Watch out for a sleeping WLAN NIC

By Jim Thor – WildPackets Professional Services

Recently, when doing a consulting engagement I came across some interesting behavior with my WNIC and thought I would pass it along as a tip.

What I noticed is that my WLAN captures were intermittent. It seemed I would capture for a short period of time, then I would quit seeing packets for a while, then I would see them again. My utilization graph looked like a cityscape.

After a little investigating, it turned out that one of the advanced settings on my WNIC had changed. It was the Sleep Mode setting and it was no longer set to ‘off’ as it should be. I am not sure how this changed as I didn’t change it, but it is a setting that can seriously affect your captures.

Most WNICs have this setting, but it may be called something slightly different. Here is a look at mine.

So, I guess the point of this tip is not only to make sure your WNICs powersave is ‘off’, but to realize that many things can change these types of settings without your knowledge or input; such as Windows updates, Supplicant software, other users (if it is a shared system), etc.