I am currently trying to setup a KVM server with two OS (pfsense & Ubuntu Server) on an Ubuntu server with three NICs (enp2s0, enp1s0, & enp3s5). This is the concept I'm trying to do: http://imgur.com/s7QqsMH
What should the /etc/network/interfaces
look like? Because virtual interfaces are needed to setup the virtual machines for pfsense and Ubuntu server OS.
[Answer]
I setup the /etc/network/interfaces to look like this:
auto br0
iface br0 inet dhcp
bridge_ports enp2s0
bridge_fd 5
bridge_maxwait 5
bridge_stp off
auto br1
iface br1 inet dhcp
bridge_ports enp1s0
bridge_fd 5
bridge_maxwait 5
bridge_stp off
auto br2
iface br2 inet dhcp
bridge_ports enp2s0
bridge_fd 5
bridge_maxwait 5
bridge_stp off