PPPoA is only used between your modem and the PPPoA server at your isp.
So you have to check that your modem configuration is ok. it is not a modem/router? does it have an ethernet or usb interface to your pc?
Its more an ethernet or usb problem.
host localhost: you are trying to access your dns to ask who is localhost. As you don't have net access, it can't work (server unavailable). Even if you had internet, it would not answer, you have to type:
it will look in your /etc/hosts file.