blocking anonymous outer identity

Hello, I have some anonymous outer identity in the autentication log of freeradius. I use freeradius version < 2.0 with EAP-TTLS and 802.1x on hte supplicant side. how can I forbid users to use an anonymous identity or to use an outer identity different from the real identity used for authentication/authorization ? I want to force users to use their own real identity based on their real credentials users@domainname without using an outer identity. I want to forbid this because if users use anonymous outer identity in the freeradius log I cannot see who is the user actually autenticating. any hints about this problem of mine ? thank you Rick