association issue

[jlhainy]

I am working in a High Density environment in a school that has an AP, 1140, in every class room to accomodate 20 to 30 clients connecting in each class room.  Using PEAP as the authentication method with Windows 7 clients.  Users are reporting that they have to leave the class room to get associated.  Once associated, they can go back in the class romm and use their device just fine.

Trying to determine what would cause such a behavior. 

[jlhainy]

Hey Scott,

After a lot of tinkering, it looks like load balancing was the culprit.  When we have it off, things are much improved.  Now, what I want to understand is why. 

[Stephen Rodriguez]

Load balancing attempts to have the client device join another AP, as it has reached a threshold of users, 12 IIRC.

What the AP does is send a messae type 17 to the client, but on teh 4th attempt the cleint is allowed on the AP.

The mechanism is to hopefully keep the AP from being to loaded with clients, but it is up to the client driver to accept that message type, and from what I know, most do not.

HTH,
Steve

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[jlhainy]

Stephen,

I understand the mechanics behind load balancing, code 17 and when the client could possibly be denied.  What I don't understand is that clients are close enough to APs, this is a high density environment, where you would think that the client would just connect to a nearby AP after it gets the code 17, but that wasn't happening. 

I guess it could have been that the client ignored code 17.  Users would have to leave the room and go back out into the hall to connect.  Then they would be on just fine.  I have had load balancing on just fine for years, even in this high density environment and either never had the issue, or the issue has been happening the whole time, and I am only just now hearing about it.

[Leo Laohoo]

it is some older HP netbooks that are having issues. 

Funny you should mention that ... We have heaps of HP netbooks.  One batch had trouble authenticating after I upgraded the WiSMs to 7.5.  So I recommended the wireless NIC cards' drivers be updated.  The tech said he went to the HP website and downloaded the drivers but the problem persists.  I went to the manufacturer's website and saw more advanced version of the drivers.  And this fixed the issues completely.

[jlhainy]

Ah, the manufacture of the NIC.  We will try that.  I have also considered tweaking eap timers.  The hard thing is that these nebooks have issues in a couple areas of the building.  Take them elsewhere and they work just fine.  I have gone full circle thinking that interference was the cause, then turned APs down, looking at EAP timeouts and I am back to interference.

Drivers may help, but what I can't get over is that if these same netbooks work just fine in other parts of the building.  The only "interference" source that I found is that there are like 120 dual band wifi graphing calculators.  I had no idea they had them and found them with Cisco Spectrum Expert.  I am kind of wishing that I had clean air at this site. 

I took a client debug called association2 that is posted above.  Have a look,  It shows attempts and it finally succedds when we leave the trouble area of the building.

[Abha Jha]

Interference, powerlevel and softwre needs to be checked.