Oguzhan Kayhan wrote: I want to use 2 freeradius servers for failover.

It seems it wont be a problem if i use mysql backend for logging etc. But, I wonder what will happen about multiple login check. Because as i know freeradius also checks radutmp file if the user is already logged in or not. And for ex...If user logs in from server1 and when he tries to login from server2...what will be the result?

He will be logged in twice. See raddb/sites-available/copy-acct-to-home-server for a way to fix this. Alan DeKok.