Public and Private IPs for VMs through network interfaces

I have an openstack cluster working OK and providing Linux and Windows VMs successfully. I am using FlatManagerDHCP and I've noticed that every launched instance provides only one network interface with the private IP obtained from the DHCP nova-network service. Association with public IPs is allocated successfully.
The instances can be accessed by anyone on the internal net and they can access the internet OK via a proxy server.
The problem is that some applications that are running inside the instance(s) cannot get the public IP via either ifconfig or ipconfig or any internal API call to get the host IP.
I have solved the problem manually but my question is if there is an automatic way to inject the public IP on Linux and Windows in another interface so the applications can get the public IP and avoid the manual injection.
If you launch VMs through Rackspace they will create two interfaces: in Linux (eth0 is the public and eth1 is the private) in Windows they create two interfaces too: Ethernet adapter private and Ethernet adapter public.
Thanks for your support.