Navigating the NetStumbler Screens
NetStumbler presents data onscreen in five modes:
Overview Mode
Overview is the default view for NetStumbler. All wireless access points are displayed on the right side of the window. The left side still shows the different modes, but none of these modes are selected. (See Figure 6-6.)
To display the Overview mode, ensure that only a top category is selected on the left window. For example, click on Channels (not a channel number).
The only marker for the mode you are currently viewing is the highlighted selection on the left window. The highlighting will turn off when you click your mouse on the right window, or on another program in Windows. In Windows terms, this is called losing focus.
Use the “number of number” display on the bottom right of a maximized NetStumbler window to ensure you are seeing all APs in the list. If the number says something like “41/41,” everything is being displayed. If it shows “10/41,” NetStumbler is filtering some of the results.
NetStumbler enables sorting of the results by clicking on the results headers in the right window. Default sorting is in descending order on “Last Seen.” This will keep the most current results at the top of the window. Another nice feature is the ability to rearrange the report headers. Click and drag a header title to move the column. Use the “Save Defaults” option on the View menu to save the new arrangement.
Channels
In the United States,Wi-Fi defines 11 channels for operation of equipment. The Channels mode filters the display for devices using only that channel. To enter this mode, expand the channels category in the left window and click on a channel. For example, channel 6 will filter the display to only show those APs broadcasting on channel 6.
SSIDs
Expand the SSIDs category and a list of every unique SSID appears in the left window. Click on one of these SSIDs and the right window will show only those access points with a matching SSID. When scanning a known network, this mode becomes helpful in filtering extraneous APs.
Filters
The Filters category has several built-in filters. Expand the Filters item to list the subcategories. See Table 6-2 for a description of the categories in NetStumbler 0.3.30. These built-in filters are just one more way to quickly sort through the on-screen display.
Signal and Noise Graphing
NetStumbler excels at visual representation. It’s probably the most usable side-feature included in the software. Figure 6-7 shows the signal strength window. Notice the great variation from high to low in this figure. This shows the signal level dropping as the laptop moved away from the access point.
The graphical nature of the window allows you to easily determine signal strength and noise levels as reported by the Wi-Fi card. Signal and noise level is displayed on the same graph and is measured in dBm. Noise appears in red, signal appears green. Although signal-to-noise ratio is not directly shown, a high signal with a low noise level reflects a good SNR.
To display the Signal Strength window, select a MAC address listed on the left window. For example, select SSIDs, then select Linksys, then 000625123456.
If the AP is active, you will see updates occur immediately on-screen at the same rate as the scanning speed. (See the Configuration section above.)