What if the wireless network is not connected?

1. Mixed wireless networks often fall off the line

Failure phenomenon

Use the Linksys WPC54G network card and Linksys WRT54G AP to build a wireless LAN that uses IEEE 802.11G protocols and a few 802.11B network adapters. The line is often dropped when using wrt54g for 54mb/s connections.

Fault analysis

In theory, the IEEE 802.11g protocol is backward-compatible with the 802.11B protocol, and devices using both protocols can be connected simultaneously to AP using the IEEE 802.11g protocol. However, from a practical point of view, as long as there is an IEEE 802.11B protocol in the network, the connection speed of the entire network will be reduced to 11MB/S (IEEE 802.11B Protocol transmission Speed).

Fault resolution

When mixing IEEE 802.11b and IEEE 802.11g wireless devices, be sure to set the wireless AP into a mixed (MIXED) mode, which can be compatible with both IEEE 802.11b and 802.11g two modes.

　　2. Wireless clients do not receive a signal

Failure phenomenon

After building the wireless LAN, the client is found to receive no signal from the wireless AP. Wireless network has no signal

Fault analysis

There are several possible causes for this failure:

(1) wireless network card distance from the wireless AP or wireless router is too far, more than the coverage of wireless networks, wireless signal to reach the wireless network card has been very weak, so that wireless clients can not be normal connection.

(2) The wireless AP or wireless router does not power up or does not work properly, causing the wireless client to not connect at all.

(3) When the wireless client distance from the wireless AP, we often use directional antenna technology to enhance the transmission of wireless signals, if the angle of the antenna has problems, will also lead to wireless clients can not connect properly.

(4) If the wireless client does not set the network IP address correctly, it cannot communicate with the wireless AP.

(5) For security reasons, wireless AP or wireless router will filter some MAC address, if the MAC address of the network card is filtered out, then also can not do normal network connection.

Fault resolution

You can use the following methods to resolve:

(1) Install antennas on the wireless client to enhance reception capability. If many clients are unable to connect to the wireless AP, install the omnidirectional antenna at the wireless AP to enhance the delivery capability.

(2) Check the LED indicator to see if the wireless AP or wireless router is working properly, and use the portable computer for close-range testing.

(3) If the wireless client uses the antenna, try to adjust the direction of the antenna, so that it faces the wireless AP or wireless router direction.

(4) Set the correct IP address for the wireless client.

(5) View the security settings of the wireless AP or wireless router and set the MAC address of the wireless client to a trustworthy MAC address.

　　3. Wireless client can receive signal normally but can't access wireless network

Failure phenomenon

The wireless network has a signal connection.

Fault analysis

The wireless network has a signal why is it not connected? The cause of the failure may be:

(1) The IP address of the wireless AP or wireless router has been assigned. When a wireless client is set to automatically obtain an IP address, it cannot access the wireless network because it does not have an available IP address.

(2) The wireless card does not have the correct IP address set. When a user sets the IP address manually, the wireless network will not be accessible if the IP address set and the IP address of the wireless AP are not within the same network segment.

Fault resolution

The following solutions can be taken:

(1) Increase the address range of the wireless AP or wireless router.

(2) Set the correct IP address for the wireless card to ensure that the IP address of the wireless AP is in the same network segment.

　　4. The wireless network can communicate normally, but cannot communicate with the Ethernet connected with the wireless router.

Failure phenomenon

Wireless clients can communicate with the wireless router normally, but cannot communicate with the Ethernet that is connected to the wireless router.

Fault analysis

The cause of this failure may be:

(1) Local area network (LAN) port connectivity failure.

(2) The IP address is set incorrectly.

Fault resolution

You can use the following workaround:

(1) Check the LAN port for the correct Ethernet connection by looking at the LAN LEDs. You should use a crossover line to connect LAN ports and Ethernet hubs.

(2) See if the wireless network and Ethernet are in the same IP address segment, only the host within the same IP address segment can communicate.

　　5. When dialing a cordless phone, it will cause strong interference to the wireless network.

Failure phenomenon

Whenever a cordless phone is dialed, the wireless network signal becomes unusually faint, often resulting in a link interruption.

Fault analysis

Since cordless phones and IEEE 802.11b are all working on 2.4GHz bands, there is a strong disruption to wireless networks when dialing a cordless phone.

Fault resolution

The general solution is to stop using a cordless phone or change the channel used by the wireless network.

　　6. When the network environment changes, can not be normal access

Failure phenomenon

Wireless networks are built in both the office and the home. While in the office, laptops can normally access the company's wireless network, but when they get home, they find they can't connect to the wireless network.

Fault analysis

There are several possible causes for this failure:

(1) The SSID (Service Set Identifier) configuration was not changed in a timely manner. Different wireless networks use different SSID and cannot ping the AP if the SSID is configured incorrectly. And the laptop will ignore the AP and look for a new AP based on the SSID configuration.

(2) WEP encryption. If a different WEP key is used, the wireless client cannot connect to the new wireless AP. If the WEP configuration is not correct, the wireless client cannot obtain the IP address from the DHCP server. If you use a static IP address, the wireless client cannot even ping the AP's IP address.

(3) IP address information. In general, wireless APs will automatically assign IP addresses to wireless clients, and if the IP address of the wireless client is set manually, then the client will not be able to communicate with the new AP.

Fault resolution

The following workaround can be used:

(1) When connecting to a new wireless network, timely change the client's SSID settings.

(2) If the access to the wireless network requires the use of a key, then access to the new wireless network, the first need to obtain the network key to access.

(3) Normally, the IP address assigned by the wireless AP can be used. If you want to use a static IP address, you must ensure that the static IP address and the IP address of the wireless AP are within the same network segment.

　　7. Set all correct, but unable to access wireless network

Failure phenomenon

The network settings are based on other users within the wireless network, including WEP encryption, SSID and IP address (automatically obtaining an IP address), and the wireless signal is displayed as Mange but cannot be connected to the wireless network.

Fault analysis

This may be the case where the network administrator has set up MAC address filtering on the wireless AP, allowing only the specified MAC address to be connected to the wireless network, and denying unauthorized users to secure the wireless network.

Fault resolution

Can contact with the management, the MAC address of your wireless card to tell him, ask him to add this MAC address to allow access to the MAC address list.

　　8. Wireless access to the home network for notebook computers for Internet sharing

Failure phenomenon

The home network uses "ADSL Modem + Broadband router" to achieve Internet sharing without the need for PPPoE dialing. The new notebook computer is not connected to the wireless network for Internet sharing.

Fault analysis

The wireless AP generally has only one LAN interface, therefore, when the wireless AP is connected to the network, it will occupy the network interface used by the original host, unless the broadband router has more ports, the wireless AP and the original host can not be connected to the broadband router, thereby sharing the Internet connection.

Fault resolution

If there are no more ports available for broadband routers, you can purchase a wireless router, a WAN port to a broadband router, a LAN port to the host, and wireless access to your laptop. In addition, the SOHO switch + wireless AP can also be used to connect the SOHO switch to the broadband router, and then connect the wireless AP and host to the SOHO switch.

　　9. Wireless AP does not have routing function

Failure phenomenon

ADSL virtual dial-up Internet access, wireless AP connected to the ADSL Modem. The desktop (the LAN port to which the wireless AP is attached) is available to the Internet, the laptop also receives the wireless signal, but is not able to access the Internet properly, and the IP address and default gateway is "not available".

Fault analysis

If the ADSL modem does not support routing, Internet Connection Sharing cannot be achieved with wireless APs.

Fault resolution

The following methods can be used to resolve:

(1) To enable the routing function of ADSL modem to achieve network Connection Sharing.

(2) Acquisition of a wireless router to connect the LAN to the desktop and WAN connection to the ADSL Modem.

(3) Install two network cards on the desktop and set it as the ICS host. A network card connected to the ADSL Modem, another network card connected to the wireless AP.

　　10. Use wireless network card to build Peer-to-peer network

Failure phenomenon

Two desktops connect to the Internet via ADSL. You are now connecting two computers by wireless means.

Fault Analysis and resolution

The method is very simple, just buy two wireless network card can. With two network cards installed in two computers, you can build a peer-to-peer network and realize all the functions of Ethernet, and can share the Internet. It should be noted that, in this way, the transfer rate will be around the IEEE 802.11B protocol theory Rate (11MB/S), that is, around 6mb/s.

　　11. Do not see other computers in the wireless network

Failure phenomenon

The wireless card appears to work, but you do not see other computers on your network in your online neighborhood.

Fault Analysis and solution

(1) Check the SSID and WEP parameter settings to make sure that the spelling and capitalization are correct.

(2) Check that the computer has file and printer sharing enabled, and verify that the file and printer sharing for Microsoft Network selection box is selected on the General tab of the wireless network properties.

　　IEEE 802.11g transfer rate is low

Failure phenomenon

In order to ensure the compatibility of wireless network standards, when we choose wireless products, we generally choose to support the IEEE 802.11b/g wireless AP and wireless network card. However, in the actual network test, we found that, in the absence of interference and limited transmission distance, the transmission rate of wireless link is still low, can not reach the nominal 54mb/s.

Fault analysis

IEEE 802.11g is not only 54mb/s, but also compatible with IEEE 802.11B wireless devices to smooth upgrade 802.11b wireless networks to 802.11g wireless networks.

Fault resolution

To accommodate existing 802.11B wireless LAN devices, 802.11G uses the same 2.4GHz frequency band as 802.11B, and uses two different OFDM (orthogonal Frequency Division multiplexing) coding techniques to communicate with the corresponding 802.11b or 802.11g devices. That is, in networks that mix 802.11b and 802.11g wireless devices, 802.11g-capable wireless devices can communicate either at 54mb/s rates and 802.11b devices, or at 11mb/s rates and 802.11b devices.

However, in the WLAN, the shared channel is used, and the data Link layer uses CSMA/CA (the carrier frame with collision avoidance to listen to multi-channel access) to control the wireless channel. In other words, when a host in the communication with the AP, the other host can only be in the listening state, once the host communication completed, the other host will be through a competitive way to achieve the control of the channel.

Therefore, in the 802.11b and 802.11g mixed wireless network, because 802.11b can not monitor 802.11g communication state, it is possible in the 802.11G device to communicate at the same time grab the wireless channel, which seriously interferes with the communication of 802.11 devices.

In order to solve this problem, the 802.11G protocol adopts "rts/cts" technology. Before sending data, a wireless LAN device sends a RTS (request to send) frame to the wireless AP, requests a wireless resource, and sends a CTS (clear to send) frame to the device if the AP does not communicate with other devices. Notifies it that it can communicate with the wireless AP. In this way, the above interference problem is avoided.