using IP address of vpn users in radius server

Hi, I have a radius server that uses ldap server for authentication and authorization. The client of radius server is a vpn server. now they are working. I want to have two groups of vpn users in vpn server base on their IP addresses. Could radius server check IP address of users if it is valid or invalid and send an ip pool number for vpn server for each user in this architecture? how can I set it?