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wu-kan committed Apr 27, 2019
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62 changes: 35 additions & 27 deletions _posts/2019-04-19-二层交换机实验.md
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Expand Up @@ -25,33 +25,35 @@ C:\>ping -t 目的主机的IP地址 !持续发出请求包,例如,C:\

|IP地址|MAC地址|
|-|-|
|192.168.1.1|00-88-99-00-13-53|
|192.168.1.2|00-88-99-00-07-61|
|192.168.1.3|00-88-99-00-14-57|
|192.168.1.4|F4-8E-38-F4-09-B4|
|192.168.1.1|00-88-99-00-07-3E|
|192.168.1.2|44-33-4C-0E-CE-82|
|192.168.1.3|00-88-99-00-0B-A7|
|192.168.1.4|00-88-99-00-13-82|

#### Wireshark以太网帧(DIXv2)截屏:
每台主机用Wireshark检测出一个其它主机发给自己的以太网帧并截屏(用anysend或者用ping IP地址产生包)。Wireshark Filter:eth.dst == 84-A6-C8-C0-BB-CF(主机的实验网网卡地址)进行过滤。
1. ![](/public/image/2019-04-19-1.png)
1. ![](/public/image/2019-04-19-1.jpg)
2. ![](/public/image/2019-04-19-2.png)
3. ![](/public/image/2019-04-19-3.png)
4. ![](/public/image/2019-04-19-4.png)

00-88-999-00-13-74
### 直接用anysend发送一个广播帧,或者用一台主机(例如,192.168.1.1)ping一个子网中不存在的IP地址(例如,192.168.1.50)来产生广播帧(ARP包)。在所有主机上用Wireshark检测这个以太网广播帧(源MAC地址为该主机的地址,目的MAC地址为广播地址)并截屏。
Wireshark Filter:eth.src == 84-A6-C8-C0-BB-CF and eth.dst == FF-FF-FF-FF-FF-FF。
Wireshark Filter:
```
eth.src == 00-88-99-00-07-3E and eth.dst == FF-FF-FF-FF-FF-FF。
```
#### 在四台主机上捕捉发给自己的广播帧并截屏:
1. ![](/public/image/2019-04-19-5.png)
1. ![](/public/image/2019-04-19-5.jpg)
2. ![](/public/image/2019-04-19-6.png)
3. ![](/public/image/2019-04-19-7.png)
4. ![](/public/image/2019-04-19-8.png)

### 在两个交换机之间再连接一条网线。
用步骤(2)的方法产生广播帧,并用Wireshark检测广播风暴(capture/interfaces), 得到实验网接口收发包的速度(packets/s),截屏该画面。注意:当发现广播风暴时要及时断开其中一条网线以避免死机。
在四台主机上捕捉广播风暴并截屏收发包的速度:
1. ![](/public/image/2019-04-19-9.png)
1. ![](/public/image/2019-04-19-9.jpg)
2. ![](/public/image/2019-04-19-10.png)
3. ![](/public/image/2019-04-19-11.png)
3. ![](/public/image/2019-04-19-11.jpg)
4. ![](/public/image/2019-04-19-12.png)

### 先在两台交换机上启动生成树算法,然后在它们之间重新连接两条网线,检测是否会出现广播风暴,截屏Wireshark。
Expand All @@ -62,47 +64,53 @@ Wireshark Filter:eth.src == 84-A6-C8-C0-BB-CF and eth.dst == FF-FF-FF-FF-FF-FF
#### 是否存在广播风暴?(是/否)
#### 经过2分钟截屏Wireshark(capture/interfaces):
1. ![](/public/image/2019-04-19-17.jpg)
2. ![](/public/image/2019-04-19-18.jpg)
3. ![](/public/image/2019-04-19-19.png)
4. ![](/public/image/2019-04-19-20.png)
1. ![](/public/image/2019-04-19-13.jpg)
2. ![](/public/image/2019-04-19-14.png)
3. ![](/public/image/2019-04-19-15.png)
4. ![](/public/image/2019-04-19-16.png)

#### 在两台交换机上执行显示生成树参数的命令并截屏:
```
(config)#show spanning-tree
```
![](/public/image/2019-04-19-13.png)
![](/public/image/2019-04-19-14.jpg)
1. ![](/public/image/2019-04-19-17.jpg)
2. ![](/public/image/2019-04-19-18.png)

#### 在两台交换机上执行显示接口f0/1和f0/2的生成树参数的命令并截屏:
```
(config)#show spanning-tree interface f0/2 或 f0/1
```
![](/public/image/2019-04-19-15.jpg)
![](/public/image/2019-04-19-16.jpg)
1. ![](/public/image/2019-04-19-19.jpg)
2. ![](/public/image/2019-04-19-20.jpg)

#### 根据上面结果填表

||网桥优先权(priority)|网桥MAC地址(BridgeAddr)|根网桥ID(DesignatedRoot)|到根的距离(RootCost)|根端口(RootPort)|指定端口(Designated)|
|-|-|-|-|-|-|-|
|Switch1|
|Switch2|
|Switch1|32768|5869.6c15.5544|32768.5869.6c15.5544|0|0|32768.5869.6c15.5544|
|Switch2|32768|5869.6c15.59f0|32768.5869.6c15.5544|0|GigabitEthernet 0/16|32768.5869.6c15.5544|

#### 显示两台交换机的MAC地址表, 通过ping让每个MAC地址表包含全部主机的MAC地址,然后截屏:
命令:
```
#show mac-address-table
```
Switch1的MAC地址表截屏:
![](/public/image/2019-04-19-21.png)
Switch2的MAC地址表截屏:
![](/public/image/2019-04-19-22.jpg)
1. Switch1的MAC地址表截屏:
![](/public/image/2019-04-19-21.jpg)![](/public/image/2019-04-19-22.jpg)
2. Switch2的MAC地址表截屏:
![](/public/image/2019-04-19-23.jpg)

### 在(4)的基础上,修改优先权令另一台交换机成为根网桥,ping通后查看生成树信息并填表:
```
(config)#spanning-tree priority 4096 !设置交换机优先权为4096。默认优先权为32768
```
1. ![](/public/image/2019-04-19-24.jpg)
2. ![](/public/image/2019-04-19-25.jpg)

||网桥优先权|网桥MAC地址|根网桥ID|到根的距离|根端口|指定端口|
||网桥优先权(priority)|网桥MAC地址(BridgeAddr)|根网桥ID(DesignatedRoot)|到根的距离(RootCost)|根端口(RootPort)|指定端口(Designated)|
|-|-|-|-|-|-|-|
|Switch1|
|Switch2|
|Switch1|128|5869.6c15.59f0|4096.5869.6c15.59f0|0|GigabitEthernet 0/16|4096.5869.6c15.59f0|
|Switch2|128|5869.6c15.59f0|4096.5869.6c15.59f0|0|0|4096.5869.6c15.59f0|

## 实验体会
两层交换机的实验进行过程中,我们遇到了诸多的问题,包括交换机、网线、防火墙处处都有可能发生问题。这使我们的实验推进十分缓慢,以致于周末来到实验室重做实验。最开始从配置IP地址都要摸索一番,到后面配置生成树总是失败,总是得不到预期的结果。总之,经过这一实验之后,我对计算机网络的组成有了更深的了解和体会。
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