freeradius and direct server return

Hi All I have a problem with freeradius and Direct Server return configuration. I use Alteon load balancer configured for DSR, freeradius listen on the virtual IP address and the real address as health check request are sent on the real IP address but client request are sent on the virtual IP address. The problem is that the server respond to client request with the real IP address instead of virtual, then the client discard the response. Is there any configuration that tells freeradius to answer using the virtual address ??? Regards Giuseppe