filter anonymous identity

[Riccardo Veraldi]

Hello, on radius 1.1.x
I have some users autenticating using an outer identity. This is 
annoying to me
because in the radius.log file I cannot identify easily who is the real 
user autenticating,
since outer identity can be anything.
How can I forbid in freeradius configuration to use an outer identity or 
anonymous ? I wish to forbid autentications which uses an outer identity.
howto have control over it ?

thank you

Rick