R3721-F3210-F3171-HP High-End Firewalls Network Management Configuration Guide-6PW101

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Figure 82 DHCP option format
Common DHCP options
Common DHCP options:
• Option 3—Router option. It specifies the gateway address.
• Option 6—DNS server option. It specifies the DNS server’s IP address.
• 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 to its routing table. If both Option 33 and
Option 121 exist, Option 33 is ignored.
• 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 150—TFTP server IP address option. It specifies the TFTP server IP address to be assigned to
the client.
• O p t ion 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 to its routing table.
If both Option 33 and Option 121 exist, Option 33 is ignored.
For more information about DHCP options, see RFC 2132 and RFC 3442.
Custom options
Some options, such as Option 43, have no unified definitions in RFC 2132.
Vendor-specific option (Option 43)
DHCP servers and clients use Option 43 to exchange vendor-specific configuration information. The
client sends a request with Option 43, including a vendor string that identifies a vendor. Upon receiving
the request, the DHCP server refers to the vendor-specific options table, and returns a response message
with Option 43 to assign the appropriate vendor-specific information to the DHCP client.
The DHCP client can obtain the following information through Option 43:
• Auto-Configuration Server (ACS) parameters, including the ACS URL, username, and password.
• Service provider identifier, which is acquired by the customer premises equipment (CPE) from the
DHCP server and sent to the ACS for selecting vender-specific configurations and parameters.