Dhcp Options; Overview; Introduction To Dhcp Options; Self-Defined Options - HP A5120 EI Series Configuration Manual

DHCP options

Overview

DHCP uses the same message format as BOOTP, but DHCP uses the Option field to carry information for
dynamic address allocation and to provide additional configuration information to clients.
Figure 16 shows the DHCP option format.
Figure 16 DHCP option format
0
Option type

Introduction to DHCP options

Common DHCP options
Option 3: Router option. It specifies the gateway address to be assigned to the client.

Option 6: DNS server option. It specifies the DNS server IP address to be assigned to the client.

Option 33: Static route option. It specifies a list of classful static routes (the destination addresses in

these static routes are classful) that a client should add into its routing table. If Option 121 exists,
Option 33 is ignored.
 Option 51: IP address lease option.
 Option 53: DHCP message type option. It identifies the type of the DHCP message.
Option 55: Parameter request list option. It is used by a DHCP client to request specified

configuration parameters. The option contains values that correspond to the parameters requested
by the client.
Option 60: Vendor class identifier option. It is used by a DHCP client to identify its vendor, and by a

DHCP server to distinguish DHCP clients by vendor class and assign specific IP addresses for the
DHCP clients.
Option 66: TFTP server name option. It specifies a TFTP server to be assigned to the client.

Option 67: Bootfile name option. It specifies the bootfile name to be assigned to the client.

Option 121: Classless route option. It specifies a list of classless static routes (the destination

addresses in these static routes are classless) that the requesting client should add into its routing
table.
 Option 150: TFTP server IP address option. It specifies the TFTP server IP address to be assigned to
the client.
For more information about DHCP options, see RFC 2132.

Self-defined options

Some options, such as Option 43, Option 82, and Option 184, have no unified definitions in RFC 2132.
7
Option length
Value (variable)
15
25