Check for network failure

The transmission medium used in the LAN mainly by twisted pair and thin cable, twisted pair is generally used for the wiring of the star network structure, and the thin cable is used for the wiring of the total linear structure.

The computer in the LAN cannot connect to the local area network, need to check:

1. Verify that the network card indicator is on and the NIC driver is installed correctly;

2, the network card and any system equipment does not conflict, whether the correct installation of the Internet Protocol, can ping the native IP address

3, the network card indicator light does not indicate that there is no problem with Internet connection;

4, for the twisted pair of jumpers, check whether the Crystal Head line is off, whether the contact is not bad; we recommend using network cable tester to check the fault computer line;

5, Example: The use of the LAN for a long time, found that one of the computer dropped packet phenomenon, and the number of lost packets is not fixed, the possible situation, with the network cable tester to detect the computer's physical link, found in the network cable white Orange Line and white Blue Line has a short-circuit

6, the dual-machine direct connection cable should use the crossover line, can not use the straight line, the normal network cable is made in accordance with the 568B standard straight line, can not be directly connected to double machine; the line order of the intersection follows the rules: one end is white orange, orange, white green, blue, white blue, green, white Brown, Brown, the other end is white green, green, white orange, blue, white blue

7, small LAN with a switch connection, a win XP operating system computer can not properly connect the network, the network parameters are set correctly, with Ipconfig/all Check network configuration information, display NIC MAC address

FF-FF-FF-FF-FF-FF; the judgment should be the NIC fault, processing: Replace the new NIC test

8, the LAN server needs to add a new device, the original PCI network card to another PCI slot, re-set the network card IP address prompt address already exists; Cause: The system does not automatically unmount the NIC operation after the original PCI slot is unplugged, thus causing the NIC to still exist in the registry. Due to the original network card setup parameters still exist, replace the PCI slot card when it is recognized as a new network card can not be set to the original IP address, which will cause IP address conflict, Workaround: Command line Input "set Devmgr_show_nonpresent-devices=1", Open the Device Manager window, view "Show hidden Devices", in the network device, right-click the gray network card, uninstall, set the IP address of the new network card;

9, the local area network uses the DHCP dynamic assignment IP address, the client obtains automatically, the server installs the network card to enter the local area network, this client computer starts slowly; solution: Specify a static IP address for the computer, reduce the system detection time, do not use the way to obtain the IP address automatically;

10, the LAN user installs a USB interface ADSL modem, the calculator opens the ADSL modem before opening, the system will stop in the black screen state, the Plug and unplug after can use; Reason: The ADSL modem uses the USB2.0 standard, And the system only installs the USB1.1 driver or does not have the correct setting in the BIOS, has enabled the USB keyboard and the mouse to prohibit the USB controller, may also be the USB modem to power through the USB interface, because the boot time is short and does not activate the device, causes the system to mistakenly consider the hardware failure, resolves:

1. Check if the system correctly identifies the USB chipset and installs the USB2.0 driver correctly;

2. Check and reset bios about USB options

11, LAN through the ADSL modem dial-up Internet, often off-line view of the ADSL modem management interface log, only the power off the ADSL modem to successfully login;

Cause: Frequent drop failure reason may be because the concurrent access is too large to cause the ADSL modem overloaded operation, it is recommended to prohibit users to use BT download and other easy to generate large data traffic, Internet access, and check all computers on the LAN for known or unknown worm virus, This kind of virus is very likely makes the network access speed extremely slow, causes the user to visit the ADSL Modem Management page to appear the ultra-long latency access phenomenon;

12, switch failure, the company's local area network is connected by 3 switches, the switch uses asymmetric ports, including two 1000base-t ports and 24 base-t ports, in the use of the process found that multiple computers at the same time to access the server transfer speed is very slow ; cause: The fault may be caused by incorrect connection of the symmetric network switching device, the switch has a different rate of ports, usually the local area network switch has 100mbps and 1000mbps two transfer rates, high-speed ports for connecting other switches or servers, low-rate port for direct connection to the computer or hub This connection method solves the connection bottleneck between the equipment and the server and the device, by increasing the server connection bandwidth and preventing the server port congestion, because the switch communicates with the high-speed port, so that all the computers in the network can enjoy the multi-server access rights equally. In addition to connecting the server to the high-speed port, it is necessary to configure the 1000BASE-T network card for the server, increase the data read rate of the server hard disk, and use the RAID-5 mode to connect multiple SCSI drives together;

Check for network failure