Managing default IP in a complex network

Hi, I work in a school and I’m tring to make some test with Rpi3 and Hassio.
172.30.x.x is the second building network so packet are catch by a static route and carry away.
10.x.x.x is the red network behind the firewall is the net of my router and some other services.
Where are the config file to change and how is possible to manage this kind o problem?