let's say channel 2) - PVST (Cisco proprietary) Supports one STP instance for each VLAN uses ISL trunk only. Doesn't support 802.1q - PVST+ (Cisco proprietary) Enhances PVST capabilities by allowing PVST to be transported over 802.q : native VLAN over "Common Spanning Tree" (over channel 1) Each per-VLAN STP is encapsulated with a special Multicast MAC and carried (over channel 2)