Internal and External Interfaces

1. Brekeke Product Name and Version: pbx ver 3.x

2. Java version:1.8.0_77

3. OS type and the version: Windows

4. UA (phone), gateway or other hardware/software involved:

5. Your problem:
i would like to have a public address for connecting to itsp and remote users aswell as an internal address for clients local to my network so they do not have to register to the external address

You don't have to assign a public IP address to Brekeke PBX physically.

Let you enable the port-forwarding in the router for forwarding SIP/RTP packets to the Brekeke PBX which has a local IP address.

With the port-forwarding, the ITSP can reach the Brekeke PBX through the router.

Refer this wiki topic.
http://wiki.brekeke.com/wiki/Set-port-forwarding