DHCP Packet Format

Here is a DHCP discover packet sent by a host interface at host5:

The DHCP message is in the payload portion of an Ethernet packet with the following fields.

Sample DHCP packet fields

Field	Description
opcode	Message op code / message type 1 = REQUEST, 2 = REPLY
yiaddr	“your” IP address (as assigned by DHCP server)
siaddr	Server IP address (in DHCPOFFER and DHCPACK)
chaddr	Client hardware address (e.g., Ethernet MAC address)

Hosts run a DHCP client application that processes DHCP protocol message exchanges. As a result, the host interface gets configured, routes are acquired, and the DNS IP address is recorded.

The DHCP protocol runs on a server within the layer 2 broadcast domain of the network the host resides in. The client application at the host exchanges DHCP messages with this server in the broadcast domain.