214 CHAPTER 17: 802.1X CONFIGURATION
In an EAPoL packet:
■ The PAE Ethernet type field holds the protocol identifier. The identifier for
802.1x is 0x888E.
■ The Protocol version field holds the version of the protocol supported by the
sender of the EAPoL packet.
■ The Type field can be one of the following:
00: Indicates that the packet is an EAP-packet, which carries authentication
information.
01: Indicates that the packet is an EAPoL-start packet, which initiates the
authentication.
02: Indicates that the packet is an EAPoL-logoff packet, which sends logging
off requests.
03: Indicates that the packet is an EAPoL-key packet, which carries key
information.
04: Indicates that the packet is an EAPoL-encapsulated-ASF-Alert packet,
which is used to support the alerting messages of ASF (alerting standards
forum).
■ The Length field indicates the size of the Packet body field. A value of 0
indicates that the Packet Body field does not exist.
■ The Packet body field differs with the Type field.
Note that EAPoL-Start, EAPoL-Logoff, and EAPoL-Key packets are only transmitted
between the supplicant system and the authenticator system. EAP-packets are
encapsulated by RADIUS protocol to allow them successfully reach the
authentication servers. Network management-related information (such as
alarming information) is encapsulated in EAPoL-Encapsulated-ASF-Alert packets,
which are terminated by authenticator systems.
The format of an EAP packet
For an EAPoL packet with the value of the Type field being EAP-packet, its Packet
body field is an EAP packet, whose format is illustrated in
Figure 68.
Figure 68 The format of an EAP packet
In an EAP packet:
■ The Code field indicates the EAP packet type, which can be Request, Response,
Success, or Failure.
■ The Identifier field is used to match a Response packet with the corresponding
Request packet.
015
Code
Data
Length
7
Identifier
2
4
N
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