How to setup routing through webmin

I have two nics installed:

The one is and the router to get the the internet is
The 2nd is and is is the dhcp and dns server for the network

How do I get devices on 10.0.100.x talk to 10.0.0.x devices? Either webmin or the cli.?

Do you want to use the phone system as a router to connect the two LAN’s? If so you can just turn on IP routing in the /etc/sysctl.conf file with the following variable:

Controls IP packet forwarding

net.ipv4.ip_forward = 0

just set it to 1.

The phone system will then act as a router so you will have to use it as a gateway for the devices in the network and as a static route for devices in the 10.0.100/0/24.

The correct way to do this is upgrade the Internet router to something with an additional network interface so you can create proper forwarding rules.