Implementation of DHCP Protocol

Dynamic Host Configuration Protocol(DHCP) is an application layer protocol which is used to provide:

1. Subnet Mask (Option 1 – e.g., 255.255.255.0)
2. Router Address (Option 3 – e.g., 192.168.1.1)
3. DNS Address (Option 6 – e.g., 8.8.8.8)
4. Vendor Class Identifier (Option 43 – e.g., ‘unifi’ = 192.168.1.9 ##where unifi = controller)

DHCP is based on a client-server model and based on discovery, offer, request, and ACK.

DHCP port number for server is 67 and for the client is 68. It is a Client server protocol which uses UDP services. IP address is assigned from a pool of addresses. In DHCP, the client and the server exchange mainly 4 DHCP messages in order to make a connection, also called DORA process, but there are 8 DHCP messages in the process.

Steps:

1) Create a network topology of a PC, a switch and a router.

2) The client is connected to Router-1, which acts like a DHCP server whose configuration         is discussed. When a client sens a DHCP request to the router then router sends any of       the available IPs to the router and assigns it.

3) Router Commands:

 Router>enable

 Router#config t

 Router(config)#int gig 0/1

 Router(config-if)# ip address 192.168.100.1    255.255.255.0

 Router(config-if)#no shut

 Router(config-if)#exit

 Router(config)#ip dhcp pool IP01

 Router(dhcp-config)#net 192.168.100.0 255.255.255.0

 Router(dhcp-config)# default 192.168.100.1

 Router(dhcp-config)#exit

 Router(config)#ip dhcp exc 192.168.100.1   192.168.100.15

 Router(config)#exit

 Router#

4) Then go to the PC and then click on DHCP icon in IP configuration.

5) Your PC will be issued an IP address with a message, "DHCP request successful"