实验拓扑

实验需求

​ 1.开启所有设备，等待STP收敛后观察STP状态

​ 2.使SW4成为根网桥

​ 3.使闭塞端口出现在SW2上

​ 4.把SW1上连接的PC的端口配置为边缘端口

实验解法

1.等待STP收敛后，查看STP运行状态，找出根网桥，闭塞端口

步骤1：根据HCL模拟器的运行机制，SW1的Mac地址应该是最小的，会成为根网桥，在SW1上查看STP运行状态，确认SW1为根网桥

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[SW1]display stp
-------[CIST Global Info][Mode MSTP]-------
Bridge ID           : 32768.7aef-e4ea-0100
Bridge times        : Hello 2s MaxAge 20s FwdDelay 15s MaxHops 20
Root ID/ERPC        : 32768.7aef-e4ea-0100, 0
RegRoot ID/IRPC     : 32768.7aef-e4ea-0100, 0
RootPort ID         : 0.0
BPDU-Protection     : Disabled
Bridge Config-
Digest-Snooping     : Disabled
TC or TCN received  : 7
Time since last TC  : 0 days 0h:0m:40s

步骤2：根据STP计算机制，所有链路开销一致，闭塞端口应该会出现在SW4上。在SW4上查看端口状态，确认SW4的g1/0/2被闭塞

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[SW4]display stp brief
 MST ID   Port                                Role  STP State   Protection
 0        GigabitEthernet1/0/1                ROOT  FORWARDING  NONE
 0        GigabitEthernet1/0/2                ALTE  DISCARDING  NONE

2.使SW4成为新的根网桥

　　分析：要想使SW4成为根网桥，最好的办法就是让SW4的优先级成为全网最小。默认优先级都为32768，只要把SW4的优先级改成比32768小就可以了

步骤1：修改SW4的优先级为4096

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[SW4]stp priority 4096
[SW4]%Jul  1 21:16:32:098 2022 SW4 STP/6/STP_DETECTED_TC: Instance 0's port GigabitEthernet1/0/2 detected a topology change.

步骤2：在SW4上查看STP运行状态，发现SW4已经成为新的根网桥

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[SW4]display stp 
-------[CIST Global Info][Mode MSTP]-------
Bridge ID           : 4096.7af0-0e17-0400
Bridge times        : Hello 2s MaxAge 20s FwdDelay 15s MaxHops 20
Root ID/ERPC        : 4096.7af0-0e17-0400, 0
RegRoot ID/IRPC     : 4096.7af0-0e17-0400, 0
RootPort ID         : 0.0
BPDU-Protection     : Disabled
Bridge Config-
Digest-Snooping     : Disabled
TC or TCN received  : 8
Time since last TC  : 0 days 0h:1m:30s

3.使闭塞端口出现在SW2上

分析：SW4成为了根网桥，按照STP计算机制，闭塞端口此时应该在SW1上。要使闭塞端口到SW2上，就需要让SW2到SW1的cost比SW4到SW1更大。H3C交换机千兆口的cost默认是20，我们可以把SW2的g1/0/2接口的cost改为1000

步骤1：在SW2上进入g1/0/2接口的接口视图，修改stp cost为1000

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[SW2]interface g1/0/2
[SW2-GigabitEthernet1/0/2]stp cost 1000
[SW2-GigabitEthernet1/0/2]%Mar 21 22:16:05:399 2018 SW2 STP/6/STP_NOTIFIED_TC: Instance 0's port GigabitEthernet1/0/1 was notified a topology change.

步骤2：在SW2上查看STP接口状态，发现SW2的g1/0/2接口已经成为了新的闭塞端口

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[SW2]display stp brief 
MST ID   Port                                Role  STP State   Protection
0        GigabitEthernet1/0/1                ROOT  FORWARDING  NONE
0        GigabitEthernet1/0/2                ALTE  DISCARDING  NONE

4.把SW1连接PC的所有接口配置为边缘接口

什么是边缘端口？从阻塞状态直接到转发状态的端口

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[SW1]interface g 1/0/3
[SW1-GigabitEthernet1/0/3]stp edged-port
Edge port should only be connected to terminal. It will cause temporary loops if port GigabitEthernet1/0/3 is connected to bridges. Please use it carefully.
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[SW1-GigabitEthernet1/0/3]int g 1/0/4
[SW1-GigabitEthernet1/0/4]stp edged-port
Edge port should only be connected to terminal. It will cause temporary loops if port GigabitEthernet1/0/4 is connected to bridges. Please use it carefully.



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