Would you like to learn how to configure DHCP Relay on Cisco Switch using the command-line? In this tutorial, we are going to show you all the steps required to configure the DHCP relay feature between virtual interfaces on a Cisco Switch 3750 using the command-line.
In our example, the DHCP server has the IP address 192.168.100.10 and is located on the Vlan 100.
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Tutorial – DHCP Relay on Cisco Switch
First, you need to access the console of your Cisco Switch.
In our example, we are going to use an Opensource software named Putty and a computer running Windows.
The Putty software is available on the putty.org website.
After finishing the download, run the software and wait for the following screen.
To access the console of a Cisco Switch model 2960 or 3750, you will need to select the Serial Connection category and use the following options:
• Connection type: Serial
• Serial line: COM1
• Speed: 9600
If COM1 does not work you will need to try to use COM2, COM3, COM4 or the next.
Using either the console, telnet or ssh, connect to the command-line of your switch and log in with a user who has administrative privileges.
On the prompt screen, enter the administrative login information.
After a successful login, the console command-line will be displayed.
Switch>
Use the enable command to enter the privilege mode.
Switch> enable
Use the configure terminal command to enter the configuration mode.
Switch# configure terminal
Create 2 new Vlans, select an identification number and add a brief description.
Switch(config)# vlan 100
Switch(config-vlan)# name Server Network
Switch(config)# vlan 200
Switch(config-vlan)# name Desktop Network
Switch(config-vlan)# exit
On the configuration mode, you need to create 2 virtual interfaces.
Switch(config)# interface vlan 100
Switch(config-if)# ip address 192.168.100.1 255.255.255.0
Switch(config-if)# exit
Switch(config)# interface vlan 200
Switch(config-if)# ip address 192.168.200.1 255.255.255.0
Switch(config-if)# ip helper-address 192.168.100.10
Switch(config-if)# exit
The command ip helper-address is responsible for redirecting all DHCP request from computers located on Vlan 200 to the DHCP server 192.168.100.10, located on the Vlan 100.
In our example, the virtual switch interfaces Vlan100 and Vlan200 were configured.
In our example, the DHCP server has the IP address 192.168.100.10 and is located on the Vlan 100.
In our example, all DHCP request from computers located on Vlan 200 were redirected to the DHCP server 192.168.100.10, located on the Vlan 100.
To test your configuration, configure a switch port on the Desktop Vlan.
Switch(config)# interface gigabitethernet0/40
Switch(config)# switchport mode access
Switch(config-if)# switchport access vlan 200
Switch(config-if)# exit
Switch(config)# exit
Connect a computer on the switch port 40, configure this computer to get an IP address using DHCP.
your computer should get an IP address from the DHCP server configured using the ip helper-address command.
Don’t forget to save your switch configuration.
Switch# copy running-config startup-config
You have successfully configured the feature: DHCP relay on Cisco Switch.
