how to do interval jail ips

[Artem Kuchin]

Hello!

I have several jails and some of the use real ips, some are just 
internal for the server like 10.0.0.x
However, i assigned all ips to the external em0 interface.
This causes problems, because of server in the same lan have 10.0.0.x 
address of their interfaces too.
So, there is a conflict.
This is just a colocation, so, i cannot control the ip assignment.

What is the correct way to assign ip address which are seen only withing 
a host?
(some kind of virtual NIC)

Artem