KB.15.15

10 Dynamic Host Configuration Protocol

The Dynamic Host Configuration Protocol (DHCP) is used for configuring hosts with IP address and

other configuration parameters without user intervention. The protocol is composed of three

components:

• DHCP client

• DHCP server

• DHCP relay agent

For more information, see “Overview of DHCP” (page 237).

Enabling DHCP relay

The DHCP relay function is enabled by default on an HP routing switch. However, if DHCP has

been disabled, you can re-enable it by entering the following command at the global configuration

level:

HP Switch(config)# dhcp-relay

To disable the DHCP relay function, enter the no form of the command:

HP Switch(config)# no dhcp-relay

Using DCHP Option 12 to send a hostname

This feature allows you to include the hostname in the DHCP packet sent to the DHCP server. This

is disabled by default. The command must be executed from the global configuration level.

Syntax:

[no]dhcp host-name-option

Sends the hostname option with DHCP packets. Use the no form of the command

to not include the hostname in the packet.

The maximum size of the hostname is 32 characters.

Default: disabled

Example 125 DHCP Option 12 command

HP Switch(config)# dhcp host-name-option

SNMP support

A MIB object supports enabling and disabling the DHCP Option 12 feature. It is added in the

hpicfDhcpclient.mib. The hostname is retrieved from the MIB variable SYSNAME. Validity

checks on the name include:

• The name starts with a letter, ends with a letter or a digit, and can have letters, hyphens, or

digits in between the first and last characters.

• The maximum size supported for a hostname is 30 characters. If SYSNAME is more than 30

characters, then DHCP Option 12 will not be included in the packet.

• The minimum number of characters supported for a hostname is one character. If the SYSNAME

in the MIB is null, then DHCP Option 12 will not be included in the packet.

228 Dynamic Host Configuration Protocol