When using Wi-Fi spectrum analyzers, it's good to remember an old Russian proverb: Trust, but verify.
Recently, I was doing some work for a company that needs BYOD Wi-Fi at several office spaces in multi-tenant buildings (insert: lame excuse for not blogging more) and we ran into what seemed to be an interference problem.
Why did I think it was an interference problem? I had already completed the following checklist:
1. Cisco AP transmit power set to level 2 or 3 (that's 20 dBm to 17 dBm if you're using 3600/3700/3800 APs)? Check.
2. RRM channels 2, 3, 4, 5, 7, 8, 9 and 10 disabled? Check.
3. Excess 2.4 GHz radios disabled based on a survey done using an iPhone 4s? (What can I say? I'm a big softy for users who over-extend the life of their smartphones. They're the real MVPs of climate change.) Check.
4. OmniPeek captures, done from potential "neighbor" trouble areas, to look for channels occupied by large amounts of Retry frames? (This one has become nec…
Nine months ago (bad way to start a blog post, I know) I wrote a blog about the future of WiFi sniffing. In the comments section (perhaps the only worse thing for a blogger to say), someone mentioned a free, Windows-based application called Acrylic WiFi. I briefly checked out the app and dismissed it as yet another Discovery utility disguised as a something more. Then I actually used Acrylic WiFi and... it works! It sniffs WiFi frames (sort of) and it does it for free (outside of the cost of an ordinary 802.11 USB adapter)! This changes everything (kind of)!
For years, the method for free WiFi sniffing on a Mac has been simple. Head down to the bottom of this post for a reminder.
Now, we can do similar things in Windows. It's not quite as simple and it's not totally free, but it works (pretty much).
1. Download and install Acrylic WiFi Free, including Monitor Mode support (and, actually, if you can find an old download of Acrylic v1, then you'll be able to save ca…
The last Sniff Wi-Fi post; on why Wi-Fi professionals should stop disabling low data rates, was met some resistance. Be it in the comments or on Twitter, several experienced Wi-Fi folks disagreed. All arguments in favor of disabling low rates (the ones that were presented to me, at least) were refuted in the text of the Leave, Leave, Leave My Rates Alone blog post. But text is a less accessible messaging method. "A picture is worth a thousand words", as the old saying goes. If pictures will get the message across better, then pictures are what I'll use. What follows is an illustrated look at why disabling low data rates is a bad idea.
It's gauche to begin an illustrated work with text, but to understand the problem with disabling low Wi-Fi data rates one must first accept some facts about Wi-Fi devices (smartphones, laptops, etc.):
1. Wi-Fi devices -- not APs -- control associations and roaming.
2. Wi-Fi devices roam based on low received signal strength (RSSI) -- …