ISC DHCP Server – Option 43 (Vendor specific attribute)

DHCP (RFC 2132) allows for vendor specific data to be distributed to clients.

Important notes:
– clients must request Option 43 in their Parameter Request List (Option 55).
– the Vendor Class Identifier (Option 60) sent by the client in the DHCP Request, must match ‘VendorName’ which is used in the ISC DHCP Server configuration below.

Example server configuration section from dhcpd.conf:

    option space VendorName;
    option VendorName.serviceName code 1 = text;
    option local-encapsulation code 43 = encapsulate VendorName;
    option VendorName.serviceName "data";

– where VendorName matches the value of the client’s Vendor Class Identifier (Option 60).
– ‘serviceName’ is used only as an internal reference within the DHCP server’s configuration, and must be different for each ‘code’ value.

Up to 256 codes may be used for each Vendor specific configuration. All fields will be returned to the client which matches the Vendor Identifier.

The DHCP server will return the Vendor attributes in the DHCP Response. The data returned is encoded in binary in the following format for each code:
Byte 0: code
Byte 1: length
Byte 2: data

Byte length+2: final data byte
… then follows the next field, starting with code, length, data‚Ķ