Wireless Troubleshooting Facts

Wireless Troubleshooting Facts

If you are having trouble establishing or keeping a wireless connection, consider the following:

Consideration	Description
Incorrect configuration	Probably the most common source of problems with wireless networking is incorrect configuration. Before considering other problems, verify that the correct SSID and WEP/WPA keys have been configured. Remember that WEP/WPA keys are not case-sensitive, but passphrases are case-sensitive.
Range and obstructions	Wireless standards have a limited range. Moving a client outside of the effective range will weaken the signal and likely cause intermittent reception while moving outside of the stated range can cause it to be completely dropped. In addition, many wireless devices have trouble transmitting through obstructions in the path. Infrared requires a line-of-sight path, while radio frequency wireless has trouble transmitting through certain materials such as concrete.
Channel interference	The 2.4 GHz frequency range is divided into 11 channels, with each channel having some overlap with the channels next to it. You might experience problems with your wireless network when other devices are trying to use the same or adjacent channels. Devices that use radio frequency wireless include: Cordless telephones Other access points in the area (for example, each of your neighbors might have a wireless network, with each configured to use a similar channel) To avoid interference, try changing the channel used on the access point. If the area has different wireless networks, configure each with a different channel with at least two channels separating the channels in use (for example you can use channels 1, 4, 8, and 11).
Atmospheric and EMI conditions	Interference from atmospheric conditions such as weather or other sources of stray radio waves (electro-magnetic interference) can degrade the signal and cause service interruptions.
Antennae orientation	For some 802.11 devices, the antenna orientation might have a small effect on signal strength. There are two types of antennas you should be aware of: Directional antenna: Creates a narrow, focused signal in a particular direction. Focused signal provides greater signal strength increasing the transmission distance. Provide a stronger point-to-point connection, better equipping them to handle obstacles. Omni-directional antenna: Disperses the RF wave in an equal 360-degree pattern. Used to provide access to many clients in a radius. For other devices such as infrared or satellite, the orientation of the receiving device is critical. For these types of devices, make sure the receivers have a line-of-sight path to communicate.
Client and access point incompatibility	In some cases, especially when using 802.11n, the wireless client might not be compatible with the wireless access point. Try updating the software that came with the wireless client, update the firmware on the access point, and research the manufacturer's Web site for additional information. Because of the large number of vendors of wireless devices for clients, Cisco wants to ensure that the vendors' devices will work with Cisco access points. The Cisco Compatible Extensions (CCX) program allows manufactures of wireless network devices to send their products to a third-party testing lab to ensure that they will work with Cisco access points.

Wireless Configuration Facts

Wireless Configuration Facts

A wireless implementation checklist should include the following configuration processes:

Method	Description
Plan access point placement and configuration	The first step in implementing a wireless solution is to plan the wireless network. Consider the following: Draw a sketch of the building or location where wireless access is required. Identify possible access point locations, taking into consideration signal strength and maximum signal distances. Place access points in central locations. Radio waves are broadcast in each direction, so the access point should be located in the middle of the area that needs network access. Devices often get better reception from access points that are above or below. In general, place access points higher up to avoid interference problems caused by going through building foundations. For security reasons, do not place access points near outside walls where the signal can be intercepted by non-authorized devices. Placing the access point in the center of the building decreases the range of the signals available outside of the building. Select the SSID for the wireless network. If the network has multiple access points, identify which channel each access point will use. Make sure that neighboring access points use non-overlapping channels. Click here for a diagram of a sample wireless network with multiple access points.
Connect the wireless access point to the wired network	Most access points require that you make a connection to the access point through the wired network in order to complete access point configuration tasks. Before connecting the access point, you can verify that the wired connection is valid by connecting a laptop to the network port. Connect the access point to the existing network with a straight-through Ethernet cable. Optionally, you could use a cross-over cable and connect a laptop or desktop computer directly to the Ethernet port on the access point. Most access points come configured with a static IP address and a subnet mask. On a host on the wired network, change the host's subnet to the same subnet of the access point. Most access points use a Web-based program for configuration. Use your browser to connect to the default IP address of the access point, then enter the default administrator name and password to connect to the configuration utility.
Configure basic access point settings	Once connected to the access point configuration utility, configure the necessary settings: Configure a static IP address (with subnet mask, default gateway, and DNS settings), or configure the access point to use DHCP. Because the access point acts much like a switch, an IP address is not required. However, configuring the IP settings allows you to connect to the access point to make configuration changes. After changing the IP address, you will need to change the IP address of the client that is connected to the access point. Configure the wireless standards to use (802.11a/b/g/n) and the operating mode (mixed, legacy, greenfield, etc.). Configure the SSID. If the access point is part of an ESS, all of the access points should share the same SSID. Configure the channel. To avoid interference between multiple access points, each access point should have a different, non-overlapping channel. On a small network with a single access point, you can set the channel to Automatic. The access point then senses other access points nearby, and (if possible) selects a channel that is not in use.
Configure a client	Install and configure a wireless client, such as a laptop with an enabled radio. When you install the wireless adapter, you use a wireless connection manager to view and connect with wireless networks. Windows XP and later comes with a built-in wireless connection manager. This connection manager uses the Wireless Zero Configuration (WZC) service. When roaming between access points, WZC automatically connects to the access point with the strongest signal. Many wireless adapters come with their own connection manager that might provide additional functionality. With most connection managers, you can view wireless networks in range that are broadcasting the SSID. Simply select the wireless network and establish the connection. A successful connection verifies that the client can communicate with the access point.
Configure security on the access point	If the access point is left connected to the network without security implementations, attackers may connect to the network, potentially circumventing all security on the wired portion of the network. When configuring the authentication method: Use Open authentication to allow anyone to connect to the wireless network. This option is typically used by businesses that provide free Internet access to customers. Use Shared Key authentication on small, private networks. With Shared Key authentication, all access points and all clients use the same authentication key. Shared Key authentication can be configured using one of three settings: A simple Shared Key setting uses the WEP key for authentication. When using this option, you should disable encryption. WPA-PSK (WPA Personal) uses WPA with a shared key. WPA2-PSK (WPA2 Personal) uses WPA2 with a shared key. Use 802.1x authentication on large, private networks. 802.1x requires a RADIUS server on the network. Users authenticate with unique usernames and passwords. When configuring encryption, select the strongest method supported by all devices: AES is used with WPA2. When using AES, all devices must be WPA2 capable. TKIP is used with WPA. Most existing devices can use WPA. If not, check to see if a firmware update is available to add WPA capabilities to the device. Use WEP only if no other encryption is supported. Note: Do not use WEP together with Shared Key authentication. Public networks typically require no encryption.
Configure client security settings	After configuring security on the access point, you will need to add security to the wireless client. Manually configure the security settings that correspond to the wireless network. When using WEP or Shared Key authentication, enter the same shared key configured on the access point. If using 802.1x authentication, enable 802.1x and configure any necessary settings. Depending on the implementation, you might be prompted for a username and password when you try to connect. Select the encryption method used on the wireless access point. After the security configurations are set, verify that the wireless client can still connect to the wireless network.
Conduct a site survey	A site survey is an evaluation of your wireless network configuration. The site survey looks for advantages and problems with the wireless network and its surroundings. When conducting the site survey: Verify that the SSID broadcast and security settings are correctly configured on each access point. Assess the signal strength and direction of wireless access points. For example, make sure that access points are not placed near outside walls where the signals will be strong outside of the building where you do not have physical control. Check for obstructions that could affect the availability of the wireless signal in various locations. Check for other wireless networks in the area, and choose a channel that does not conflict with other networks. Perform cell-shaping. Cell-shaping uses directional antennae and shielding methods to locate the wireless access points in secured areas in order to adjust their transmittal power. If you find something of concern during the site survey such as a strong signal strength outside of the building, troubleshoot the issue and then conduct another site survey to confirm that the issue is resolved.