Wireless network connection failure processing method (3)

9. Wireless AP does not have routing function

Symptom

Use ADSL virtual dialing mode to connect to the Internet, and the wireless AP is connected to the ADSL Modem. The desktop (the LAN port connected to the wireless AP) can access the Internet normally, and the laptop receives the wireless signal, but cannot access the Internet normally, and the IP address and default gateway are displayed as “unavailable”.

Failure Analysis

If the ADSL Modem does not support the routing function, Internet connection sharing cannot be achieved using the wireless AP.

Troubleshooting

The following methods can be used to solve:

(1) Enable the routing function of ADSL Modem to realize network connection sharing.

(2) Purchase a wireless router, connect the LAN to the desktop, and connect the WAN to the ADSL Modem.

(3) Install two network cards on the desktop and set them as ICS hosts. One network card is connected to the ADSL Modem, and the other network card is connected to the wireless AP.

10. Using a wireless network card to build a peer-to-peer network

Symptom

Two desktop computers access the Internet through ADSL. Now connect the two computers wirelessly.

Troubleshooting Analysis

The method is very simple, just buy two wireless network cards. By installing two NICs on two computers, you can set up a peer-to-peer network and implement all the functions of Ethernet, and you can share the Internet. It should be noted that when using this method, the transmission rate will be about the general theoretical speed of the IEEE 802.11b protocol (11 Mb/s), that is, about 6 Mb/s.

11. Cannot see other computers in the wireless network

Symptoms

The wireless network card display works normally, but other computers on the network are not visible in the network neighborhood. .

Fault Analysis and Solution

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

(2) Check if the file and printer sharing is enabled on the computer, and make sure the "File and Printer Sharing for Microsoft Network" check box is selected in the "General" tab of the wireless network properties.

12. IEEE 802.11g transmission rate is lower

Symptom

In order to ensure the compatibility of wireless network standards, we generally choose to support IEEE when selecting wireless products. 802.11b/g wireless AP and wireless network card. However, in actual network testing, we found that the transmission rate of the wireless link is still low and does not reach the nominal 54 Mb/s without interference and limited transmission distance.

Failure Analysis

IEEE 802.11g not only has a transmission speed of 54Mb/s, but also is compatible with IEEE 802.11b wireless devices, so that 802.11b wireless network can be smoothly upgraded to 802.11g wireless network.

Troubleshooting

In order to be compatible with existing 802.11b WLAN devices, 802.11g uses two different OFDM (orthogonal) in addition to the same 2.4 GHz band as 802.11b. Frequency division multiplexing) coding techniques to communicate with corresponding 802.11b or 802.11g devices. That is, in a network that uses 802.11b and 802.11g wireless devices, wireless devices using 802.11g can communicate with 802.11b devices at a rate of 54 Mb/s, and at Mbps with 802.11b devices. Communicate.

However, in the WLAN, the shared channel is used, and the data link layer uses CSMA/CA (Carrier Frame Multiple Access with Collision Avoidance) to control the wireless channel. That is to say, when one host communicates with the AP, other hosts can only be in the listening state. Once the host communicates, other hosts will control the channel through competition.

Therefore, in the wireless network used by 802.11b and 802.11g, since 802.11b cannot monitor the communication status of 802.11g, it is possible to preempt the wireless channel while communicating with the 802.11g device. Interfere with the communication of 802.11 devices.

To solve this problem, the 802.11g protocol uses the "RTS/CTS" technology. Before sending data, the WLAN device sends an RTS (Request To Send) frame to the wireless AP to request to use the wireless resource. If the AP does not communicate with other devices, it sends a CTS (Clear To Send) frame to the AP. The device notifies it that it can communicate with the wireless AP. In this way, the above interference problem is avoided.