Our school has a 4402 WLC and thirty five 1142N AP's over 5 floors. We've used this setup for about 5 years. Up until December 2013, we had a single SSID using AES/PSK encryption. Never had any problems with client connections. In December, we replaced all of our closet switches with new Cisco switches as well as fiber runs in the backbone. Wifi hardware remains the same. However, we broke out our SSIDs between STAFF and the 4 graduating classes. Kept the same encryption for each SSID.
In January we started to see lots of simultaneous client drops for Lenovo laptops with internal 2.4ghz realtek chip cards. A class of 40 kids would see 20-30 laptops disconnect at the same time. (yellow triangle in Windows 7 showing for the connection). After maybe 5 minutes, connections returned. This was happening every day at almost the same time frame...in the morning. In our troubleshooting efforts, we even removed the WLC and had clients connecting directly to an AP....still dropping and reconnecting. We then tried newer AP's borrowed from a local vendor....no improvement.
After pulling our hair out spending countless hours with TAC, we think it's a problem with the encryption and the realtek chip. So we bought several Buffalo 5ghz usb mini's and these seem to work much better.
But......now we're seeing a totally different class of clients, Dell latitude machines with dual band wifi cards, are experiencing group disconnects at the other end of the building!!!!
I'm looking for some fresh new ideas.....any thoughts???
Lenovo laptops with internal 2.4ghz realtek chip cards
Can you try to go to the RealTek website and update the drivers to the wireless NIC? There has been known issues with a lot (and I mean A LOT!) of wireless NIC cards and the way they behave.
You will always get rogue APs. One of my controllers has sniffed out >1300 rogue APs.
Can you specify what firmware is your controllers running on? Do you have DCA and TPC enabled to automatic?
What is the exact model of the wireless NIC?