Is it possible to recognize clients not by their IP addresses?

Hi!! The format of ${raddbdir} /clients.conf defines NAS by its IP pool. And what if I'd like to have a pool of NASes each using unique secret but not to specyfy their IP or domain names to the freeradius config files? Is it possible to do so? When I was trying to create 2 client sections for same IP pool but diferent secrets only the second was working. #clients.conf client 0.0.0.0/0{ secret = test1 shortname = public1 } client 0.0.0.0/0{ secret = test2 shortname = public2 } And with such configuration sending requests with 'secret = test1' always fails :(