/etc/network/interfaces

auto lo
iface lo inet loopback

#ke dalam umum
auto eth0
iface eth0 inet static
address 192.168.11.1
netmask 255.255.255.240
network 192.168.11.0
broadcast 192.168.11.15
dns-nameserver 192.168.11.1
dns-search umum.net

# ke jaringan luar
auto eth1
iface eth1 inet static
address 192.168.10.1
network 192.168.10.0
netmask 255.255.255.224
broadcast 192.168.10.31
gateway 192.168.10.1
dns-nameserver 192.168.11.1
dns-search umum.net

# ke modem
auto eth2
iface eth2 inet static
address 192.168.1.2
netmask 255.255.255.0
network 192.168.1.0
broadcast 192.168.1.255
gateway 192.168.1.1

auto dsl-provider
iface dsl-provider inet ppp
pre-up /sbin/ifconfig eth2 up # line maintained by pppoeconf
provider dsl-provider