You little friends and everyone I talk about in this chapter the basic principles and configuration switches.
First let us look at what is the switch and its definition:
- Switch (Switch) meaning "switch" is an electrical (optical) signal forwarding network device. It can provide an electrical signal path exclusive of any two network nodes is an access switch. The most common switch is an Ethernet switch. Other common as well as telephone voice switches, fiber optic switches.
- Exchange is needed at both ends of the transmission of the communication information, a method of manually or automatically apparatus, the information to be transmitted to collectively meet the requirements of technology on the respective route. Depending on the operating position of the switch can be divided into WAN switches and LAN switches. WAN Switch is a kind of device to complete the information exchange function in a communication system, its use in the data link layer. A plurality of switch ports, each port having a bridging function, can be connected to a local area network or a high-performance server or workstation. In fact, the switch is sometimes referred to as multi-port bridges.
- Network switch, an expansion of the network equipment, can provide more sub-network connection port so as to connect more computers. With the advance development of the communication industry and the national economy, information technology, network switch market showed a steady upward trend. It is a cost-effective, highly flexible, simple and easy to implement and so on. Ethernet technology has become the most important LAN networking technology, network switch has become the most popular switches.
- Switch is the English name of the switch, this is the original product upgrading and updating from the hub, and the hub in appearance is not very different. Since the ends of the communication information to be transmitted, through the device, or the information to be transmitted to an artificial manner to meet the requirements of the standard corresponding to the router, the switch technology is technology. Up from the broad analysis, in a communication system for information exchange functions implemented device is a switch.
The device is Ethernet Switch
Theoretical principles :( Layer)
1. Data link layer functions
2. Ethernet frame format
works 3. The switch
command switch 4.
Layer principles located between the network layer and the physical layer
一：数据链路层功能：
1.数据链路的建立、维护和拆除
2.帧包装、帧传输、帧同步
3.帧的差错恢复
4.流量控制（QUS）
二：以太网发展：
1.X-Wire：2.94兆实验性以太网
2.DIX：10兆以太网应用
3.IEEE 802.3：10兆以太网标准
4.千兆以太网：100/1000兆以太网
三：以太网MAC地址（长度为48位，48个二进制）
1.用来识别一个以太网的某个单独的设备或一组设备
- 前24比特（供应商标识）
其中前24位比特中第8位：0-物理地址（单播地址）
1-组播地址（组播地址） - 后24比特（供应商对应网卡的唯一编号）
四：以太网帧格式：
前导码（7字节）
起始定界符（1字节）
目的地址（6字节）
源地址（6字节）
类型（2字节）
数据（46~1500字节）
帧校验序列（4字节）
具体如下图所示：
交换机设备简介：
1.Crsco交换产品体系：（以思科设备为例） - Crsco2960系列交换机
- Crsco3560系列交换机
- Crsco4500系列交换机
- Crsco6500系列交换机（ISP运营商网络）
CDN就近推送
双介质：光纤和网线
交换机的工作原理：- 交换机的转发原理：
- 初始状态
- MAC地址学习（记录源MAC地址）
- 广播未知数据帧
- The recipient to respond
- Switches for Unicast Communications
Here we illustrate: For example, we now have a new switch, respectively, 3 single PC 1.2.3 ABC in his port, then the PC will own A source MAC address and want to send the destination MAC address table packaged separately into a data frame transmitted to the switch through port 1, first received after the switch will do is to record the PC a source MAC address, then the switch does not know which port in the target, so all he can only be sent as broadcast, this time coincides with the MAC address of the PC B, after receiving the broadcast found himself the recipient, and this time he will switch to respond to its own MAC address as the source MAC and the MAC address sent from the other party as a destination MAC packed into a data frame to the switch response through port 2, the switch will still be recorded to the source MAC address of the PC of B, the switch will have been aware of the need for communication is a PC, a and PC-B, through the port is 1 and 2, then you can communicate to them the unicast.
Ethernet interface operating mode switch:
1. simplex: only transmit data (e.g., loud speaker unit) in a single direction between two data stations 
2. Half: between two data stations can bi-directional data transfer, but It can not be (e.g., walkie-talkie) 
3. Full duplex: bi-directional and simultaneous data transfer of data between two stations (e.g., present telephone)
Exchange rate Ethernet interfaces:
1. Interface connection for consultations
2. negotiation fails impassable
Configuration before preparation:
- Before the connection configuration
① Console cable
2. physical connection
① computer COM port
② switch / router Console port
3. The connection software
① HyperTerminal
② other software
specifically as shown below: