How to use the network tester

Network administrators are not only responsible for the safe operation of corporate networks and servers, but also need to ensure the connectivity of various network devices. The links connecting these network devices are inseparable from various network cables. How can we determine whether the problem lies with the network cables? Replacing the network cable is certainly possible, but the problems with the original network cable are entangled. Today, the author will take out the secret weapon to introduce to the readers of IT168 how to use a network cable tester to determine the continuity and line sequence type of the network cable.

　　1. Introduction to Computer Network Cable Tester
　　The computer network cable tester is very small, about the size of a wallet. The main body of the device is divided into two parts, the middle part can be installed and disassembled, and a leather case is usually given with the device, which protects the device on the one hand and is also convenient to carry on the other hand (as shown in Figure 1).

 

figure 1

 

　　We can see ten lights on the left and right sides of the front panel of the device. These indicators correspond to the line sequence of the connected network cables. If you are testing ordinary Category 5 or Category 5e twisted pair cables, you only need to pay attention to the first eight lights (as shown in Figure 2).

 

figure 2

　　After we pick up the cable tester, we can see that there are several interfaces. The main interfaces on the left are RJ11 telephone line interface and RJ45 network cable interface respectively, and the movable part on the right is only the RJ45 interface (as shown in Figure 3).

 

 

image 3

 

　　2. How to use the computer network cable tester
　　In actual use, if the network cable is short, we can connect the two ends of the network cable to the two RJ45 interfaces of the cable tester. If the network cable is long and it is not convenient to remove it, we can remove the mobile end on the right and take it to the remote and main body for testing. This installable and uninstallable method makes the cable tester more convenient to use.

　　After we plug the network cable into the two RJ45 interfaces, we can turn on the cable tester. Then we will find that the lights on both sides are flashing in sequence. This is because the cable tester will detect the connectivity of each line sequence of the network cable in sequence during measurement. If the left side flashes in the order of 12345678 and the right side flashes in the order of 36145278, it means that our network cable is a reverse line (cross line). If the flashing order of the left and right sides is the same, both are 12345678, it means that the network cable currently being tested is a positive line (straight-through line) (as shown in Figure 4).

 

Figure 4

 

　　Of course, in actual use and measurement, the most common problem we encounter is not measuring whether the network cable is a positive line or a negative line, because many devices can already make adaptive judgments on the line sequence. Most of the time we need to know what is wrong with the network cable in our hands. At this time, we can easily find out through a cable tester. For example, after connecting the network cable, when the left main body flashes to a certain light and the right side does not flash, it means that the problem lies in the line sequence and there is a disconnection in the middle; if after connecting the network cable, when the left main body flashes to a certain light and two lights are on on the right, it means that part of the line sequence of the network cable is damaged during production, resulting in the occurrence of wiring problems. One line on the left corresponds to two lines on the right. Such a network cable is also unqualified. In the mildest case, crosstalk will occur, and in the worst case, it cannot be connected directly (as shown in Figure 5).

 

Figure 5

　　3. Summary
　　The computer network cable tester is cheap, but it can play a role at the critical moment. I believe it will become a good helper for network administrators, contributing to enterprise maintenance and network management, so that we can know the cause of cable failure, thus saving a lot of manpower, material resources and network management energy.