ZyXEL Communications MES3500-24, User Manual

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MES3500-24/24F User’s Guide
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H A P T E R
3 1
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.
31.1.2 Sub-Option Format
There are two types of sub-option: “Agent Circuit ID Sub-option” and “Agent Remote ID Sub-
option”. They have the following formats.
PPPoE IA
PPPoE Server
PPPoE Client
Table 93
PPPoE Intermediate Agent Vendor-specific Tag Format
Tag_Type
(0x0105)
Tag_Len Value i1 i2
Table 94
PPPoE IA Circuit ID Sub-option Format: User-defined String
SubOpt Length Value
0x01
(1 byte)
N
(1 byte)
String
(63 bytes)