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Chapter 47 PPPoE
XS3800-28 User’s Guide
346
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”.
47.1.2.3 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 or 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 ports.
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 ports.
• The Switch discards PADO and PADS packets which are sent from a PPPoE server but received on an
untrusted port.
47.2 PPPoE Intermediate Agent
Use this screen to configure the Switch to give a PPPoE termination server additional subscriber
information that the server can use to identify and authenticate a PPPoE client.
Click SWITCHING > PPPoE Intermediate Agent to display the screen as shown.
Table 163 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)