http://www.cisco.com/c/en/us/support/docs/long-reach-ethernet-lre-digital-subscriber-line-xdsl/asymmetric-digital-subscriber-line-adsl/71108-adslguide-pppoa-dynmcstep.html?referring_site=RE&pos=1&page=http://www.cisco.com/c/en/us/support/docs/dial-access/dial-on-demand-routing-ddr/10219-23.html