Core Issue
This error message appears when 128-bit encryption is used in place of the 104-bit encryption.
Resolution
This 128bit isn't supported on the Access point error message is seen on controllers when the key lengths shown are actually the number of bits that are in the shared secret and do not include the 24-bits of the IV. Many products, which includes the Aironet products, mention a 128-bit WEP key when in reality, it is a 104-bit key with 24-bit IV. On the controller, the key size of 104-bit is 128-bit. The 128-bit key size on the controller is actually a 152-bit key. So in order to set the 128-bit key, set with the 104-bit.
Note: Users are not able to run Wi-Fi Protected Access 2 (WPA2) and static Wired Equivalent Privacy (WEP) on the same WLAN. By default, WPA2 uses Advanced Encryption Standard (AES) for encryption. Users can create two WLANs, one with WPA2 and one with static WEP and assign them to the same interface on the controller.
Refer to these documents for more information:
Problem Type
Configure / Configuration issues
Error message
Products
Wireless LAN Controllers
Lightweight Access Points