DHCP (Dynamic Host Configuration Protocol) is a client/server protocol that automatically assigns IP addresses and configuration information to devices on a network, reducing the need for manual setup. It supports three methods of IP address allocation: dynamic, automatic, and static, with various message types for communication between clients and servers. While it offers benefits such as simplified management and mobility for users, DHCP relies on UDP, which is less secure and cannot utilize DNS for configured hosts.

1. DHCP (Dynamic Host Configuration Protocol)
Mohammed Hisham P.M
By
Mohammed Hisham P.M

2. What is DHCP?
Dynamic Host Configuration Protocol (DHCP) is a client/server protocol that
automatically provides an Internet Protocol (IP) host with its IP address and other
related configuration information such as the subnet mask and default gateway.
Clients should require no manual configuration by the user to connect to the
network.
Each client should be able to discover appropriate configuration information
dynamically.
This is normally accomplished through the use of a Dynamic Host Configuration
Protocol [UDP]
Mohammed Hisham P.M
DHCP
 Requires little or no administrative overhead, after initial configurations of the
DHCP server.
 Dynamically maps IP addresses to MAC addresses.
 Addresses can be leased for a predefined amount of time before the lease
expires and must be renewed by the client.

3. Three methods of allocating IP-addresses
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●
DDynamic allocation: A network administrator assigns a range of IP addresses to
DHCP, and each client computer on the LAN is configured to request an IP address
from the DHCP server during network initialization. The request-and-grant process
uses a lease concept.
●
AAutomatic allocation: The DHCP server permanently assigns a free IP address to a
requesting client from the range defined by the administrator
●
SStatic allocation: The DHCP server allocates an IP address based on a table with
MAC address/IP address pairs, which are manually filled in (perhaps by a network
administrator). Only clients with a MAC address listed in this table will be allocated an
IP address.

4. DHCP Message Format
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( There are >100 Options )

5. DHCP Message Type
• Message type is sent as an
option.
Value Message Type
1 DHCPDISCOVER
2 DHCPOFFER
3 DHCPREQUEST
4 DHCPDECLINE
5 DHCPACK
6 DHCPNAK
7 DHCPRELEASE
8 DHCPINFORM

6. Client IP: ??
Gateway: ??
DNS: ??
Client IP: 192.168.1.10/24
Gateway: 192.168.1.1
DNS: 192.168.1.6
Normal DHCP Operation
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DHCPDISCOVER
Broadcast for a DHCP Server
Pool: 192.168.1.0/24
Gateway: 192.168.1.1
DNS Server: 192.168.1.6
DHCPOFFER
MAC unicast with configuration
information
DHCPREQUEST
Broadcast requesting
configuration information sent
in DHCPOFFER
DHCPACK
Acknowledge configuration
information and begins lease

7. DHCP – a client-server protocol
• DHCP operates in a Client/Server environment and uses the
following messages
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DHCPDISCOVER : Client request for server
DHCPOFFER: DHCP server replies to client with configuration information

8. DHCPREQUEST: Client requests the use of configuration information from one of the
DHCP servers that sent an offer
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DHCPRELEASE:Client requests a release of its DHCP configuration
DHCPACK: from DHCP server acknowledges that Client can now begin to use
configuration information

9. }It relieves the network administrator of a great deal of manual configuration
work.
}The ability for a device to be moved from network to network and to a
automatically obtain valid configuration parameters for the current network can
be of great benefit to mobile users.
}Because IP addresses are only allocated when clients are actually active, it is
possible, by the use of reasonably short lease times and the fact that
mobile clients do not need to be allocated more than one address, to
reduce the total number of addresses in use in an organization.
Mohammed Hisham P.M
DHCP Pros
DHCP Cons
}Uses UDP, an unreliable and insecure protocol.
}DNS cannot be used for DHCP configured hosts.

10. }It relieves the network administrator of a great deal of manual configuration
work.
}The ability for a device to be moved from network to network and to a
automatically obtain valid configuration parameters for the current network can
be of great benefit to mobile users.
}Because IP addresses are only allocated when clients are actually active, it is
possible, by the use of reasonably short lease times and the fact that
mobile clients do not need to be allocated more than one address, to
reduce the total number of addresses in use in an organization.
Mohammed Hisham P.M
DHCP Pros
DHCP Cons
}Uses UDP, an unreliable and insecure protocol.
}DNS cannot be used for DHCP configured hosts.