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

[Sebo PL]

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 :(