Wireless Network Troubleshooting

By Shaun Hummel

Overview

The process of troubleshooting your network if it has wireless components is somewhat more complex than wired infrastructure. In fact you must troubleshoot both wired and wireless infrastructure to determine the problem. The methodology of starting with cabling from the client and working through the OSI model to the application layer is effective. The wireless client traffic doesn't see any cabling until there has been association with the access point. In essence there is a data link between wireless client and access point. With that established there is data link traffic between access point and wired network switch.

The wired client has a Cat 5 cable plugged into the desktop that terminates at a wired switch. All clients associating at a specific access point now share a single Cat 5 cable running from access point to switch. That makes troubleshooting easier since cabling is a source of a lot of network problems, however any problems with that cable affects all clients. It is important to minimize the number of access point clients for maximum performance. Commercial network implementations average 10 - 24 clients per access point.

The key with troubleshooting is to determine what has changed. Sometimes it is hardware that isn't working or some change made such as new software, configured equipment or additional employees stressing the network. It could be a specific issue or several problems. Start with the client adapter, determine the specific symptoms and go from there.

The following is a series of questions that can used as a guideline during the troubleshooting process:

1. Can the wireless client associate with any access point?
2. Can you ping the switch IP address?
3. Can you ping the router?
4. Can you ping the DHCP server?
5. Does the client obtain an IP address?
6. Is the WAN circuit available?
7. Has new software been installed on the client?
8. Do all clients experience the problem?
9. Is it random or a specific pattern?
10. Is it server specific or application specific?
11. Is the DNS server IP address setting correct?
12. Is there a firewall that is filtering traffic?

Tools

a. Wireless client software shows status information such as access point association, DHCP enabled, IP address, default gateway, DNS server address.
b. Windows control panel shows wireless adapter settings, firewall configuration etc.
c. Ping will verify that network routing is working.
d. Network packet sniffers examine packet information such as protocols, filtered programs or errors with applications.
e. Spectrum analyzers detect frequency interference and possible sources.

Common Wireless Problems

Wireless Client Settings

• Upgrade the manufacturer client adapter driver.
• Implement current Windows operating system service pack.
• Examine client data rate, transmit power, preamble, roaming decision, WPA settings.
• Confirm shared keys if implemented aren't mismatched between client and AP.
• Examine IP address settings. DHCP will send specific settings to each client. Those clients without DHCP must configure IP address, subnet mask, default gateway and DNS server IP address.
• The client SSID name configured should match what is configured at the AP.

RSS Feed

 Follow @Stephen Bucaro

 Basics and Certification
 Technologies and Media
 Protocols and Standards
 Troubleshooting and Support
 Network Security
 Cisco Certification