Simple Network check (2)

Article Title: Simple Network check (2 ). Linux is a technology channel of the IT lab in China. Includes basic categories such as desktop applications, Linux system management, kernel research, embedded systems, and open source.
2. confirm that there are no problems with the online devices such as the network line, hub, modem, and so on:
Hardware:
　　　
After you have completed the network card check (please confirm that the network card can really work !!!), Check your network lines, hubs, and modem! The online connection of these network devices varies depending on the way you connect to the Internet and the location you are located on. However, there are usually three online methods that can be simplified and traditional!
　　　
The fixed IP address and the "communication gate IP address" are known: this usually happens in academic networks or companies that have already planned the network size. therefore, you only need to add the network line to the reserved network hole to bring it online!
　　
　　　
· Features: in this online status, enterprise or academic organizations usually enable DHCP services to automatically assign IP addresses to you, therefore, you can connect to the network as long as the first step is "no problem with the network card! In this online status, the Hub is usually used as the machine connection to the machine, so your network line needs a "normal" network line.
　　　
Problem: a common problem that cannot be connected to a network may be:
　　　
1. network cable may be faulty: ask the network administrator to determine whether the network cable type from the user's computer to the reserved network hole is "jumper 』, you can use the network line of another normally connected computer to test your machine;
　　　
2. the internal network does not provide services for automatically allocating IP addresses through DHCP: In this case, you must know the "IP domains of computers around you" and "public communication gateway IP addresses 』. That is, the fixed IP address and communication gate that your computer can possess! It is best to have the IP address of the main DNS, and install it according to the settings here!
　　　
3. simple validation methods:
§ If you already know your IP address and the IP address of the communication gate, you can first enter the correct IP address in the first step;
§ After "MSDOS mode" is enabled, enter: ping xxx. xxx. xxx. xxx (Your IP address or the IP address of the communication Gate), if there is a response, it indicates that there is no problem connecting your computer to the communication gate;
§ If there is no way to respond, it indicates that the computer at the Communication gate may be faulty ??? Cool tolerance? Flane stretch? Shu
　　　
4. Basically, this online check method is relatively simple. as long as the network card is no problem, the network line is correct, and the communication gate host operates normally, it will be okay!
　　　
　　　
· Connect to your ISP using a modem (56 Kbps or a small turtle modem of ADSL): This online mode usually occurs when only one computer is used by a common household user. since there is only one computer, therefore, you only need to check the network line and modem. The online mode can be shown as follows:
　　
　　　
· Features: in this online status, you usually need to install the "online program". please first confirm that your online program is normal (about online programs, whether it is a traditional modem or a turtle, you should be able to get the manual from the applying vendor. Generally, you can install it according to the above steps ??. Why? Yao Badong-neeching? DSL network connection is "RJ-45 network line", but the traditional modem is connected to the communication port, the connection line is not the same! In addition, you must have an ISP account and password to connect to the Internet!
　　　
Problem: possible problems that cannot be brought online:
　　　
1. the line connecting to the ADSL modem is incorrect: note that the network line connecting the computer to the ADSL modem is handled by the jumper. therefore, if you use a normal network line, it cannot be connected! (What is jumper? The general network line is called "RJ-45", the use of RJ-45 online? Must I use a HUB )? All computers must be connected to the HUB before they can communicate with each other. If only two computers are online? Do you want to use a HUB? But you have to perform the operation for your RJ-45 joint? Connect the 1st line at one end to the 3rd line at the other end? The 2nd line at one end is connected to the 6th line at the other end. The direction is the network cable on the left of the connector? Copper wire to yourself (such )? From top to bottom .)
　　
　　　
2. the modem is broken: do not doubt that it will actually break down. Usually there are some signals on the small turtles of ADSL. if the signals on the turtles are incorrect when you start the system, you may need to ask the Engineers of China Telecom to check them out ??
　　　
3. online program setup error: This problem occurs frequently in different operating systems. for example, some ADSL dialing programs are only used for Windows 98, windows ME may have to use a newer dial-up version!
　　　
4. simple validation methods:
Generally, an ADSL modem has a default IP address of 192.168.1.1 (the subnet mask is 255.255.255.0), but different ADSL turtles may have different default IP addresses, you can view the corresponding IP address of your turtle on the China Telecom website. (Generally, except for the IP address 10.0.0.1 of cisco 676, the IP address of your PC should be set to 10.0.0.2. All other types of turtles can be set by this method)
Assume that you have set your IP address to 192.168.1.2 in step 1, then enable "start" --> "assembly" --> "MSDOS mode", and enter ping 192.168.1.1, if there is a response, it means that the process from the computer to the modem is smooth! Then you can proceed to step 3!
If there is no response, and you are sure that the turtle is not broken, please first find a patch cord that can be normally connected to other computers to connect your computer to the turtle, to check whether there is any problem with your network line.
　　　
5. most of the above is about the online method of small turtles targeting ADSL. However, either Cable or ADSL modem will have a default virtual IP address, you can use the above method to confirm the connection from the computer to the modem!
　　　
Using a Hub as an intermediary to bring multiple computers online through a modem: this is the most popular network connection method called "shared bandwidth". The Online icons are as follows: basically, after connecting all computers through the Hub, you can (1) connect to the ADSL turtle directly; or (2) first through the self-built host with the NAT function, or the IP address sharer is connected to the Internet. This situation is troublesome because there are a lot of network cables (each computer has one, and another from the Hub to the modem ), you must be sure that you know exactly the form of your network line, and the connection method is OK.
　　
　　　
· Features: This method is generally applicable to the use of more than two computers in the home or multiple computers in the same dormitory! If you are applying for China Telecom, you can only use the Hub to access the Internet from two computers at the same time. if you are using Seednet, you can connect up to five computers at the same time to the network! Of course, if you can use Linux or Windows 2000 to set up a NAT host, or if you have enough money to buy an IP address Sharer, then you can connect to more than 100 computers ?? 《? Zookeeper ?? Twist more close? Why? Why? Why 7 then? NE Hub problem, because there is a Up-link hole!
　　　
Problem: possible problems that cannot be brought online:
　　　
1. network cable problems: in general, if you do not use the Hub Up-link hole, then from the PC to the Hub must use the "normal RJ-45 network line 』, the Hub to the modem is also the use of normal network lines, as the host directly to the modem is to use the "jumper RJ-45 』! Be sure to clarify here! (It is usually the first time that DIY partners who share bandwidth are most likely to make mistakes ).
　　　
2. Hub problems: when selecting a Hub, you must note whether the Hub can automatically identify the 10/100 M full/half duplex working environment. Taking laruence as an example, laruence once bought the wrong Hub. Since the network card of our machine is new and old, there are several old network cards that only reach 10 M, however, the Hub purchased by laruence only supports a network environment of 10 M or 100 M, but cannot be automatically identified. to match the old network card, laruence had to adjust the Hub to 10 M and could not exert his original skill !! Therefore, please pay attention to your needs when buying a Hub!
§ Suggestion 1: If you really have a lot of money, the most expensive Hub in the sales market is right, because the price is usually automatically recognized as the 10/100 Mbps network type; if you are not rich, please refer to the following suggestions;
§ Suggestion 2: if almost every PC in your network system accesses the Internet independently, the transmission rate of the home Internet is greatly increased to 100 KBytes/s, however, the cheapest kind of Hub's lowest transmission rate can reach around 1000 KBytes/s, so you only need to buy the cheapest kind;
§ Recommendation 3: If your network type is related to other computers on nearby networks, in addition, the amount of data is very large (for example, the network type of the general University Research Office), it is best to select a Hub that can automatically identify 10/100 M!
Another problem with the Hub is the Up-Link hole. because different forms of the Hub have different Up-Link hole configurations, for example, a friend of laruence has bought a sub-brand Hub, although he has five holes, the Up-Link hole is shared with the fourth hole. if you have used the fourth hole, the Up-link hole cannot be used, so it lacks elasticity, another common D-Link Hub is the cheapest five-hole Hub. its Up-Link hole can also be adjusted to a normal network hole through the buttons at the bottom, then you can connect to five computers at the same time! (What is the Up-Link hole? Generally, the Hub reserves a hole as the connection hole connecting the second Hub to increase its scalability. this is a simple Up-link hole. In addition, some of the hub's Up-link holes can even be used when the patch cord holes, for example, you connect the Hub and the modem online with a patch cord's RJ-45 network line to the Up-link hole, then this line is automatically converted to normal! However, for detailed specifications, please refer to the specification of each Hub)
　　　
3. simple validation methods:
§ First confirm that the network card of each computer is working properly;
§ Connect the normal holes of the computer and Hub with a normal RJ-45 network line (not Up-Link );
§ Connect the modem and Hub of ADSL with normal RJ-45 network line;
§ If you are using a host, connect the Hub to the host with a normal network line, and connect the host to the ADSL modem with a jumper;
§ Because the same IP address cannot exist in the same CIDR block, different IP addresses must be entered for each computer in step 1, which can be set to 192.168.1.2 ~ 192.168.1.10 and so on. As for the subnet mask, all are 255.255.255.0;
§ After each computer is restarted, you can check the connection between the computer and the computer by pinging 192.168.1.3 and so on.