Lan classic Q &

From China Network Management Forum

Hell genie 1. Q: What are the cabling sequence of twisted pair wires? What are the differences between different arrangement methods? Will the network transmission speed be affected?
There are two types of standards: EIA/tia568a and EIA/tia568b. EIA/tia568a is sorted as follows: white/green, green, white/orange, blue, white/blue, orange, white/brown, and Brown. ---- ordered line.
EIA/tia568b are sorted as follows: white/orange, orange, white/green, blue, white/blue, green, white/brown, and brown. the two standards are the same and will not affect the network speed. ---- Jumper.
2. Q: under what conditions will a direct connection be used? Under what circumstances is crossover used?
Generally, there may be an X mark next to the port of the network device. The NIC or router does not have this mark. The rule is: The X mark and the X mark are connected with a straight line, and the X mark or the X mark and the X mark are connected with a cross line.
3. Q: After my network is upgraded from a hub to a vswitch, I feel that the speed has not improved much. Why?A: This situation needs to be analyzed from the following aspects:
1. First, check whether the network is in the M status. The specific practice is to confirm that the network cable is in a category 5 or above, the network cable practice follows the M standard, and the network adapter supports the m working status. Only the above conditions are met, A vswitch can work at m to maximize the performance advantage of the vswitch.

2. If the network works normally before the upgrade, the data exchange volume is not large, and data conflicts and broadcast storms do not occur frequently, the network performance improvement after the upgrade may not be obvious, this is normal.

3. There is also a situation that is caused by improper network structure settings. For example, if a hub is placed on the first-level connection server and a switch is placed on the next level to connect to the workstation, in this way, the data exchange is still carried out through the hub, and the performance advantages of the switch are not shown. Therefore, the rationality of the network structure should be fully taken into account in networking, and devices with better performance should be placed at the highest level in the entire network.

4. How can I view the IP address of a computer on the lan?
View your methods
Ipconfig
Winipcfg
Ping your machine name
View Network Connection Properties.
Check other users' machine names
Q: Is this normal if my adaptive Nic only flashes at a red light and the green light is not on?
A: First, you should understand the meaning of the red light and green light of the adaptive Nic. The red light represents link/Act (connection/work), that is, the red light is always on when the connection is established, and the data is flickering during transmission; the green light represents fdx (Full Duplex), that is, the full duplex state is on, and the half duplex state is off. If a half-duplex network device (such as the hub) is connected to an adaptive network adapter, because this network adapter is an adaptive network adapter, it will also work in the half-duplex status, so it is normal that the green light is not bright.

5. Q: How do I connect to the uplink port of the vswitch? Can I use the nearest adjacent port after uplink port is used?A: The uplink port is a common port on a vswitch. It is used to facilitate cascade between two vswitches. It uses the same channel as its adjacent common UTP port. Therefore, if the uplink port is used, another common port adjacent to it cannot be used. These two ports are called shared ports and cannot be used at the same time. When cascade, you can use a general network cable (both ends of the network cable follow the same standard, that is, the same as EIA/TIA
568a or 568b) connects the common port of a vswitch to the uplink port of another vswitch. If both devices are connected using uplink ports, either end of the network cable must use EIA/TIA.
568a standard, the other end uses the EIA/TIA 568b standard.
6. Q: After I install the NIC, a yellow Nic appears in system> Device Manager. No. How can this problem be solved?A: The NIC is prone to resource conflicts with other devices, especially when multiple plug-in cards are installed in the system. The solution is as follows:
1. Replacing the NIC on the motherboard is the best solution.
2. Find the "Resource Type" list in the "Resources" tab of the "properties" Window of the NIC, select the "resource" in conflict, and click "change settings, change the conflicting IRQ interrupt number or I/O address.

3. Some PCI NICs forcibly occupy irq10, which is in conflict with IRQ interruptions on some display cards that forcibly occupy irq10. In this case, you can set "Assign" in the BIOS.
IRQ for VGA is set to disabled, and no fixed interruptions are allocated to the display card.
4. Run the setup program in the floppy disk attached to the ENI. Set the NIC to non-PNP mode, and set the IRQ interrupt number and I/O address to the address not occupied by the system; in the bios, change the corresponding interrupt number from PCI/ISA to legacy.
Isa.
If the above method cannot solve the fault, we recommend that you try another Nic.
7. Q: After Windows XP is installed, the system may fail to detect the modem or establish a connection using the modem. What is the reason?A: In Windows XP, modem usually conflicts with another COM port. First, you can open the "Add/delete hardware wizard" to confirm windows
Whether XP recognizes the COM port. If the wizard detects a COM port conflict, the modem and physical COM ports may use the same com number. In this case, you need to set the modem to another unused COM port, or disable the physical COM port. After resolving the COM port conflict, check whether the modem has recovered. In addition, if the "Device Manager" cannot correctly identify the COM port, you can try to manually add the port. To check the port configuration and repeated ports, You can first open "set manager ", double-click "port (COM and LPT)" to view the COM port list. Right-click the port to be configured and click "properties" to confirm that the port and resource settings are correct. If a duplicate COM port is used, right-click it and click "Uninstall ".

In addition, incorrect COM port settings may affect the normal operation of the modem. You can first check the current IRQ and input/output settings of the modem COM port, then compare these settings with the recommended settings in the modem specification. To check the COM port settings, click "Device Manager", double-click "port (COM and LPT)" to view the COM port list, and right-click the COM port used by modem, the "communication port properties" dialog box is displayed. Click the "Resources" tab to view the current COM port settings. Unless other settings are recommended in the instruction manual, we recommend that you use the standard settings of the COM port in Table 1 for your modem.

If you want to use other COM port settings, clear the "use automatic settings" check box, click "change settings", and enter the expected port settings in "value.
1. Line or hub Problems
(1) ping the IP addresses of other hosts and check whether the connection speed of other computers is normal. If the connection speed is normal, jump to step 2nd. Otherwise, perform the following operations.
(2)
Check whether the NIC prompt light on the chassis is flashing. If the light flashes, the connection between the local host and the hub is normal. Otherwise, check whether both ends of the network cable are plugged in and whether the power of the hub is on.
(3)
Check whether the indicators for ports on the hub and other computer ports are normal. If the connection is normal, the connection between the connected network device and the computer is normal. Otherwise, check whether the two ends of the network cable have been inserted and use the network cable tester to re-test the connection of the network cable.

2. Other computer problems
(1)
Check whether the NIC lights of other computers are flashing. If the NIC lights are not on, it may be because the NIC is not correctly installed or is not properly connected to the network connection device. Open Control Panel ---- system ---- Device Manager and check whether there is a network adapter.
(2) If the protocol is installed, select "Control Panel" ---- "network" ---- "configuration" to check whether each computer is installed with TCP/IP and netbeui protocols. If no, add the above Protocol and delete the IPX/SPX protocol.

(3)
Whether the IP address is set correctly. This check is especially important when you only select to install the TCP/IP protocol. In MS-DOS mode, run the ipconfig command to display the machine's IP address and subnet mask (Subnet
And check whether the IP address is in the same CIDR block as other computers.
(4)
Whether file and printer sharing are configured. Open "Control Panel" ----- "network" ---- "configuration" ---- "file and print sharing", check whether the check boxes "allow other users to access my files" and "allow other computers to use my printer" are selected. If not, select this option.

(5)
Whether it is a Microsoft network user, Microsoft-friendly login or Windows login, the user name and password are required when the computer starts. If you do not enter the user name and password, follow the instructions to log on to Windows98, but Press Cancel to enter, so it will not appear in the network neighbor. Check "start"-"deregister" to check whether there is a computer name after "deregister". If it is displayed as "deregister"

(6)
Sometimes the NIC configuration is normal, and the network neighbors can see themselves (not others) and Ping themselves,
This is mainly because the NIC is not properly installed (however, such NICs are generally old, such as the ISA interface ). Check the nic I/O and DMA Number:
1. Use the NIC in DOS to check whether the I/O and DMA of the disk are consistent with those in windows. Otherwise, change the configuration in Windows to dos.
2. Open the chassis and check whether the NIC jumper is set to auto mode. If not, change it to auto and then reinstall the NIC in windows.

8. How to Find network faultsAfter a network problem occurs, do not worry. Keep yourself awake. Find out where the problem is, generally in the following situations:
1. When the entire network is disconnected, it may be a problem with the switch or hub. It depends on whether the switch or hub is working properly.
2. Only one computer cannot access the network, that is, when the computer's "Network Neighbor" is turned on, it can only see the local computer, but not other computers. It may be due to a problem with the connection between the network card and the switch, so we should first look at the RJ-45 crystal head is not bad contact. Then, use the wire measuring instrument to test whether the line is broken. Finally, check whether the port on the vswitch works properly.

3. You cannot see the Local Computer in "Network Neighbor", or use the "ping" command to start "Start/run". When the IP address of the local computer cannot be pinged, it indicates that there is a problem with your network settings. The first thing you think of is the network card. Open the "control panel/system/device management/network adapter" setting window, in this window, check whether there are any interruptions and I/O address conflicts. Generally, the ne2000 series Nic is irq3 AND THE 8029 chip Nic is irq10. If no Nic conflict exists, check whether the driver is in good condition and reinstall the NIC Driver.

4. other computers in the network can be seen in "Network neighbors", but you cannot access them. This may be caused by a problem in your network protocol settings. Delete your previous network protocols, reinstall them, and reset them.
What is the role of this special IP address in network management?
127.0.0.1 is the IP address loop of your Nic, if 127.0.0.1
Ping failure indicates that your network card is faulty. 127.0.0.1 refers to the local machine. You can install IIS to create a homepage, and enter 127.0.0.1 in the browser to see the homepage you have made. Ping
If 127.0.0.1 fails, the local TCP/IP software is faulty. Ping the local IP address. If it fails, the NIC is faulty. It is used to detect problems.