Wireless Troubleshoot FAQs

[Ramkumar Jayaseetharamar]

This document contains the Q and As for most frequently faced issues in wireless network

Q) Wireless Clients doesn’t associate /communicate to other devices in the wireless network?

A) Perform the following checks to troubleshoot basic connectivity issues in Wireless Network

1. Check if the client receives sufficient signal from the access point. If not adjust the location of the client to receive AP’s signal. You can check the signal strength from client utility.
2. Check if there is a security mismatch between client and the device. Make sure that the authentication methods are configured identically on the client and the access point. If  authentication is done with a Pre-shared key , make sure they are configured identically on both the devices.
   
3. Check if the SSID is configured to be broadcasted on the AP so that clients can locate the access point. Make sure that the SSID is identical between the devices. SSID is case-sensitive and they should match.
4. Check the IP address on the client.  Make sure that the SSID is configured with appropriate VLAN and that the DHCP pool for the subnet is configured on the DHCP server. Normally DHCP server on the access point provides  IP address to the clients. If  you have external DHCP server , make sure that the switch is configured to allow the VLANs. If  DHCP is not an option , configure a static IP for the client and check if it works.
   
5. Check if the wireless adapter is properly installed on the client. See the device manager to check if the device driver is installed for the adapter. If not reinstall the update the drivers.

        For further troubleshooting refer the document Troubleshooting Connectivity in a Wireless LAN Network.

Q) Clients experience intermittent connectivity on the wireless LAN?

A)  Check for the following issues

1. Wireless networks experience interference from both 802.11 and Non-802.11 devices. Neighbor APs  acting on the same channel ,  within the coverage area of your AP causes interference. Change the channel on which your AP acts or change the frequency domain (802.11 standard) on which your AP acts. Non 802.11 devices like Microwave ovens , Bluetooth devices , Cordless phones cause interference in 2.4 GHz frequency. They need to be found and dislocated.
2. Avoid placing the device near the heat sources. They tend to affect the wireless signal.
3. Ensure that devices are compatible with each other. Check the Product’s data sheet for compatibility.
4. Check if the devices in the network are stable. New firmware fixes certain bugs that were present in the earlier firmware versions. Ensure that devices have latest firmware.

Q)  How do we troubleshoot the corrupted firmware in the device?

A)  Unstable firmware leads to loss of wireless connectivity. Perform one of the following steps

1. Reboot the device and check if it works.
2. Reset the device either through Hardware or Software.
3. If the problem still persist , download and use the latest firmware from Cisco. You can also contact Technical Support.

To download software for the wireless products go to Download Software link on Cisco.com.

To download firmware for small business products go to  http://www.cisco.com/cisco/psn/web/solutions/small_business/products/firmware.html . This site doesn't require registration.

Q) How do we improve throughput for the Wireless LAN?

A) Try one of the following steps to improve throughput on Wireless LAN

1. As the number of users increase , performance decreases. Consider deploying additional access points so as to load balance the users.
2. As distance between AP and client increases , signal strength and correspondingly data rates starts decreasing. Adjust the location of the   
   devices so as to increase the data rates.
3. Speed varies depending on the 802.11 standard used by the adapter. 802.11a or 802.11g devices are faster than 802.11 b or older 802.11 devices because of the encoding scheme used in data transmission. As of late 802.11n  devices are even faster than 802.11 a or 802.11g devices.
4. Mixed environment generally reduces the throughput of the devices. Eg. Presence of a 802.11b devices in a 802.11g environment reduces the 
   throughput of  802.11g devices in the network.
5. Avoid using both Layer 2 and Layer 3 encryption at a time in the wireless environment. It is sufficient to have Layer 2 encryption for indoor environments. Too high encryption causes overhead to the device’s hardware which leads to reduced throughput.
   

Q) How do we improve the coverage area of  a WLAN?
A) Coverage area can be improved using one of the following methods

1. Use additional APs on Non-overlapping channel.
2. Increase power level on the APs.
3. Use repeaters to improve the coverage area.
4. Place the APs in optimum locations to provide sufficient coverage. You can use the Site Survey / Planning software available from various vendors to calculate the number of access points and placement of the APs.
5. Use the adapters / access point that has Diversity antennas.  As of late MIMO technology is found to increase the coverage.

Q) We are unable to access GUI of the Access Point through a PC on the network?
A) Perform the following checks

1. Check if the device is reachable . Check the physical layer and layer 3 connectivity using the ping command.
2. Check the settings on the browser. Make sure to check that Proxy settings are disabled on the browser.  Also make sure if browser is confiugred to allow Pop-Ups
   
3. Disable any firewall installed on the computer and check if you are able to access the GUI.
4. GUI of the device can be accessed either using http/https. Ensure that these services are enabled on the device.
5. Ensure that  the username/password used is correct and has sufficient privilege to access the device.

Q) Is there any document available for initial configuration and general troubleshooting on Linksys series Access Point?                         
A) For general configuration and some basic troubleshooting refer Q & A section of the document on each models at

Small Business Wireless Access Point Models.

Q) Wireless Bridges don’t communicate with each other?

A)  Wired networks can be connected using wireless bridges. Perform the following checks

1. Check if the bridges are configured as Root and Non-Root bridges respectively.
2. Check if there is a LOS between the bridges for maximum signal strength reception. Use the alignment utility to align the antennas for maximum signal strength reception.
   

3. Data Rate mismatch between the bridges cause loss of connectivity.

For further troubleshooting refer Troubleshoot Common Problems with Wireless Bridged Networks.

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Q) 521 series LAP (Lightweight Access Point) doesn’t join the WLC?

A) Cisco LWAPP protocol is used for communication between AP521 and WLC 526. For more information on how LAP joins the WLC refer the document
Lightweight AP Registration on a Wireless LAN Controller.

Perform the following steps if the LAP doesn't join the WLC

1. Check if the AP has an IP address assigned either statically or through DHCP to communicate with the controller.
2. Make sure that AP is reachable to the WLC.
3. AP should be configured to discover the WLC.
   
4. Make sure that the switch is configured to allow the VLAN of the AP and WLC.
5. Only 2 WLCs with a maximum of 24 LAP is supported per network. Additional access points are not supported.

For further troubleshooting refer the document Troubleshoot a Lightweight Access Point Not joining a Wireless LAN Controller.

Q) How do we convert a AP521 from Autonomous to Lightweight mode?

A)You can convert a AP521 from Autonomous to Lightweight mode using CCA. For the procedure on conversion  refer

Upgrading Software on the Cisco 521 Autonomous AP.

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