Pre-requisites sometimes necessary to remove RADIUS Server:
1. To completely remove the Radius server from a controller, it must first be removed from any associated WLAN Service.
2. To disable the Radius server from a WLAN service, go to VNS > WLAN Service > Auth & Acct Tab > Select desired Radius server > Select "Remove" > Save.
3. To remove the Radius server from the Controller, go to VNS > Global > Authentication > Select desired Radius server in checkbox > Select "Remove" > Save
4. To disable Radius Authentication for Controller Login, go to Controller > Administration > Login Management > Select RADIUS Authentication tab > Uncheck "Use server for Authentication" > Save.
Once All above steps have been verified, remove the RADIUS Server from VNS Tab > Global Dropdown > Administration > Put checkbox in RADIUS Server you would like to remove > Click Delete Selected