网络拓扑图

在这里插入图片描述

交换机信息

交换机1信息：

<H3C>dis stp
-------[CIST Global Info][Mode MSTP]-------
 Bridge ID           : 32768.06fd-8165-0100
 Bridge times        : Hello 2s MaxAge 20s FwdDelay 15s MaxHops 20
 Root ID/ERPC        : 0.08c0-212c-0ff0, 22002
 RegRoot ID/IRPC     : 32768.06fd-8165-0100, 0
 RootPort ID         : 128.51
 BPDU-Protection     : Disabled
 Bridge Config-
 Digest-Snooping     : Disabled
 TC or TCN received  : 10
 Time since last TC  : 0 days 0h:3m:17s

交换机2信息：

<H3C>dis stp
-------[CIST Global Info][Mode MSTP]-------
 Bridge ID           : 32768.06fd-8651-0200
 Bridge times        : Hello 2s MaxAge 20s FwdDelay 15s MaxHops 20
 Root ID/ERPC        : 0.08c0-212c-0ff0, 22022
 RegRoot ID/IRPC     : 32768.06fd-8651-0200, 0
 RootPort ID         : 128.2
 BPDU-Protection     : Disabled
 Bridge Config-
 Digest-Snooping     : Disabled
 TC or TCN received  : 11
 Time since last TC  : 0 days 0h:4m:45s

交换机3信息

<H3C>display stp
-------[CIST Global Info][Mode MSTP]-------
 Bridge ID           : 32768.06fd-8d6a-0300
 Bridge times        : Hello 2s MaxAge 20s FwdDelay 15s MaxHops 20
 Root ID/ERPC        : 0.08c0-212c-0ff0, 22022
 RegRoot ID/IRPC     : 32768.06fd-8d6a-0300, 0
 RootPort ID         : 128.4
 BPDU-Protection     : Disabled
 Bridge Config-
 Digest-Snooping     : Disabled
 TC or TCN received  : 18
 Time since last TC  : 0 days 0h:5m:28s

交换机4信息

<H3C>display stp
-------[CIST Global Info][Mode MSTP]-------
 Bridge ID           : 32768.06fd-93dc-0400
 Bridge times        : Hello 2s MaxAge 20s FwdDelay 15s MaxHops 20
 Root ID/ERPC        : 0.08c0-212c-0ff0, 22022
 RegRoot ID/IRPC     : 32768.06fd-93dc-0400, 0
 RootPort ID         : 128.2 
 BPDU-Protection     : Disabled
 Bridge Config-
 Digest-Snooping     : Disabled
 TC or TCN received  : 20
 Time since last TC  : 0 days 0h:5m:52s

根桥判断

交换机1：32768.06fd-8165-0100
交换机2：32768.06fd-8651-0200
交换机3：32768.06fd-8d6a-0300
交换机4：32768.06fd-93dc-0400
从上面比较可以看出“交换机1”的网桥ID最小，因此此交换机将作为网桥的“根”。

检测端口

交换机1

<H3C>display stp brief
 MST ID   Port                                Role  STP State   Protection
 0        GigabitEthernet1/0/1                DESI  FORWARDING  NONE
 0        GigabitEthernet1/0/2                DESI  FORWARDING  NONE
 0        GigabitEthernet1/0/3                DESI  FORWARDING  NONE
 0        Ten-GigabitEthernet1/0/50           ROOT  FORWARDING  NONE

交换机2：

<H3C>display stp brief
 MST ID   Port                                Role  STP State   Protection
 0        GigabitEthernet1/0/1                ROOT  FORWARDING  NONE
 0        GigabitEthernet1/0/2                DESI  FORWARDING  NONE
 0        GigabitEthernet1/0/3                DESI  FORWARDING  NONE

交换机3

<H3C>display stp brief
 MST ID   Port                                Role  STP State   Protection
 0        GigabitEthernet1/0/1                ALTE  DISCARDING  NONE
 0        GigabitEthernet1/0/2                DESI  FORWARDING  NONE
 0        GigabitEthernet1/0/3                ROOT  FORWARDING  NONE
 0        Ten-GigabitEthernet1/0/50           DESI  FORWARDING  NONE

交换机4

<H3C>display stp brief
 MST ID   Port                                Role  STP State   Protection
 0        GigabitEthernet1/0/1                ROOT  FORWARDING  NONE
 0        GigabitEthernet1/0/2                ALTE  DISCARDING  NONE
 0        GigabitEthernet1/0/3                ALTE  DISCARDING  NONE

标记端口

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ALT，意味着端口是有STP协议关闭的。

最后结果

去掉ALTE标记所在线路，最终结果如下：
在这里插入图片描述

模拟断路

手动关闭交换机4上的G1/01端口

[H3C-GigabitEthernet1/0/1]shu
[H3C-GigabitEthernet1/0/1]shutdown

接下来会出现一些提示信息

%Sep  1 10:43:12:614 2023 H3C STP/6/STP_DETECTED_TC: Instance 0's port GigabitEthernet1/0/3 detected a topology change.
%Sep  1 10:43:12:616 2023 H3C IFNET/3/PHY_UPDOWN: Physical state on the interface GigabitEthernet1/0/1 changed to down.
%Sep  1 10:43:12:616 2023 H3C IFNET/5/LINK_UPDOWN: Line protocol state on the interface GigabitEthernet1/0/1 changed to down.

检查线路

交换机1

<H3C>display stp brief
 MST ID   Port                                Role  STP State   Protection
 0        GigabitEthernet1/0/1                DESI  FORWARDING  NONE
 0        GigabitEthernet1/0/2                DESI  FORWARDING  NONE
 0        GigabitEthernet1/0/3                DESI  FORWARDING  NONE
 0        Ten-GigabitEthernet1/0/50           ROOT  FORWARDING  NONE

变为：

<H3C>dis stp brief
 MST ID   Port                                Role  STP State   Protection
 0        GigabitEthernet1/0/1                DESI  FORWARDING  NONE
 0        GigabitEthernet1/0/3                DESI  FORWARDING  NONE
 0        Ten-GigabitEthernet1/0/50           ROOT  FORWARDING  NONE

GigabitEthernet1/0/2 端口没有信息，也就是“物理断开了”

交换机2：

<H3C>display stp brief
 MST ID   Port                                Role  STP State   Protection
 0        GigabitEthernet1/0/1                ROOT  FORWARDING  NONE
 0        GigabitEthernet1/0/2                DESI  FORWARDING  NONE
 0        GigabitEthernet1/0/3                DESI  FORWARDING  NONE

交换机3

<H3C>display stp brief
 MST ID   Port                                Role  STP State   Protection
 0        GigabitEthernet1/0/1                ALTE  DISCARDING  NONE
 0        GigabitEthernet1/0/2                DESI  FORWARDING  NONE
 0        GigabitEthernet1/0/3                ROOT  FORWARDING  NONE
 0        Ten-GigabitEthernet1/0/50           DESI  FORWARDING  NONE

交换机4

<H3C>display stp brief
 MST ID   Port                                Role  STP State   Protection
 0        GigabitEthernet1/0/1                ROOT  FORWARDING  NONE
 0        GigabitEthernet1/0/2                ALTE  DISCARDING  NONE
 0        GigabitEthernet1/0/3                ALTE  DISCARDING  NONE

改变为：

[H3C]dis stp brief
 MST ID   Port                                Role  STP State   Protection
 0        GigabitEthernet1/0/2                ALTE  DISCARDING  NONE
 0        GigabitEthernet1/0/3                ROOT  FORWARDING  NONE

GigabitEthernet1/0/1 线路“物理断开”了，
GigabitEthernet1/0/3 变成了ROOT