Troubleshooting in Network Operations
During network operations or system installations, there can be various reasons why a network cannot connect. Apart from some settings or software prohibiting the network from being connected, most issues are caused by the following reasons:
1. The network card is not installed correctly or the card itself has issues. Generally, if the network card is plugged in and the system does not prompt, it indicates that the card is not seated properly or there is an issue with the port; if after installing the driver the loopback ping is correct but pinging the local IP fails, first check if the network card has issues; if the local IP pings successfully but adjacent computers cannot communicate, check the network cable or the network card interface. The best way to test a network card is to use a working network card of the same model to replace the problematic one. Before using the replacement method, it is best to check if the local network card is properly seated and try using a different slot.
2. Issues with the TCP/IP protocol. Problems with communication between computers are mostly caused by the TCP/IP protocol. Due to the inherent fragility of TCP/IP, it can easily lead to communication issues, typically manifested as adjacent computers being unable to communicate (the network neighborhood or search for computers yields no results); in some cases, although the Internet connection is normal, adjacent computers cannot communicate. The solution is to re-add the TCP/IP protocol. Special care should be taken when deleting this protocol in Windows 2000 and later systems, as doing so may lead to system crashes, so ensure that the protocol can be correctly re-added before restarting. Testing method: after excluding connection errors and network card interface issues, if the local IP pings successfully but adjacent computers cannot communicate, attention should be paid to whether the TCP/IP protocol is causing the fault.
3. Driver issues. This problem mainly occurs with generic network cards where incorrect drivers are used, leading to various unexpected issues. Testing method: if the loopback ping is correct but pinging the local IP fails, it indicates that the network card driver may have issues (hardware faults should be ruled out) and that the network card driver is installed incorrectly.
4. Network setting issues. Network settings include IP, subnet mask, gateway, and DNS, and for dial-up connections, also include username and password. Therefore, when network faults occur, first check if the settings are correct. For networks using DHCP services, this issue is much simpler as there is no need for manual settings.
Common Fault Solutions in Network Maintenance
With the popularization of the Internet, everyone has a certain understanding of networks, but in daily use, one may encounter various issues. Below is a brief overview of some common problems to share solutions for minor issues during network usage.
1. Slow access to network neighborhood. The connection speed between computers is not only very slow, but only a portion of the computers can be found. First, since some computers can be seen, it indicates that the network connection is normal, and the network card drivers and communication protocols are correctly installed; second, since the IP address and subnet mask are correct, the IP address information is set correctly; third, since the domain names and workgroups are the same, one should be able to find other users in the same workgroup quickly. Possible causes for these issues include: a. The NetBEUI protocol is not installed. TCP/IP is not an efficient protocol; therefore, in small local area networks, the more efficient and resource-friendly NetBEUI protocol is usually used. b. The network card driver has defects. Although many network cards use the same chipset, the drivers are not identical. Although defective drivers may not necessarily lead to communication failures, they often significantly impact transmission efficiency. Therefore, confirm that the selection and installation of the network card driver are correct.
2. When to use a straight-through cable and when to use a crossover cable? a. The following situations must use a crossover cable: I. When two computers are directly connected through network cards; II. When cascading ordinary ports of a hub or switch together. b. The following situations must use a straight-through cable: I. When connecting a computer to a hub or switch; II. When a hub or switch connects to another hub or switch’s ordinary port using an Up-Link port; III. When a hub or switch connects to the LAN port of a router. c. The following situations can use either a straight-through cable or a crossover cable:
I. When the RJ-45 port of a hub or switch has polarity detection capabilities, it can automatically determine the connected device and switch between MDI/MDI-II; II. When specific ports of a hub or switch have MDI/MDI-II switches, allowing selection between using a straight-through or crossover cable for connection.
3. Hub + router cannot share the Internet, which may cause computers connected to the hub to be unable to access the Internet for three reasons: a. Hub malfunction. The symptom is that computers on the hub cannot ping each other, nor can they ping the router. This fault only affects all computers connected to the hub. b. Cascading faults. For example, incorrect wiring sequence in the jumper between the router and hub, or jumper connectivity faults, or using incorrect cascading ports. The symptom is that computers on the hub can ping each other but cannot ping the router. However, the Internet access of computers directly connected to the router’s LAN port will not be affected. c. Broadband router malfunction. If the LAN port is faulty, the result will be similar to cascading faults; if there is a routing fault, computers in the network will be unable to access the Internet, regardless of whether they are connected to the router’s LAN port or the hub.
4. “Local connection” only sends but does not receive, which may be due to the following reasons: a. The network card is incompatible with Windows XP or has poor compatibility; try installing another operating system. b. There are issues with the network cable; although tested using the replacement method, it is best to move the faulty computer to a networked computer for replacement. c. If the network card is 10/100Mbps adaptive, try setting the card speed to 10Mbps (select the network card properties, click the “Configure” button in the “General” tab, and choose 10 Half Mode in the “Link Speed/Duplex Mode” under the “Advanced” tab). d. “Bytes sent are present, while bytes received are 0” indicates that the line is sending data normally, but receiving has issues. Therefore, the possibility of connectivity faults is the highest, which may also be due to poor contact at the connection points (RJ45 ports of the network card, hub, or information socket).
5. IP address conflict occurs when the IP address used by a computer is identical to that of another computer on the same network, leading to communication failures. Generally, IP address conflicts are caused by improper IP address allocation by network administrators or other users setting IP addresses arbitrarily. Since the MAC address of the network card is unique, the network administrator can use the MAC address to find the computer with which there is a conflict and instruct it to change the IP address. Using the “ipconfig /all” command, one can view the computer’s IP address and MAC address. Finally, using the command “ARP -s [IP address] [MAC address]”, this legitimate IP address can be bound to your network card’s MAC address.
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