In the process of building a computer network system and daily maintenance work, we have summarized common problems and their solutions that we encounter, hoping to exchange ideas with everyone.
The LAN management software can help businesses maintain the LAN, making the company's local area network run more smoothly.
Correct installation and configuration of the network card
1. First, ensure that the network card used is supported by the operating system and the correct network card driver program is being used.
2. If after configuration, errors occur upon restarting the system or if the network card configuration information cannot be checked using winipcfg, it indicates that the network card has not been detected by the operating system. For ISA interface network cards, you can use the setup program that comes with the network card to correctly set parameters such as interrupt (IRQ) and input/output address range (I/O address) under a pure DOS environment. Network cards with jumpers should adjust the jumpers according to the network card manual to ensure the jumper settings are correct. For PCI interface network cards, try changing the slot. After the configuration is completed, restart the system and check again whether the network card is normal.
3. The network card is normally detected upon restarting, but cannot interconnect with other machines. This is mainly due to several situations: incorrect subnet mask or IP address configuration, network cable disconnection, incorrect network protocol, or incorrect routing. The solution is to first ping the loopback address (127.0.0.1) of this network card. If it is reachable, it means that the TCP/IP on this machine is working properly; if it is unreachable, reconfigure and restart the computer. Some network cards have a default setting of 100M speed, which may also cause network disconnection. It is necessary to set its speed to 10M, 100M, or adaptive cable speed according to the speed of the connected hub (hub) or switch (switch).
Network communication issues
In actual work, it is common to encounter problems with LAN communication being slow. During LAN maintenance, the specific manifestation is that when one node in the LAN pings other hosts, it shows a very small data packet (such as 24 bytes), requiring hundreds or even thousands of milliseconds, making file transfers very slow.
When encountering this situation, first check the status indicator lights of the hub or switch. If the COL light flashes or stays yellow, it indicates that there is congestion of data packets on the network. You need to check if there are duplicate IP address allocations in the same LAN or if the LAN IP address segmentation overlaps. Then find a pair of computers confirmed to be normal (tested with a crossover straight-through cable). Under the condition of continuously pinging between the two machines, unplug and plug the network cables on the hub one by one to see which network cable causes the problem? Often, it is due to a short circuit in a certain network cable causing confusion in network transmission data, thus leading to network congestion. If all network cables and hosts have no problems, then please use a multimeter to measure the voltage between the ground wire and neutral wire of the network equipment. If the voltage exceeds 3 volts, it indicates that there is a problem with the power supply system of the hub, static electricity cannot be released in time, interfering with the data signal. In the LAN, data propagates in the form of square waves, decaying quickly and easily interfered with. If the power supply system of the network equipment does not have a reliable grounding wire, it is equivalent to directly using a two-phase power without a ground wire. The static electricity of the hub can only dissipate through the air, and the conductivity of the air is very poor. Static electricity has nowhere to go, and after some time, touching the hub with your hand will feel tingling. In addition to grounding the power supply of network equipment, the chassis must also be grounded because the chassis and the ground wire of the power supply are actually not connected. Most of the static electricity induced by the square wave itself is stored on the chassis, and static electricity is the archenemy of the square wave.
The main function of the hub is to replicate the host's signal into several copies, placing one on each port. Taking an 8-port 10M hub as an example, the actual transmission rate of each port is only 10M/8=1.25M, and cascading cannot exceed 5 levels. In addition to serving the same role as the hub, the switch places data signals on demand. The 10M or 100M speed indicated in the manual is the actual speed of each port. When needed, VLAN (virtual subnetwork) technology can be used to divide the ports of the switch into several subnets. Subnets cannot communicate with each other, which is beneficial for network control and improves network security. Therefore, the author suggests that under financial conditions, it is best to use a LAN switch instead of a hub. For example, the QuanXiang QS-516VF Ethernet switch (16-port 10/100M auto-adaptive) has VLAN functionality.
Twisted Pair Cable Issues
The correct connection of twisted pair cables is also very important. Incorrect connections of the 8-core 4-pair twisted pair cables will also affect communication effects. In the 10 Base-T standard, the 1st and 2nd are a pair of wires, and the 3rd and 6th are another pair. In the transmission of a pair of wires, since the lines are twisted, they cancel out the eddy currents, slowing down the attenuation of data signals. If the lines are incorrectly used, they will not play the role of eddy current cancellation in twisted pair cables, reducing both the transmission distance and speed. If both sides have the same wire sequence, it indicates that it is a direct connection line to the hub. If the 1st and 3rd, 2nd and 6th are crossed, it is a direct connection line between two machines, also known as a hub cascade line.