# sysctl net.ipv4.conf.default.forwarding
net.ipv4.conf.default.forwarding = 1
# netstat -nr
192.168.1.0     0.0.0.0         255.255.255.240 U         0 0          0 eth2
192.168.1.0     0.0.0.0         255.255.255.0   U         0 0          0 eth1
0.0.0.0         192.168.1.254   0.0.0.0         UG        0 0          0 eth1
#
# cat /etc/network/interfaces
# The loopback network interface
auto lo
iface lo inet loopback

# The primary network interface
allow-hotplug eth1
iface eth1 inet static
        address 192.168.1.23
        netmask 255.255.255.0
        network 192.168.1.0
        broadcast 192.168.1.255
        gateway 192.168.1.254
        # dns-* options are implemented by the resolvconf package, if installed
        dns-nameservers 192.168.1.254

# Another network interface
allow-hotplug eth2
iface eth2 inet static
        address 192.168.1.1
        netmask 255.255.255.240
        network 192.168.1.0
        broadcast 192.168.1.15
        #gateway