OK so here's a weird one for all of you. I'm at a client site helping them optimize their network for their VOIP (Spectralink/Polycom) phones. They also have a bunch of Panasonic Toughbooks the doctors use. I turned on some of the usual stuff I do to optimize for voice but as part of that I happened to turn on 802.11h support. Pretty soon we got complaints about the Toughbooks not being able to connect. Oh and only some of their Toughbooks, the one's that broke used a Intel Wireless-N 7260 card. The one's that work use an Intel 6000 series card.
I went over the changes that I made and reversed things one at a time to see what might be the issue. turned out it was the 802.11h setting. As soon as I diabled it, boom laptop connects. Hmm, I thought. That is weird as the specs online say it supports 802.11h. So I setup a packet capture. The card negotiates the connection right up to doing part of the EAP exchange (they use PEAP) and then part way through the exchange the card just stops responding to the APs EAP packets. I can see an EAP-Request packet going to the client and it just doesn't respond.
Not sure if anyone else has seen this, but was strange enough I thought to post it here for others. PS, client drivers were latest from Intel, from Feb 2014.