/etc/ppp/peers/dsl-provider:
plugin rp-pppoe.so eth1
noipdefault
defaultroute
hide-password
lcp-echo-interval 60
lcp-echo-failure 3
noauth
persist
mtu 1492
mru 1492
user "xxx@PROVIDER"
/etc/ppp/pap-secrets:
"xxx@PROVIDER" * "myfunkypass"
/etc/network/interfaces:
auto mydsl
iface mydsl inet ppp
provider dsl-provider
Replace eth1 by your dsl ethernet link device name, xxx by username, PROVIDER by your provider, and myfunkypass by your password.
Enable with ifup mydsl, disable with ifdown mydsl.