理论知识：

MSTP 特点：
1、可以将一个或多个VLAN划到一个MSTP多生成树里，之后每个交换机以单位收敛成独立的生成树
2、可以优化转发路径和链路利用率
3、STP默认就是MSTP

实践1
配置环境：配置端口为Trunk模式，并放行所有VLAN

[SW1]interface GigabitEthernet 0/0/1  
[SW1-GigabitEthernet0/0/1]port link-type trunk  
[SW1-GigabitEthernet0/0/1]port trunk allow-pass vlan ALL  
[SW1-GigabitEthernet0/0/1] quit  
[SW1]interface GigabitEthernet 0/0/2  
[SW1-GigabitEthernet0/0/2]port link-type trunk  
[SW1-GigabitEthernet0/0/2]port trunk allow-pass vlan all  

[SW2]interface GigabitEthernet 0/0/1  
[SW2-GigabitEthernet0/0/1]port link-type trunk  
[SW2-GigabitEthernet0/0/1]port trunk allow-pass vlan all   
[SW2-GigabitEthernet0/0/1]quit  
[SW2]interface GigabitEthernet 0/0/2  
[SW2-GigabitEthernet0/0/2]port link-type trunk   
[SW2-GigabitEthernet0/0/2]port trunk allow-pass vlan all  

[SW3]interface GigabitEthernet 0/0/1  
[SW3-GigabitEthernet0/0/1]port link-type trunk  
[SW3-GigabitEthernet0/0/1]port trunk allow-pass vlan all  
[SW3-GigabitEthernet0/0/1]quit  
[SW3-GigabitEthernet0/0/2]port link-type trunk   
[SW3-GigabitEthernet0/0/2]port trunk allow-pass vlan all   

VLAN的配置

[SW1]vlan batch 10 20  
[SW2]vlan batch 10 20  
[SW3]vlan batch 10 20

实例配置

[SW1]stp region-configuration  
[SW1-mst-region]region-name mst-region  #配置MST域名称 
[SW1-mst-region]instance 10 vlan 10 #创建实例和VLAN映射关系 
[SW1-mst-region]instance 20 vlan 20  
[SW1-mst-region]active region-configuration #激活MST域

[SW2]stp region-configuration   
[SW2-mst-region]region-name mst-region  
[SW2-mst-region]instance 10 vlan 10   
[SW2-mst-region]instance 20 vlan 20  
[SW2-mst-region]active region-configuration 

[SW3]stp region-configuration  
[SW3-mst-region]region-name mst-region  
[SW3-mst-region]instance 10 vlan 10  
[SW3-mst-region]instance 20 vlan 20  
[SW3-mst-region]active region-configuration

指定根网桥

[SW1]stp instance 10 root secondary   
[SW1]stp instance 20 root primary #配置SW1的VLAN10、VLAN20根网桥

[SW3]stp instance 10 root primary   
[SW3]stp instance 20 root secondary #配置SW3的VLAN根备用网桥

查看MSTP区域

小结

在根的选举上,STP、RSTP、MSTP没有区别，只需要指明优先级，优先级需要配置4096的倍数