When using loopback addresses, you will want to give it a host mask (255.255.255.255) not the actual subnet mask.
We use loopbacks on all of our devices and I have a /28 designated for loopback use, and each loopback interface gets a host address from that /28.
When you do this, the network and broadcast addresses of the subnet become valid hosts. If your subnet starts at 0 and ends at 15, you can assign .0 or .15 to the interface.
