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Knowledge networks are social networks that bring together knowledge participants. It can create and transfer knowledge between individuals, organizations and outside organization, and people can collaborate and share information through a knowledge network. The goal is to connect technology with people and realize an effective combination of intellectual capital, structural capital and client capital. It can be divided into an internal knowledge network and an external knowledge network. The former emphasizes sharing of knowledge between employees and organizations within organization, while latter emphasizes sources of knowledge outside organization, including communities, national and social relationships, and competitors. The following are basic network details collected and compiled by editor. Sample essays for study, welcome to review.

Summary and study of basic knowledge of network (1)

1. Making a connecting line of a network cable (twisted pair)

There are two twisted-pair manufacturing standards, 568A and 568B, with 568B being more commonly used in everyday life. The 568B standard is sorted by colors: 1 - orange and white, 2 - orange, 3 - green and white, 4 - blue, 5 - blue and white, 6 - green, 7 - brown and white, 8 - brown (standard 568B). can be converted to standard 568A Medium orange-green interchangeable, orange-white green-white interchangeable), a straight line is to ensure that twisted-pair pin sequence at both ends of twisted-pair is same; Green and white match (you can understand that one end adopts 568A standard and other end adopts 568B standard).

Once network cable is done, next big problem is network testing. The most commonly used parameters for network testing are [-t] and [-a]. The following methods can be used to check network connectivity, correct installation and settings of network card: firstly, ping 127.0.0.1 to check network loopback, and secondly, ping local IP address to verify that network card is installed correctly. and settings are not corrupted; Address to check if network cable is well connected and whole network is working smoothly; last thing to check is ISP's DNS (some ISPs prohibit IP address Ping DNS server, which is worth noting) or gateway to see if internet connection is broken.

2. Network troubleshooting

There are many reasons why some networks cannot be connected during network operation or system installation. With exception of some settings or programs that prevent network connection, most of them are caused by following reasons:

1. The network card is installed incorrectly or there is a problem with network card itself. Generally, when a network card is inserted, system does not prompt whatstarts that network card is inserted incorrectly or there is a problem with interface; after installing driver, ping loop goes through correctly, but own IP ping fails. , first check if there is a problem with network card; , you should first check if there is a problem with network cable or network card interface. The best way to detect a network card is replacement method, that is, using a problematic network card to replace a regular network card of same model. Before using replace method, it's better to check if local NIC is inserted. You can also try another slot.

2. Problems with TCP/IP protocol. There is a problem with inability to communicate between microcomputers, in most cases caused by TCP/IP protocol. Since TCP/IP protocol itself is very fragile, communication can be easily broken. The general performance is that communication between neighboring computers cannot be established (I cannot find it among network neighbors or search computers). ;But I can't communicate. The solution to this problem is to re-add TCP/IP protocol. Special care should be taken to add TCP/IP protocol on systems released after Win 2000. Removing this protocol may cause system to crash, so make sure protocol can be added correctly before restarting. Detection method: After fixing connection errors and NIC interface errors, ping local computer's IP connection, but neighboring computer cannot communicate. You should pay attention to whether failure is caused by TCP/IP protocol.

3. Problem with driver. This problem mainly occurs with some brand name network cards. Since there is no correct driver, only some compatible drivers can be used, which leads to various unexpected problems. The detection method is that ing loop works correctly, but ping of one's own IP address fails, indicating that there may be a problem with network card driver (the cause of network card hardware failure should be ruled out) and network card driver. not installed correctly.

4. Problem with network setup. The network settings include IP, mask, gateway and DNS, etc. Dial-up Internet access also includes a username and password. Therefore, after a network failure occurs, first check if there is a problem with settings. Some networks that use DHCP services make this problem much easier, and you don't have to configure network yourself.

3. Solutions to common network maintenance errors

1. Slow access to My Network Places. Not only is connection between computers very slow, but only a subset of them can be found.

First, because you see some computers, it means that network connection is normal, and network card driver and network communication protocol are installed correctly;

Secondly, byas long as IP address and subnet mask are correct, it means that IP address information is correct; thirdly, since domain name is same as workgroup name, you will be able to find other users in same group. working group very quickly. Then there may be following reasons: a) NetBEUI protocol is not installed. TCP/IP is a low-performance protocol, so a small local area network usually uses NetBEUI protocol, which takes up less system resources and is more efficient.

b, network card driver is defective. Although many network cards use same chipset, drivers are not identical. While faulty drivers do not necessarily cause communication failures, they often reduce transmission efficiency. Therefore, you should make sure that network card driver is selected and installed correctly.

2. When to use a straight line and when to cross?

a. Crossing lines should be used in following situations:

I. When two computers are connected directly via a network card;

II. When cascading common ports of a hub or switch.

b. Straight cables must be used in following situations:

I. When computer is connected to a hub or switch;

II. When a hub or switch is connected to shared port of another hub or switch with an Up-Link port;

III. When a hub or switch is connected to router's LAN port.

in. Both straight and crossover cables can be used in following cases:

I. The RJ-45 port of hub or switch has a polarity recognition function, which can automatically detect connected device at other end and automatically switch between MDI/MDI-Ⅱ;

II. A specific port of hub or switch is equipped with an MDI/MDI-Ⅱ switch, which can be used to connect to other hub devices with straight-through or crossover cables by switching switch.

3. Hub + Router cannot share Internet. There can be three reasons why a computer connected to a hub cannot access Internet:

a. The hub itself is faulty. The symptom is that computers on hub cannot ping each other, let alone router. This failure only affects all computers connected to hub.

b) Cascading failure. For example, cascading jumper between router and hub is using wrong line sequence, jumper connection is wrong, or wrong cascading port is being used. The symptom is that computers on hub can ping each other, but router can't. However, this will not affect Internet access from computers connected directly to router's LAN port.

c. Broadband router failure. If it failsmouth of LAN, result will be similar to a cascading failure. Connect to a hub.

4, optical transmission and reception of "local connection" may be caused by following reasons.Reason:

a. The network card is incompatible or incompatible with Windows XP. Try installing other operating systems.

b, There is a problem with network cable. Although replacement method has been tested, it is best to move failed computer to a computer connected to network for replacement.

c, if network card is adaptive 10/100 Mbps, you can try to set speed of network card to 10 Mbps (select properties of network card, click "Configuration" button in "General" tab and click "Advanced Tab" button Under Link Speed/Duplex Mode, select 10 Half Mode).

d, "There are bytes sent, but number of bytes received is 0", indicating that line is sending data normally, but there is a reception problem. Therefore, probability of a connection failure is greatest, and it may also happen that connector (crystal head and RJ45 port of network card, hub and data connector) is not in good contact.

5, IP address conflict. This means that IP address taken by this computer is exactly same as that of another computer on same network, causing communication to fail. Typically, IP address conflicts are caused by misallocation of IP addresses by network administrators or by accidental setting of IP addresses by other users. Since MAC address of a network card is unique, you can ask network administrator to find computer that is in conflict with you by MAC address and order it to change IP address. Use "ipconfig /all" command to view computer's IP address and MAC address. Finally, use "ARP -s IP address physical address of network card" command to associate this legal IP address with MAC address of your network card.

4. General Network Troubleshooting Steps

The first step in network failure analysis is to understand failure phenomenon.

Describe in detail symptoms and possible causes of failure. To this end, it is necessary to determine specific failure phenomenon, and then determine type of cause of failure phenomenon. For example, host is not responding to client requests for service. Possible reasons for failure are host configuration issues, interface card failure, or loss of router configuration commands.

In second step, gather information you need to identify possible cause of failure. Ask users, network administrators, administrators, and other key personnel questions about outage. Extensive collection of useful information from network management systems, protocol analysis traces, reports router diagnostic command outputs, or manuals software.

The third step is to consider possible causes of malfunction based on information collected. SomeThe causes of malfunction can be ruled out depending on relevant circumstances. For example, based on certain data, you can exclude hardware failures and pay attention to software causes. Whenever possible, try to reduce possible causes of failure so that an effective failure diagnostic plan can be planned as soon as possible.

The fourth step is to make a diagnostic plan according to latest possible causes of malfunction. Start diagnostic activity with only one of most likely causes of failure so that you can easily restore original failure state. Attempting to return to original state of fault is much more difficult if more than one cause of fault is being considered at same time.

The fifth step is to implement a diagnostic plan and carefully perform each step of testing and observation until symptoms of malfunction disappear.

The sixth step is to validate result each time parameter is changed. Analyze results to determine if issue is resolved, and if not, continue until it is resolved.

Summary and study of basic knowledge of network (2)

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53----DNS System Protocol

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80----Hypertext Transfer Protocol (HTTP)

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443----Hypertext Transfer Protocol Secure (HTTPS)

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1863----MSN communication port

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109----Post Office Protocol v.2 (POP2)

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110----Post Office Protocol v.3 (POP3)

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995----Secure Post Office Protocol v.3 (POP3S)

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143----interactive mail access (IMAP)

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993----Interactive Mail Access Security Protocol (IMAPS)

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25----Simple Mail Transfer Protocol (SMTP)

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465----Special Note: Secure Simple Mail Transfer Protocol (SMTPS) in ISA/TMG uses port 587 (SMTPS) in Exchange

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119----Network News Transfer Protocol (NNTP)

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563----Network News Transfer Protocol for Security (NNTPS)

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23----Telnet protocol

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68(UDP)----DHCP (response)

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67(UDP)----DHCP (request)

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546----DHCPv6 protocol

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389----Lightweight Directory Access Protocol (LDAP)

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636----Lightweight Directory Access Protocol Secure (LDAPS)

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3269----Security Lightweight Directory Access Protocol

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50389----Lightweight Directory Protocol used by Exchange Server EdgeSync process

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50636----Lightweight directory access protocol used by Exchange Server EdgeSync process

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137----NetBIOS Name Service Protocol

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138----NetBIOS Datagram Protocol

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139----NetBIOS session protocol

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123----Internet Time Protocol (UDP)

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520----Routing Information Protocol

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161----Simple Network Management Protocol (SNMP)

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162----Simple Network Control Protocol - Traps

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9988----Windows Communication Foundation protocol.

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5355---- Local link multicast name resolution

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7----echo protocol (TCP/UDP)

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135----Exchange Server Publishing Protocol for RPC access from external networks.

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79----Joint program protocol

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21----FTP File Transfer Protocol

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8080 --- The protocol used by HTTP clients (such as Internet Explorer) to send HTTP requests to HTTP outbound proxies.

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1494----Citrix Smart Console architecture protocol

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1723----PPTP

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1701----L2TP

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445----Microsoft CIFS

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1433----Microsoft SQL

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1755----Microsoft Media Streaming Protocol (MMS)

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1812 --- Dial-in Remote Authentication Service (RADIUS) protocol

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1813 --- Dial-up Remote User Authentication Accounting Protocol

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3389----Remote Desktop Protocol (Terminal Services RDP)

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520----Routing Information Protocol (RIP)

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513----Remote login protocol (Rlogin)

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135----RPC protocol

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554 ---- Real Time Streaming Protocol (RTSP)

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5060----Session Initiation Protocol - Outgoing protocol for establishing VOIP and IM sessions. (SIP)

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5061----SIP over TLS is an encrypted outbound protocol for establishing VOIP sessions and instant messaging. (SIPS)

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1080----A protocol that allows client/server applications to use network firewall services. (SOCKS)

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22----Secure Shell Protocol (SSH)

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3544----Teredo protocol

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69----Simple File Transfer Protocol (TFTP)

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43----Whois alias/protocol (WhoIs)

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9988----Windows Communication Foundation protocol. (WCF)

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Resume and study basic knowledge of network (3)

1) What is a link?

A link is a connection between two devices. It includes cable types and protocols usedused by one device to communicate with another.

2) What are layers of OSI reference model?

There are 7 OSI layers: physical layer, data link layer, network layer, transport layer, session layer, presentation layer and application layer.

3) What is a backbone network?

A backbone network is a centralized infrastructure designed to distribute different routes and data across different networks. It also manages bandwidth and various channels.

4) What is a local network?

LAN is short for Local Area Network. It refers to connection between a computer and other network devices located in a small physical location.

5) What is a node?

A node is a point where a connection occurs. It can be a computer or a device that is part of a network. Two or more nodes are required to form a network connection.

6) What is a router?

A router can connect two or more network segments. These are intelligent network devices that store information such as paths, hop counts, etc. in their routing tables. With this information, they can determine best route for data transfer. Routers operate at OSI network layer.

7) What is a two-dot link?

Indicates a direct connection between two computers on network. A peer-to-peer connection does not require any other network equipment other than connecting cables to network cards of two computers.

8) What is anonymous FTP?

Anonymous FTP is a way to give users access to files on public servers. Users who are allowed to access data on these servers do not need to identify themselves, they must be logged in as anonymous guests.

9) What is a subnet mask?

The subnet mask is combined with IP address to identify two parts: extended network address and host address. Like an IP address, a subnet mask is 32 bits long.

10) What is maximum allowed UTP cable length?

One segment of UTP cable has an allowable length of 90 to 100 meters. This limitation can be bypassed using repeaters and switches

11) What is data encapsulation?

Data encapsulation is process of breaking information into smaller, manageable chunks before it is sent over network. During this process, source and destination addresses are added to header, along with parity.

12) Describe network topology

Network topology refers to layout of a computer network. It shows physical location of devices and cables, and how they connect to each other.

13) What is

___

___ stands for Virtual Private Network, a technology that allows a secure channel to be created over a network such as Internet.

For example, ___ allows you to setl secure dial-up connection to a remote server.

14) Briefly describe NAT.

NAT stands for Network Address Translation. It is a protocol that allows multiple computers on a public network to share a single Internet connection.

15) How does network layer work in OSI reference model?

The network layer is responsible for data routing, packet switching, and network congestion control. Routers operate below this layer.

16) How does network topology influence your decisions when building a network?

The network topology determines which medium should be used to connect devices. It also serves as basis for materials, connectors and leads suitable for installation.

17) What is RIP?

RIP, short for Routing Information Protocol, is used by routers to send data from one network to another.

It efficiently manages routing data by broadcasting its routing table to all other routers on network. It determines network distance in jumps.

18) What are ways to protect computer networks?

There are several ways to do this. Install a reliable and up-to-date antivirus program on all computers. Make sure firewall is installed and configured correctly. User authentication would also be very helpful. All this together forms a highly reliable network.

19) What is a network card?

Network Card is an abbreviation for Network Interface Card. This is connected to a PC to connect to Shenbei network. Each network card has its own MAC address, which identifies PC on network.

20) What is a WAN?

WAN stands for Wide Area Network. It is interconnection of geographically dispersed computers and devices. It connects networks located in different regions and countries.

21) What is importance of OSI physical layer?

The physical layer performs conversion of data bits into electrical signals and vice versa. This is a consideration and setup for network equipment and cable types.

22) How many layers are there in TCP/IP?

There are four layers: network layer, internet layer, transport layer, and application layer.

23) What are proxy servers and how do they protect computer networks?

The proxy server primarily prevents external users from identifying IP address of internal network. Not knowing correct IP address or even determining physical location of network. A proxy server can make a network virtually invisible to outside users.

24) What is function of OSI session layer?

This layer provides protocols and methods for communicating between two devices on a network by holding sessions. This includes setting up session, managing exchange of information during session, and unwind process after session ends.

25) How important is implementationie fault-tolerant system? Are there any restrictions?

Fault-tolerant systems ensure that data is always available. This is achieved by eliminating single points of failure. However, there are certain situations where this type of system will not be able to protect data, such as accidental deletion.

26) What does 10Base-T mean?

The number 10 means data transfer rate, in this case 10 Mbps. "Base" means main band. T stands for twisted pair, which is cable used for this network.

27) What is a private IP address?

Dedicated IP addresses are assigned for use on internal network. These addresses are used on internal network and cannot be routed on external public network. This ensures that there are no conflicts between internal networks, while a private IP address range can also be reused across multiple internal networks as they do not "see" each other.

28) What is NOS?

NOS or Network Operating System is specialized software whose main task is to provide a computer with a network connection so that it can communicate with other computers and connected devices.

29) What is DoS?

A DoS or Denial of Service attack is an attempt to prevent users from accessing Internet or any other network service. This attack can come in many forms, consisting of a group of permanents. The usual way to do this is to reboot system server so that it can no longer handle legitimate traffic and is forced to reboot.

30) What is OSI and what role does it play in computer networks?

OSI (Open Systems Interconnection) as a reference model for data communication. It consists of 7 layers, and each layer defines a specific aspect of how network devices connect and communicate with each other. One layer can deal with physical media being used, while another layer determines how data is actually transferred over network.

31) What is purpose of cable shielding and twisted pairs?

Its main purpose is to prevent crosstalk. Crosstalk is electromagnetic interference or noise that can affect data transmitted over a cable.

32) What are benefits of sharing addresses?

Address sharing provides inherent security benefits by using address translation rather than routing. This is because hosts on Internet can only see public IP address of external interface on computer providing address translation, and not private IP address on internal network.

33) What is a MAC address?

MAC, or Media Access Control, uniquely identifies a device on a network. It is also known as a physical address or Ethernet address. Status MAC addresst of 6 bytes.

34) What is equivalent TCP/IP application layer or layers in terms of OSI reference model?

The TCP/IP application layer actually has three peers in OSI model: session layer, presentation layer, and application layer.

35) How can I determine IP class of a given IP address?

By looking at first octet of any given IP address, you can determine if it is in class A, B, or C. If first octet starts with bit 0, address is in class A. If it starts with bit 10, address belongs to class B. If it starts with 110, then it is a class C network.

36) What is main purpose of OSPF?

OSPF, or Open Shortest Path First, is a link-state routing protocol that uses routing tables to determine best path for communication.

37) What is a firewall?

Firewalls are used to protect internal networks from external attacks. These external threats can be hackers who want to steal data, or computer viruses that can destroy data instantly. It also prevents other users from external networks from accessing private network.

38) Describe star topology

A star topology consists of a central hub connected to nodes. It is one of easiest to set up and maintain.

39) What is a gateway?

A gateway provides a connection between two or more network segments. This is usually computer that runs gateway software and provides translation services. This translation is key to allowing different systems to interoperate on network.

40) What are disadvantages of a star topology?

The main disadvantage of a star topology is that once central hub or switch is damaged, entire network becomes unusable.

41) What is SLIP?

SLIP or Serial Line Interface Protocol is actually an old protocol developed in early days of UNIX. This is one of protocols used for remote access.

42) Give some examples of private network addresses.

10.0.0.0 with subnet mask 255.0.0.0

172.16.0.0 with subnet mask 255.240.0.0

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192.168.0.0 with subnet mask 255.255.0.0

43) What is tracert?

Tracert is a Windows utility that can be used to trace data collection path from router to target network. It also shows number of hops completed during entire transmission route.

44) What is function of a network administrator?

A network administrator has many responsibilities that can summarize into 3 main functions: network setup, nnetwork settings and network maintenance/troubleshooting.

45) Describe disadvantages of peer-to-peer networks.

When you access a resource that is shared by a workstation on a network, performance of that workstation is degraded.

46) What is a hybrid network?

A hybrid network is a network configuration that uses a client-server architecture and a peer-to-peer network.

47) What is DHCP?

DHCP is an acronym for Dynamic Host Configuration Protocol. Its main task is to automatically assign IP addresses to devices on network. It first checks next available address that is not already occupied by any device and assigns it to network device.

48) What is main purpose of ARP?

The main job of ARP or Address Resolution Protocol is to map known IP addresses to MAC layer addresses.

49) What is TCP/IP?

TCP/IP is an acronym for Transmission Control Protocol/Internet Protocol. It is a set of protocol layers designed to communicate across different types of computer networks (also called heterogeneous networks).

50) How to use a router to manage a network?

The router has a built-in console that allows you to configure various settings such as security and data logging. You can assign restrictions to your computer, such as resources you are allowed to access or specific times of day when you can surf Internet.

You can even place restrictions on sites that are invisible to entire web.