Hi Alan, Thanks for reply.
The Android device wasn't configured with the CA used by FreeRADIUS. So... add the CA to the android system, and configure it to use that CA when authenticating to FreeRADIUS.
I created freeradius CA certificate according to https://wiki.freeradius.org/config/Certificates link. Then eap config for using new created ca.pem Also i downloaded ca.pem file to my Android device but still getting same error. eap_ttls: ERROR: TLS Alert read:fatal:unknown CA I dont understand what you mean with "use that CA when authenticating to FreeRADIUS". What i read in EAP-TTLS, auth server sends the certificate and client validates for open a secure tunnel. Why client have to sent the certificate ? Regards. [http://www.nevotek.com/nevotekmail/logo.png] Mesut Ozturk R&D Senior Developer P: +902122867576 E: mesut@nevotek.com F: +902122867476 W: www.nevotek.com [http://www.nevotek.com/nevotekmail/maps-icon.png] Santa Clara-CA, USA<https://www.google.com/maps/place/5201+Great+America+Pkwy+%23320,+Santa+Clara,+CA+95054,+USA/@37.4063062,-121.978682,923m/data=!3m2!1e3!4b1!4m5!3m4!1s0x808fc9cc6fc08be1:0xa189e7ab47ebcdc!8m2!3d37.4063062!4d-121.9764933?hl=en> [http://www.nevotek.com/nevotekmail/maps-icon.png] Istanbul, TURKEY<https://www.google.com/maps/search/teknokent,+Istanbul,+Turkey/@41.106333,29.015257,876m/data=!3m1!1e3?hl=en> [http://www.nevotek.com/nevotekmail/maps-icon.png] Dubai, UAE<https://www.google.com/maps/place/Internet+City,+Building+%2314+-+Dubai+-+United+Arab+Emirates/@25.0984488,55.1609574,1052m/data=!3m2!1e3!4b1!4m13!1m7!3m6!1s0x3e5f6b696d88a9ab:0x6d495147845cd0f1!2sInternet+City,+Building+%2314+-+Dubai+-+United+Arab+Emirates!3b1!8m2!3d25.0983618!4d55.1631953!3m4!1s0x3e5f6b696d88a9ab:0x6d495147845cd0f1!8m2!3d25.0983618!4d55.1631953?hl=en> [www.nevotek.com]<www.nevotek.com>