Operation Manual – DHCPH3C S7500E Series Ethernet Switches Chapter 1 DHCP Overview1-51.4 DHCP Options1.4.1 DHCP Options OverviewThe DHCP message adopts the same format as the Bootstrap Protocol (BOOTP)message for compatibility, but differs from it in the option field, which identifies newfeatures for DHCP.DHCP uses the option field in DHCP messages to carry control information andnetwork configuration parameters, implementing dynamic address allocation andproviding more network configuration information for clients.Figure 1-4 shows the DHCP option format.Figure 1-4 DHCP option format1.4.2 Introduction to DHCP OptionsThe common DHCP options are:z Option 6: DNS server option. It specifies the DNS server IP address to beassigned to the client.z Option 51: IP address lease option.z Option 53: DHCP message type option. It identifies the type of the DHCPmessage.z Option 55: Parameter request list option. It is used by a DHCP client to requestspecified configuration parameters. The option contains values that correspond tothe parameters requested by the client.z Option 66: TFTP server name option. It specifies a TFTP server to be assigned tothe client.z Option 67: Bootfile name option. It specifies the bootfile name to be assigned tothe client.z Option 150: TFTP server IP address option. It specifies the TFTP server IPaddress to be assigned to the client.For more information about DHCP options, refer to RFC 2132.1.4.3 Self-Defined OptionsSome options have no unified definitions in RFC 2132. The formats of someself-defined options are introduced as follows.
