Some useful links containing further information are provided below:

High Availability (HA), Feature Description

https://docs.progress.com/bundle/loadmaster-feature-description-high-availability-ha-ga

Microsoft - Virtual Network Address Spaces page

http://msdn.microsoft.com/en-us/library/azure/09926218-92ab-4f43-aa99-83ab4d355555 - Virtual Network Address Spaces page section

Microsoft - Configure a Virtual Network Gateway in the Management Portal

http://msdn.microsoft.com/en-us/library/azure/jj156210.aspx