I can speak from Slackware 10.1 or 10.2
First do you have the necessary packages installed? Namely rp-pppoe.
It comes standard with Slackware 10.1 and 10,2
If you are using Slackware 10.1,
the commands are
Answer all the questions post to you with the correct information
then to start and stop the adsl connection use the following command respectively
For Slackware 10.2, the command is pppoe instead of adsl, ie. pppoe-setup, pppoe-start, pppoe-stop
You don't have to configure the NIC network properties.