$ cat /etc/network/interfaces
# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).

# The loopback network interface
auto lo
iface lo inet loopback

# The primary network interface <-------- connectée au routeur
auto eth1
iface eth1 inet static
address 192.168.1.2
netmask 255.255.255.0
gateway 192.168.1.1

iface eth0 inet dhcp <-------------------- réseau local

auto eth0

--------------------------------------------------------------------------
$ ip route list
192.168.1.0/24 dev eth1  proto kernel  scope link  src 192.168.1.2
default via 192.168.1.1 dev eth1
--------------------------------------------------------------------------
$ ifconfig
eth0      Lien encap:Ethernet  HWaddr 00:11:2F:96:BB:0F
          adr inet6: fe80::211:2fff:fe96:bb0f/64 Scope:Lien
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          Packets reçus:721 erreurs:0 :0 overruns:0 frame:0
          TX packets:357 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 lg file transmission:1000
          Octets reçus:46362 (45.2 KiB) Octets transmis:88798 (86.7 KiB)
          Interruption:177 Adresse de base:0x8000

eth1      Lien encap:Ethernet  HWaddr 00:80:C8:F9:CD:3A
          inet adr:192.168.1.2  Bcast:192.168.1.255  Masque:255.255.255.0
          adr inet6: fe80::280:c8ff:fef9:cd3a/64 Scope:Lien
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          Packets reçus:15383 erreurs:0 :0 overruns:0 frame:0
          TX packets:14893 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 lg file transmission:1000
          Octets reçus:12288540 (11.7 MiB) Octets transmis:2302405 (2.1 MiB)
          Interruption:217 Adresse de base:0xbc00

lo        Lien encap:Boucle locale
          inet adr:127.0.0.1  Masque:255.0.0.0
          adr inet6: ::1/128 Scope:Hôte
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          Packets reçus:5708 erreurs:0 :0 overruns:0 frame:0
          TX packets:5708 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 lg file transmission:0
          Octets reçus:1760494 (1.6 MiB) Octets transmis:1760494 (1.6 MiB)