chaddr: This field contains the MAC address of the client to help the
client know that the received DHCPOFFER message is indeed intended
for it.
yiaddr: This field contains the IP address assigned to the client by the
server.
options: This field contains the associated subnet mask and default
gateway. Other options that are typically included in the DHCPOFFER
message are the IP address of the DNS servers and the IP address lease
and renewal time.Once the client receives a DHCPOFFER message, it
starts a timer and waits for further offers from other
DHCP servers that might serve the same client subnet.
Lease Request
After the client has received the DHCPOFFER from the
server, it responds with a DHCPREQUEST message that
indicates its intent to accept the network configuration
information contained in the DHCPOFFER message. The
client moves to the Request state in the DHCP state
machine. Because there might be multiple DHCP servers
serving the same client subnet, the client might receive
multiple DHCPOFFER messages, one from each DHCP
server that received the DHCPDISCOVER message. The
client chooses one of the DHCPOFFER messages; in
most implementations of the DHCP client, this is the
first DHCPOFFER received. The client replies to the
server with a DHCPREQUEST message. The DHCP
server chosen is specified in the Server Identifier option
field of the DHCPREQUEST message. The
DHCPREQUEST message has as a destination address
the all-subnets broadcast address once more, so all
DHCP servers receive this message and can determine if
their offer was accepted by the client. The source IP
address of the DHCPREQUEST message is still 0.0.0.0
since the client has not yet received a confirmation from
the DHCP server that it can use the offered IP address.
Lease Acknowledgment
The DHCP server receives the DHCPREQUEST message
from the client and acknowledges it with a DHCPACK