Lab 118: Configuring DHCP on Cisco Router

DHCP stands for Dynamic Host Configuration Protocol. It is a service which allows you to configure TCP/ IP settings such as IP address and subnet mask on the clients (PC, laptop, printer, etc.) automatically. Typically, DHCP is configured on a dedicated server for better performance. The server can be either Windows-based or Linux-based. DHCP can also be configured on a Cisco router or switch. However, some advance functionalities may not be supported by the DHCP server configured on a Cisco router or switch.

In this exercise, we will explain how to configure DHCP on a Cisco router (or on a manageable switch).

To perform this exercise, we will use the following topology.

Lab 118: Configuring DHCP on Cisco Router 1

First, add the required devices in Cico Packet Tracer and connect them appropriatley. In the preceding topology, Router1 will act as DHCP server while Router2 and PC1 will act as DCHP clients. Let’s begin the exercise.

1.  On Router1, execute the following commands to configure an IP address.

Router( config)# int fa0/ 0 
Router( config-if)# ip add 
Router( config-if)# no shut

2.  Next, create a DHCP pool named DhcpPool1. Use IP address as the default gateway and DNS server. Use as network ID.

Router( config)# ip dhcp pool DhcpPool1 
Router( dhcp-config)# default-router 
Router( dhcp-config)# dns-server 
Router( dhcp-config)# network 
Router( dhcp-config)# exit

By default DHCP server will start to assign IP addresses from the first IP address of the assigned network ID and it will be 8. However, we have already configured this IP addresses manually on Fa0/ 0 interface of Router1. To avoid the confliction between DHCP assigned and manually assigned IP addresses, you can exclude one or more specific IP addresses or IP ranges from the DHCP pool. DHCP server will not distribute these IP addresses to any of the DHCP client.

3.  The following commands will exclude to IP addresses that will not be distributed by DHCP server.

Router( config)# ip dhcp excluded-address 
Router( config)# exit

Lab 118: Configuring DHCP on Cisco Router 2

4.  On Router2, we will assign an IPv4 address on the Fa0/ 0 interface through the DHCP server. To do this, execute the following commands.

Router( config)# int fa0/ 0 
Router( config-if)# ip add dhcp 
Router( config-if)# no shut

5.  Wait for a few seconds and then execute the following command to view the IP address on Router2.

Router2# show ip int brief


Router2( config)# do show ip int brief

Note: Adding the do command before the show command allows you to execute privilege mode commands from the global configuration mode.

Lab 118: Configuring DHCP on Cisco Router 3

6.  Once you have configured an IP address on Router2, switch to PC1, and try to obtain TCP/ IP settings through the DHCP server. To do so, open the console of PC1, select the Desktop tab. On the available options, click IP Configuration and then select the DHCP radio button.

7.  After a few seconds, DHCP server will assign an IP address from the configured DHCP pool along with a default gateway and DNS server IP addresses.

Lab 118: Configuring DHCP on Cisco Router 4

8.  In the preceding figure, you can see that IP address has been assigned by the DHCP server.

9.  To verify the connectivity between PC1 and Router1, execute the following command at the Command Prompt window.


10.  You should be able to ping successfully, as shown in the following figure.

Lab 118: Configuring DHCP on Cisco Router 5

11. Save the configuration of each device and also save the topology and name is as DHCP Topology.

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