which attribute identifies the client?

Hallo, I can see in the logs the "client" calling my radius, e.g: Wed Apr 1 13:28:06 2015 : Auth: Login OK: [jsmith@unipd.it] (from client radius_garr_1 port 0 cli e4-d5-3d-b2-29-ca) Wed Apr 1 13:28:07 2015 : Auth: Login OK: [anonymous@rug.nl] (from client economia.unipd.it port 3 cli 94-eb-cd-6d-e0-ad) which is the attribute containing the "client" (radius_garr_1, economia.unipd.it,...)? I'd like to use it in the %{...} form to perform some filtering in the authorize section of inner-tunnel file. Thanks a lot, Stefano