you have a separate ADSL PCI card? like old dishnet dsl? or the new sangoma adsl card? then only you need pppoe if you connect via ethernet? then like how vignesh said "sudo dhclient eth0" or "sudo dhclient3 eth0" or "pump" and also check before you type this? whether the CPE (your adsl device if external has dhcp on, if not then activate dhcp and then try this command), and if you are doing it via USB? then check this if its in the kernel, if no then make a custom kernel. "cat /boot/config-`uname -r` | grep -i CONFIG_USB_NET_CDCETHER=m " or "cat /boot/config-`uname -r` | grep -i grep -i CONFIG_USB_USBNET=m" and check if its echoed out. if yes then?
"sudo modprobe usbnet && lsmod | grep -i usbnet"
make a backup of the /etc/network/interfaces with this command
"sudo mv /etc/network/interfaces /etc/network/interfaces.bak"
type this in your favourite editor "sudo vi /etc/network/interfaces"
allow-hotplug usb0
mapping hotplug
script grep
map usb0
iface usb0 inet static
address 192.168.2.14
netmask 255.255.255.0
broadcast 192.168.2.255
up iptables -I INPUT 1 -s 192.168.2.15 -j ACCEPT
and then type
"sudo /etc/init.d/networking restart"
"sudo dhclient eth0"
"ping yahoo.com"
these codes and hints were copied from
USB networking - maemo.org wiki
good luck happy Linux.
-paul