学员提问：
配置：
no file verify auto
spanning-tree mode pvst
spanning-tree extend system-id
生成树是pvst，还是pvst + 呢？用什么命令可以准确看出是PVST+？
捷盈讲师及学员解答：
51-4506-sw1(config)#spanning-tree mode ?
mst Multiple spanning tree mode
pvst Per-Vlan spanning tree mode
rapid-pvst Per-Vlan rapid spanning tree mode
51-4506-sw1#show spanning-tree summary total(用这个命令可以看出你的交换机是用的哪个)
Switch is in pvst mode
Root bridge for: VLAN0010-VLAN0025
Extended system ID is enabled
Portfast Default is disabled
PortFast BPDU Guard Default is disabled
Portfast BPDU Filter Default is disabled
Loopguard Default is disabled
EtherChannel misconfig guard is enabled
UplinkFast is disabled
BackboneFast is disabled
Configured Pathcost method used is short