实验

拓扑

配置

正常情况下

命令

S1配置

<Huawei>
<Huawei>sys
Enter system view, return user view with Ctrl+Z.
[Huawei]sys S1
[S1]stp mode stp
Info: This operation may take a few seconds. Please wait for a moment...done.
[S1]

S2配置

<Huawei>
<Huawei>sys
Enter system view, return user view with Ctrl+Z.
[Huawei]sys S1
[S1]stp mode stp
Info: This operation may take a few seconds. Please wait for a moment...done.
[S1]

S3配置

<Huawei>
<Huawei>sys
Enter system view, return user view with Ctrl+Z.
[Huawei]sys S3
[S3]stp mode stp
Info: This operation may take a few seconds. Please wait for a moment...done.
[S3]

S4配置

<Huawei>sys
Enter system view, return user view with Ctrl+Z.
[Huawei]sys S4
[S4]stp mode stp
Info: This operation may take a few seconds. Please wait for a moment...done.
[S4]

验证

S1为非根交换，1口是跟端口RP，2口是阻塞端口AP

[S1]dis stp br
 MSTID  Port                        Role  STP State     Protection
   0    GigabitEthernet0/0/1        ROOT  FORWARDING      NONE
   0    GigabitEthernet0/0/2        ALTE  DISCARDING      NONE
[S1]

S2为跟交换，1口、2口都是指定端口DP

[S2]dis stp brief 
 MSTID  Port                        Role  STP State     Protection
   0    GigabitEthernet0/0/1        DESI  FORWARDING      NONE
   0    GigabitEthernet0/0/2        DESI  FORWARDING      NONE
[S2]

S3为非根交换，1口、3口、4口为指定端口DP，2口为跟端口

[S3]dis stp brief
 MSTID  Port                        Role  STP State     Protection
   0    GigabitEthernet0/0/1        DESI  FORWARDING      NONE
   0    GigabitEthernet0/0/2        ROOT  FORWARDING      NONE
   0    GigabitEthernet0/0/3        DESI  FORWARDING      NONE
   0    GigabitEthernet0/0/4        DESI  FORWARDING      NONE
[S3]

S4为非根端口,1口为跟端口RP，2口为阻塞端口AP

[S4]dis stp brief
 MSTID  Port                        Role  STP State     Protection
   0    GigabitEthernet0/0/1        ROOT  FORWARDING      NONE
   0    GigabitEthernet0/0/2        ALTE  DISCARDING      NONE
[S4]

按要求

将S1配置为根交换机
- 原理
  
  跟交换机的选举是通过BID的优先级值、BID的MAC地址、PID的比较实现
- 命令
  1
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  [S1]stp priority 0
  #或者
  [S1]stp root primary

验证

将S2配置为备根交换机
- 原理
  
  将S2的优先级的值修改我比S1大，但是比S3、S4小，缺省值是32768
- 命令
  1
  2
  3
  [S2]stp priority 4096
  # 或者
  [S2]stp root secondary

验证

将S3的2口配置为阻塞端口(阻塞端口与指点端口之间对比)
- 原理
  
  阻塞端口比较的是端口发送BPDU报文时，RPC值、端口BID的优先级值+MAC地址、端口PID的值
- 命令
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  <S3>sys
  Enter system view, return user view with Ctrl+Z.
  [S3]int g0/0/1
  [S3-GigabitEthernet0/0/1]stp cost 220000

验证

[S3]dis stp brief 
 MSTID  Port                        Role  STP State     Protection
   0    GigabitEthernet0/0/1        ROOT  FORWARDING      NONE
   
   # 2口的端口为阻塞端口
   0    GigabitEthernet0/0/2        ALTE  DISCARDING      NONE
   0    GigabitEthernet0/0/3        DESI  DISCARDING      NONE
   0    GigabitEthernet0/0/4        DESI  DISCARDING      NONE
[S3]

将S4的1口配置为阻塞端口（阻塞端口与根端口进行对比）
- 原理
  
  阻塞端口比较的是端口发送BPDU报文时，RPC值、端口BID的优先级值+MAC地址、端口PID的值
  
  由于SW3的1口的开销值修改了，那么SW4交换到根交换的RPC值、BID的值都一致，且SW4涉及确定根端口，所以需要看对端的PID-即SW3交换3口的PID
- 命令
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  <S3>sys
  Enter system view, return user view with Ctrl+Z.
  [S3]int g0/0/3
  [S3-GigabitEthernet0/0/3]stp port priority 144

验证

[S4]dis stp brief 
 MSTID  Port                        Role  STP State     Protection
   0    GigabitEthernet0/0/1        ALTE  DISCARDING      NONE
   0    GigabitEthernet0/0/2        ROOT  DISCARDING      NONE
[S4]

配置

图表

命令	备注
stp mode {stp \| mstp \| rstp}	配置STP模式，缺省是MSTP
stp priority 4096	配置BID的优先级值，0~61440 都是4096倍数
stp root primary / secondary	配置BID，自动修改BID的优先级值，指定主/备根交换机
stp pathcost-standard {dot1q-1998 \| dot1q \| legacy}	配置路径开销值的标准
开销标准	legacy：cost=1200000，华为私有 802.1d标准：cost=165535 802.1t标准：cost=1~200000000，默认
stp cost 10	修改STP开销
stp port priority 144	修改PID优先级的值，都是16的倍数
display stp [brief]	显示STP配置信息和参数
display stp int g0/0/1	显示端口STP详细信息