This ppt contains what is dhcp, it's need, advantages, disadvantages, IP address assignment process and types, DHCP architecture and lastly some differences.

1. SUBJECT : NMA
CHAPTER-2 NETWORK PROTOCOLS AND
SERVICES
TOPIC: DYNAMIC HOST CONFIGURATION
PROTOCOL(DHCP)
By: Kansara Mansi
Chaudhari Nimisha
Dave Tarang
Rahul Gadhvi

2. WHAT IS DHCP?
DHCP stands for ‘Dynamic Host Configuration Protocol’.
It is an extension of an earlier network IP management protocol, Bootstrap
Protocol (BOOTP).
It is a network protocol used on IP network 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.
The primary reason DHCP is needed is to simplify the management of IP address
on network.
No two can have the same IP address and configuring them manually will likely
lead to error.
Even on small network manually assigning IP address can be confusing,
particularly with mobile devices that require IP address on a non permanent
basis.

3. DHCP ORIGINS
DHCP was developed by Microsoft in early 1990’s as a workstation
configuration solution for enterprise network and particularly for it’s own
35,000 node network rollout.
After determining the TCP/IP was the optical protocol for their needs,
Microsoft realized that the task of manually assigning IP address to
thousands of machines located at various sites in fifty country was
enormous as was the continued traciking of those address as computer
where added to and removed from the network.
DHCP is based on two earlier protocols : RARP and BOOTP.
RARP  BOOTP  DHCP

4. REVERSE ADDRESS RESOLUTION
PROTOCOL (RARP)
Reverse ARP is a networking protocol used by a client machine in a local area network to
request its Internet Protocol address (IPv4) from the gateway-router’s ARP table.
The network administrator creates a table in gateway-router, which is used to map the
MAC address to corresponding IP address.
When a new machine is setup or any machine which don’t have memory to store IP
address, needs an IP address for its own use.
So the machine sends a RARP broadcast packet which contains its own MAC address in
both sender and receiver hardware address field.
A special host configured inside the local area network, called as RARP-server is
responsible to reply for these kind of broadcast packets.
Now the RARP server attempt to find out the entry in IP to MAC address mapping table.
If any entry matches in table, RARP server send the response packet to the requesting
device along with IP address.
RARP is not being used in today’s networks. Because we have much great featured
protocols like BOOTP (Bootstrap Protocol) and DHCP( Dynamic Host Configuration
Protocol).

5. ADDRESS RESOLUTION PROTOCOL (ARP)
Address Resolution Protocol is a communication protocol used for discovering physical
address associated with given network address.
 Typically, ARP is a network layer to data link layer mapping process, which is used to
discover MAC address for given Internet Protocol Address.
In order to send the data to destination, having IP address is necessary but not
sufficient; we also need the physical address of the destination machine.
ARP is used to get the physical address (MAC address) of destination machine.
Before sending the IP packet, the MAC address of destination must be known.
 If not so, then sender broadcasts the ARP-discovery packet requesting the MAC address
of intended destination.
 Since ARP-discovery is broadcast, every host inside that network will get this message
but the packet will be discarded by everyone except that intended receiver host whose IP
is associated.
Now, this receiver will send a unicast packet with its MAC address (ARP-reply) to the
sender of ARP-discovery packet.
After the original sender receives the ARP-reply, it updates ARP-cache and start sending

6. ARP AND RARP
ARP RARP

7. BOOTSTRAP PROTOCOL (BOOTP)
The Bootstrap Protocol is a networking protocol used to by a client for obtaining
an IP address from a server.
It was originally defined as specification RFC 951 and was designed to replace
the Reverse Address Resolution Protocol (RARP), also known as RFC 903.
 Bootstrap protocol was intended to allow computers to find what they need to
function properly after booting up.
BOOTP uses a relay agent, which allows packet forwarding from the local
network using standard IP routing, allowing one BOOTP server to serve hosts on
multiple subnets.
BOOTP was largely replaced by the more efficient Dynamic Host Configuration
Protocol (DHCP), which has more options and flexibility. However, it has found
renewed utility in diskless media center PCs.

8. BOOTSTRAP PROTOCOL (BOOTP)
Client and Server on Same
network
Client and Server on Different
network

9. DHCP OBJECTIVES
DHCP is a Client-Server protocol which is used to provide the following
information to a computer that is booted for the 1st time:
1. IP Address
2. Subnet Mask
3. IP of Router (default gateway)
4. IP of name server (DNS)

10. DIFFERENCE BETWEEN ARP AND RARP
S.NO ARP RARP
1. ARP stands for Address Resolution Protocol.
Whereas RARP stands for Reverse Address
Resolution Protocol.
2.
Through ARP, (32-bit) IP address mapped into
(48-bit) MAC address.
Whereas through RARP, (48-bit) MAC address
of 48 bits mapped into (32-bit) IP address.
3. In ARP, broadcast MAC address is used. While in RARP, broadcast IP address is used.
4.
In ARP, ARP table is managed or maintained by
local host.
While in RARP, RARP table is managed or
maintained by RARP server.
5.
In Address Resolution Protocol, Receiver’s MAC
address is fetched.
While in RARP, IP address is fetched.

11. DIFFERENCE BETWEEN BOOTP AND
DHCP
S.NO BOOTP DHCP
1. BOOTP stands for Bootstrap Protocol.
While DHCP stands for Dynamic host configuration
protocol.
2. BOOTP does not provide temporary IP addressing.
While DHCP provides temporary IP addressing for only
limited amount of time.
3. BOOTP does not support DHCP clients. While it support BOOTP clients.
4. In BOOTP, manual-configuration takes place. While in DHCP, auto-configuration takes place.
5. BOOTP does not support mobile machines. Whereas DHCP supports mobile machines.
6.
BOOTP is face down to errors due to manual-
configuration.
Whereas in DHCP errors do not occure mostly due to
auto-configuration.

12. ADVANTAGES OF DHCP
DHCP is easy to implement
The implementations does not required any additional cost.
Duplicate or invalid assignment of IP addresses are prevented.
It simplifies administration of the network
It supports multiple scopes

13. DISADVANTAGES OF DHCP
DHCP server can be single point of failure.
DHCP server has no secure mechanism.
The machine name doesn’t change when new IP address is assigned
Client is not able to access the network in the absence of the DHCP server.

14. WAYS TO EITHER ASSIGN OR SEND IP
ADDRESS TO CLIENT
 There are three ways that a DHCP server either assigns or
sends an IP address to a client:
1.Dynamic Allocation
2.Automatic Allocation
3.Static Allocation

15. DYNAMIC ALLOCATION
 A network administrator reserves a range of IP addresses for
DHCP, and each DHCP client 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 with a
controllable time period, allowing the DHCP server to reclaim
and then reallocate IP addresses that are not renewed.

16. AUTOMATIC ALLOCATION
 The DHCP server permanently assigns an IP address to a
requesting client from the range defined by the administrator.
 This is like dynamic allocation, but the DHCP server keeps a
table of past IP address assignments, so that it can
preferentially assign to a client the same IP address that the
client previously had.

17. STATIC ALLOCATION
 Also commonly called manually allocation and reservations.
 The DHCP server issues a private IP address dependent upon each client's client id
(or, traditionally, the client MAC address), based on a predefined mapping by the
administrator.
 This feature is variously called static DHCP assignment by DD-WRT, fixed-address by
the dhcpd documentation, address reservation by Netgear, DHCP reservation or static
DHCP by Cisco and Linksys, and IP address reservation or MAC/IP address binding by
various other router manufacturers.
If no match for the client's client ID (if provided) or MAC address (if no client id is
provided) is found, the server may or may not optionally fall back to either Dynamic or
Automatic allocation.

18. DHCP ARCHITECTURE
DHCP means DYNAMIC HOST CONFIGURATION PROTOCOL.
The DHCP architecture consists of DHCP clients, DHCP servers, And
DHCP relay agents on a network.
The clients interact with servers using DHCP messages in a DHCP
conversation to obtain and renew IP address leases.

19. DHCP CLIENTS
 A DHCP client is any network enabled device the supports the ability
to communicate with a DHCP server for the purpose of obtaining
dynamic leased IP configuration and related optional information.
The client obtains automatic IP from DHCP server, every time IP
address is different.
DHCP provides support for client computers running any of the
following operating system :• Windows 8
• Windows 7
• Windows Vista
• Windows server
2012
• Windows server
2008
• Windows xp
• Windows server
2003
• Windows 2000
• Windows 98
• Windows millennium
edition
• Windows anti
version 4.0

20. DHCP SERVER
DHCP server is used to centrally allocate TCP/IP configurations to
computer automatically without setting it manually. But if
It saves you plenty of time to set up and manage TCP/IP network
especially if you have a big network.
A server can be installed as standalone server or a built-in feature
on most network routers.
If your network router does support this feature, you can define a
pool of IP address and other configurations to be allocated to
computers.
The IP address will be leased for a period of time, therefore unused
IP address for the durations of lease will be put back to unallocated
pool.
If the IP address is actively used, your computer will ask the server

21. DHCP RELAY AGENT
The core function of DHCP relay agent is to convert a broadcast DHCP
packet into a unicast one, and forward it to a DHCP server.
DHCP relay agent is any TCP/IP host which is used to forward request and
replies between DHCP server and client when the server is present on the
different network.
Relay agents receive DHCP messages and then generate a new DHCP
message to send out on another INTERFACE.
Generally, DHCP messages are broadcasted. So, in order for the messages
to be exchanged between a DHCP client (PC) and DHCP server, both the
client and server have to reside on the same subnet. That is because routers
do not forward any broadcast IP packet to other interfaces.
Thus a broadcast DHCP packet sent by a DHCP client cannot be delivered to
DHCP server on different subnet through a router.
To address this problem, the concept of a DHCP relay agent has been
adopted, enabling the DHCP relay agent function in the router, that allows
DHCP messages to be exchanged between a DHCP client and DHCP server
residing on different subnets.

22. INTERACTIONS BETWEEN CLIENT &
SERVER.DHCP servers & DHCP clients communicate through a series of DHCP
messages.
To obtain a lease, the DHCP client initiates a conversation with a DHCP
server using a series of these DHCP messages.
DHCP MESSAGES :
DHCPDISCOVER : Used by clients system to locate DHCP servers and requesr an IP address
DHCPREQUEST : Used by servers to offer IP address to clients.
DHCPDECLINE : Used by clients to reject an IP address offered by a server.
DHCPACK : Used by servers to acknowledge a client’s acceptance of an offered IP address.
DHCPNAK : Used by servers to reject a client’s acceptance of an offered IP address.
DHCPRELEASE : Used by client’s to terminate a lease.
DHCPINFORM : Used by client’s that have already been assigned an IP address to request
additional configurations parameters.