Question { 4215 }

What is DHCP & work?

Answer

Short for Dynamic Host Configuration Protocol, a protocol
for assigning dynamic IP addresses to devices on a network.
With dynamic addressing, a device can have a different IP
address every time it connects to the network. In some
systems, the device's IP address can even change while it
is still connected. DHCP also supports a mix of static and
dynamic IP addresses.
Dynamic addressing simplifies network administration
because the software keeps track of IP addresses rather
than requiring an administrator to manage the task. This
means that a new computer can be added to a network without
the hassle of manually assigning it a unique IP address.
Many ISPs use dynamic IP addressing for dial-up users.

DHCP Process
How DHCP Works in an Ethernet/IP LAN environment and
assumes the client is obtaining a fresh lease without
foreknowledge of the DHCP server's IP address. Note that
this is highly simplified.
I.A client boots and initializes its network hardware
II.The client sends out a DHCPDISCOVER message formatted as
follows:
A.The source MAC is the client's MAC
B.The destination MAC is all 1's indicating a hardware-
layer broadcast (FFFFFF-FFFFFF)
C.The message type is set to DHCPDISCOVER
III.The server hears the DHCPDISCOVER request and responds
A.The source MAC is the server's MAC
B.The destination MAC is the client's MAC
C.The message type is DHCPOFFER containing:
1.Server-provided IP address from pool of free addresses
(the server should but is not required to check for address
conflicts before offering the IP address).
2.List of DHCP configuration parameters
D.Client responds with DHCPREQUEST message and does one or
more of the following:
1.requests values for the server-offered parameters from a
single server (rejecting all offers from other servers)
2.confirm the correctness of the previously allocated IP
address (after the client had rebooted or lost connection
to the network)
3.requests extension of the lease on the specific address
already supplied.
E.The server responds with
1.a DHCPACKnowledge to confirm the server-offered options
and IP previously confirmed by the client -
- or-
2.a DHCPNOACKnowledge to reject the server-offered options.
- or -
3.a DHCPDECLINE message to indicate to the server the
address is in use.
F.The client retains the information throughout the period
of its lease.
G.The client sends a DHCPRELEASE message to release its IP
address at the DHCP server when it is leaving the network.