extract different field from ldap on nas's ip address base

[arjuna at ts.infn.it]

 > Is it possible to extract (to filter) different field in a ldap entry on
> the base of the "nas" ip address?

ok i've found out this old thread

http://lists.cistron.nl/pipermail/freeradius-users/2004-December/039132.html

and it was realy usefull, but i still have problem to make the rule in
users file match the packet....

can someone tell me where to find out a guide, tutorial, README about the
fields i can use in the rules inside users file?

thanks,
arjuna