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XGS-4526/4528F/4728F User’s Guide
299
CHAPTER 31
PPPoE
This chapter describes how the Switch gives a PPPoE termination server additional
information that the server can use to identify and authenticate a PPPoE client.
31.1 PPPoE Intermediate Agent Overview
A PPPoE Intermediate Agent (PPPoE IA) is deployed between a PPPoE server and
PPPoE clients. It helps the PPPoE server identify and authenticate clients by adding
subscriber line specific information to PPPoE discovery packets from clients on a
per-port or per-port-per-VLAN basis before forwarding them to the PPPoE server.
31.1.1 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.
The Tag_Type is 0x0105 for vendor-specific tags, as defined in RFC 2516. The
Tag_Len indicates the length of Value, i1 and i2. The Value is the 32-bit number
0x00000DE9, which stands for the “ADSL Forum” IANA entry. i1 and i2 are PPPoE
intermediate agent sub-options, which contain additional information about the
PPPoE client.
PPPoE IA
PPPoE Server
PPPoE Client
Table 95 PPPoE Intermediate Agent Vendor-specific Tag Format
Tag_Type
(0x0105)
Tag_Len Value i1 i2