Fixed Wireless Technology

Wireless LAN Tools Part 3: Discovery and Planning

In part three of this four part study, we tackle the toughest part of WLAN deployment, patrolling your network.

by Lisa Phifer VP Core Competence, Inc. [August 10, 2004]

WLAN Analyzers are essential tools for anyone who administers a network with 802.11 Wi-Fi devices, authorized or otherwise. Part 1 of this series identified several open source and commercial tools. Part 2 explained how to combine those tools with PDAs, laptops, desktops, adapters, antennas, and GPS receivers to create an analysis toolkit.

Here in Part 3, we show how to use WLAN analyzers to carry out several common tasks: wireless node discovery, rogue detection, site surveys, and basic troubleshooting.

To offer a product-independent overview of common WLAN analyzer capabilities, this article includes examples drawn from a wide variety of tools identified in Part 1. To learn about the features of any individual tool, please follow links to vendor websites.

WLAN discovery
Whether you know it or not, there's an excellent chance that Wi-Fi access points and stations exist in or near your facility. Entry level Wi-Fi routers are cheap and readily available at office supply stores. Intel Centrino and other Wi-Fi adapters are shipping with newly purchased laptops and some PDAs. Employees and visitors are bringing these and other Wi-Fi devices into your workplace. Your neighbors are probably using them as well.

To discover wireless devices in your vicinity, just launch one of the open source or shareware stumblers identified in Part 1 and wander around your office, creating a file of discovered devices for later reference. Be sure to cover upstairs, downstairs, immediately outside your office, and adjacent public areas like hallways, stairwells, and rooftops. Repeat the stumble a few times—for example, on different days, at different times—until the discovered device count appears stable.

At this stage, your objective is merely to find existing APs and their network names (SSIDs), channel assignments, signal strength, and (when using a GPS) approximate location. Most stumblers indicate whether APs use some kind of security (e.g., WEP, TKIP) and are currently active (e.g., first/last time seen). For example, scan output from KisMAC, a free stumbler for MacOS X, is shown above.

Some stumblers also provide real-time traffic or signal graphs, like the NetStumbler Received Signal Strength Indicator plot shown above.