There are two possible scenarios where private IP subnets might be involved with LoadMaster GEO.
The first is when "Location"-based responses are required to bind certain internal IP client subnets to certain resource locations. In this circumstance, the normal GEO IP-based approach will not work as there is no way to understand how to bind internal ranges to different resource locations. To achieve this, use the "Location" scheduling method and manually bind internal subnets to specific predefined Locations that correspond to countries and regions. You can find out more about how to create IP Range bindings in the IP Range Selection Criteria section of the GEO Feature Description.
The second scenario is when both internal and external DNS zones exist for the domain in a split-brain DNS scenario where both Public and Private IP addresses exist for the same FQDN. The LoadMaster GEO will automatically respond with the Private IP address for requests originating from private IP subnets and Public IP addresses for requests from Public IP ranges. Behavior when the preferred IP is unavailable can be controlled using the "Isolate Private/Public Sites" setting, which is detailed in the Add an FQDN section of the GEO Feature Description.