using IP address of vpn users in radius server

[Eric]

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?
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