Computer Network Technology and Application

Chapter 12 Basic knowledge of local area network (4)
（1）在三层交换机上进行VLAN网络的划分（必须的）。本案例采用端口划分的方法，将三层主交换机的端口2、3、4、5、6、7、8分别划分属于独立的VLAN。

(2) Choose a layer 20 switch in the three VLANs of the sales department, after-sales service department and finance department, and connect them directly to the ports of the main layer 24 switch.The reason for using a Layer [-] switch is that these departments do not require much network bandwidth and the number of computers is small. Each VLAN has only [-] machines, so a [-]-port switch can be used to realize the departmental LAN.

(3) Due to the large number of computers in the design department, a Gigabit switch and several Layer [-] switches are used to implement the department's local network.The reason for choosing a gigabit switch is to consider the number of computers in the design department and the demand for network bandwidth.

(4) As for the server, since it needs to provide data resources and management services, and the server itself has very high requirements on network bandwidth, a gigabit switch should also be selected for connection.

(5) As for the network cable, Category 5 twisted pair (RJ-45) is used to connect the network cable in this case.If possible, multimode fiber can be used between Layer [-] switching and Gigabit switches, and between servers and switches.

(6) The purpose of using a router is to isolate external dangers.

3.6.2 Wireless LAN Solution

1. Wireless local area network in the home
The ADSL access solution designed for home users, considering that home users use less terminal equipment and it is not easy to lay too many lines in the furniture environment, uses a wireless ADSL router as the access device, so that it can be directly connected to the desktop and adapted to The flexible and mobile features of the notebook reduce the cumbersome wiring.

Description:

(1) The junction box is connected to the telephone line, one is connected to the modem, and the other is connected to the telephone.

(2) The modem is responsible for the conversion of analog signals and digital signals.

(3) The wireless router can be connected to mobile devices wirelessly, such as laptops, etc., and can also be connected to computers with wires, that is, the router and computer can be connected in both wired and wireless ways.Twisted pair cables are sufficient for wired mode, and the computer needs to be equipped with an Ethernet card; if wireless mode is used, the computer needs to be equipped with a wireless network card.

(4) This type of access is also suitable for small businesses and offices.

2. Wireless LAN in the office
Description:

(1) The access router solves the connection problem with the Internet.

(2) The switch can be an ordinary two-layer switch, and the switch and wireless router are connected through a twisted pair.

(3) The router and the computer can be connected in both wired and wireless ways.Twisted pair cables are sufficient for wired mode, and the computer needs to be equipped with an Ethernet card; if wireless mode is used, the computer needs to be equipped with a wireless network card.

【chapter summary】

This chapter has a lot of content, the main line is LAN, from the definition, type, characteristics to the network protocol of LAN, among which the MAC layer protocol is the most important.We introduced the media access control methods of CSMA/CD, Token Ring and Token Bus respectively, and then took Ethernet as an example to introduce the characteristics of 10M, 100M and 1000M Ethernet networks, and introduced the main components, equipment and software for building a local area network. Commonly used network equipment bridges and switches in LAN; based on switches, switched Ethernet and VLAN are introduced.In the last subsection of this chapter, three cases are used to illustrate the establishment methods of enterprise, office and home networks.In order to learn wireless network better, this chapter arranges the experiment of wireless local area network.

【Difficulties in this chapter】

Media access control method.

virtual network technology.

Ethernet network technology and application.

Exercise 3
[-]. Multiple choice questions

1. In order to isolate the MAC sublayer from the physical layer, () is adopted in the 100Base‐T standard.

A. Network card RJ-45 interface
B. Media Independent Interface MII
C. RS‐232 interface
D. Optical fiber interface
2. Optical fiber data transmission is achieved by light ().

A. Refractive transmission
B. Frequency Hopping Transmission
C. Diffuse reflection transmission

D. Code division multiplexing transmission
3. According to the type of transmission medium, Ethernet cards are mainly divided into thick cable network cards, thin cable network cards, twisted pair network cards and ().

A. RJ-II network card
B. Optical network card
C. CATV network card
D. ADSL network card
4. Which of the following descriptions about CSMA/CD is correct ().

A. Explain that the station detects the collision after sending the frame

B. Explain that during the period when the station sends the frame, the collision is detected at the same time

C. Explain that the station sends the frame and detects the collision is not performed on the same station

D. Indicates that a frame sent on one station detects a collision only if the other station does not receive it

5. Fast Ethernet switches are divided into () according to the structure.

A. Star
B. Shared and exchanged

C.10M and 100M network

D. Full duplex and half duplex

6. Which of the following statements is wrong? () A. Ethernet switches can filter the passing information

B. The speed of the port in the Ethernet switch may be different
C. VLANs can be divided in interactive Ethernet
D. A local area network composed of multiple Ethernet switches cannot have loops
7. The MAC address exists in the computer ().

A. Memory
B. Network card
C. hard disk
D. High speed buffer
8. Which of the following descriptions about Ethernet is correct? () A. Data is sent by broadcast
B. All nodes can send and receive data at the same time
C. When two nodes communicate with each other, the third node does not detect the signal on the bus
D. There is a control center in the network to control the sending and receiving of all nodes
Two, short answer questions
1. The fundamental difference between short-answer switching and shared switches.

2. Short answer the difference between the IEEE802 standard and the TCP/IP protocol.

3. What are the basic methods of dividing VLAN?

4. How does Token Ring avoid data transmission conflicts?

5. For mobile computers, what are the advantages of wireless LAN?

Experiment [-] Learn how to set up a simple wireless network
【Purpose】

(1) Learn how to set up a local area network in the office or home.

(2) Learn to use simple methods to test the connectivity of the network.

【Experimental content】

(1) Connect the hardware.

(2) Configure the router.

(3) Test the connectivity of the network.

[class hours] 2
【Experimental Requirements】

(1) Master the simple wireless network connection method.

(2) Master the connection of equipment and the method of testing network connectivity.

【Experimental conditions】

(1) At least two computers and a wireless router.

(2) Twisted pair.

(3) Wireless network card.

【Experimental steps】

1. Configure the computer

(1) Network card configuration of the computer

One computer uses a wired network card and the other computer uses a wireless network card.In the experiment, D-LINK wireless network card 1 is used, and its main parameters are as follows.

① Network standard: IEEE802.11b, 802.11g.

②Data transmission rate: 54Mbps.

③ Effective working distance: 100 meters indoors and 400 meters outdoors (environmental factors will adversely affect the working range).

④Frequency range 2.4GHz.

⑤Antenna: Integrated built-in antenna.

⑥Bus interface: USB.

⑦Security performance: WEP64/128-bit data encryption (user selection), Wi-FiTM protected access.

⑧Status indicators: activity, connection.

Wireless network card
Special reminder: Be sure to read the instruction manual of the network card carefully, and follow the instructions for all operations.

(2) Set the network properties of the computer

Open the control panel, double-click to open the network connection, select the network card, click "Internet Protocol (TCP/IP)", click "Properties", see configuration, and click "OK".

2. Configure the wireless router

(1) Choose a router: because the number of connected computers is relatively small, choose a router with the following parameters.

① Network standards: IEEE802.11g, IEEE802.11b, IEEE802.3, IEEE802.3u.

②Data transmission rate: 108Mbps.

③Effective working distance: indoor 100 meters, outdoor 300 meters.

④Support network protocol: CSMA/CA protocol with confirmation frame ACK.

⑤Network interface: 1 WAN interface, 4 LAN interfaces.

⑥Security performance: 64/128 bit WEP, 802.11X, WPA1‐Wi‐Fi protected access, WPA‐PSK (domain public key).

⑦ Status indicators: power, WAN, LAN (10/100), WLAN (wireless connection).

Tip: There are many brands and types of wireless routers in the market, and this textbook uses a commonly used one as an example.If you want to know more brands, you can go to the local computer accessories store or browse on the Internet platform.

(2) Configure the wireless router: Insert one end of the twisted pair cable into one of the LAN switch ports of the wireless router, and insert the other end into the RJ-45 interface of a computer's wired network card.

(3) Turn on the computer to enter the system, and enter the IP address of the wireless router configured by the manufacturer in the browser address bar:

192.168.0.1.

(4) Enter the user account information for managing the wireless router in both the "Username" and "Password" text boxes.Click the "OK" button to enter the first page of the configuration interface.

(5) Use the "Setup Wizard" to quickly and easily set up the router.

①Set up Internet connection: If it is dial-up Internet access such as ADSL, enter the PPPoE setting interface, and fill in the PPPoE account and password.If the residential broadband is used, the interface of "Set Dynamic IP Address" will appear.

②Set up wireless connection.

Wireless network ID (SSID): Set the wireless network name, use the default or set it to ABC.

Channel: The default is channel 6, there is no need to change it if there is no special situation.

WEP security mode: set the wireless network access password, select 64Bit means you need to enter a 10-digit password, and 128Bit requires 26 digits.

WEP Password: Enter a password of at least 10 digits.

(6) REACTIVATE.

3. Detect the connectivity method of the network

(1) Test the local network card.

Ping127.0.0.1<Enter> (IP of other computer) (2) First check the connectivity between the computer and the router.

Enter the CMD operating environment and enter the following commands:

Ping192.168.0.1<Enter> There may be two specific return information:

Timed Out
Reply from…………

The former means that there is no corresponding return and cannot be connected; the latter means that there is information returned and the connection has been made.

【Questions and Thoughts】

If there are more than 4 computers, how can all computers access the Internet through the router?
(End of this chapter)