Uses for VIPs include network address translation (especially, one-to-many NAT), fault-tolerance, and mobility.
[1] In addition, if there are multiple actual IP addresses, load balancing can be performed as part of NAT.
VIP addresses are also used for connection redundancy by providing alternative fail-over options for one machine.
For this to work, the host has to run an interior gateway protocol like Open Shortest Path First (OSPF), and appear as a router to the rest of the network.
Uses for VIPs include network address translation (especially, one-to-many NAT), fault-tolerance, and mobility.