交换机的基本原理与配置(Basic principle and configuration of switch)

交换机基本原理与配置

数据链路层功能

以太网帧格式

交换机的工作原理

交换机的命令执行

数据链路层

  位于网络层与物理层之间

  图示

  数据链路层的功能

  数据链路的建立、维护与拆除

  帧包装、帧传输、帧同步

  帧的差错恢复

  流量控制

  以太网帧格式

 Ethernet II帧格式

 图示

 循环冗余法 -帧校验

以太网帧格式

前导码(Preamble)包含8字节。前7字节的值为0xAA,而最后1字节的值为0xAB。在 DIX

以太网中,前导码被认为是物理层封装的一部分,而不是数据链路层的封装

目的地址(DA)包含6字节。DA标识了帧的目的站点的 MAC地址。DA

可以是单地址(单个目的地)、组播地址(组目的地)或广播地址。

源地址〈SA)包含6字节。SA标识了发送帧的站点的 MAC地址。SA一定是单播地址(即第8位是0)。类型域包含2字节,用来标识上层协议的类型,如 0800H表示IP协议。

数据域包含46~1500字节。数据域封装了通过以太网传输的高层协议信息。由于cSMA/CD

算法的限制,以太网帧不能小于某个最小长度。高层协议要确保这个域至少包含46字节。如果实际数据不足46字节,则高层协议必须执行某些(未指定)填充算法。数据域长度的上限是任意的,但已经被设置为 1500字节。

帧校验序列(Fcs)包含4字节。FCS是从DA开始到数据域结束这部分的校验和。校验和的算法是 32位的cRc (cyclicRedundancy Check,循环冗余校验法)。

MTU:1500最大传输单元

总长度:64-1518

             命令行帮助

                  ?的作用

                      显示命令

                      显示参数

                      命令列表

                  Tab键

                      补齐命令

                      提示命令

                  快捷键

                      <Ctrl-A>光标移动到命令行的开始位置

                      <Ctrl-E>光标移动到命令行的结束位置

 用户视图模式<Huawei>切换至系统视图模式[Huawei]

 <Huawei>system-view

1.历史命令查询

[Huawei] display history-command

2.配置主机名

<Huawei> system-view

[Huawei] system Routerl

3.状态信息查询

<Huawei>display version   #####查看VRP版本

<Huawei>display users     #####查看用户终端信息

4.进入接口模式并查看信息

<Huawei>sys

[Huawei]int e0/0/1

[Huawei-GigabitEthernet0/0/1]dis this #######查看当前视图下的配置信息

5.配置文件管理命令

[Huawei]display saved-configuration    #####查看设备保存的信息

[Huawei]display currend-configuration  #####查看设备当前配置的信息

<Huawei>reset saved-configuration      #####擦除存储设备中的配置文件(初始化)

<Huawei>compare configuration          #####比较当前配置信息与存储设备中的保存文件是否一致

6.关闭华为的信息提示中心

[Huawei]undo info-center enable

或者

<Huawei>undo terminal monitor

————————

Basic principle and configuration of switch

Data link layer functions

Ethernet frame format

How the switch works

Command execution of switch

data link layer

Between network layer and physical layer

Illustration

Functions of data link layer

Establishment, maintenance and removal of data link

Frame packaging, frame transmission, frame synchronization

Frame error recovery

flow control

Ethernet frame format

Ethernet II frame format

Illustration

Cyclic redundancy – frame check

Ethernet frame format

The preamble contains 8 bytes. The value of the first 7 bytes is 0XAA, while the value of the last 1 byte is 0xab. In Dix

In Ethernet, the preamble is considered as a part of the physical layer package rather than the data link layer package

The destination address (DA) contains 6 bytes. Da identifies the MAC address of the destination station of the frame. DA

It can be a single address (single destination), a multicast address (Group destination), or a broadcast address.

The source address (SA) contains 6 bytes. SA identifies the MAC address of the station sending the frame. SA must be a unicast address (i.e. bit 8 is 0). The type field contains 2 bytes to identify the type of upper layer protocol. For example, 0800h represents IP protocol.

The data field contains 46 ~ 1500 bytes. The data domain encapsulates the high-level protocol information transmitted through Ethernet. Due to CSMA / CD

Due to the limitation of the algorithm, the Ethernet frame cannot be less than a minimum length. The high-level protocol should ensure that this domain contains at least 46 bytes. If the actual data is less than 46 bytes, the high-level protocol must perform some (unspecified) filling algorithm. The upper limit of the data field length is arbitrary, but has been set to 1500 bytes.

The frame check sequence (FCS) contains 4 bytes. FCS is the checksum from Da to the end of data domain. The algorithm of checksum is 32-bit CRC (cyclic redundancy check).

MTU: 1500 maximum transmission unit

Total length: 64-1518

Command line help

? Role of

Display command

Display parameters

Command list

Tab key

Complement command

Prompt command

Shortcut key

& lt; Ctrl-A> Move the cursor to the beginning of the command line

& lt; Ctrl-E> Move the cursor to the end of the command line

User view mode & lt; Huawei> Switch to system view mode [Huawei]

 <Huawei>system-view

1. Historical command query

[Huawei] display history-command

2. Configure host name

<Huawei> system-view

[Huawei] system Routerl

3. Status information query

<Huawei>display version   #####查看VRP版本

< Huawei> display users     ##### View user terminal information

4. Enter the interface mode and view the information

<Huawei>sys

[Huawei]int e0/0/1

[Huawei gigabitethernet 0 / 0 / 1] dis this ########## view the configuration information in the current view

5. Configuration file management command

[Huawei]display saved-configuration    ##### View information saved by the device

[Huawei]display currend-configuration  ##### View information about the current configuration of the device

< Huawei> reset saved-configuration      ##### Erase the configuration file in the storage device (initialization)

< Huawei> compare configuration          ##### Compare whether the current configuration information is consistent with the saved file in the storage device

6. Close Huawei’s information prompt Center

[Huawei]undo info-center enable

perhaps

<Huawei>undo terminal monitor