2.2.6 DHCPv4 Option Code 77 (0x4D) - User Class Option

This section describes the message format of the User Class Option sent by DHCPv4 clients and DHCPv4 servers, and the values for this option that are predefined on DHCPv4 servers that implement this specification. The format of this option varies from the implementation described in [RFC3004] in that the User Class Data field format is changed. The use of this alternate format is indicated by the presence of a Vendor Class Identifier Option (section 2.2.3), which can occur anywhere in the same message.