Chapter 28 PPPoE
GS1920 Series User’s Guide
233
option example is “Switch/07/0123” and indicates the PPPoE packets come from a PPPoE client
which is connected to the Switch’s port 7 and belong to VLAN 123.
WT-101 Default Circuit ID Syntax
If you do not configure a Circuit ID string for a specific VLAN on a port or for a specific port, and
disable the flexible Circuit ID syntax in the PPPoE > Intermediate Agent screen, the Switch
automatically generates a Circuit ID string according to the default Circuit ID syntax which is
defined in the DSL Forum Working Text (WT)-101. The default access node identifier is the host
name of the PPPoE intermediate agent and the eth indicates “Ethernet”.
28.1.2.3
Port State
Every port is either a trusted port or an untrusted port for the PPPoE intermediate agent. This
setting is independent of the trusted/untrusted setting for DHCP snooping or ARP inspection. You
can also specify the agent sub-options (circuit ID and remote ID) that the Switch adds to PADI and
PADR packets from PPPoE clients.
Trusted ports are connected to PPPoE servers.
•
If a PADO (PPPoE Active Discovery Offer), PADS (PPPoE Active Discovery Session-confirmation),
or PADT (PPPoE Active Discovery Terminate) packet is sent from a PPPoE server and received on
a trusted port, the Switch forwards it to all other ports.
•
If a PADI or PADR packet is sent from a PPPoE client but received on a trusted port, the Switch
forwards it to other trusted port(s).
Note:
The Switch will drop all PPPoE discovery packets if you enable the PPPoE
intermediate agent and there are no trusted ports.
Untrusted ports are connected to subscribers.
•
If a PADI, PADR, or PADT packet is sent from a PPPoE client and received on an untrusted port,
the Switch adds a vendor-specific tag to the packet and then forwards it to the trusted port(s).
•
The Switch discards PADO and PADS packets which are sent from a PPPoE server but received on
an untrusted port.
Table 107
PPPoE IA Circuit ID Sub-option Format: Using Identifier String and Variables
SubOpt
Length
Value
0x01
(1 byte)
N
(1
byte)
Identifier
String
(53 byte)
delimiter
(1 byte)
Slot ID
(1 byte)
delimiter
(1 byte)
Port No
(2 byte)
delimiter
(1 byte)
VLAN
ID
(4
bytes)
Table 108
PPPoE IA Circuit ID Sub-option Format: Defined in WT-101
SubOpt
Length
Value
0x01
(1 byte)
N
(1
byte)
Access
Node
Identifier
(20 byte)
Space
(1
byte)
eth
(3
byte)
Space
(1
byte)
Slot
ID
(1
byte)
/
(1
byte)
Port No
(2
byte)
:
(1
byte)
VLAN
ID
(4
bytes)
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