关于PVST的概念，这里就不详细叙述了。网上很多资料里都总结了这些命令，感觉有不小的实用性，于是再次列出：
启用生成树：
Switch(config)#spanning-tree vlan vlan-list
设置根网桥：
Switch(config)#spanning-tree vlan vlan-list root primary | secondary(主根|从根)
修改网桥的优先级
Switch(config)#spanning-tree vlan vlan-list priority Bridge-priority
修改端口成本
Switch(config-if)#spanning-tree vlan vlan-list cost cost
修改端口优先级
Switch(config-if)#spanning-tree vlan vlan-list port-priority priority
配置上行速链路:
配置上行速链路的作用：当接入层或汇聚层的交换机主用的上行链路断开的时候，被阻塞的端口迅速装换到转发状态，不需要经过侦
听和学习状态，配置了上行速链路后交换机的优先级变为49152，成本增加3000
Switch(config)#spanning-tree uplinkfast
配置端口速链路:
配置速端口的作用：不经过侦听和学习状态，直接进入到转发状态，但是该端口依然会运行生成树协议，如果检测到环路，也能够将
转发状态转换为阻塞状态，配置在连接终端的接口上。
Switch(config-if)#spanning-tree portfast
查看生成树的配置:
Switch#show spanning-tree
查看某个VLAN的生成树详细信息:
Switch#show spanning-tree vlan vlan-id detail
这是一个简单的实验，但是很清楚地能看出真正要表达的东西。配置如下：
Swtch0:
Switch#vlan database
% Warning: It is recommended to configure VLAN from config mode,
  as VLAN database mode is being deprecated. Please consult user
  documentation for configuring VTP/VLAN in config mode.
Switch(vlan)#vlan 2
VLAN 2 added:
    Name: VLAN0002
Switch(vlan)#exit
APPLY completed.
Exiting....
Switch(config)#int f0/1
Switch(config-if)#switchport mode trunk
Switch(config-if)#int f0/2
Switch(config-if)#switchport mode trunk
Switch(config-if)#exit
Switch(config)#spanning-tree vlan 1 root primary
Switch(config)#
%LINK-5-CHANGED: Interface FastEthernet0/1, changed state to down
%LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/1, changed state to down
%LINK-5-CHANGED: Interface FastEthernet0/2, changed state to down
%LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/2, changed state to down
%LINK-5-CHANGED: Interface FastEthernet0/1, changed state to up
%LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/1, changed state to up
%LINK-5-CHANGED: Interface FastEthernet0/2, changed state to up
%LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/2, changed state to up
Switch(config)#^Z
%SYS-5-CONFIG_I: Configured from console by console
Switch#show s
Switch#show sp
Switch#show int f0/4 switchport
Name: Fa0/4
Switchport: Enabled
Administrative Mode: dynamic auto
Operational Mode: static access
Administrative Trunking Encapsulation: dot1q
Operational Trunking Encapsulation: native
Negotiation of Trunking: On
Access Mode VLAN: 1 (default)
Trunking Native Mode VLAN: 1 (default)
Voice VLAN: none
Administrative private-vlan host-association: none
Administrative private-vlan mapping: none
Administrative private-vlan trunk native VLAN: none
Administrative private-vlan trunk encapsulation: dot1q
Administrative private-vlan trunk normal VLANs: none
Administrative private-vlan trunk private VLANs: none
Operational private-vlan: none
Trunking VLANs Enabled: ALL
Pruning VLANs Enabled: 2-1001
Capture Mode Disabled
Capture VLANs Allowed: ALL
Protected: false
Switch#show int f0/3 switchport
Name: Fa0/3
Switchport: Enabled
Administrative Mode: static access
Operational Mode: static access
Administrative Trunking Encapsulation: dot1q
Operational Trunking Encapsulation: native
Negotiation of Trunking: On
Access Mode VLAN: 2 (VLAN0002)
Trunking Native Mode VLAN: 1 (default)
Voice VLAN: none
Administrative private-vlan host-association: none
Administrative private-vlan mapping: none
Administrative private-vlan trunk native VLAN: none
Administrative private-vlan trunk encapsulation: dot1q
Administrative private-vlan trunk normal VLANs: none
Administrative private-vlan trunk private VLANs: none
Operational private-vlan: none
Trunking VLANs Enabled: ALL
Pruning VLANs Enabled: 2-1001
Capture Mode Disabled
Capture VLANs Allowed: ALL
Protected: false
Appliance trust: none
 
Switch1:
Switch#vlan database
% Warning: It is recommended to configure VLAN from config mode,
  as VLAN database mode is being deprecated. Please consult user
  documentation for configuring VTP/VLAN in config mode.
Switch(vlan)#vlan 2
VLAN 2 added:
    Name: VLAN0002
Switch(vlan)#exit
APPLY completed.
Exiting....
Switch#conf t
Enter configuration commands, one per line.  End with CNTL/Z.
Switch(config)#int f0/1
Switch(config-if)#switchport mode trunk
Switch(config-if)#int f0/2
Switch(config-if)#switchport mode trunk
Switch(config-if)#exit
Switch(config)#spanning-tree vlan 2 root primary
Switch(config)#
%LINK-5-CHANGED: Interface FastEthernet0/3, changed state to up
%LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/3, changed state to up
Switch(config)#int f0/3
Switch(config-if)#switchport mode access
Switch(config-if)#switchport access vlan 2
Switch(config-if)#
%LINK-5-CHANGED: Interface FastEthernet0/4, changed state to up
%LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/4, changed state to up