shooting Table 9-2: WLAN Troubleshooting - First Considerations Recent WLAN changes Considerations Hardware changes Have any new hardware devices been added to the network? Is the new hardware from the same manufacturer as existing hardware, or one that has been certified for interoperability? Configuration changes Have any configuration settings been changed recently? Operating channel changes, security mechanisms enabled, keys or passphrases changed? Software changes Have software or firmware upgrades recently been installed? Are any set-up changes required as a result of newly installed patches to client computer or network operating systems, device drivers or firmware? Environmental changes - Has any hardware recently been moved, such as an physical access point possibly creating an RF coverage hole? Have partitions walls or furniture (metal filing cabinets) been rearranged in the operating area, potentially affecting the RF propagation pattern? Environmental changes - Have any new wireless networks or other RF sources RF environment been installed in the operating environment or in the neighbourhood? (For example a fast-food restaurant in the next building with microwave ovens along the shared wall.) Usage pattern changes Have any new applications been installed which make use of the WLAN, particularly those requiring high continuous or peak bandwidth? Have there been any changes in network usage, for example a new user group with high bandwidth demands? Troubleshooting using WLAN Analysers Dedicated WLAN analysers are available to monitor and troubleshoot enterprise scale installations. These systems include tools for site surveying, security assessment, network performance monitoring and troubleshooting that can help the network manager in the tasks of designing, implementing, securing and finally troubleshooting WLANs. Analysers are available either as stand-alone hardware or as software packages that can be run on a laptop or handheld computer. Some examples are shown in Figure 9-1. Chapter Nine Table 9-