Lab 32: Configuring the Cisco IOS DHCP Server

Lab Objective:

The objective of this lab exercise is for you to learn and understand how to configure the Cisco IOS DHCP server.

Lab Purpose:

Configuring the Cisco IOS DHCP server is a fundamental skill. DHCP (Dynamic Host Configuration Protocol) provides dynamic addressing information to hosts on a network. Typically, physical DHCP servers (such as Microsoft Windows servers) are used to provide addressing information to DHCP clients (which are devices that request configuration via DHCP). However, Cisco IOS routers can also be configured to act as DHCP servers and provide dynamic addressing to DHCP clients. As a Cisco engineer, as well as in the Cisco CCNA exam, you will be expected to know how to configure the Cisco IOS DHCP server.

Certification Level:

This lab is suitable for CCENT and CCNA certification exam preparation.

Lab Difficulty:

This lab has a difficulty rating of 7/10.

Readiness Assessment:

When you are ready for your certification exam, you should complete this lab in no more than 10 minutes.

IMPORTANT NOTE: In order to test DHCP functionality, you will need a workstation DHCP client configured to receive IP addressing information via DHCP. If you do not have a DHCP client, feel free to substitute it with another Cisco IOS router configured as a DHCP client by using the ip address dhcp command on the interface connected to the DHCP router.

Lab Topology:

Please use the following topology to complete this lab exercise:

Task 1:

Configure the hostnames on R1 and Sw1 as illustrated in the topology.

Task 2:

Configure VLAN50 named DHCP_VLAN on Sw1. Assign the FastEthernet0/2 and FastEthernet0/3 interfaces on Sw1 to this VLAN. Ensure that the ports immediately transition to the Spanning Tree Forwarding state. This is actually an ICND2 requirement but I’ve slipped it in here (we’ll do a PortFast lab in the ICND2 section).

Task 3:

Configure R1 as a Cisco IOS DHCP server with the following settings:

  • DHCP pool name: CCNA-DHCP-POOL
  • DHCP network:
  • DNS server:
  • WINS server:
  • Default gateway:
  • DNS domain:
  • DHCP lease time: 5 days 30 minutes

Some of the options above are not available in Packet Tracer, so you may want to use GNS3.

Ensure that you exclude the IP address of the router interface from the DHCP pool.

Task 4:

Verify your DHCP configuration on the connected workstation (or other DHCP client) and verify that your Cisco IOS DHCP server is showing a leased DHCP address.

Configuration and Verification

Task 1:

For reference information on configuring hostnames, please refer to earlier labs.

Task 2:

Sw1#config t 
Enter configuration commands, one per line.  End with CTRL/Z. 
Sw1(config-vlan)#name DHCP_VLAN 
Sw1(config)#interface range fastethernet0/2 – 3 
Sw1(config-if-range)#switchport mode access 
Sw1(config-if-range switchport access vlan50 
Sw1(config-if-range)#spanning-tree portfast 
%Warning: portfast should only be enabled on ports connected to a single host. Connecting hubs, concentrators, switches, bridges, etc... to this interface when portfast is enabled, can cause temporary bridging loops. 
Use with CAUTION 

%Portfast will be configured in 2 interfaces due to the range command 
but will only have effect when the interfaces are in a non-trunking mode. 
Sw1(config-if-range)#no shutdown 

Task 3:

R1#config t 
Enter configuration commands, one per line.  End with CTRL/Z. 
R1(config)#ip dhcp pool CCNA-DHCP-POOL 
R1(dhcp-config)#lease 5 0 30 
R1(config)#ip dhcp excluded-address 

R1#show ip dhcp pool CCNA-DHCP-POOL 

Utilization mark (high/low) : 100 / 0 
Subnet size (first/next) : 0 / 0 
Total addresses : 254 
Leased addresses : 0 
Excluded addresses : 1 
Pending event : none 

1 subnet is currently in the pool 
Current index IP address range Leased/Excluded/Total - 0 / 1 / 254

Task 4:

I used another router as a DHCP client, as you can see below. If you use a host, then configure it to obtain the IP address via DHCP.

Router(config)#int f0/0
 Router(config-if)#ip address dhcp
 Router(config-if)#no shut
 %LINK-5-CHANGED: Interface FastEthernet0/0, changed state to up
 %DHCP-6-ADDRESS_ASSIGN: Interface FastEthernet0/0 assigned DHCP address, mask, hostname Router3

Router#show ip dhcp binding
 IP address   Client-ID/      Lease expiration          Type Hardware address    0060.47BC.7A01    --                     Automatic

The ipconfig /all command on a Windows-based workstation would show the following:

NOTE: If you have configured another Cisco IOS device as a DHCP client to test your configuration, you should see the following output:

Router#show ip dhcp pool 

Utilization mark (high/low)    : 100 / 0 
Subnet size (first/next)       : 0 / 0 
Total addresses                : 254 
Leased addresses               : 1 
Excluded addresses             : 1 
Pending event                  : none 

1 subnet is currently in the pool 
Current index        IP address range           Leased/Excluded/Total  -      1    / 1  / 254



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