Setup ICRadius with failover

We have an ICRadius server running on an old Linux box. We need to set up a 2nd installation of ICRadius on a new box for redundancy. Then we need to set up a 3rd installation on another new box so we can retire the oldest machine and still have failover. The primary server should update the data on the secondary server every 15 minutes automatically. Documentation on ICRadius can be found at www.icradius.org. The winning bidder may receive additional maintenance and support work on these systems, and may have additional opportunity to work on our internal infrastructure (intranet) which interfaces the RADIUS server.