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Most people do not understand the knowledge points of this article "what are the common faults in the exchange unit network and how to solve them", so the editor summarizes the following contents, which are detailed, the steps are clear, and have a certain reference value. I hope you can get something after reading this article. Let's take a look at this article "what are the common faults in the exchange unit network and how to solve them?"

Failure 1: the network cannot communicate when the switch is powered on

[failure phenomenon]

The switch cannot connect to other networks when it is just turned on, so it will take a while to wait. In addition, after using it for a period of time, the speed of accessing other computers is fast, and if you do not use the network for a period of time, the speed of access will slow down again.

[fault analysis]

Because this switch is a manageable switch, in order to avoid the existence of topological rings in the network, which leads to network paralysis, the managed switch enables spanning tree protocol by default. In this way, even if there is a loop in the network, only one path will be retained and the other links will be automatically cut off. Therefore, when the switch is powered on, each port needs to enter the monitoring, learning and forwarding state in turn, which takes about 3-5 minutes.

If you need to start the switch quickly, you can start "PortFast" on the port directly connected to the computer so that the port immediately and permanently transitions to the forwarding state, so that the device can connect to the network immediately, avoiding the waiting time necessary for the port to transition from the listening and learning state to the forwarding state.

[troubleshooting]

If you need to forward data quickly after the switch is powered on, you can disable the extended Tree Protocol or set the port to PortFast mode. However, it should be noted that although these two methods omit the port detection process, once a topological ring is generated between the network devices, the network communication will be paralyzed.

Failure 2:5 port switch can only use 4 ports

[failure phenomenon]

There are four computers in the office, but only one information socket, so a five-port (one of which is a UpLink port) switch is configured. It was thought that four computers were just connected to four interfaces, and one UpLink port was used to connect to the local area network, but after being connected to the network, Port 1 adjacent to the UpLink port could not be used normally.

[fault analysis]

A UpLink port cannot be seen as a separate port because it is actually a port from a neighboring port, but with a different connection object. With the UpLink port, a hub device can connect to a normal port of another hub device using a straight-through line, eliminating the need for crossover lines.

The chips of switches and hubs are usually × 4, so the ports of hub equipment are mostly 4 ports, 8 ports, 16 ports, 24 ports and so on. If made into 5 ports, 3 modules will be wasted, thus increasing the cost.

[troubleshooting]

The failure can be solved by replacing the 4-port switch with the 8-port switch.

Fault 3: the "COL" indicator is on or flashing, unable to communicate

[failure phenomenon]

Computers in the local area network access the server through a hub, but one day it is found that all client computers can not connect with the server, and the Ping between clients is intermittent. Check the hub and find that the "COL" indicator is on or blinking continuously.

[fault analysis]

The "COL" light is used to indicate collisions and conflicts in the network. The "COL" light keeps flashing, indicating that the conflict has occurred; when the "COL" light is on, it indicates that a large number of conflicts have occurred. The cause of a large number of conflicts may be a hub failure or a network card failure. In general, the possibility of failure of the network card is relatively small, so the focus is on the troubleshooting of the hub.

[troubleshooting]

Replace the hub and the network returns to normal.

Failure 4: server connection is intermittent after upgrading to gigabit network

[failure phenomenon]

The original server uses a 10/100Mbit/s network card, running normally. However, after installing a 1000Mbit/s network card and using it to connect to the 1000Base-T port of the central switch, the connection between the server and the network is intermittent and unstable, which can not provide normal network services. Using the network cable tester to test the network, it is found that there is no problem with the connectivity of the twisted pair link.

[fault analysis]

The connection is normal during 100Mbit/s, but the failure occurs only when upgrading to 1000Mbit/s. It seems that the cause of this failure may be a Category 5 cabling problem. Although theoretically speaking, super-five systems support the transmission rate of 1000Mbit/s, but if the quality of twisted pair, distribution frame, network cable and other network equipment is not very good, or there is something wrong with the termination process, the 1000Mbit/s bandwidth can not be achieved.

Because 1000Base-T needs to use all four pairs of twisted pair, the effective transmission rate of each pair is 250Mbit/s, and complete full-duplex transmission, 1000Base-T has higher requirements for the electrical performance of twisted pair, such as signal attenuation, echo, return loss, crosstalk and anti-electromagnetic interference. If the performance of twisted pair or other accessories is not good, there will be serious crosstalk between online pairs, resulting in communication failure.

[troubleshooting]

Considering that the performance of five types of cabling systems may not be able to meet the requirements of gigabit network systems, the failure is solved after being replaced by category six cabling products.

Fault 5: although the Link lights keep flashing, the network speed is extremely slow.

[failure phenomenon]

The speed of the server surfing the Internet is very slow, it is very slow to open the web page at first, and then even the web page cannot be opened, and the Ping website cannot resolve the address. At first I thought it was a DNS setup or a server failure, but these are all working properly. Try Ping other computers and find that the packet loss rate is very high. At this time, the Link indicator of the switch keeps flashing, and the data exchange is very frequent, indicating that the computer is constantly sending and receiving data packets. When the switch is turned off and then turned on again, the failure is alleviated, but it occurs again after a period of time.

[fault analysis]

Judging from the failure phenomenon, this is a broadcast storm within the network. Broadcast storms can be caused by many reasons, such as worms, switch port failures, network card failures, link redundancy without spanning Tree Protocol enabled, network cable ordering errors or interference. It is a convenient way to check the switch lights when a network failure occurs, and you can visually view network connectivity and network traffic.

[troubleshooting]

As far as the current situation is concerned, worm is the main cause of network paralysis. Update the system patch for the server in time, and install the network version of the virus detection software, upgrade the virus database for the server in time, after the server installs the anti-virus client program, the fault can be solved.

Failure 6: server resource sharing failure

1. Unable to assign access to the user

[failure phenomenon]

The whole network uses a Windows domain and the client is Windows2000 Professional. The IP of the server is set to 192.168.0.1 and the DNS of the router is 127.0.0.1, and the internal IP address of the router is 192.168.0.1. All the clients use the way of obtaining IP address automatically, and they all belong to the DomainUser group. When the server sets up shared files, permissions can be specified, but cannot be accessed.

[fault analysis]

In the Windows domain, NTFS permissions and share permissions are used to set access to shared folders. However, NTFS permissions are higher than shared folder permissions, which means that you must first set NTFS permissions for the folders you want to share, and then set shared folder permissions for them. If there is a conflict between the two, the NTFS permission will prevail.

[troubleshooting]

Assign NTFS permissions to users before specifying shared folder permissions. For example, if you need to create a shared folder TESTA for user A, so that the shared folder can be completely controlled by user An and accessed by any other user, you must first set the access rights of TESTA, specify "full control" permissions for user A, and set "read-only" permissions for Everyone. Similarly, you should do the same when setting shared folder permissions.

two。 Shared folders cannot be displayed in Network neighbors

[failure phenomenon]

Some folders have been shared, but cannot be viewed in Network neighbors, but some shared files on the same computer can be seen.

[fault analysis]

Since some shared folders are visible, the computer's network configuration and connection are basically normal. And this is not really a fault, but a type of configuration that belongs to shared properties. In the Windows system, there are two main types of shared files, one is for system calls, the other is for other users to access. Shared files for system calls do not appear in Network neighbors, but can be displayed with commands such as "Net View"; shared files accessed by other users are visible in "Network neighbors".

So how do you configure invisible shared folders? Just add a dollar sign after the name of the shared folder. For example, in the system, the folder automatically created for each user is such a shared type folder, each user can only see his own user folder, but can not see other people's user folder. There are also some disks that are shared after installation, but their shared file names are all followed by a "symbol, so the client user cannot see them.

[troubleshooting]

Delete the "$" symbol after the shared file name, and the shared files that cannot be displayed can appear in the "network neighbor".

Failure 7: hubs and routers cannot share Internet access

[failure phenomenon]

Multiple computers use broadband routers and hubs, and use hubs to expand ports to form a network to share Internet. After the connection is completed, the three machines directly connected to the LAN port of the broadband router can access the Internet, but the computers connected through the hub cannot access the Internet, no matter whether the cross line or parallel line is used between the router and the hub, and the light connected to the router LAN port on the hub is not on. In addition, what is the reason why the computers on the hub cannot Ping the router or Ping other computers?

[fault analysis]

(1) failure of the hub itself

The fault is that the computers on the hub cannot Ping each other, let alone Ping the router. This failure can only affect all computers connected to the hub.

(2) Cascade failure

For example, the cascade jumper between the router and the hub uses an incorrect line sequence, or a jumper connectivity failure, or an incorrect cascade port. The symptom is that computers on the hub can Ping each other, but cannot Ping the router. However, Internet access to computers directly connected to the router LAN port will not be affected.

(3) Broadband router failure

If it is a LAN port failure, the result will be similar to a cascade failure: if it is a routing failure, the result will be that no computer in the network will be able to access the Internet, whether connected to the router's LAN port or to the router.

[troubleshooting]

From the point of view of the failure phenomenon, the computer connected to the hub can neither Ping the router nor Ping other computers, so it is preliminarily concluded that it should be the connection fault between the computer and the hub. At this time, you can first replace a network cable to try, if still can not troubleshoot, you can replace the hub to solve.

Fault 8:IP address conflict

[failure phenomenon]

Recently, the following situation often occurs on my computer, indicating that "the system has detected an address conflict between the IP address xxx.xxx.xxx.xxx and the network hardware address 0005 3B 0C 12 B7. The network operation of this system may be suddenly interrupted", and then lose the line for about a minute and restore the network connection. What is the reason for this and how to solve it?

[fault analysis]

This system prompt is a typical IP address conflict, that is, the IP address used by this computer is exactly the same as the IP address of another computer on the same network, resulting in communication failure. The MAC address of the network card that conflicts with this computer is "00 05 3B 0C 12 B7". In general, IP address conflicts are caused by improper allocation of IP addresses by network administrators, or by other users setting IP addresses indiscriminately.

[troubleshooting]

Because the MAC address of the network card is unique, you can ask the network administrator to find the computer that conflicts with you with the help of the MAC address, and modify the IP address. Using the "IPCONFIG / ALL" command, you can view the IP address and MAC address of your computer. Finally, use the command "ARP-S IP address network card physical address" to bind this legal IP address to your network card MAC address.

The above is about the content of this article on "what are the common faults of the switch network and how to solve them?" I believe we all have a certain understanding. I hope the content shared by the editor will be helpful to you. If you want to know more about the relevant knowledge, please pay attention to the industry information channel.

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