LAN Maintenance and Optimization Techniques

When building and maintaining a local area network (LAN), you will inevitably encounter various types of faults. Troubleshooting and system optimization are among the most basic tasks of LAN maintenance. I have been working as a network administrator for eight years, and below I would like to share some small experiences accumulated during my work. These include troubleshooting and optimizing performance from different perspectives, summarizing some LAN management and optimization experiences and techniques, with an emphasis on the correct installation and reasonable configuration of network cards and network cables. Hopefully, this will help everyone better maintain computers, manage networks, and thus make better use of networks in their work.

When performing LAN maintenance, have you ever thought about how to carry out your work more efficiently? Can you pinpoint network issues quickly? Below, we will briefly discuss LAN maintenance and optimization.

1. Connect according to rules

Each computer in the LAN is connected using twisted-pair cables. However, simply connecting two computers with a twisted-pair cable does not guarantee communication. We must follow specific connection rules. The distance of twisted-pair cable connections should not exceed 100 meters. If the distance between two computers exceeds 100 meters, a conversion device must be used.

When connecting conversion devices and switches, we must perform crossover wiring. This is because Ethernet generally uses two pairs of twisted-pair cables, located at positions 1, 2, 3, and 6. If the original paired wires are separated and used individually, significant crosstalk can occur, which can significantly impact network performance. In a 10 Mbps network environment, this issue may not be noticeable, but in a 100 Mbps network environment, if there is heavy traffic or long distances, the network may fail to connect.

2. Check the network card first when encountering faults

In the process of LAN maintenance, network disconnection is a common occurrence. When encountering such issues, we should first carefully check whether the network card settings in each connected machine are normal. To do so, we can sequentially open "Control Panel/System/Device Manager/Network Adapter" settings window. In this window, check for any interrupt number or I/O address conflicts (it's best to set all machines' interrupts to the same value for easier comparison). Continue until the property of the network adapter shows "This device is working properly," and ensure that at least your own computer can be found in "My Network Places." This indicates that the network card configuration has no problems.

3. Confirm that the network cable and network equipment are working normally

After checking that the network card has no issues, we can try to view other computers in the network through "My Network Places." If still unable to see other machines in the network, it could indicate a problem due to interrupted network connections. Common network connection faults include internal breaks in the network cable, poor contact between twisted-pair cables and RJ-45 connectors, or quality issues with network connection devices themselves, or connection problems. At this point, we can use a cable tester to check if the line is broken, then use substitution methods to test the quality of network equipment. If neither the network cable nor the network card itself has any issues, we should then check if the problem lies in software settings, such as incorrect interrupt numbers potentially causing failures.

4. Check if the driver program is intact

After checking the hardware and confirming it is fine, next check if the driver program itself is damaged. If it is not damaged, ensure it is installed correctly. If these can be judged as normal and there are no device conflicts yet still cannot connect to the network, the network adapter can be deleted in system settings. Then restart the computer, and the system will detect new hardware and automatically search for and install the driver.

5. Correctly configure the network card

If the network medium is confirmed to have no issues but still cannot connect, return to the network card settings. Check for any device resource conflicts. Many times, conflicts don't always trigger warnings. Possible device resource conflicts include: NE2000-compatible network cards conflicting with COM2, both using IRQ3, (Realtek RT8029) PCI Ethernet network cards and video cards both "liking" IRQ10.

To resolve such device conflicts, we can follow these steps: First, disable COM2 in the settings window and forcibly set the network card interrupt to 3; if there is a conflict between PCI interface network cards and video cards, we can solve it by not assigning an IRQ to the video card, setting the "Assign IRQ for VGA" item in CMOS to "disable."

6. Disable the PnP function of the network card

Some network cards support PnP functions but after installation, they may not work well or even fail to work. To solve this problem, we can disable the PnP function of the network card. To disable the PnP function, the network card's setup program must be run (usually included in the driver package). After starting the setup program, enter the setup menu. Disable the PnP function of the network card and modify the IRQ setting to a fixed value. Save the settings and exit the setup program. If no other devices occupy this IRQ, it can ensure that there will be no IRQ conflicts.

Additionally, if installing Windows 98/2000/XP operating systems, it must be ensured that the operating system does not handle the corresponding interrupt type as a PnP-enabled IRQ. Therefore, in the "CMOS," the interrupt type should be changed from "PCI/ISA PNP" to "Legacy ISA." Using this method can resolve most PnP network card device conflicts, though it may not be effective for all PCI network cards, as some network cards' setup programs do not provide an option to disable the PnP function.