Find a large collection of basic Wireless LAN faults

This article mainly gives you a detailed explanation of the basic faults of the wireless LAN and provides a detailed explanation of some problems. I hope you can read this article to help you.

If a problem occurs in your wireless network, it may be caused by various factors. When you try to solve this problem, it may involve hardware vendors, network configurations, and many other factors.
When a wireless network is faulty, you should first troubleshoot several key issues. Some hardware problems may cause network errors and incorrect configuration may also cause the network to fail. In this article, we will introduce some methods and techniques for troubleshooting wireless network errors. This article focuses on basic wireless networks, rather than special wireless networks)

Hardware troubleshooting

When there is a connection problem with only one access point and one wireless client, we may quickly find the client with the problem. However, when the network is very large, it may not be that easy to locate the problem.
In a large wireless network environment, if some users cannot connect to the network, but other customers do not have any problems, it is likely that one of the many access points has a fault. Generally, by looking at the physical location of the client with network problems, you can probably determine which access point has a problem.
When all customers cannot connect to the network, the problem may come from many aspects. If your network only uses one access point, the access point may have hardware problems or incorrect configuration. In addition, it may be due to too much radio interference or a connection problem between the Wireless Access Point and the wired network.

Check the connectivity of the Access Point

To determine the cause of the network connection failure, first check whether the computer in the network environment can connect to the Wireless Access Point normally. A simple detection method is to enable command line mode on a computer in your wired network, and then ping the IP address of the wireless access point. If the Wireless Access Point responds to the ping command, this proves that the computer in the wired network can connect to the Wireless Access Point normally. If the Wireless Access Point does not respond, it may be due to a problem in the wireless connection between the computer and the wireless access point, or the Wireless Access Point itself has a fault.
To determine what the problem is, you can try to ping the IP address of the wireless access point from the wireless client. If the problem succeeds, the network connection of the computer may be faulty, for example, the network cable is damaged.
If the wireless client cannot ping the wireless access point, the Wireless Access Point itself is abnormal. You can restart it, wait about five minutes, and then use the ping command to view its connectivity through the computer and wireless client in the Wired Network.
If the ping to the wireless access point still does not respond, it indicates that the wireless access point is damaged or the configuration is incorrect. At this time, you can connect this possibly damaged wireless access point to a normal network through an available network cable. You also need to check its TCP/IP configuration. Then, ping the Wireless Access Point again on the wired network client. If the connection still fails, the wireless access point is damaged. Then you should replace the new wireless access point.

Configuration problems

The quality of wireless network devices is generally trustworthy. Therefore, the biggest problem is generally caused by the configuration of devices rather than the hardware. With this in mind, let's take a look at several common network connection failures caused by misconfiguration.

Test Signal Strength

If you can directly ping the Wireless Access Point through the network cable, but not wirelessly, you can basically identify that the fault of the wireless access point is temporary. If the problem persists after debugging, you can check the signal strength of the Access Point. Although most network administrators do not have a standard method for measuring the signal strength of wireless networks, most network adapter manufacturers will include a mechanism for measuring the signal strength.

Try changing the channel

If you find that the signal strength is weak after testing, but you haven't made any changes recently, you can try to change the channel of the Wireless Access Point and use a wireless terminal to check whether the signal is enhanced. Since modifying the connection channel on all wireless terminals is not a small project, you should first test it on a wireless terminal to prove it is effective before it can be implemented in a large area. Remember, sometimes wireless network failures may suddenly improve because an employee hangs up his cell phone or closes the microwave oven.
Not long ago, I took my notebook to work at a friend's house. I decided to connect to my friend's network because I used wireless networks. When I got home, I didn't use this notebook any more. After two weeks, when I opened my notebook again, I found that it could not connect to my wireless network. Soon I found the root cause of the problem: I forgot to change the Service Identifier (SSID, Service Set Identifier) back to my own network ID. Remember, if your SSID does not specify the network correctly, your laptop will not ping the wireless access point, and it will ignore the existence of the wireless access point, search for the corresponding Access Point Based on the given SSID.

Test the WEP Key

Check WEP encryption settings. If WEP is set incorrectly, you cannot ping the wireless access point from the wireless terminal. You must specify different WEP keys for wireless network adapters and Access Points of different vendors. For example, some wireless NICs require you to enter a hexadecimal key, while others require you to enter a decimal key. Similarly, some vendors adopt 40-bit and 64-bit encryption, while others only support 128-bit encryption.
To make WEP work properly, all wireless clients and access points must match correctly. Most of the time, although the wireless client seems to have configured WEP correctly, it still cannot communicate with the wireless access point. In this case, I usually restore the wireless access point to the factory state, re-enter the WEP configuration information, and start the WEP function.

Tricky WEP configuration problems

Up to now, the most common configuration-related issue has been the use of the WEP protocol. In addition, the problems caused by WEP are also quite tricky, because the symptoms of problems caused by WEP mismatch are very similar to many serious problems. For example, if WEP is configured incorrectly, the wireless client will not be able to obtain the IP address from the DHCP server of the wireless network, even if the DHCP function is provided by the Wireless Access Point ). If the wireless client uses a static IP address, it cannot ping the IP address of the Wireless Access Point. This often makes people mistakenly think that the network is not connected.

The basic skill for determining whether WEP is configured incorrectly or network hardware is to use the wireless NIC driver and the built-in diagnostic function of the operating system. For example, one of my laptops uses Windows XP and is equipped with a Linksys Wireless Nic. When I move the mouse to the wireless network map icon in the system taskbar, a summary of the network connection information will pop up. When the connection channel and SSID are set correctly, you can connect to the wireless access point even If WEP is set incorrectly. At this point, you will see that the connection signal strength is zero from the taskbar. Whether or not WEP is set correctly, the Linksys Nic displays the connection signal strength. You can also know that the network is connected, although it may not be able to ping the wireless access point.

If you right-click the Wireless Network icon in the taskbar and select View Available Wireless Network View Available Wireless Networks in the pop-up menu, you will see Wireless Network Connection) dialog window. This dialog box displays the SSID numbers of all wireless networks in the current channel, including the networks you are not connected. Therefore, if you find that your wireless network number is in the list, but you do not seem to be able to connect properly, you can rest assured that your network connection is no problem, and the problem is that the configuration is correct.

Note:
The wireless network connection dialog box also provides a region where you can enter the WEP Key. When you try to connect to a wireless network, you can enter the WEP Key of the network. I have been unable to correctly connect to the target network many times, but it was successful by manually entering the WEP key in this area. Generally, after entering the WEP key here, the network will be connected successfully immediately.

DHCP configuration problems

Another reason for your failure to access the wireless network may be caused by a DHCP configuration error. The DHCP server in the network is a key factor for your normal use of the wireless network.

Many new wireless access points feature DHCP servers. Generally, these DHCP servers allocate the IP address range 192.168.0.x to the wireless client. In addition, DHCP Access Points do not accept connection requests from IP addresses that are not assigned by themselves. This means that wireless clients with static IP addresses or clients that obtain IP addresses from other DHCP servers may not be able to connect to the access point normally.
When I first installed a wireless access point with a DHCP service, I allowed it to assign an IP address to my wireless terminal. However, the IP address range of my network is 147.100.x.y, which means that although the wireless client can connect to the Wireless Access Point and get an IP address, the laptop cannot communicate with other computers in the Wired Network, because they belong to different address segments. In this case, there are two solutions:
Disable the DHCP service of the Access Point and allow the wireless client to obtain the IP address from the standard DHCP server in the network.
Modify the IP address range of the DHCP service so that it applies to your existing network.
Both methods are feasible, but you need to look at the firmware function of your wireless access point. Many wireless access points allow you to use one of the methods, and few wireless access points can support these two methods.

Problems with multiple access points

Assume that two wireless access points work in the default mode at the same time. In this case, each access point will assign a 192.168.0.X IP address to the wireless client. The problem is that the two wireless access points cannot distinguish which IP address is allocated by themselves and which is allocated by the other access point. Therefore, IP address conflicts may occur in the network in the morning or evening. To solve this problem, you should set different IP Address allocation ranges on each access point to prevent overlapping IP addresses.

Note the customer list

Some access points have a customer list, and only end customers in the list can access the access point. This may also be the root cause of network problems. This list records the MAC addresses of all wireless terminals that can access the Access Point. From a secure perspective, it can prevent unauthenticated users from connecting to your network. This function is usually not activated. However, if the user accidentally activates the customer list, the list does not save any MAC address, so no matter how you set it, all wireless clients cannot connect to this access point.

I also encountered a problem caused by setting the user list when multiple access points exist in the network. Some administrators think that as long as a customer list is set on an access point, these authenticated customers can access any access point on the network. Otherwise, if you want the access point to activate the customer list function to improve security, you should make the same settings for each access point on the network, in this way, confirmed users can connect to any access point of the network, while unconfirmed users cannot connect to any access point.