urity has paralleled the advances in technology aimed at increasing speed, network capacity and other functional capabilities. With the ratification of the 802.11i security enhancements in 2004, and the launch of the WPA2 implementation by the Wi-Fi Alliance, the foundations are in place for future WLAN installations to deliver true wired equivalent privacy over the inherently open wireless medium. However, security is only assured when these powerful technological capabilities are supported by properly implementing the practical security measures described in this chapter. CHAPTER Wireless LAN Troubleshooting Analysing Wireless LAN Problems As with any problem-solving exercise, resolving wireless LAN problems requires a systematic approach, first in analysing the symptoms to try to narrow down the possible cause, and then in investigating potential solutions. If a step-by-step approach to network implementation was followed, as described in Chapter 7, then troubleshooting will typically be called for when a change in network or device performance occurs - either something worked before and now does not, or now does not perform as it did before. Start by asking a number of questions to clarify the nature and extent of the problem (Table 9-1). This will help to narrow down the range of possible root causes. The starting point for diagnosis should be a review of any recent changes in the network hardware or configuration, in the operating environment or pattern of usage, as summarised in Table 9-2. Answering some of these questions may require further investigation, such as a repeat RF site survey if increased RF interference is a possible cause of performance degradation. The systematic approach should continue when testing possible solutions to the problem, using the strategies described in Table 9-3. The majority of WLAN problems fall into two categories, connectivity - when one or more client stations are unable to establish a connection to the network, and performance - when the data throughput and response ti