dhcp subrange

FR Version 2.1.10 Hello, for many of you this question is obvious, but I have doubts. I recently requested your assistance in compiling the dhcp for FR, but I'm mulling over and do not know how to configure a range of my network to run as dhcp. The question is: if I want to set a range for dhcp in the FR, a server dhcp must be previously installed, such as dhcp3-server?, or can I do it in the /etc/freeradius/sites-enabled/dhcp file? If, for example, I am currently allocating fixed ips in the range 10.18.0.0/16 at file "users", as I reserve a subrange of the range for that other users can have ips assigned by dhcp? Thanks, Laura