My set up: multiple servers with FreeRadius 1.1.0, MySQL 5.0.27 with Master-Master replication After some trouble with duplicate entries in the radius accounting table due to non-unique Acct-Session-Id's, I switched to using the acct_unique module. acct_unique { key = "User-Name, Acct-Session-Id, NAS-IP-Address, Client-IP-Address, NAS-Port" } This works fine as long as the Client-IP-Address remains a constant during a session. But when the connection to the ISP drops for a moment, a new Client-IP-Address will be used and the Acct-Unique-Session-Id will change in the middle of a session. This causes a new session to be inserted into the accounting table. The new session simply continues using all the values of the previous session as the NAS is not aware of the Client-IP-Address change. This will cause that the time of the first session and the second session are added, even it is the same session. This is pretty bad for prepaid tickets as their life is shortend. I like to change the acct_unique set up and exchange the Client-IP-Address with another more steady parameter like NAS-Identifier or Called-Station-Id or Calling-Station-Id or Framed-IP-Address. I am going to use the following: acct_unique { key = "User-Name, Acct-Session-Id, NAS-IP-Address, Calling-Station-Id, NAS-Port" } The Calling-Station-Id (end-user MAC address) would not change during a session and is not really user selectable. While the Called-Station-Id and NAS-Identifier could occur multiple times as this might be a configurable NAS parameter. Any recommendations on this?