2.2.6.2 User Class Option Sent by DHCPv4 Server to DHCPv4 Client
DHCPv4 clients MAY<15> request the user classes configured on the DHCPv4 server by sending a DHCPINFORM message containing OPTION_PARAMETER_REQUEST_LIST (Option 55) ([RFC2132] section 9.8) with OPTION_USER_CLASS (Option 77) ([RFC3004] section 4) as one of the requested options. On receiving the message, the DHCPv4 server SHOULD<16> send a DHCPACK message to the DHCPv4 client containing one or more User Class Options (one for each user class configured on the DHCPv4 server) in the format shown as follows.
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Option Code |
Option Length |
User Class Binary Data Length |
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User Class Binary Data (variable) |
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Padding (variable) |
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User Class Name Length |
User Class Name (variable) |
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User Class Description Length |
User Class Description (variable) |
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Option Code (1 byte): This MUST be 77 (0x4D) to indicate the User Class option for DHCP.
Option Length (1 byte): The unsigned length, in bytes, of the User Class Option, not including the Option Code and Option Length fields.
User Class Binary Data Length (2 bytes): Size of the User Class binary data in octets.
User Class Binary Data (variable): Binary data of a User Class set on the DHCPv4 server.
Padding (variable): Padding to align the User Class binary data to 4-byte boundary.
User Class Name Length (2 bytes): Size of the User Class Name in octets.
User Class Name (variable): Name of a User Class set on the DHCPv4 server.
User Class Description Length (2 bytes): Size of the User Class Description in octets.
User Class Description (variable): Description of a User Class set on the DHCPv4 server.