I got a call recently from my friend working with a network infrastructure/service provider. He was asked to design a solution for one of the clients. The client had 12 public IP adresses allocated. But the problem was that these addresses were in the same subnet! He had to connect a few servers that were to be made accessible to the public. He had the budget to buy just one router and no switches. So?
The problem was that each router interface should be on a different subnet. So it was difficult to use the allocated public IPs to devices on different router ports.
One solution that I proposed was to use private IPs on all devices phyisically, and then to implement static NAT mappings for the servers into the available public IPs and dynamic NAT mappings for two LANs he had to connect to the Internet. 🙂