DHCP Options 43, 55, and 60 and Other Customized Options

The following table describes the option behavior for several options described in RFC 2132.
Option Code
Option Name
Option Description/Behavior
Vendor Specific Information
Sent from server to client. Vendor-specific information that the DHCP server has been configured to offer to the client. The information is sent to the client only if the server has a Vendor Class Identifier (VCI) in its table that matches the VCI in the client’s DHCPREQUEST.
An Option 43 packet can contain multiple vendor-specific pieces of information. It can also include encapsulated, vendor-specific extensions of data.
Parameter Request List
Sent from client to server. List of configuration parameters (option codes) that a DHCP client is requesting, possibly in order of the client’s preference. The server tries to respond with options in the same order.
Vendor Class Identifier (VCI)
Sent from client to server. Vendor type and configuration of a DHCP client. The DHCP client sends option code 60 in a DHCPREQUEST to the DHCP server. When the server receives option 60, it sees the VCI, finds the matching VCI in its own table, and then it returns option 43 with the value (that corresponds to the VCI), thereby relaying vendor-specific information to the correct client. Both the client and server have knowledge of the VCI.
You can send custom, vendor-specific option codes that are not defined in RFC 2132. The option codes can be in the range 1-254 and of fixed or variable length.
Custom DHCP options are not validated by the DHCP Server; you must ensure that you enter correct values for the options you create.
For ASCII and hexadecimal DHCP option types, the option value can be a maximum of 255 octets.

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