Basic principle and configuration of switch

Catalog

One . Data link layer functions

Two . Ethernet

3、 ... and . How switches work

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One . Data link layer functions

The data link layer is responsible for
1、 Establishment of data link 、 Maintenance and removal
Physical address 、 Network topology
2、 Frame packaging 、 Frame transmission 、 Frame synchronization
Framing ： Encapsulate data in frames , Send... In order
Delimitation and synchronization ： produce / Identify frame boundaries
3、 Frame error recovery
Error recovery ： Retransmission is adopted
4、 flow control
Flow control and adaptive control ： Ensure the stability of intermediate transmission equipment and the matching of transmission rate between transceiver and transmitter

Two . Ethernet

1. Ethernet MAC Address

Ethernet MAC Address by 48 Bit binary number composition , Usually divided into 6 paragraph , In hexadecimal notation , for example :08 - 00 - 5a - e3 - 93 - 6c. The top 24 Bit is the manufacturer to IEEE The requested vendor number , after 24 Bit is the serial number of the network interface card .
MAC Address No 8 Position as 0 when , It means that we should MAC The address is unicast address ; by 1 when , It means that we should MAC The address is multicast MAC Address . The address of a physical network card must be a unicast address , That is the first. 8 It must be 0; A multicast address is a logical address , Used to represent a group of recipients , Not a receiver .

2. Ethernet frame format

Lead code ： It is used to synchronize the sending and receiving rates of both parties in the process of data transmission
Frame start delimiter ： Used to identify the beginning of Ethernet frame
Destination address ： The goal is MAC
source address ： Source MAC
type ： Identify the type of upper layer protocol , Such as 0800H Express IP agreement
data ： Upper data
Frame check sequence ： Check data and fill fields by cyclic redundancy check , Equivalent to error checking , If correct , receive data , If not , Retransmission .

  The preamble is part of the physical layer encapsulation , Sort the data , Retransmission in segments , When the last frame is checked, check whether the transmitted data corresponds , If the data corresponds to the time of sending , Then it means that the data is complete , The transmission succeeded ; If it is not a one-to-one correspondence , It indicates that the transmission was unsuccessful , Need to retransmit .

3、 ... and . How switches work

1. The principle of switch forwarding

The initial state ,MAC Address learning , Broadcast unknown data frame , The receiver responds , The switch realizes unicast communication

analysis ： The initial state of the switch is unknown ,A Want to be with B signal communication , First , Switch to learn MAC Address ,A and B When communicating , Go through the switch , At this time, exchange opportunity records A Of MAC Address and interface . Only A, No, B, So the switch should broadcast （ Flooding state ）, Notify all hosts , If you are looking for your own, open it , If you don't find your own, discard the data .B After seeing that you are looking for yourself , To give A Respond ,B to A The response also needs to go through the switch , At this time, exchange opportunity records B Of MAC Address and interface . such A Follow B Unicast communication is realized .

 

2、 Working mode of Ethernet interface

Simplex : Data can only be transmitted in a single direction between two data
Half duplex ： Data can be transmitted Bi directionally between two data stations , But not at the same time
full duplex ： Two data stations can transmit data in both directions and at the same time

3、 Basic commands of the switch
1. Switch from user view mode to system view mode

[Huawei]system-view

2、 Configure host name
[Huawei]system-view

3、 Status information query
[Huawei]display version -------- see VRP edition
[Huawei]display users -------- View user terminal information

4、 Enter the interface mode and view the information
sys---------->[Huawei]int e0/0/1-------->[Huawei-GigabitEthernet0/0/1]dis this

View the configuration information in the current view

5、 Profile management commands
[Huawei]display saved-configuration ----------> View the information saved by the device
[Huawei]display current-configuration-----------> View information about the current configuration of the device
reset saved-configuration-------------> Erase the configuration file from the storage device ( initialization )
compare configuration---------------> Compare whether the current configuration information is consistent with the saved file in the storage device

6、 Shut down Huawei's Information Center
[Huawei]undo info-center enable perhaps undo terminal monitor

7、 Never time out
[Huawei]user-interface console 0
[Huawei-ui-console0]idle-timeout 0 0

8、 Configure duplex and rate commands
sys
[Huawei]int g0/0/1
[SW1-Ethernet0/0/1]undo negotiation auto---------------> Turn off auto negotiation
[SW1-Ethernet0/0/1]speed 100-----------------------------> Adjust to rate 100M
[SW1-Ethernet0/0/1]duplex full ----------------------------> Switch to full duplex mode

explain ：full:Full-Duplex( Full duplex mode ),half：Half-Duplex( Half duplex mode )

9、 Save settings
save

expand ：
10、 Set remote login password
[Huawei]user-interface vty 0 4
#0 Is the initial value ,4 Is the end value . Open at the same time 5 A session enters the switch to configure commands
[Huawei-ui-vty0-4]authenticaation-mode password
[Huawei-ui-vty0-4]set authentication password simple 222
[Huawei-ui-vty0-4]user privilege level 3
[Huawei-ui-vty0-4]dis this

use SecureCRT link eNSP
● Double click to open a device 【 View 】 and 【 To configure 】, open 【 To configure 】--- Window configuration ： Serial number ：2000  ### This is the port number
● open SecureCRT Click on 【 link 】---【Protocol】Telnet----【Hostname】127.0.0.1----【Prot】2000
● The current terminal is opened --- To break off 【disconnect】---- conversation 【session options】----- Force one character pattern at a time 【Force charater at atime mode】--- preservation 【OK】
● Right click the current terminal --- link 【reconnect】

Huawei switch command ：

Three views of Huawei switches ：
<Huawei> User view
[Huawei] The system view
[Huawei-Ethernet0/0/1] Interface view
[Huawei-vlan10]vlan View

<Huawei>display version   // View version number
Huawei Versatile Routing Platform Software
VRP (R) software, Version 5.110 (S3700 V200R001C00)   VRP： The operating system platform of Huawei equipment , After installing this system, many protocols can be supported , Function, etc
Copyright (c) 2000-2011 HUAWEI TECH CO., LTD  // Indicate that this is a Huawei device

Quidway S3700-26C-HI Routing Switch uptime is 0 week, 0 day, 0 hour, 3 minutes   // Indicate how long it has been running , Start counting when you turn it on

<Huawei>dis ver   ---> Commands can be abbreviated

<Huawei>display saved-configuration   Use display saved-configuration The command can view the configuration file information when the switch is next started
<Huawei>display current-configuration The configuration in effect during the operation of the switch is called the current configuration
<Huawei>display startup When the switch is powered on , Read the configuration file from the default storage path to initialize the switch , Therefore, the configuration in this configuration file is called initial configuration

  ---- More ----   Appear when there are too many commands to turn over more, Press the space and enter key to continue reading , If you don't watch it, just ctrl+c
  
<Huawei>system-view or    <Huawei>sys                 // Enter the system view
  
[Huawei]sysname sw1 or    [Huawei]sys sw1            // Change device name , distinguish 2 A short sys It means different
  
[sw1]display bridge mac-address 
System bridge MAC address: 4c1f-ccf1-10b5       // Displays the switch mac Address

<Huawei>dis int Ethernet0/0/1       // View interface details , Including status 、mac Address, etc
Ethernet0/0/1 current state : UP
Line protocol current state : UP
Description:
Switch Port, PVID :    1, TPID : 8100(Hex), The Maximum Frame Length is 9216
IP Sending Frames' Format is PKTFMT_ETHNT_2, Hardware address is 4c1f-ccf1-10b5
Last physical up time   : 2021-02-19 17:04:16 UTC-08:00
Last physical down time : 2021-02-19 16:23:41 UTC-08:00
Current system time: 2021-02-19 17:09:28-08:00
Hardware address is 4c1f-ccf1-10b5
    Last 300 seconds input rate 0 bytes/sec, 0 packets/sec
    Last 300 seconds output rate 0 bytes/sec, 0 packets/sec
    Input: 0 bytes, 0 packets
    Output: 17017 bytes, 143 packets
    Input:
      Unicast: 0 packets, Multicast: 0 packets
      Broadcast: 0 packets
    Output:
      Unicast: 0 packets, Multicast: 143 packets
      Broadcast: 0 packets
    Input bandwidth utilization  :    0%
    Output bandwidth utilization :    0%

[Huawei]int e0/0/1  
[Huawei-Ethernet0/0/1]display this         // Display the current configuration of the interface

[Huawei]quit   // Go back to the next level
<Huawei>

[Huawei-Ethernet0/0/1]return   // If cross layer return is used return or ctrl+z
<Huawei> 

<Huawei>save  // Save settings

[Huawei]clear configuration interface e0/0/1      // Clear the interface configuration , Interface needs to be specified

<Huawei>reset saved-configuration—— Clear the saved configuration
<Huawei>reboot—— restart （ The unsaved current configuration will disappear ）

？： Order help / Command prompt
TAB key ： Command Completion

<Huawei>sys   // For setting console Never time out when connecting lines , The default is 10min
[Huawei]user-interface console 0
[Huawei-ui-console0]idle-timeout 0

Switch to other interfaces directly in interface mode without exiting the current view
[SW1]int e0/0/2
[SW1-Ethernet0/0/2]int e0/0/1
[SW1-Ethernet0/0/1]

see mac Address table
<SW1>dis mac-address

Configure duplex mode and rate
[SW1-Ethernet0/0/1]undo negotiation auto   # Turn off the self negotiation function , The default is auto negotiation , You need to turn it off first and then set the rate manually

[SW1-Ethernet0/0/1]duplex full/half     //full full duplex ,half Half duplex

[SW1-Ethernet0/0/1]speed 10/100     // Configure interface rate 10M/100M

<SW1>undo terminal monitor   Turn off the monitoring function
Info: Current terminal monitor is off.

[R1]undo info-center enable It is forbidden to pop up interface information
Info: Information center is disabled.

If you want to cancel the command or activate the interface, you can use undo