Tech Support: 1.888.678.9427 - Comnet CWGE24MS2 Installation And Operation Manual

INSTALLATION AND OPERATION MANUAL
» Depending on the network topology, since the PADI was broadcast, the PPPoE client may receive
PADO packets sent by multiple PPPoE servers. Among these PPPoE servers, the PPPoE client selects
the one whose PADO packet arrived the earliest and unicasts a PADR packet to the PPPoE server.
» PPPoE IA intercepts PPPoE discovery frames from the client and inserts a unique line identifier
(circuit-id /remote-id) using the PPPoE Vendor-Specific tag (0x0105) to PADR (PPPoE Active Discovery
Request) packets. The PPPoE IA forwards these packets to the PPPoE server after the insertion.
» The PPPoE server generates a unique session ID for the session and sends the session ID to the
PPPoE client through a PADS packet. If no error occurs, the session will thus be established and
PPPoE moves on to the Session stage.
PPPoE Intermediate Agent Tag Format
If the PPPoE Intermediate Agent is enabled, the Switch adds a vendor-specific tag to PADI (PPPoE
Active Discovery Initialization) and PADR (PPPoE Active Discovery Request) packets from PPPoE
clients. This tag is defined in RFC 2516 and has the following format for this feature.
Tag_Type
(0x0105)
The Tag_Type is 0x0105 for vendor-specific tags, as defined in RFC 2516. The Tag_Len indicates
the length of Value, #1 and #2. The Value is the 32-bit number 0x00000DE9, which stands for the
"ADSL Forum" IANA entry. #1 and #2 are PPPoE intermediate agent sub-options, which contain
additional information about the PPPoE client.
Sub-Option Format
There are two types of sub-option: "Agent Circuit ID Sub-option" and "Agent Remote ID
Suboption".They have the following formats.
SubOpt
0x01
(1 byte)
SubOpt
0x02
(1 byte)
The 0x01 in the first field identifies this as an Agent Circuit ID sub-option and 0x02 identifies this
as an Agent Remote ID sub-option. The next field specifies the length of the field. The Switch

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Table 1 PPPoE Intermediate Agent Vendor-specific Tag Format
Tag_Len Value
Table 2 PPPoE IA Circuit ID Sub-option Format: User-defined String
Length Value
N String
(1 byte) (64 bytes)
Table 3 PPPoE IA Remote ID Sub-option Format
Length Value
N MAC Address or String
(1 byte) (64 bytes)
#1 #2
CWGE24MS2
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