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802.11i, Authentication and You

January 4, 2012 at 5:00 am PST

Not too long ago I was assigned to a troubleshooting and remediation project for a hospital here in the SF bay area. The problem, after much troubleshooting and lab recreations, was determined to be due to an unique issue with client roaming and authentication. During the course of troubleshooting my coworker and myself often found ourselves explaining 802.1X and 802.11i to others working on the troubleshooting effort, or requesting technical updates. So based on that experience, I started thinking this might a be a good topic to cover here.

Let’s review the some of typical components of the enterprise wireless security model.

What is 802.1X?
802.1X is not a protocol, but rather a framework for a “port-based” access control method.  802.1X was initially created for use in switches, hence the port-based terminology, which really doesn’t fit too well in wireless since users don’t connect to a port. In the end it’s meant to be a logical concept in the 802.11 world.  802.1X was adopted for wireless networks with the creation of 802.11i to provide authenticated access to wireless networks. At a high level. the framework allows for a client that has connected to the WLAN to remain in a blocked port status until it has been authenticated by a AAA server. Essentially the only traffic allow through this virtual blocked port is EAP traffic, things like HTTP would be dropped.

What is EAP?

EAP  (Extensible Authentication Protocol) is the authentication method used by 802.1X. It can take on various forms, such as PEAP, EAP-TLS, EAP-FAST, to name a few. There is one thing to remember when determining what EAP type to use in your network, is that it is dependent upon what your client and AAA server supports. This is it, your AP or AP/Controller hardware or code version will play no part in version is supported. Unless your AP/controller is acting as the AAA server, but I’ll stay away from that in this post. I think this can be a point of confusion for people who haven’t read much or anything about EAP methods. So, if some one asks what version of EAP the AP will support, all you need to do is ask them, what does their Client and AAA server support.

What is 802.11i?

Simply put, 802.11i is an amendment to the original 802.11 standard to address the well documented security short comings of WEP. It incorporates WPA  as a part of the 802.11i amendment and adds the fully approved WPA2 with AES encryption method. 802.11i  introduces the concept of a Robust Security Network (RSN) with the Four-way handshake and the Group key Handshake.

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