We need a back-end that contains a list of users with their passwords. You can choose to use the file /etc/freeradius/3.0/users instead of a full LDAP installation for small configurations (1-3 users), but you will feel the administrative pain very quickly. Do yourself a favour and save yourself from unneeded pain: use LDAP.
# Clients
The clients are the devices that will contact the RADIUS server for authentication. Clients can be any of the following:
* a switch
* a firewall
* an access point
* an application (web applications included)
* another RADIUS server acting as a proxy (think spaceFED)