# nano /etc/network/interfaces

    auto lo
    iface lo inet loopback

    auto ens3
    iface ens3 inet static
            address 1.2.3.4
            netmask x.x.x.x
            gateway 4.3.2.1
            post-up echo 1 > /proc/sys/net/ipv4/conf/ens3/proxy_arp

    auto vmbr0 vmbr1
    #NAT sub network, not bridged
    #10.0.0.0/8
    #192.168.0.0/16 (192.168.0.0-192.168.255.255, one space)
    #192.168.0.0/
    iface vmbr0 inet static
            address  10.0.0.1
            netmask  255.0.0.0
            bridge_ports none
            bridge_stp off
            bridge_fd 0
            post-up   echo 1 > /proc/sys/net/ipv4/ip_forward
            post-up         iptables -t nat -A POSTROUTING -s '10.0.0.0/8' -o ens3 -j MASQUERADE
            post-down iptables -t nat -D POSTROUTING -s '10.0.0.0/8' -o ens3 -j MASQUERADE

    #private sub network2
    #No Nat Subnetwork, Bridged
    iface vmbr1 inet static
            address  10.0.0.2
            netmask  255.0.0.0
            bridge_ports ens3
            bridge_stp off
            bridge_fd 0
            #add here each new Public IP for any Container
            #we need to tell here the Host to use the default gateway for this IP
            post-up         route add 2.3.4.5 dev vmbr1