proxied server and right flamed IP to ppp clients

[lscrlstld]

Is there any way to ensure (or check) that the proxied server assigned a
right framed IP within a specific range of IPs?
unlang perhaps?

Main Server proxy to +-> freeradius Server 1
                     |   (must be use ip pool 10.0.0.0/24)
              +------+
              |      |
              |      +-> freeradius Server 2
              |          (must be use ip pool 10.0.1.0/24)
              |
Main server check if the framed IP is within the correct pool, if not
reject.

Thank you.