Wireless troubleshooting

PREVIOUS: 802.11 protocols

Troubleshooting wireless problems can require an amount of ongoing support that many might not anticipate -- particularly after following all the expert advice and spending a lot of time preparing and planning a wireless network. In this section of the Wireless Protocols Learning Guide find out how to handle wireless connectivity issues, debugging and wireless capacity planning.

Wireless troubleshooting

Going wireless may avoid the expense of cabling and wired LAN drops, but wireless networks still require effective technical support and troubleshooting.

Smooth operation starts with a well-designed wireless LAN (WLAN). Site surveys, RF modelling and automated RF management systems are all investments that pay dividends by reducing help desk calls.

But no WLAN can escape the need for troubleshooting. Environmental conditions and network usage change. Equipment failures and software glitches occur. Eventually, wireless users require assistance. Good wireless network troubleshooting tools and a systematic approach can help you isolate and resolve those problems faster.

When wireless LAN (WLAN) users experience connectivity trouble, the problem may lie on the client side or the network side. Learning how to troubleshoot wireless connectivity problems that stem from issues associated with the network side of the WLAN solution can ensure that workers stay connected and maintain their productivity.

Problems experienced by wireless users run the gamut, from radio interference and client misconfiguration to loose access point LAN cables and cranky applications. As with wired troubleshooting, a systematic approach is needed to track down the problem without overlooking common causes or running in circles. And following the connection from client to server, verifying operation of every component in between, is still a sensible approach for wireless. Doing this simply requires an understanding of wireless devices, protocols and your own WLAN's architecture.

When you encounter trouble connecting a wireless host (desktop, laptop, PDA) to an office network, these debugging steps can be helpful:

1. Start by rechecking physical connections.
2. Verify that your wireless adapter is installed and working properly.
3. Verify that your wireless router's LAN settings are correct.
4. Verify your client's TCP/IP settings.
5. Once your client has a valid IP address, use "ping" to verify network connectivity.
6. If your wireless client still cannot connect, get a valid IP address or ping your router, it is time to consider wireless-specific problems.
7. If a matched wireless client and router can "hear" each other but still cannot connect or exchange traffic, look for a security mismatch.
8. Ensure RADIUS is working.
9. If RADIUS is working but the client's access requests are rejected, look for an 802.1X Extensible Authentication Protocol (EAP) or user login problem.
10. Finally, if your wireless client connects and pings successfully, but encounters intermittent network connectivity problems (e.g., some pings work, some fail), you may be experiencing poor signal strength, RF interference or disconnection caused by AP roaming.

Most enterprise WLAN switch and access point vendors sell their own network management software that provides for planning, provisioning and/or monitoring. A few examples include Aruba Networks Mobility Management System, Bluesocket BlueView Management System, Cisco Wireless Control System and Wireless LAN Solution Engine (WLSE), Colubris Networks NMS and RF Planner, Trapeze Networks RingMaster, and Siemens HiPath Wireless Convergence Software.

Usage reporting on wireless local area networks (WLANs) is becoming increasingly important as organisations rely more and more on wireless communication for mission-critical and real-time applications.

Think of it this way: Imagine you are in a hospital, and the hospital uses a WLAN for guest Internet access, employee email, and not-so-trivial things such as patient monitoring and lifeline/lifecare applications. The last thing you want as an administrator is for a guest or employee network request to consume all available bandwidth, making it impossible to transmit the lifeline application. Until 802.11e (WLAN QoS) becomes a reality, capacity planning via WLAN usage reporting is a necessity.

Implementing 802.11g in an office with few if any open spaces can present its own type of problem -- picture an office with slim hallways in between separate closed-in rooms and multiple blocks of this design on the same floor. Workers will definitely notice the probable disconnection and reconnection as they move about the floor and their devices switch APs. But even the standard installation of one AP per 3,000 square feet might not remedy the issue. Several options should be considered to improve the situation and prevent dropped connections.