DHCP definition
DHCP stands
for dynamic host configuration protocol and is a network protocol used on IP
networks where a DHCP server automatically assigns an IP address and other
information to each host on the network so they can communicate efficiently
with other endpoints.
In addition
to the IP address, DHCP also assigns the subnet mask, default gateway address,
domain name server (DNS) address and other pertinent configuration parameters.
The primary
reason DHCP is needed is to simplify the management of IP addresses on
networks.
DHCP works
on a client-server model. Being a protocol, it has its own set of messages that
are exchanged between client and server.
1. DHCPDISCOVER
It is a DHCP
message that marks the beginning of a DHCP interaction between client and
server. This message is sent by a client (host or device connected to a
network) that is connected to a local subnet. It’s a broadcast message that
uses 255.255.255.255 as destination IP address while the source IP address is
0.0.0.0
2. DHCPOFFER
It is DHCP message
that is sent in response to DHCPDISCOVER by a DHCP server to DHCP client. This
message contains the network configuration settings for the client that sent
the DHCPDISCOVER message.
3. DHCPREQUEST
This DHCP message
is sent in response to DHCPOFFER indicating that the client has accepted the
network configuration sent in DHCPOFFER message from the server.
4. DHCPACK
This message is
sent by the DHCP server in response to DHCPREQUEST received from the client.
This message marks the end of the process that started with DHCPDISCOVER. The
DHCPACK message is nothing but an acknowledgement by the DHCP server that
authorizes the DHCP client to start using the network configuration it received
from the DHCP server earlier.
DHCP uses the port numbers 67 & 68.
DHCP messages from a client to a server are sent to the 'DHCP server' port (67), and DHCP messages from a server to a client are sent to
the 'DHCP client' port (68).
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