This group network mainly completes the networking, step-by-step networking and solution of the internal network of colleges and universities.
This paper mainly introduces the networking situation of the college and the contents to be completed in the whole networking process. This paper mainly introduces the design idea, technical difficulties and solutions of campus network.
1. The introduction explains the goal of campus network construction.
2. The design requirements of the campus network, which briefly introduces the design requirements of the college. As well as the number of connection points and the general network concept.
Keywords: network, scheme, topology diagram, campus network
introduce
In today's network information age, faced with new demands and challenges, a modern platform based on Intranet/Internet technology and a high-speed multimedia campus network have been established for the technical level of scientific research, teaching and management of the school and for the research, development and training of high-level talents.
The principle of the whole high-speed multimedia campus network construction is "economic and efficient, leading and affordable".
The main goal of campus network construction is to establish a interaction management system for administration, teaching and teachers and students based on campus network, and gradually establish a school information management network to realize office automation.
Planning campus network should discuss three elements, namely, carrying infrastructure, carrying facilities and carrying information.
Demand analysis
The campus network of colleges and universities is generally a large and medium-sized network with 300 to 500 nodes. Network applications are more complex than medium-sized campus networks, and require higher communication. Therefore, it has been required to convert 100 megabytes to the desktop and support multimedia applications.
Therefore, the campus network center uses FlexHammer24 switches to stack, providing high-density adaptive ports of10100 m. The secondary node switches choose μHammer2 or μHammer24 switches according to the specific situation, and the secondary nodes that need multimedia applications and require large bandwidth such as multimedia classrooms and electronic reading rooms choose μHammer24 switches to provide10/60. Ordinary classrooms use μHammer2 switch, providing 10M/ 100m port to access the user's desktop.
FlexHammer and μHammer switches also have the function of dividing VLAN, which makes the local area network of each department self-contained and isolates the broadcast storm. At the same time, FlexHammer's three-layer switching function enables the necessary restricted access between different user groups to be realized, thus making the design of application network more free and flexible.
Design principles:
The principle that school needs are the premise.
Quality and matching principle
Principle of giving consideration to equipment selection
Comprehensive principle of technology application
Adhere to the standard principle
Campus network construction has two main objectives:
One is to share resources and information with the outside world, such as connecting with universities, ministries and provinces at home and abroad through Cernet, and connecting with other countries through the Internet;
The second is the sharing and information exchange of campus resources, such as campus administrative management system, teaching management system, remote retrieval and data reading system of library resources by teachers and students of all grades.
It can be compared with enterprise's Internet/Intranet, but it has its particularity in application because of teaching needs, such as multimedia teaching transmission. Therefore, we fully consider the application requirements of campus network to determine the solution.
System problems and user needs
1. Establish a campus network integrated wiring system.
2. Establish the school information management system based on Intranet.
3. Establish a high-speed multimedia campus network teaching system.
4. Have a perfect network security mechanism;
5. It can be smoothly connected with the original stand-alone and independent small LAN to protect the original investment. Adequate internet connection.
Plan analysis:
1. In this campus network, the backbone switch is Ltnetcomm's gigabit backbone LTS6808G, and the IP switch LTP9524x brings extremely high backplane bandwidth to the network. LTP9524X supports IEEE802. 1Q VLAN and IGMP protocols, and can divide VLANs. The function of IP switch realizes the communication between VLANs, and supports VOD system to make its operation more perfect.
2. Install a Gigabit switch in each building.
3. In places where traffic requirements are not great, expand the number of ports by three-level switching to the desktop.
4. In order to make the system run stably, continuously and safely, this system adopts Chroma9 100 series DSP UPS, a high-performance digital online uninterruptible power supply from Beijing Kelaimao Company. Advanced technologies such as DSP, large-screen LCD and intelligent battery management are adopted.
Achieve high performance, high efficiency, high reliability and intelligence of UPS. To provide absolutely pure and stable uninterrupted power supply for users' important equipment, combined with double frequency conversion technology, completely isolate bad power supplies such as power failure, peak, frequency drift, power drop and harmonics.
Combined with intelligent power monitoring software, it provides reliable, safe and complete power protection for servers, network devices and client devices in the network.
5. Ultramicro 8060 rack server is a high-performance and high-reliability Internet rack server, which adopts 4U cabinet chassis and supports four PIII Xeon processors.
It is specially designed for service providers, with small floor space, easy wiring and convenient management and maintenance. Users can flexibly install and stack servers in parallel according to their own needs, thus improving the availability of services. The highly integrated design enhances the interoperability of the system, and Ethernet, SCSI, graphics and server management controller are closely integrated in one platform. Internet rack server is the best choice for service providers. A large number of 7U servers can provide various Internet services for ISP/ICP users, which greatly expands the business of ISP/ICP. Ultramicro 8060 rack server can run stably on various operating system platforms, and its latest technology, high reliability and high performance ensure that it can be competent in key fields such as WEB server, ERP, e-commerce and data center server.
Principles of campus network construction
Network construction should follow the principles of demand, overall planning, step-by-step implementation, maturity and reliability.
Requirements of campus network construction
Overview of software scheme
Campus teaching information service system
Multimedia courseware making room multimedia computer room
Multimedia electronic reading room in multimedia comprehensive classroom
Virtual internet service
Campus internal communication service system
Campus Network bulletin board system Campus Internal E-mail
Campus homepage
Campus BBS
Overview of hardware scheme
It mainly adopts Ethernet network equipment of CISCO, 3COM, ACCTON and other companies, servers of IBM, HP, CENTURY and other companies or brands, and integrated wiring products of ORTRONICS, AMP and other companies.
The main equipment are:
Design requirements of campus network
I. Modern Education Center (Network Management Center)
1. Ten multimedia classrooms (10 computer room, 52 rooms/room, bandwidth 10K).
2. Voice classroom (10,52/room)
3. Projection classroom (6, 1/ classroom)
4. Office computer (10)
5. Electronic reading room (100)
6. Computer room (50 for 600 and 50 for 200 (there are 8 computer rooms))
Two. Administration Center of Administration Building (86 information points)
1.5 sets of planned finance
2. The hospital has set up 2 sets.
3. Two TV stations run by the Party.
4. Enrollment and Employment 1 unit
5. General Affairs Section 3
Three. Teaching building (3 teaching buildings (optical fiber))
No.1 teaching building (64 points)
No.2 teaching building (46 points)
No.3 teaching building (57 points)
Four. Experimental building (2 experimental buildings)
1 Laboratory Building 1 14 points (major)
Laboratory Building No.2 122 is ordinary (for chemical engineering, seiko and office use).
Verb (abbreviation for verb) library
75 office computers
Two electronic reading rooms, 100 units/unit.
design instruction
5. 1 system overview
Network platform plays an important role in the whole campus network system and is the foundation of the whole network. On the network platform, data transmission, information release, resource sharing, BBS, office automation system, VOD system, distance education system, NTERNET interface and data exchange with other brother schools will all run on this network. Therefore, the quality of backbone network directly affects the operation efficiency, speed and network performance of future network systems. Therefore, establishing a high-speed, multi-functional, reliable and easy-to-expand backbone network to solve the existing bandwidth problem and meet the needs of future development is an important topic in campus network construction.
1. Construction target
The overall goal of campus network construction is to build a high-speed computer network system that can realize various comprehensive network applications by using various advanced and mature network technologies and communication technologies and adopting a unified network protocol (TCP/IP), and all departments in the campus are connected through the network.
The network should not only have the general functions on the network, such as e-mail, FTP, online forum, online library, search engine, online chat, data transmission management, processing and inquiry, but also realize the functions of video on demand, teleconference, Internet phone (IP phone) and so on. It is a high-speed multimedia internet, and finally realizes the resource sharing of the whole campus system.
Through the integration of network system resources, we can change the traditional mode and realize multi-level and interaction, thus improving the quality and expanding the scale.
2. Construction principles
2. 1 Serve the administrative management, computer-aided teaching and leadership decision-making of all departments in the school.
2.2 overall planning, unified standards, joint construction, rolling development, while building, while applying, while seeing benefits, make full use of the advantages of Chinese government network, and gradually establish an efficient information network system covering ordinary government systems in cities and counties.
2.3 Pay full attention to the security of network systems and information, and establish an advanced network management system and security management system. Establish a complete information control and authorization management mechanism.
2.4 In a limited time and scale, efforts should be made to reduce costs and improve the cost performance of the system.
2.5 Adopt mature advanced technology, take into account the future development trend, do what you can, advance appropriately, and leave room for development.
2.6 Give full play to the enthusiasm of all parties and build computer networks and information networks simultaneously.
3. Realize the function
It is required that it can not only realize the general functions on the existing network, such as e-mail, FTP, online forum, online library, search engine, online chat, data transmission, processing and query, but also realize the functions of video on demand (VOD), video conference, Internet phone (IP phone) and so on. It is a high-speed multimedia internet, which can realize the resource sharing of the whole campus system.
4. Main technical problems
4. 1 Build Gigabit network backbone
From the congested10 Mbps * * workgroup LAN to today's high-performance network backbone, with the evolution of the network to today's arbitrary point-to-point connection mode, the demand for border applications forces network vendors to continuously develop several generations of higher-performance LAN technologies.
Layer 2 switches began to provide hardware-based packet processing capabilities. Layer 3 switching capability enables them to replace other functions of LAN routers to speed up the transmission speed of backbone networks. Today, network managers have regarded Layer 3 switching as a practical need to expand the core performance of the backbone.
Layer 3 switching. Layer 3 switches retain the advantages of Layer 3 topology and services without the disadvantages of traditional LAN routers that process data packets based on software. Layer 3 topology has many beneficial advantages in network segmentation, security, manageability and broadcast suppression. In addition, its ability to identify various application layer protocols helps to implement policy-based network control. Therefore, the next generation switch must support hardware-based packet processing to promote the transmission of various major routable protocols: IP, IPX and AppleTalk.
The main design limitation of bus-based switches is the operating frequency that TDM must adopt. On the standard 19 inch backplane, the frequency is extremely difficult to exceed 50MHZ. Due to this limitation, the actual maximum capacity of the backplane of a bus-based switch averages 2Gbps. In addition, there are still many problems in this design, including the ability of live replacement of interface cards, fair access to bandwidth, and effective support of parallel backplane for broadcasting and multicast, which further increase the inherent complexity of this design.
4.2 Information security issues
The insecurity of user information is mainly caused by the fact that users are in the Ethernet environment. Therefore, in order to ensure the security of user information, it is necessary to isolate users in the Ethernet environment. At present, VLAN technology is mainly used, which is defined by IEEE802.3q and IEEE 802.1q. The basic idea is that for each layer of equipment, the downlink ports are in a VLAN. The upstream port is in the VLAN of each port, and the transmitted Ethernet frame is a traditional Ethernet frame without VLAN ID. On the one hand, the number of users supported by the network is not limited by the number of VLANs; on the other hand, when assigning static IP addresses, users only need to be assigned an IP address.
5. Network planning
There are 1 south teaching building, north teaching building, experimental building and library building in the campus. More than 200 information points. Generally speaking, for the sake of network security and performance, medium-sized networks need to be divided into multiple VLAN, which can be divided according to different classes and units, or according to user IP subnets. Computer classrooms and users visiting various office departments can't communicate with each other, so they can only access campus network resources, thus shielding the broadcast storm. With the help of Layer 3 switch, cross-VLAN access can be realized.
Building access switches should have Gigabit uplink ports, which can increase the density of access ports by stacking or adding modules, support network management protocols such as SNMP, and monitor and manage the status of all devices through the network. Gigabit DES-3624 series switches, 1 master switch DES-3624i, can be stacked with up to 3 slave switches DES-3624, providing 9410100base-tx ports. DES-3624i can be downloaded from 1 port 1000Base-T module DES-36 1T, 1000Base-SX module DES-36 1G and1000base-. Of course, 1 SC or 2 MT-RJ 100Base-FX optical fiber modules can also be extended on the front panel slots of DES-3624i and DES-3624 to realize long-distance 100 megabits uplink.
Gigabit series switches support port trunking, VLAN, flow control and port mirroring, which can increase network connection bandwidth, improve network performance and make the network easier to monitor. IGMP multicast protocol can effectively reduce the network traffic during multimedia transmission. Support SNMP and RMON network management protocols, meet the requirements of standardized network management, and can be monitored, managed and remotely configured through the D-View full Chinese network management system of the network.
If the school doesn't need to exchange technology three times for the time being, here we provide two schemes for comparison and selection, and explain their network design respectively.
5.2 backbone network design
Three-layer switching scheme
1. Wiring and network planning
Establish a network center (laboratory building) to connect all buildings (library building and south and north teaching buildings); According to the distance between the network center and the building, outdoor armored 4-core single-mode optical fiber wiring is used to adopt link aggregation technology and backup lines. Optical fiber wiring adopts star structure, that is, it radiates from the network center of the experimental building to other buildings. Six types of twisted pair are used for vertical and horizontal wiring in buildings. If the building is large, indoor multimode optical fiber can also be partially used.
Network structure includes network center and building equipment room. Because the number of information points in the North Teaching Building, the South Teaching Building and the Experimental Building is less than 90, stacking switches can be used to connect directly to the desktop between building equipment, thus reducing the network level and improving the reliability and manageability. Because there are many information points in the library building, it is suggested to use DHS-3226 as the access switch in the building.
2. Core switch
The central switch adopts D-Link Gigabit DGS-3308FG independent three-layer switch with network management. This kind of switch combines the performance of two-layer and three-layer switches, integrates IP routing function, and replaces CPU with ASIC chip, which greatly enhances the transmission performance of building switches. According to the fact that DGS-3308FG is a three-layer switch with full Gigabit interface, it has six 1000Base-SX ports and two GBIC slots. According to the actual demand, DGS-DGS-7011000base-sx or DGS-702 1000Base-LX can be selected to connect the GBIC interface module. 16Gbps switch backplane can provide line-speed packet forwarding rate of 12 Mbps, and supports RIP, RIP II and OSPF routing protocols. It is a campus network center switch with high cost performance.
IEEE802.3x flow control allows multiple servers to connect with the switch to realize fast and reliable data transmission. In 2000M full-duplex mode, the switch can provide high-speed data transmission channel to the server, thus minimizing data transmission loss. DES-3624i switch supports SNMP and other network management protocols, which is convenient for monitoring and managing the status of all devices through the network. Support IEEE802. 1d spanning tree protocol.
Each building access switch adopts gigabit DES-3624 series or DES-3226 trunk switch.
DES-3226 is an independent switch with 24 1 0100base-TX ports. The backplane can be plugged with1Gigabit modules, with a bandwidth of 8.8Gbps, which is suitable for floors with few users. DES-3226 can select two 1000Base-T modules DES-322T, two 1000Base-SX modules DES- 132G and two 1000Base-LX modules DES- 132GL. The front panel slot can be expanded with 1 port or 2 ports of SC 100Base-FX multi-film optical fiber module DES-131f/132f, realizing long-distance 100 megabits uplink. The front panel slot can also be expanded with 1 port or two SC 100Base-FX single-film optical fiber modules DES-131fl/132fl, so as to realize ultra-long 100-megabyte uplink.
Connect 100M to the desktop with EDS- 1624 switch as the polarity switch.
3. Network management and storage
The network management server is equipped with a D-View network management system, which can monitor and manage all network devices.
The network center is equipped with NL360 network storage server for storing courseware and e-books.
4. Connection between Hangzhou Distance Education Network and Internet.
The school is equipped with the receiving equipment of Hangzhou Distance Education Network. In addition, if you want to improve the autonomy of internet access, you can apply for renting an ADSL line to realize private internet access. If necessary, the 1 ISDN module can be installed for link backup.
Configure NL360 network storage server as WWW, FTP and email server.
In order to ensure network security, prevent external invasion and control the access behavior of internal users, DFL-2000 firewall can be installed between the router or proxy server and the campus network.
5. Program function
Adopt high-performance three-layer switching technology to ensure the high performance and high security of large campus network;
Have operator-level fault tolerance to ensure the high reliability of the network;
Support a variety of network interface types, including MAN remote connection;
Enhanced multimedia and QoS function support, which can meet the needs of large-flow multimedia transmission;
The Chinese network management system is easy to manage and maintain.
Using DGS-3308FG and DES-3624 stack groups, the number of new modules and stack switches can be increased according to the development of campus network, which has strong expansibility.
It can support a variety of rates and media types, upgrade and expand the network backbone while making full use of the original equipment, and has high flexibility.
Support D-View full Chinese network management system, which is easy to manage and maintain;
6. Relevant equipment parameters
DGS-3308FG
1 DB-9 RS232 control port
Switching mode: store/forward
Routing protocols: RIP- 1, RIP-2.
MAC address list: 8K per device
IP routing table: 2K per device
RMON group: 1, 2, 3, 9
Automatic identification of IP address: through DHCP client and Bootp client.
Front panel fault diagnosis LED indicator
Built-in universal power supply
Standard 19 inch rack
Emi: FCC class a, C-Tick, VCCI a class, BSMI a class.
Safety: UL/CUL, TUV/GS
5.3 server technical parameters
The server is the place where the network server is used the most. The selection criteria of servers largely depend on the types of central customers and application types. As far as primary and secondary schools are concerned, Web applications and database applications still account for the main part of all kinds of applications in the whole data center. Therefore, the responsiveness of the network to the server largely reflects the rationality of the server hardware architecture design, the ability of CPU or SMP to allocate processes or threads of the operating system, and the performance of disk I/O. As well as the feasibility and stability, and heat dissipation, power consumption and easy installation are also the key inspection and evaluation objects. Based on the above considerations, the selected server must have the characteristics of high reliability, strong I/O throughput, fast data processing speed, good scalability and manageability.
reliability
Redundancy is an important means to eliminate single point failure of the system. It can be divided into component level and system level. System-level redundancy refers to the redundancy of the whole server system, and component-level redundancy mainly includes the following points:
1, hot plug redundant power supply
2. Hot-swap redundant disks and RAID technology
3. Memory fault tolerance with ECC check
4. CPU redundancy supporting SMP technology.
5. Redundancy and fault tolerance of multiple I/O cards (network card and disk controller)
6. Multi-segment PCI bus redundancy
7. Input and output throughput capacity
The server can provide network platform, file service, printing service, website information browsing service and other Internet/intranet services. In order to speed up access and get quick response, the network, hard disk and I/O throughput are required to be larger, which can be considered from the following aspects:
1, using PCI bus concurrent operation to improve the system I/O throughput.
2. Support intelligent I/O technology, reduce the burden of main CPU and optimize bus transmission.
3. Adopt advanced SCSI technology.
4. Support high-speed hard disk with 10000 rpm or more, and the track patrol time is less than 7 ms.
5. The server with the I/O throughput of the above advanced technology can completely meet all the service requirements of the campus network at present and in the future.
Powerful processing ability
The data processing ability of the server is mainly determined by the processing ability of CPU, expandable large-capacity memory and system bandwidth.
1, CPU Pentium 4 2.0 dual processor;
1, supporting GB ECC and EDO memory;
2. Support 400 MHZ and above parallel FSB bus.
3. Only the server that meets the above conditions can break through the bottleneck and improve the system bandwidth of the server.
4. Integrated dual 1000M network controller.
High expansibility
Considering the expansion of network scale in the future, high scalability must be considered when selecting servers. With the support of additional devices, the server can support higher performance and speed.
maneuverability
In order to ensure the normal operation of the whole system and reduce the cost of network maintenance, it is necessary to use a server with excellent system management function. Specific indicators are as follows:
1, which supports external management bus (XIMB) and ISC(Intel server control) management software to realize remote management of the system;
2. Monitor the system motherboard, power supply, temperature in the chassis and fan status, and give an alarm through the network in time;
Another common method can greatly improve the security of the server, which is clustering.
Schematic diagram of dual-machine hot standby:
Inspur Xin Ying NL360 server technical indicators:
High performance: NL360 adopts powerful Xeon processor, supports hyper-threading technology, can simulate four processors based on two physical processors, and has strong transaction processing ability; Dual-channel Ultra 160 SCSI controller, combined with the latest DDR memory and PCI-X technology, greatly improves the data transmission rate, can maximize the capabilities of high-performance devices such as 1000M network card, and break through the bottleneck of traditional data transmission.
High reliability: ECC memory used in NL360 can correct most memory errors and reduce downtime; RAID technology provides NL360 with absolutely reliable data protection and accelerated transmission functions. Redundant dual power supplies can make the system run continuously 24*7. Dual Gigabit network cards can realize high-speed data transmission through network card redundancy technology to ensure smooth network.
High availability: NL360 supports hot-swappable hard disks and hot-swappable power supplies, which facilitates online maintenance, keeps users' key business uninterrupted, and eliminates data disasters.
High scalability: NL360 supports dual-channel Xeon processors at most, and its storage can be expanded to 4 built-in and 9 hot-swappable hard disks at most, and it can aggregate up to nearly 1000G of mass storage, and the DDR memory can reach 1.2 GB. Coupled with the application of dual power supply, users can easily upgrade according to their own needs to meet the demanding requirements of rapidly growing business data and work tasks.
Manageability: NL360 adopts standard server management: it supports the monitoring of CPU temperature, system voltage and fan speed; Support AC power failure recovery; In addition, NL360 also supports blue dolphin intelligent installation navigation software and Falcon server management software independently developed by Inspur. All the designs make it easy for users who lack professional managers to manage their own business and greatly reduce the total cost of ownership.
Technical specifications:
This processor supports two Intel Xeon processors with a maximum frequency of 2.2GHz.
Secondary cache 5 12KB
System bus 400MHz
Memory ECC registers DDR memory, and the maximum capacity can be extended to 12GB.
Hard disk controller dual channel Ultra 160 SCSI controller
Store 4 internal hard disks and 9 hot-swappable hard disks, and support18g/36g/73g ultra160 SCSI hard disks.
I/O expansion slot 1 64-bit 133MHz PCI-X expansion slot; Two 64-bit 100MHZ PCI-X expansion slots; 1 64-bit 66MHz PCI-X expansion slot and 2 32-bit 33MHzPCI expansion slots.
The network integrates two Intel 1000Mbps network controllers.
Display integrated 8M video memory.
Power supply 460W or 550W single power supply, optional 1+ 1 400W tower dual power supply.
Optical drive 50x IDE optical drive
Floppy drive1.44m 3.5-inch floppy drive
Keyboard mouse PS/2 keyboard and PS/2 mouse
I/O port 1 serial port, 1 parallel port and 2 USB ports.
The monitoring and management function supports Inspur Blue Dolphin to intelligently install navigation software, which can easily complete system setup, driver production and automatic installation of operating system. Support Inspur Falcon server management software, which can realize comprehensive server equipment information monitoring, automatic alarm and recovery, remote management and other functions.
Operating systems Windows NT4.0, Windows 2000 Server, Netware5.0, UnixWare7. 1 1, Red Hat Linux7.3.
The working environment temperature is 5℃~35℃
The power supply voltage is 220 volts and 50 hertz.
The system size is 467mm* height * 376mm* width * 5 18mm depth.
Inspur Xin Ying NP 120 server technical indicators:
High performance: NP 120 adopts Xeon processor and supports hyper-threading technology. It can simulate two logical processors on the basis of 1 physical processor, and effectively improve resource utilization. At the same time, Xeon processor has 5 12KB large-capacity secondary cache, which reduces the time to extract data from the processor to the hard disk and significantly improves the system performance. The transfer rate of DDR memory is twice that of SDRAM. Among the disk systems that are prone to performance bottlenecks, NP 120 uses 10000 rpm SCSI hard disk, which greatly improves the data transmission rate through dual-channel Ultra 160 SCSI controller. As the central equipment of the network, the quality of data exchange between the server and the outside world is very important. NP/KOOC-0/20 is equipped with/KOOC-0//KOOC-0/000 M and/KOOC-0//000 M network controllers, which have high network bandwidth and support network load balancing, and can reasonably allocate network bandwidth for different tasks and improve work efficiency.
High reliability: NP 120 adopts ECC DDR memory, which can correct most memory errors and reduce downtime;
NP 120 supports network card redundancy, provides redundant links, and ensures smooth network at all times.
Concluding remarks
The quality of design scheme, especially the campus network. It is closely related to the designer's mastery of all aspects of his computer hardware.
In the process of networking, due to my limited network knowledge and complete independence, it can be said that the whole networking process is groping and practicing. But happily, through such a learning and application process, I completed the networking of the campus network. Considering the factors of price and performance, I went to many computer hardware manufacturers when writing this paper, which made me have a great understanding of it and spent some time.
But on the whole, this scheme still has many shortcomings. For example:
Limited by the development conditions and time, this scheme is only a simple operation that reflects the gradual mode of small LAN.
These are all areas that need improvement. The network is far from reality and needs me to enter.
The line is constantly supplemented and improved. Through this graduation project, I learned a lot of new things and found many problems, some of which have been solved in the design process, and some have yet to be learned slowly in the future.
As long as you study, you will have more problems and difficulties, but you will gain more.
Take the exam and contribute.
[1] Network Basic Machinery Industry Press, 2002
[2] LAN connection and maintenance, Electronic Industry Press, 2002
[3] 100 Network Fault Case, Machinery Industry Press, 2002.
[4] Hands-on instructions-LAN assembly and maintenance, 200 1
[5] Campus Network Technology and Management Zhang Jiping editor Southeast University Press, 200 1
[6] Lan. Stratum and Management. edited by Hao Wenhua. Machinery Industry Press, 2003.