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
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 PPPoE client sends the PPPoE Max-Payload tag in a PPPoE Active Discovery Initiation (PADI) packet
and if the PPPoE server can support a Maximum Transmission Unit (MTU)/Maximum Receive Unit (MRU)
higher than 1492 octets, it responds with an echo of the clients tag in the PPPoE Active Discovery Offer
(PADO) packet. The client sends the same tag in the PPPoE Active Discovery Request (PADR), and the
server echoes the client tag in a PPPoE Active Discovery Session-confirmation (PADS) packet.