PPPoE/v6 Administrator's Guide

Introduction
Packet Types
Chapter 1 15
Packet Types
Table 1-1 lists the packets exchanged between the host and the access
concentrator during the discovery stage.
Table 1-1 Packet Types
Packet Description
PADI The host sends the PPPoE Active Discovery Initiation
(PADI) packet with the destination address set to the
broadcast address.
PADO When an access concentrator receives a PADI that it
can serve, it responds to the host by sending a PPPoE
Active Discover Offer (PADO) packet. The destination
address is the unicast address of the host that sent
the PADI.
PADR Since the PADI was broadcast, the host may receive
more than one PADO. The host examines the PADO
packets it receives and selects one. The host then
sends one PPPoE Active Discovery Request (PADR)
packet to the access concentrator that it has selected.
The destination address field is set to the unicast
Ethernet address of the access concentrator that sent
the PADO.
PADS When the access concentrator receives the PADR
packet, it prepares to start a PPP session. It generates
a unique session ID for the PPPoE session and
responds to the host with a PPPoE Active Discovery
Session-confirmation (PADS) packet. The destination
address field is the unicast Ethernet address of the
host that sent the PADR.
PADT Either the client or the server sends a PPPoE Active
Discovery Terminate (PADT) packet to terminate a
PPP session. The destination address field is a unicast
Ethernet address. When a PADT is received, no further
PPP traffic is sent through that session.