IP Pool
From FreeRADIUS Wiki
FreeRADIUS has several IP Pool modules which have the ability to assign dynamic IP address to RADIUS sessions types where the NAS has control over the the users IP.
This includes PPP and other types of dialup access (GPRS for example) but does not include WiFi, WiMAX and Ethernet networks as although they may use RADIUS for AAA, they typically use a separate protocol called DHCP to assign IP addresses which is not supported by FreeRADIUS Server.
Usage
IP Pools are assigned with the FreeRADIUS Server specific Pool-Name attribute. The Pool-Name is then processed by whichever IP Pool module(s) you have configured.
Note: For any IP Pool module to function correctly it must receive accounting packets from your NAS, including Interim-Updates
IP Pool Modules
FreeRADIUS Server currently includes the following IP Pool modules: