• DHCP stands for Dynamic Host Configuration Protocol.
  • It is a client server-based architecture which involves DHCP client and DHCP server.
  • It is a messaging system for the communication between the DHCP server and DHCP client.
  • It allows the clients to acquire their IP address dynamically.
  • DHCP uses UDP port numbers 67 for destination server and port number 68 for the client.

The DHCP messaging system’s message and their types are given below:

  • Discover
  • Offer
  • Request
  • Acknowledgment

Every DHCP server that receives the message, responds with a DHCP offer containing:

  • The IP Address being offered to the DHCP client.
  • The network mask offered to the DHCP client.
  • The amount of time the client can keep and use this address.
  • The IP address of the DHCP server makes this offer.

Components of DHCP

Before start configuring DHCP, it is important to understand all of its components.

A list of DHCP components are given below:

DHCP Server: DHCP Server is a networked device that is used to run the DHCP service and hold the information about the IP address or related configuration.

DHCP Client: DHCP client receives configuration information from a DHCP Server. It can be a computer, mobile phone, or any other device that requires connectivity to the network.

IP address pool: IP address pool is the range of IP addresses that are available to DHCP clients. These addresses are generally handed out sequentially from lowest to highest.

Subnet: Subnet helps us to keep networks manageable.

DHCP relay: DHCP relay is responsible for forwarding the requests and responses between the DHCP clients and the DHCP servers.

Configure DHCP

There are following steps involve configuring DHCP on a Router –

Step1: Create the Network topology:


Step2: On the router0, configure an IP address to the router’s interface that is connected to the switch and act as the default gateway.


Step3: Now, create an ip dhcp pool and named it as Cisco. In this Pool, provide a Network address that has given to the DHCP clients.

After creating the DHCP pool, assign the router’s interface ip address as a default-router address for clients.


Step4: In this step, we will exclude ip address range by typing “ipdhcp excluded address” command.


After completing all the above steps, click on any PC then go to Desktop -> IP Configuration ->DHCP.


You see that the ip address is configured automatically, as it is shown in the above screenshot.

Advantages of DHCP

DHCP offers the following advantages:

  • IP address management –DHCP provides easier IP address management scheme. In a network, without DHCP, you must assign IP addresses manually. But When the DHCP is enabled, the DHCP server provides IP address automatically.
  • Centralized network client configuration – In the DHCP, all configuration information is stored in one place that is“DHCP data store.” It does not need a client to change the configuration. It can make changes for multiple clients just by changing the information stored in the data store.
  • Support of local clients and remote client – DHCP supports both local clients and remote client by providing the IP addresses automatically to each client that work on a network.
  • Large network support –There are millions of clients that can use DHCP. The DHCP uses multithreading to process the clients request simultaneously. 
  • Remove Delicacy – DHCP removes duplicate or invalid assignment of IP addresses. Therefore, no chance of conflicts in IP addresses.

Disadvantages of DHCP

  • Makes router busy – When we configure DHCP on a router, it will make the router busier and consume some additional memory.
  • Security Issues – In DHCP, there is a high-security risk. Because the information is sent over the network, that’s why there may be a chance of information getting lost or hacked by someone.
  • The client is not able to access the network in the absence of a DHCP server.

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