Generally speaking, the network card will not easily strike, most of which are network failures caused by errors in settings and hardware connections. When checking network failures, you can generally start with the network settings of the system (mainly check whether the IP address, DNS and gateway are wrong or lost, etc.), and then check the physical connection. There will be many specific faults, such as: whether the twisted pair connector is good, whether the twisted pair is broken, whether the hub slot is easy to use (try another slot).
In the process of twisted pair wiring, it is more likely that the network is "connected" and "unconnected" in the line sequence problem. Many users often use the wrong connection method of one-to-one correspondence in wiring. When the connection distance is short, the system will not have connection failures. But when the connection distance is long, the network is busy or running at high speed, it is easy... The core is to make the two pins 3 and 6 the same pair (link according to the T568A or T568B standard).
The distance between a user's server and the switch is changed from 5 meters to 60 meters. According to the same link method, the connection cannot be reached anyway. Why? In Ethernet, two pairs of twisted pairs are generally used, arranged in 1, 2, For the positions 3 and 6, if instead of using two pairs of wires, the wires used in the original pair are used separately, crosstalk will be formed (SplitPair error means that the wires are not installed according to the correct wire markings, so The transmission performance failure caused by it) has a great impact on the network performance. The 10M network environment is not obvious. In the 100M network environment, if the traffic is large or the distance is long, the network will be unable to connect.
The above phenomenon is the reason. Since the pairing line is not used in 3 and 6, there is no problem when the distance is short. However, once the distance becomes longer, the fault occurs. All you need to do is to re-order the RJ45 head and everything will be back to normal. In addition, several twisted-pair cable manufacturers, in order to better exceed twisted-pair performance standards, have two pairs of twisted pairs in the four-pair twisted pair more twisted than the other two pairs - huh, of course, the standard orange , orange-white and green-green-white, so it's best to use them for 1, 2, 3, 6.
Twisted pair wiring
Therefore, in the process of network construction, after the integrated wiring is completed, the twisted pair should be tested. Structured cabling unshielded twisted pair testing can be divided into continuity testing and certification testing. The continuity test focuses on the connection performance of the structured wiring and does not care about the electrical characteristics of the structured wiring, which can ensure that every connection made is correct. The certification test refers to testing the structured cabling system according to the standard to determine whether the structured cabling meets the design requirements.
Usually, the channel performance of structured cabling depends not only on the construction process of the cabling, but also on the quality of the cables and related connection hardware used. Through testing, it can be confirmed whether the installed cables, related connection hardware and their processes can meet the design requirements. This testing includes connection performance testing and electrical performance testing. Cable installation is an installation process-based job. Since no one can work completely without errors, we must conduct link testing to ensure that cable installation meets performance and quality requirements. In the absence of test tools, the connection may work with some errors. Common connection errors include wrong cable labels, open connections, and shorts.
Open circuit and short circuit During construction, open circuit or short circuit faults will occur due to problems such as lack of tools, wiring skills or in-wall threading technology.
Reverse the same pair of wires and connect them in reverse at both ends, for example, one end is 1-2, and the other end is 2-1.
Wrong pair Connect one pair of wires to the other pair on the other end, such as 1-2 on one end and 4-5 on the other.
String winding The so-called string winding means that the original two pairs of wires are separated and then reconstituted into a new pair. Since the end-to-end connectivity is not affected when such a fault occurs, the cause of the fault cannot be detected with a common multimeter, only by using a dedicated cable tester.
The certification test does not improve the channel performance of the integrated wiring, but only confirms whether the installed cables, related connecting hardware and their processes can meet the design requirements. The results are valid only if the test equipment that meets the specific requirements is used and the test is carried out according to the corresponding test method. For example, use the Pentascanner Class 5 tester for Class 5 testing. The method is: first connect the two ends of the jumper with the tester, then press AutoTEST to test, then press F1 to display the test result, and finally print the test result.
Some of the problems in the testing process mainly include the following aspects:
1. The near-end crosstalk failure may be caused by the problem of the near-end connection point, or because of the string pair, external interference, short-circuit at the far-end connection point, performance problems of the link cable and connection hardware, not the same type of product, and the end of the cable. quality problems, etc.
2. The reason for the failure of the wiring diagram may be that the joints at both ends are open, short-circuited, crossed or broken, or because of wrong bridging.
3. The reason for the failure of attenuation may be that the cable is too long or the temperature is too high, or the connection point problem, or it may be the performance problem of the link cable and the connection hardware, or it may not be the same type of product, or it may be the end of the cable. quality problems, etc.
4. The length of the failure may be caused by the cable being too long, open circuit or short circuit, or the total length of the equipment connection and jumper is too long.
5.The reason for the failure of the tester may be that the tester does not start (the problem can be solved by replacing the battery or charging), the tester cannot work or cannot perform remote calibration, the tester is set to an incorrect cable type, the tester Set to incorrect link structure, the tester cannot store the automatic test results, and the tester cannot print the stored automatic test results, etc.
