$ cat /etc/network/interfaces
# interfaces(5) file used by ifup(

and ifdown(

auto lo
iface lo inet loopback
auto dsl-provider
iface dsl-provider inet ppp
pre-up /sbin/ifconfig eth1 up # line maintained by pppoeconf
provider dsl-provider
auto eth1
iface eth1 inet static
address 192.168.137.1
netmask 255.255.255.0
auto ppp1
iface forts inet ppp
provider forts