I have successfully created a schema like this with VirtualBox, but now I have to do a final project and I would like to do it with KVM and Virtual Machine Manager (virt-manager).
I am having some doubts and troubles creating the network.
There is a photo of it. Some text is in Spanish, but it is not relevant.
As you see the firewall must have three NICs. One bridged to the physical network (from which I will access Internet) and other two for the virtual networks.
I have created a Bridged connection named br1 with physical eth1 as slave.
And then, I created two virtual networks, one named 'dmz' and the other one 'lan'. I created them as isolated networks without dhcp. I do not know if this is correct, but when the assistant gives me the option to choose either isolated or forwarded to physical network, if I choose forwarded NAT, it auto-assigns me a gateway, which I do not want, because I want the firewall itself to be the gateway for both virtual networks. I saw that if I choose routed mode, it does not assign a gateway, but still I am confused about what interface should I choose.
I tried to explain the best way I can, but as you see I am a little bit lost with this virtualization software, if you have any questions I will try to clarify them.
I am trying to connect both virtual networks through the firewall (to have some control with iptables) to Internet.