PPPoE requires certain signals and information to establish, accept, control and terminate the session.
The basic signalling is shown below.
A. (PPPoE Active Discovery Request), PADI (PPPoE Active Discovery Initiation)
B. (PPPoR Active Discovery Request), PARP (PPPoE Active Discovery Initiation)
C. (PPPoE Active Discovery Reaching), PADI (PPPoE Active Discovery Initiating)
D. (PPP Active Discovery Request), PADI (PPP Active Discovery Initiation)
A
https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/bbdsl/configuration/15-mt/bba-15-mt-book/bba-ppoe-client.pdf
The client broadcasts a PPPoE active discovery initiation (PADI) packet.
The host then sends a singlePPPoE active discovery request
(PADR) packet to the access concentrator that it has chosen.