Block access by Tunnel client IP?

[ST Wong (ITSC)]

 Hi all,

I'm using freeradius 2.1.3.    Would like to know if it's possible to
block access (maybe in users file) by checking  following criteria ?

Acct-Tunnel-Client-Endpoint:0 = "137.*.*.*" 

Would anyone please help?  Thanks.

Regards,
/ST Wong  (st-wong at cuhk.edu.hk)